Spatial patterns in the population dynamics of the scallop Psychrochlamys patagonica were analyzed in Uruguayan waters of the southwestern Atlantic Ocean between 35°50′S (northern edge of the species distribution) and 36°50′S. The water depth ranged from 75–135 m. Survey stations were located every 10 miles on parallel transects along the latitudinal gradient. Population structure revealed three modal classes differing in strength between latitudes, indicating recruitment variability. However, the second mode was weak between 35°50′S and 36°10′S, suggesting poor recruitment at the northern end of the scallop's distribution. Relative numbers of recruits decreased with latitude, whereas recruit density was directly related with spawner density, reaching asymptotic values at highest adult densities. Growth curves (size-at-age data) differed between latitudes and a likelihood ratio test indicated that these differences could be explained by the combination of the von Bertalanffy parameters H_∞K. Predicted mean weight for a standard length of 60 mm H followed a nonlinear increase from northern to southern latitudes. Natural mortality (M) decreased with latitude, being more than 3 times higher at 36°00′S (1.77 y⁻¹) than at 36°40′S (0.46 y⁻¹). Projected biomass was zero from 35°50′S to 36°10′S, increasing toward southern latitudes. The clear spatial patterns found seem to be caused by a marked environmental gradient at the northern end of the study area that constrains the geographic range of P. patagonica. Given the sedentary life-history characteristics of P. patagonica, its persistent spatial structure and the marked spatial patterns in its population dynamics, a set of spatially explicit management tools, such as rotation of fishing areas and reproductive refuges, should be used.

Bay scallops (Argopecten irradians [Lamarck]) are a culturally and economically important component of Florida's nearshore marine community. However, many of the local populations that compose the bay scallop metapopulation in Florida have virtually disappeared since the 1950s. This study reports the results of a 3-year effort to restore bay scallop populations at 4 sites along the west central coast of the state (Tampa Bay, Anclote, Homosassa and Crystal River). During late summer of 1997, 1998 and 1999, wild adult scallops were retrieved from each of those four target sites and induced to spawn in the laboratory. The resultant offspring were grown to at least 20-mm shell height in a nursery setting and then transplanted to cages deployed at the site where their parents were originally harvested. The growth, survival and reproductive development of the planted scallops were recorded on an approximate 6-week schedule. Results suggest that caged scallops generally grew more slowly than their wild counterparts and that at most of the planting sites mortality was high, especially during late summer. Reproductive development and spawning, although delayed in the caged scallops relative to their wild conspecifics, appears to have proceeded in an otherwise normal fashion. Approximately 1,100 scallops survived and spawned during the first year of the project, whereas ~4,700 and 12,000 scallops survived to spawn in the second and third years of the project, respectively. Studies were also conducted to determine the optimal stocking density and the best placement of the cages. Results of the density study indicate that planting at lower densities increased growth and survival but did not necessarily result in more live scallops at the time of spawning. Results of the cage-placement study, which compared scallops planted in cages either inside or outside of a seagrass bed and either mounted on legs or placed directly on the sediment, revealed that scallops planted directly on the substrate within a seagrass bed suffered higher mortality and slower growth than did scallops planted in the other three treatment combinations. Overall results of this 3-year project suggest that planting cultured scallops in cages can be a successful strategy for increasing the local spawner stock density of bay scallops in depleted populations and, ultimately, for increasing larval supply to the metapopulation.

Giant scallops, Placopecten magellanicus, respond to the presence of starfish predators with an escape response consisting of a series of rapid valve adductions that allow the scallop to jump or swim away from the predator. To evaluate the coordination of the activity of the tonic and phasic muscles during such escape responses, we recorded their force production by attaching a force gauge to the shell of intact scallops and then stimulating the scallops with starfish. These recordings showed series of phasic contractions (claps) separated by prolonged tonic contractions. Numerous characteristics could be quantified from these recordings including the maximal force, mean force during the first minute, force, frequency and number of claps per series, as well as the force and duration of tonic contractions. The number of claps per series declined and the duration of the tonic contractions increased as the escape response continued. For most scallops, phasic and tonic contractions produced similar levels of force that changed little during the escape responses. The alternation between phasic and tonic contractions suggests that periods of tonic contraction allow the phasic muscle to recuperate and facilitate subsequent phasic contractions. Principal component analysis (PCA) confirmed the coordination between the phasic and tonic adductor muscles, because characteristics of each type of contraction, were closely associated. This method combines the advantages of stimulation of scallops by their predators with the simplicity of force gauge measurements. Force production during escape responses by individual scallops was highly reproducible, suggesting these measurements have considerable potential for tracking changes in the physiologic status of giant scallops.

Gonadosomatic index, germ cell differentiation, ovarian cycle and first sexual maturity in female Patinopecten yessoensis were studied by histologic and cytologic observations. In the early vitellogenic oocyte, the Golgi complex, mitochondria and endoplasmic reticulum were involved in the formation of lipid droplets. In the late vitellogenic oocyte, exogenous substances, namely, glycogen particles and lipid granular substances appeared in the germinal epithelium passed into the ooplasm through the microvilli of the vitelline envelope. Yolk granules and multivesicular bodies were involved in the formation of proteid yolk granules in the late vitellogenic oocyte. Vitellogenesis occurs by endogenous autosynthesis and exogenous heterosynthesis. The auxiliary cells function as nutritive cells in the formation and development of the previtellogenic and early vitellogenic oocytes in their early stages. Monthly changes in the gonadosomatic index were closely associated with ovarian developmental phases. The annual ovarian cycle of this species can be classified into 5 stages; early active stage (September to October), late active stage (November to February), ripe stage (March to May), spawning stage (April to June) and spent/inactive stage (June to September). The percentage of first sexual maturity was 56.3% in individuals of 61.0–70.9 mm in shell height, and 100% in those >81.0 mm.

Chloramphenicol, erythromycin and furazolidone were used in larval culture of Argopecten ventricosus at 4 concentrations: 0.5, 1.0, 3.0 and 6.0 mg/L to evaluate larval survival and prophylactic effect of these antibiotics. The use of concentrations higher than 1.0 mg/L induced a significant (P < 0.05) increase in larval survival. The bacteriostatic effect of antibiotics was studied with direct and indirect bacterial count methods. Total bacteria and Vibrio spp. showed a reduced density in culture tanks (55.6% and 98.1%, respectively), when larvae were treated with 6.0 mg/L of chloramphenicol and erythromycin. The results of the study indicate that 6.0 mg/L of chloramphenicol and erythromycin enhance larval condition and survival, reducing potential pathogens in culture tanks.

Light, transmission and scanning electron microscopical studies were carried out to characterize the hemocytes of the scallop Chlamys farreri (Jones & Preston). Five types of hemocytes were recognized: type 1 small hyalinocytes (2.44 ± 0.11 μm, 45% to 50%), type 2 large hyalinocytes (4.83 ± 0.28 μm, 15–20%), type 3 small granulocytes (4.07 ± 0.15 μm, 15% to 20%), type 4 medium granulocytes (7.20 ± 0.26 μm, 20–25%) and type 5 large granulocytes (13.87 ± 0.73 μm, 3% to 5%). Granulocytes showed larger sizes and smaller N/C ratios than hyalinocytes. The mean hemocyte concentration was about (3.03 ± 0.11) × 10⁷ cells mL⁻¹. Among hemocytes, 42.6% are granular cells and 57.4% are agranular cells. These gave a relatively systematic classification scheme for hemocytes of Chlamys farreri. Three kinds of granules were identified: high electron-dense granules, low electron-dense granules and medium electron-dense granules based on TEM studies. Both granulocytes and hyalinocytes showed phagocytic response to the two strains of bacteria, E. coli and Rickettsia-like organisms. The phagocytic ability of granulocyte was significantly higher (30% to 40%) than that of hyalinocyte (4.8% to 14%).

For commercial development of a European scallop culture industry based on natural collection of seed, a method of predicting time and location of peak spatfalls is essential. Planktonic identification of scallop larvae using light microscopy, which would allow development of such a prediction technique, has been deemed impossible. Researchers have instead focused on the use of scanning electron microscopy of the hinge structure or development of biotechnological methods to resolve the difficult identification in plankton samples. This study presents details of morphological characteristics, excluding ultrastructural traits of the hinge, that have been used to identify king scallops, Pecten maximus, larvae during their planktonic phase in Mulroy Bay, Ireland over the last 26 years. The most useful features for identification of king scallop larvae in natural plankton samples were the pointed anterior end, the indistinct umbo, the pale color and the length–height relationship. These characteristics for identification of king scallop larvae in natural plankton samples have led to development of a technique for prediction of time and location of scallop spatfall and commercial collection of scallop spat at intensities exceeding 3000 spat per collector bag.

The major restriction to expansion of scallop culture and scallop fishery enhancement in Europe is a reliable source of scallop spat. In Ireland, production of spat from the natural settlement in Mulroy Bay has exhibited considerable variation over the last 25 years. In this study data available on king scallop spawnings have been reviewed with the objective of understanding why in some years spat are abundant and in others scarce. Similar spawning periods of king scallops, Pecten maximus in two locations 10 km apart, supported the use of scallops from the Broad Water for gonad monitoring rather than from the North Water spat production site where scallop dredging is legally prohibited. Using weekly determination of gonad index, gonad weight and relative gonad height, five partial spawnings were recorded between April to August in 1 year, with scallops capable of spawning 1 week and re-maturing to a pre-spawning level the following week. Sampling frequency significantly influenced the number and size of spawnings recorded, date of the spawning and duration of the spawning event. These results have major implications for data collected using sampling intervals greater than 1 week and purporting to represent the reproductive cycle of this scallop. Based on weekly monitoring of scallop gonads during summer months between 1993 to 2004 there was no significant correlation between intensity of the scallop spatfall and size of the gonad prior to spawning, magnitude of spawning event, date of spawning period within June and July and duration of the spawning event.

Chromosomal location of the 5S ribosomal RNA gene was studied in the eastern oyster, Crassostrea virginica Gmelin, using fluorescence in situ hybridization (FISH). Metaphase chromosomes were obtained from early embryos, and the FISH probe was made by PCR (polymerase chain reaction) amplification of the 5S rRNA gene and labeled by incorporation of digoxigenin-11-dUTP during PCR. Hybridization was detected with fluorescein-labeled antidigoxigenin antibodies. Two pairs of FISH signals were observed on metaphase chromosomes. Karyotypic analysis showed that the 5S rRNA gene cluster is interstitially located on short arms of chromosomes 5 and 6. On chromosome 5, the 5S rRNA genes were located immediately next to the centromere, whereas on chromosome 6, they were located approximately half way between the telomere and the centromere. Chromosomes of C. virginica are difficult to identify because of their similarities in size and arm ratio, and the chromosomal location of 5S rRNA genes provides unambiguous identification of chromosomes 5 and 6. Previous studies have mapped the major rRNA gene cluster (18S-5.8S-28S) to chromosome 2, and this study shows that the 5S rRNA gene cluster is not linked to the major rRNA genes and duplicated during evolution.

Along the east coast of central Florida in the Indian River Lagoon system, intense recreational boating activity occurs year-round, and intertidal reefs of the eastern oyster Crassostrea virginica (Gmelin) with dead margins (mounds of disarticulated shells) on their seaward edges are commonly found adjacent to major boating channels. These dead margins are caused, at least in part, by boat wakes and extend significantly higher above the high water line than reefs lacking dead margins (pristine reefs). To determine if these “impacted” oyster reefs alter recruitment and subsequent survival of C. virginica, three 8-wk field trials were run between May 2001 and April 2002 in Mosquito Lagoon. During each trial, data were also collected on total sediment loads, silt/clay fractions and relative water motion. Although recruitment did not differ between impacted and pristine reefs, juvenile survival was significantly reduced on impacted reefs. Additionally, larval recruitment and subsequent mortality were greatest during our summer trial. Total sediment loads, percent silt/clay, and relative water motion were significantly higher on impacted reefs. For these three variables, the largest values were consistently found at the bases of exposed (seaward) regions of impacted reefs. By documenting a positive relationship between reduced success of C. virginica and dead margins, and knowing that boat wakes contribute to the development of dead margins, we have provided the first cause and effect mechanism between intense recreational boating activity and increased oyster morality.

The monthly variation in the biochemical composition of the digestive gland, the adductor muscle and the gonad and its relationship with the gonadal index (GI) were studied during 2 years in a wild population of Hyotissa hyotis living in the Gulf of California. Protein was the main constituent of the gonad, digestive gland and adductor muscle. Temperature (20°C to 24°C) favored the accumulation of protein in the muscle during gametogenesis. Carbohydrates and lipids were stored in the gonad, digestive gland and adductor muscle during the spring gametogenesis to support the reproduction effort. Three spawning periods were detected, one in the first year and two during the second.

Oyster producers in the Pacific Northwest region of the United States export large quantities of oysters to international markets. Proposed changes to international limits for heavy metals content in shellfish could drastically curtail exports and impact the viability of this environmentally-friendly industry. “Supply-side” solutions such as moving oyster farms to uncontaminated sites or short-term depuration would incur substantial costs in terms of labor and infrastructure and displace workers in already economically challenged coastal communities, whereas selective breeding could benefit both producers and consumers within the current infrastructure. We studied the feasibility of selective breeding to reduce heavy metal content through a quantitative genetic analysis of heavy metals accumulation in the Pacific oyster, Crassostrea gigas by opportunistically sampling a factorial mating experiment initiated in 2000 to study the effects of parent size on offspring growth and survival. The experiment consisted of all possible crosses among six males (sires) and five females (dams). At harvest, we measured four performance traits (yield, survival, whole oyster live weight and shucked meat dry weight) and the accumulated levels of four heavy metals (copper, lead, zinc and cadmium). Analyses of variance testing for sire and dam effects and bootstrap estimates of heritability showed that all of these traits have a genetic basis. Further, half-and full-sib family means correlations revealed genetic trade-offs between copper and cadmium content and performance traits. Preliminary indications are that selective breeding to reduce heavy metals accumulation is possible, but that genetic trade-offs between metal content and performance should be taken into account in designing any program of selective breeding in this species.

The reproductive cycle of Hyotissa hyotis at Isla La Ballena, Gulf of California, was studied from August 1995 to December 1996. The histologic analysis revealed that spawning in H. hyotis occurred as a continued phenomenon throughout virtually the whole period of study, with a steep rise in the spawning effort during the warmest season in July and August. Optimal temperature for peak spawning was between 27°C and 28.5°C; however, spawning organisms were found at a temperature as low as 20.5°C. A significant correlation between spawning and temperature was observed. The sex ratio of adult organisms did not significantly differ from 1M:1F. Gonad-Index (GI) values are indicative of gonad development, hence these may be regarded as a reliable indicator of the time of spawning. Maximum GI values coincided with the highest percentage or organisms in the maturity stage. No significant relationship was detected between GI and temperature.

The proposed introduction of the nonnative Suminoe oyster Crassostrea ariakensis to the east coast of the United States to restore the wild oyster fishery and/or for commercial aquaculture is contingent on perceived benefits outweighing costs. Trials conducted at six sites distributed across North Carolina evaluated the likely biologic success of aquaculture of C. ariakensis by assessing the oyster's growth, mortality and fouling under alternative methods and seasons of deployment. Of the six sites at which oysters were deployed, growth of C. ariakensis was greatest at the high-salinity sites, Hoop Pole Creek (29–32 ppt) and Newport River (25–30 ppt) and lowest at the low-salinity site, Nags Head (4 ppt). Across sites, growth was consistently lower (by 50%) in suspended floats than in fixed racks held 15 cm off the bottom. Only on the muddiest sediments (Newport River), where growth in tissue mass was 50% greater and growth in shell mass 20% greater on raised than bottom racks, did growth differ detectibly with rack elevation. In spite of low mortality and fouling over winter, predation in summer by blue crabs resulted in mortality approaching 50% at one of the sites (Swan Quarter) and heavy settlement by Polydora spp. produced a greater than 25% cover of mud-blisters on 84% to 97% of oysters. Consequently suitability of C. ariakensis for sale on the high-valued half-shell market may be contingent on completion of grow-out before summer Polydora spp. infestation. Results indicate that whereas at high salinity sites grow-out from a 27-mm deployment size is typically achieved within 5 mo, at medium salinity sites >7 mo is required. Failure to remove oysters at medium salinity sites from the water prior to summer may result in heavy Polydora spp. infestations that necessitate sale on the lower-valued shucked market. Irrespective of target market, it is recommended that C. ariakensis be grown in fixed racks as opposed to floating structures to maximize rates of growth without compromising survivorship.

To assess the role of live oysters in providing habitat, community metrics of resident fishes and decapod crustaceans were compared among 3 habitat treatments: live oyster clusters; cleaned, articulated shell and sand bottom. Sampling was conducted during three seasonally wet and three seasonally dry months using 1-m² lift nets deployed on an intertidal oyster reef in the Caloosahatchee estuary, Florida. Metrics used to assess relative habitat value included organism density, biomass and species richness. Species-specific comparisons were also made. Results indicate that organism density, biomass and richness were all greater for treatments with shell (live oyster clusters or cleaned, articulated shell) compared with the sand-bottom (no-shell) treatment. Two patterns emerged from species-specific comparisons: (1) species found in live and articulated shell (e.g., flatback mud crab, green porcelain crab) might require shelter; and (2) species found in association with articulated, cleaned shell (i.e., frillfin goby) might use empty oyster boxes for spawning substrate. There was little evidence to suggest that any of the decapods or fishes present were specifically selecting habitat with living oysters present.

Quahog parasite unknown (QPX) is a protistan parasite that causes significant mortalities among hard clams, Mercenaria mercenaria, in the northeastern United States and Canada. This pathogen has been successfully isolated from clams from different geographic locations, and in vitro cultures are being used in investigations of the parasite's genetic makeup, virulence and environmental tolerances. Many of these investigations require an easily reproducible, quantitative method to rapidly measure QPX cell viability and proliferation. Therefore, a fluorometric microplate technique was developed using fluorescein diacetate (FDA) as an indicator of cell viability. The developed technique provides a good estimate of the biovolume of live QPX cells. Fluorescent signals are correlated with the number and the size of individual QPX cells. Optimal experimental conditions included an FDA concentration range of 30–50 μM with an incubation period of 15–30 min in the dark. This FDA assay was used to investigate the dynamics of in vitro growth of QPX. Results showed that the growth dynamic is different among QPX isolates. For instance, exponential growth lasted for 1 week in two QPX isolates cultured from clams collected from New York and Massachusetts; whereas a third isolate (from New York) grew exponentially during 2 weeks under similar experimental conditions. While there are limitations to in vitro studies that must be recognized, research using cultured QPX cells is indispensable and will probably lead to significant progress in our knowledge of the biology and physiology of this parasite.

Young prespawning oysters, Ostrea edulis, were held over 6 mo at two different Bonamia ostreae-endemic sites in Ireland, to determine to what extent they could become infected with this protozoan parasite. Prevalence and intensity of infection were monitored, using the traditional method of ventricular heart smears and polymerase chain reaction (PCR). Results showed that 0 and 1 oysters were susceptible to infection. Infection was observed in the naïve and previously exposed oysters 2 months post relaying. Of ventricular heart smears and PCR, PCR was the more sensitive diagnostic technique in detecting B. ostreae in most of the oysters. Current methods recommended by the Office International Epizooties (OIE) and the European Union (EU), histology and screening of heart smears for B. ostreae, may be inadequate because certain low levels of infection may go undetected.

The modulation of Perkinsus marinus proliferation and subtilisin gene transcription by host (oyster) tissue was examined. Perkinsus marinus cells were cultured for 4 weeks in media supplemented with extract from either one of four different Crassostrea virginica stocks or with extract from one of two other Crassostrea species, C. ariakensis and C. gigas. After 4 weeks in culture, we determined cell counts and relative subtilisin gene transcription levels using quantitative real-time polymerase chain reaction (qRTPCR). Cell proliferation and subtilisin gene transcription were significantly lower when P. marinus cells were grown in the presence of homogenate from any of the three oyster species than in unsupplemented media. Perkinsus marinus subtilisin gene transcription was also significantly lower in cells cultured in media supplemented with homogenate from either C. ariakensis or C. gigas, than in media containing extract from the native oyster host, C. virginica. Gene transcription levels among cells grown in media supplemented with homogenate from the different stocks of C. virginica were not significantly different from one another.

Perkinsus marinus, a protozoan pathogen of the eastern oyster, Crassostrea virginica, infects oysters at high prevalences along the east coast of the United States. P. marinus was previously reported to be frequently apoptotic among the intestine epithelial cells in oysters collected from Long Island Sound. In this work, we study whether apoptotic activity of P. marinus cells is consistent with the distribution patterns of the parasite in the field in Long Island Sound and Chesapeake Bay. Prevalences and intensities of P. marinus infections were compared between Chesapeake Bay and Long Island Sound oysters during a 5-year period, from 1997 to 2001. In situ hybridization for apoptosis was performed on archived oyster histological tissues to detect differences in apoptotic indices (% of apoptotic P. marinus cells) between Chesapeake Bay and Long Island Sound oysters. Parasite apoptotic indices in Chesapeake Bay oysters were compared between different oyster habitat salinities. Two different P. marinus in vitro isolates, Chesapeake Bay isolate ATCC 50439 and Long Island Sound isolate ATCC 50508 were grown in cell cultures and exposed to different temperatures and salinities for 24 h. In situ hybridization assays for apoptosis were performed on cytospin preparations of the exposed cell cultures. During the five-year-period, the prevalences and intensities of P. marinus infections were significantly higher in Chesapeake Bay oysters. There was a significant increase in the prevalences and mean intensities of P. marinus infections in Chesapeake Bay oysters between the periods 1997–1998 and 1999–2001. This was largely because of increases in infection prevalences and mean intensities in Chesapeake Bay oysters from the low-salinity zone, where actual salinities and P. marinus associated disease in oysters were elevated by extended drought conditions during 1999–2001. Such a trend was not observed in Long Island Sound or in the higher-salinity zones of Chesapeake Bay. There was significantly more apoptosis of P. marinus in oysters from lower salinities than in those from higher salinities in Chesapeake Bay. Although temperature and salinity during a 24-h in vitro exposure affected apoptosis in both strains of P. marinus, the apoptosis dynamics significantly differed between the two P. marinus isolates with changes in salinity (11.6‰ to 37.8‰), but not temperatures (4°C to 35°C). The Chesapeake Bay isolate had an immediate decline in apoptosis at salinities above 11.6‰, and its apoptotic indices were low throughout the tested salinity range. The Long Island Sound isolate had high apoptosis at all salinities except 28‰, which is the approximate salinity where the Long Island Sound oysters are grown. We conclude that parasite apoptosis is an important factor regulating the distribution of P. marinus infections in the field. Our results suggest that Chesapeake Bay and Long Island Sound P. marinus strains may have evolved distinct genetic or phenotypic traits. The Long Island Sound strain reflects its adaptation to high-salinity oyster hosts, whereas the Chesapeake Bay strain possibly reflects adaptation to oyster hosts from low and variable estuarine salinities.

The Town of Islip, NY has collected a long-term data set (1977–2004) on northern quahog (hard clam), Mercenaria mercenaria, abundance. The data comprise approximately 350 duplicate 1 m² samples each year taken with a clam shell bucket. All samples were sieved through a 6.4 mm sieve and the hard clams enumerated by size. In addition, clam landings data for the town waters are available for the same time period. Clam populations have declined from their peaks in the 1970s to very low levels in the 1990s and 00's. These dramatic shifts in population abundance have made the exploration of spawner/recruit relationships possible. A number of alternate models were attempted, but based on knowledge of the biology of the species and other factors, all but two did not appear to be plausible. The two models (2nd order polynomial and Log) yielded high r² values and intercepted the 0 axis between 0.5 and 0.75 adult clams m⁻² indicating a density dependent effect on recruitment. The polynomial model also suggested a carrying capacity level of about 5 adult clams m⁻² and a density dependent upper level of density. This is the first time a spawner recruit relationship has become apparent for hard clams.

Mactra veneriformis, Ruditapes philippinarum, and Meretrix lusoria are dominant clams in Japanese tidal flats. Juveniles and adults of these species were reared in the laboratory and the effects of salinity on their sand burrowing activity and growth- and clearance-rates were examined. Juveniles of each species (shell length 10–16 mm) filtered water actively in the salinity range of 11.8–34.6 psu, with clearance rates not affected by salinity. The clams showed positive growth in the above salinity range, but growth rates were retarded at 11.8 psu, probably because of increased respiration at low salinity levels. In 6.1-psu seawater, adult Ma. veneriformis dug into the sand after a few days acclimation, Me. lusoria did not and R. philippinarum died. At 10.8 psu, adult Ma. veneriformis filtered water actively, Me. lusoria dug into the sand but did not filter water, and R. philippinarum neither dug into sand nor filtered water. These results indicate that the clam species examined are euryhaline but that the response to low-salinity water (≤11 psu) by adult clams (shell length 31–37 mm) differed among species: Ma. veneriformis is the most adaptable to low-salinity water, followed (in order) by Me. lusoria and R. philippinarum. These differences, however, are not consistent with the distribution patterns of these clam species in the Shirakawa tidal flat (Japan), where salinity varies spatially and temporally.

Replacement of live microalgal diets is a significant challenge in developing cost-effective and reliable production methods for bivalves. In this study, the results of growth experiments are reported with juvenile Manila clams, Tapes philippinarum, fed on a heterotrophically grown, spray-dried, Schizochytrium-based product (SZ; Docosa Gold, Sanders Brine Shrimp) or a spray-dried, Haematococcus pluvialis-based product (H; Sanders Brine Shrimp) either alone or as supplements for rations of living algae. The effects of additions of bentonite, a naturally occurring silt, in combination with SZ and H on the growth of Manila clams were also investigated. Results showed that SZ and H supported clam growth when added as supplements to rations of a mixed diet of the live algae Isochrysis galbana and Chaetoceros calcitrans. Increases in clam wet weight with a 1/4 ration of live algae and a supplement of a full ration (equivalent to the dry weight of the full algal ration) of SZ or H were similar to those of clams fed on a full live algal ration alone. The results indicated that up to 75% substitution of live algae is possible using heterotrophically grown, spray-dried SZ or H without significantly reducing the live (wet) growth of the clams. No significant differences in clam growth rate (% wet and organic weight increase) were found when bentonite was added to diets containing different concentrations of H.

By frequent sampling from May 2001 to October 2002, we examined spatio-temporal variations in densities of different life stages (planktonic larvae, new settlers and small, large and commercial individuals) of Corbicula japonica in the Kiso estuaries (the Ibi-Nagara Estuary and the Kiso Estuary). Planktonic larvae were found for a much longer period (mainly in June to December 2001 and in April to October 2002) than reported in previous studies. Densities of planktonic larvae were significantly higher in the Kiso Estuary than in the Ibi-Nagara Estuary, whereas the reverse was true for new settlers and commercial individuals, indicating that larval settlement processes may be critical in establishing significant differences in the density of benthic stages between these estuaries. Ontogenetic habitat shift of the clam was detected in the Ibi-Nagara Estuary but not in the Kiso Estuary: the main habitats for new settlers and small individuals were located in the upper parts of the Ibi-Nagara Estuary and large and commercial individuals were located in the middle part. On the other hand, in the Kiso Estuary, all life stages from new settlers to commercial individuals were found mainly in the upper part. The above distribution patterns of C. japonica were much different from those of 3 other bivalves (Ruditapes philippinarum, Musculista senhousia and Mactra veneriformis) that are also common and abundant in these estuaries: high densities of these 3 bivalves were always found around the river mouths throughout their ontogeny.

We developed a polyclonal antibody from egg proteins of the butter clam, Saxidomus purpuratus, to quantify eggs using an enzyme-linked immunosorbent assay (ELISA). SDS-PAGE showed that the egg protein was composed of several peptides with molecular weights of 247, 200, 99, 91, 54 and 47 kDa. An immunoblotting assay indicated that the egg-specific antibodies were developed from the 200 and 99 kDa peptides. The rabbit anticlam egg IgG was able to detect as little as 0.078 μg/mL of S. purpuratus egg protein by ELISA. A weight-normalized gonadosomatic index (GSI, mg dry egg/mg dry tissue) was determined to follow the monthly changes in egg production of the clams. Clam-egg protein could be detected by ELISA during the entire sampling period (December to July), and GSI ranged from 0.035 (December) to 0.156 (February). The fecundity of the clams was measured from two spawning peaks in February and May and was estimated to be 22.6 million eggs (GSI of 0.16) in February and 16 million eggs in May (GSI of 0.15). The indirect ELISA used in this study was rapid, affordable and sensitive enough to assess minute amounts of egg protein, which is difficult to measure using traditional methods such as induced spawning or histology.

Histologic examination of the nonnative green mussel, Perna viridis, and the native scorched mussel, Brachidontes exustus, at three locations in Tampa Bay, Florida, indicated that cycles of gametogenesis and spawning were similar between species. Major spawning periods occurred in the spring (April) in conjunction with increasing water temperature and the fall (September to November) as the water temperature was declining. Over the summer, both species appeared to undergo varying levels of redevelopment, partial spawning and resorption of oocytes. Gametogenesis was limited over the winter. Differences between populations in levels of gametogenic activity and the timing of the fall spawn were most likely related to differences in salinity and available food at the three sites. A higher fecundity (caused by the faster growth rate and greater maximum size of P. viridis) may result in displacement of native bivalves in Tampa Bay, including B. exustus.

Infection of Gymnophallus sp. in the bearded horse mussel (Modiolus barbatus) was studied in samples collected during 1 year in the Mali Ston Bay (eastern Adriatic Sea). Mean prevalence of sporocyst was low (3.5%), which peaked in February (7.1%), whereas the mean metacercariae prevalence was 8.1%, peaking in September (16.7%). Histologically the Gymnophallus sp. sporocyst infection in bearded horse mussel resulted in clear reaction of bivalve tissue, where the induced changes depend strongly on the site of trematode infection. Retardation of gametogenesis, necrosis of connective tissue and hemocytic infiltration are the main histological features of infection in this new host.

The taxonomic identity of mussels in the southern hemisphere is still unclear, and the Mytilus that inhabit on the Pacific coast of South America has been considered by different authors as M. chilensis, M. edulis, M. edulis chilensis and M. galloprovincialis. To clarify the taxonomic identity of these mussels four samples from the northern limit of the distribution of Mytilus were taken as well as European control samples of M. edulis and M. galloprovincialis for comparison. Thirty allozyme loci were studied and 9 loci (Aco-1, Ap-1, Est-D, Gpi, Idh-1, Lap-1, Mpi, Me-2 and Odh) were partially diagnostic between the European M. edulis and M. galloprovincialis control samples, as previously reported. Chilean samples showed for four of the above partially diagnostic loci intermediate frequencies for typical alleles of M. edulis and M. galloprovincialis between those of the control samples, but they were closer to those of M. edulis for Ap-1 and Mpi and to those of M. galloprovincialis for Aco-1 and Est-D. The locus Lap-1 showed allele frequencies similar to those of M. edulis, whereas the most frequent allele of the loci Gpi, Idh-1 and Odh was that typical of M. galloprovincialis but at a higher frequency. Moreover, the partially diagnostic loci Me-2 and Lap-2, Pgm-2 and Pp showed important differences with regard to the control populations. Genetic distances, dendrograms and multidimentional scaling as well as principal component analysis on allele frequencies and factorial correspondence analysis on individual genotypes showed that South American samples were genetically closer to European M. galloprovincialis than to M. edulis but having particular and characteristic allele frequencies.

The Chilean blue mussel formerly Mytilus chilensis Hupe 1854, have been recently subject to a taxonomic revision using electrophoretically generated genetic data concluding that mussels from South America should be included tentatively in Mytilus edulis. The molecular genetic characterization (restriction fragment length polymorphism) of samples from 8 natural populations along the whole natural distribution of the Chilean blue mussel using 3 PCR-based nuclear DNA markers (ITS, Glu-5 and Me) was carried out. One of the markers (ITS) showed a similar banding pattern than M. edulis and M. galloprovincialis, whereas the other markers (Glu-5 and Me) showed a specific banding pattern found only in M. galloprovincialis. Also, a very low number (3.9%) of mussel hybrids (M. edulis–M. galloprovincialis) using two codominant markers was detected in the present study. The molecular evidence suggests that M. galloprovincialis is present in the southern coast of Chile, whereas no evidence for the occurrence of Mytilus trossulus was found.

Recent research indicates that abiotic environmental factors, including temperature, may be as important as chemical cues in controlling the induction of metamorphosis of marine invertebrate larvae. In this study, the effects of elevated temperature or heat shock on the induction of metamorphosis in the tropical marine gastropod, Strombus gigas, are examined. Elevations in temperature above culture temperatures (28°C to 29°C) to 37°C to 38°C induced high levels of metamorphosis (77% to 100%), equivalent to those induced by a known algal associated inducer, an extract of Laurencia poitei. The age for competency to metamorphosis and the exposure time needed to induce this process were similar for heat shock and for the algal-associated cue. Understanding the interaction between abiotic and biotic factors during metamorphosis may help to better predict recruitment patterns for this commercially important species.

The processes of gonad development through a year are analyzed for Strombus pugilis from Seybaplaya, Campeche. During gametogenesis second order oocytes appear close to the wall of the follicles, with a diameter 90–250 μm. The cytoplasm is granular, the nucleus is located on the periphery, with a diameter of 15–35 μm, a nucleolus 7–8 μm. Spermatozoids have an acrosome of 5–7 μm, shaped like a coma. In females gametogenesis was registered in two pulses, with 2 peaks of 60%, February to June and September to October. Mature females were found during the 8 months of sampling with peaks during May and August (80%). Spawning was discontinuous, suggesting storage of mature gametes for the right time to spawn. In males gametogenesis was present in a low percentage from March to October, with a maximum of 20%. Maturity was present on just a 10% during July, with constant spawn through the year. Copula has been observed only during egg laying seasons; males seem to keep mature sperms in the prostate gland. Strombus pugilis from the coasts of Campeche presented a fast gonad recovery for males, requiring longer for females. Having missed most of the autumn and early winter months leaves a big gap on the processes of gonad recovery and early gametogenesis. Apparently there is no correlation between salinity, temperature and the reproductive cycle, but this population has the potential for reproducing through the year.

Zidona dufresnei (fine snail) is a common gastropod species in the Southwestern Atlantic Ocean, which has been exported to Asian countries for human consumption since 1988. Landings of Z. dufresnei increased from 1974 to a maximum record of 1,300 mt (whole shelled animal) in 1997, followed by a steady decline through 2002. No resource management effort have been applied to this species since the beginning of its catch history, about 30 y ago. Information provided in this work, together with previous studies on the reproductive biology and population dynamics of Z. dufresnei, will contribute to establish effective precautionary polices to manage this resource. We suggest that Z. dufresnei is in a phase of over-exploitation since 1988 until present, we propose a rational management as size selectivity, with a minimum capture size of 16 cm, closure of the fishery during the reproductive season, from September to December and to rotate the fishing areas. This study provides historical and updated information as an attempt to implement corrective measures towards a better management of the fishery on the Argentine Continental Shelf.

The effect of egg quality on larval period and postlarval survival was investigated for the abalone Haliotis discus hannai. Broodstock were conditioned for spawning at different effective accumulative temperatures (EAT) and the subsequent larvae were used in experiments. Larval period until spontaneous metamorphosis or death and postlarval survival without food were investigated. Larval period and postlarval survival of offspring from broodstock conditioned at 1,650 and 2,350°C·days EAT were greater than those of larvae from 1050 and 1150°C·days EAT conditioned broodstock. Biochemical composition and egg cytoplasm diameter were measured as egg quality from broodstock conditioned under different EAT treatments. There was a positive correlation between lipid and protein content in eggs. Protein and lipid content showed positive correlations with larval period and postlarval survival without food. The eggs from higher EAT tended to contain higher protein and lipid contents, but there was no significant difference in protein levels among broodstock conditioned at different EAT. No relationship was found between egg cytoplasm volume, which calculated using egg cytoplasm diameter and larval period or postlarval survival. These results suggest that the quality of eggs became higher as EAT increased, and that protein and/or lipid were important for larval and postlarval survivorship. For H. discus hannai, the biochemical composition of eggs may be more important than yolk volume for early development and survival of larvae and postlarvae.

A fluorescence in situ hybridization (FISH) technique was used for elucidating the telomeric sequence and its chromosomal location in the Pacific abalone Haliotis discus hannai. The vertebrate telomere PNA (peptide nucleic acid) probe, the oligonucleotide (TTAGGG)₇ and (TTAGG)₇ probes were used for the analysis. FISH with the PNA and (TTAGGG)₇ oligonucleotide probes displayed clearly defined signals on the telomeric regions of all metaphase chromosomes and interphase nuclei. On the other hand, the (TTAGG)₇ probe, which has one base less than probe (TTAGGG)₇, did not display clearly defined signals. These results suggest that the telomere of H. d. hannai is composed of a (TTAGGG)_n sequence, which is typically found in vertebrates and other molluscs. FISH-derived signals were not observed at interstitial sites of H. d. hannai chromosomes. Hence, this species is unlikely to possess any nontelomeric sites of the telomeric sequence. The successful use of FISH in this study suggests that the FISH technique may also be extended for other analytical purposes pertaining to this and other abalone species.

The chromosomes of the blue abalone Haliotis fulgens and the yellow abalone Haliotis corrugata were analyzed by means of DAPI staining, and fluorescence in situ hybridization with 18S-5.8S-28S rDNA, telomeric (TTAGGG)_n and (GATA)_n repeats DNA probes. The diploid chromosome number found was 36 for both California abalone species. However, the karyologic comparison between H. fulgens and H. corrugata indicated that the blue abalone has 8M 8SM 2ST, whereas the yellow abalone has 10M 7SM 1ST. The physical location of 18S-5.8S-28S rDNA clusters was found in the terminal region of the long arms of two pairs of submetacentric chromosomes (4, 11 and 2, 4 respectively). Localization of heteromorphisms of FISH-rDNA between homologue chromosomes and between sister chromatids, and the presence of interstitial hybridization signals was found in metacentric and onto submetacentric chromosomes. The presence of microsatellites (TTAGGG)_n and (GATA)_n was evidenced after FISH treatment by DNA probes. The telomeric sequence occurred at the ends of all mitotic chromosomes in both abalone species, whereas the (GATA)_n repetitive sequence was found on chromosomal interstitials zones and at the ends of some chromosomes, this was manifested after FISH on interphase nucleus. In addition, this study contributes with new karyologic information of haliotids from California and gives support to the Tethys model about biogeographical origin, from the Mediterranean Sea to the East Pacific Ocean.

The fluorescence fading and chromosome imaging method were used together to analyze chromosomal DNA contents (haploid set) in Pacific red abalone Haliotis rufescens (Archaeogastropoda: Haliotidae). The fluorescence intensity was measured each 1.6 sec in H. rufescens chromosomes (2 n = 36) stained with DAPI. The fluorescence of each chromosomal type was recorded using color digital images of 24 bits. These kind of images allowed converting the RGB (true color) images to pseudocolor images to quantify the fluorescence intensity by means of 256 levels of brightness. Algorithms built with MATLAB software were used to determine the area under the curve (fading function). Therefore, estimates of DNA contents in individual chromosome types were obtained. Their DNA contents were related with chromosomal sizes (P < 0.001). The DNA values found showed a range from 0.1106 ± 0.0045 pg (chromosome # 1) to 0.0890 ± 0.0060 pg (chromosome # 18). The genome size calculated for H. rufescens by sum of all chromosomal DNA contents was 1.77 ± 0.005 pg. This study describes an alternative imaging method to analyze the chromosome morphology and chromosomal DNA contents in molluscs, and represents an alternative approach to the lack of cell lines required in flow cytogenetics.

The Japanese abalone “tokobushi” (Haliotis diversicolor Reeve) supports a valuable fishery off Tanegashima Island, southern Japan. However, catches have been declining, probably caused by over harvesting and other factors. Understanding the effects of macroalgal type and water temperature on the consumption rates of tokobushi has applications for the management of its population such as to identify sites with appropriate quality and quantity of macroalgae and the favorable water temperature during stock enhancement. Under controlled conditions, the effects of macroalgal type and water temperature on the macroalgal consumption rates of tokobushi were evaluated. On a short-term basis (24-h feeding), consumption rates were higher on leathery brown algae (Sargassum fusiforme, Sargassum patens, Sargassum duplicatum, Sargassum alternato-pinnatum, Undaria pinnatifida and Laminaria japonica), corticated red algae (Acanthophora spicifera, Gracilaria gigas, Carpopeltis affinis and Ceramium sp.) and foliose green algae (Ulva pertusa and Enteromorpha intestinales) than on siphonous green algae (Codium spp.) and filamentous green algae (Chaetomorpha crassa and Cladophoropsis zollingeri). Averaged across 20 species of macroalgae, the mean consumption rate was 4.96 ± 0.27%wet-TW.d⁻¹ (wet alga and wet abalone; TW = total weight) or 1.37 ± 0.19%dryTW.d⁻¹ (dry alga and dry abalone). On a long-term basis (20 days feeding), tokobushi had higher consumption rates on the green alga Ulva pertusa and the brown alga Sargassum fusiforme than on the red alga Meristotheca papulosa. When presented with a choice of species (3 days feeding), tokobushi ate more of the brown alga Sargassum fusiforme and the red alga Gracilaria gigas than the green alga Codium cylindricum. Consumption rates generally increased with temperature. Generally, tokobushi prefer macroalgae with high percent dry weight composition, most of which are brown and red algae, and eat more at water temperatures around spring/fall (17°C, 21°C) and summer (27°C) in Kagoshima, Japan.

Juvenile pink abalone Haliotis corrugata (initial mean length = 10.7 ± 0.3 mm; initial mean weight = 0.15 g) were grown under laboratory conditions in an aerated flow-through seawater system at 21 ± 1°C. For 131 days, abalone were fed diets containing three different levels of protein (42%, 36% and 32%), each level containing two ranges of starch:lipid ratios (1.5–1.8 or 3.2–3.6). The gross energy content of the diets ranged from 4.26–3.68 kcal/g. Within a particular protein level, growth did not differ significantly. When dietary protein levels exceeded 32%, a trend of higher growth of abalone was observed for dietary treatments that contained lower levels of lipid (higher starch to lipid ratios). The amount of protein consumed daily for the 32% dietary protein is apparently insufficient to meet requirements for energy and maximum growth. No notable diet-dependent differences in the proportional composition (dry weight) of the shell and the soft tissue, and the energy content of the soft tissue were observed. Daily food intake and consumed energy were significantly different among treatments, being inversely related to the calculated P:E ratios. The increased consumption may have been somewhat overestimated because of loss arising from lower water stability of the diets. Ammonia excretion ranged from 7.9–4.8 μg NH₄ /h /g abalone but was not significantly different among treatments except for the treatment containing 32% crude protein and a low carbohydrate:lipid ratio. Specific Dynamic Action (SDA) comprised nearly 50% of measured oxygen consumption and did not significantly differ among treatments. Respiration increased during the night showing a typical circadian pattern reported in Haliotis genera. Measured mucus production did not vary among treatments. Carbohydrate preferentially serves as the principal energy source and a consistent amount of dietary protein is also used as an energy source, regardless of dietary protein content. Within a developed energy budget, approximately 70% of the ingested energy was lost through feces, and approximately 25% of the ingested energy was metabolized, with 7% to 10% channeled to growth. A direct determination of available digestible energy was not possible because of the inability to collect sufficient feces to estimate fecal energy. The results suggest that practical diets should include levels of dietary protein that are approximately 35% protein to meet requirements for energy and maximum growth. In addition, carbohydrates seem to be the preferred energy source and lipid levels should be minimized to the extent that essential fatty acids requirements are met.

Cryopreservation of sperm is seen as an important step in developing effective hatchery culture techniques for the black-lip pearl oyster, Pinctada margaritifera. As a preliminary investigation into cryopreservation of the gametes of this species we tested 5 cryoprotectant agent combinations for their ability to retain sperm motility: (1) 1 M trehalose and 5, 10 and 15% dimethyl sulphoxide (DMSO); (2) Hanks calcium-free balanced salt solution (C-F HBSS) and 5%, 10% and 15% DMSO; (3) C-F HBSS and 5, 10 and 15% propylene glycol (PG); (4) 1 M trehalose and an equal combination of DMSO and PG making up 5, 10, 15% total volume; and (5) C-F HBSS and an equal combination of DMSO and PG making up 5%, 10% and 15% total volume. Total, rapid and progressive sperm motilities were estimated through computer assisted sperm analysis (CASA). Sperm cryopreserved in 1 M trehalose and 5% DMSO retained the highest total (86.0 ± 1.2% SE), progressive (46.0 ± 1.2% SE) and rapid (25.1 ± 0.6% SE) motilities of all cryoprotectant solutions, whereas those cryopreserved with PG generally retained poor motility. Although the 1 M trehalose and 5% DMSO treatment compared favorably with that of fresh sperm for total motility (P < 0.01), all cryoprotectant treatments were poor at retaining the proportion of original rapid and progressively moving sperm. This study highlights the potential for cryopreservation of gametes from P. margaritifera, which will benefit selective breeding and conservation programs with this important commercial species.

Spat of blacklip pearl oyster, Pinctada margaritifera (L.), recently have been found to suffer mass mortalities every autumn in farms in subtropical Japan. We investigated what rearing conditions improve growth and survival of the spat in one of the farms. From September 2002, spat with mean ±SD dorsoventral measurement 14.5 ± 2.4 mm were reared in trays (33 cm × 21 cm × 8 cm) with combinations of different spat densities (12, 24, 36, 72 or 144 spat tray⁻¹), tray partitioning (trays with or without partitions) and suspension depths (2 or 6 m). Three months later, spat densities and tray partitioning significantly affected the growth: greater for 12–36 spat tray⁻¹ (mean ± SD: 12.2 ± 3.5 mm) than for 72–144 spat tray⁻¹ (7.7 ± 4.3 mm) and for partitioned trays (12.2 ± 4.1 mm) than for nonpartitioned trays (8.5 ± 4.0 mm). Yet, no set of rearing conditions significantly explained the great variation in the survival rate (mean: 51.4%, range: 0.0% to 100.0%). When two groups of spat reared separately in the farm and laboratory were transferred to the same aquarium, cross infection occurred. It is possible that spat-density and tray-partitioning dependent factors (e.g., food abundance and space per spat) affected mainly the growth, whereas other factors including a putative infectious agent affected mainly the survival rate.

We applied quantitative histochemical techniques and digital image analysis to study seasonal cycles of use of lipid and protein reserves during vitellogenesis in the pearl oyster Pinctada mazatlanica. Female gonad samples were collected seasonally during an annual cycle and processed histologically to characterize the gametogenic cycle, analyze variations in the frequency and size of vitellogenic and postvitellogenic oocytes and calculate the ooplasm:nucleoplasm ratio for both types of oocytes. Lipid and protein inclusions in each type of oocyte were identified using Sudan Black B and Schiff's ninhydrin stains. In both cases, quantification of lipid and protein components was performed through measuring variations in the color coverage area of the oocyte with a digital image analysis system. With this procedure, we calculated a lipid index and a protein index to refer oocyte quality. The lipid index was higher in winter, suggesting a strategy towards storage in the gonad. The protein index was highest during spring in vitellogenic oocytes and during winter in postvitellogenic oocytes, indicating that proteins are actively used during oocyte growth. These results, together with data of the ooplasm:nucleoplasm ratio, suggest differential accumulation of lipid and protein components within the ooplasm during oocyte development. Quantitative histochemistry and digital image analysis represent a combination of reliable techniques for evaluating reproductive processes and oocyte growth and quality.

Octopus tankahkeei is a new species of cephalopod found recently in the Southern China Sea. It belongs to the class Cephalopoda, Octopoda, Octopodidae and Genus Octopus. Its discovery has attracted much attention from the fisheries industry because it has quickly become a gastronomic favorite of consumers. Because of its popularity, the aquaculture of this species would be of great economical value. The description of the sperm ultrastructure will provide information regarding the fertilization mechanism of this organism and yield an understanding of the optimal method to culture this species. In this report, the ultrastructure of the spermatozoon of Octopus tankahkeei was investigated using electron microscopy. The mature spermatozoon consists of three parts: head, neck and tail. The head contains an acrosome and the nucleus. The spiral and cone-shaped acrosome has many equidistant striations on its surface. The thin cylinder-shaped nucleus has a deep concavity at the post fossa. The neck contains mainly the basal body. The basal body, which is located in the post fossa demonstrates a typical 9 2 arrangement of the axoneme. The axoneme is surrounded by 9 bundles of peri-condensed fiber that parallel the axoneme, forming the “9 9 2” arrangement. The tail is composed of middle piece, principal piece and end piece. The “9 9 2” arrangement of the middle piece is enwrapped with a mitochondrial mantle and a fibrous sheath outside. The principal piece begins at the site where the mitochondrial mantle disappears, but is still enwrapped with a fibrous sheath outside. The end piece begins at the site where the fibrous sheath disappears, but contains 9 bundles of peri-condensed fibers that taper backward. Granular material appears on the exterior of every peri-condensed fiber and diminishes gradually until it completely disappears along with the peri-condensed fiber. The end piece terminates with typical 9 2 arrangement.

The fatty acid composition of whole egg masses was investigated in 4 marine nudibranchs collected from the southwest of Spain: Polycera aurantiomarginata, Polycera quadrilineata, Berghia columbina and Berghia verrucicornis. The four species are carnivorous. All nudibranchs were characterized by high levels of n-3 polyunsaturated fatty acids (n-3 PUFA), mainly eicosapentaenoic acid (20:5n-3), docosapentaenoic acid (22:5n-3) and docosahexaenoic acid (22:6n-3). Other major fatty acids were the saturated palmitic (16:0) and stearic (18:0) acids, the monounsaturated oleic acid (18:1n-9) and the n-6 PUFA arachidonic (20:4n-6) and docosatetraenoic (22:4n-6) acids. Relative high percentages of the plasmalogen derivatives 16:0DMA and 18:0DMA were also detected. Univariate analysis showed that egg fatty acids from P. aurantiomarginata and P. quadrilineata significantly differed from those of B. columbina and B. verrucicornis. Higher levels of saturated fatty acids and 22:6n-3 and lower percentages of 18:0DMA, 22:4n-6 and 22:5n-3 were found in the spawns of both species of Polycera as compared with both of Berghia. Analysis of the bryozoon Bugula neritina and the sea anemone Sagartia troglodites, main preys of Polycera and Berghia respectively, showed that the differences observed in egg fatty acid composition were likely related to diet. Fatty acids of the fully developed embryos from P. aurantiomarginata and B. columbina, sampled immediately prior to hatching, were analyzed to investigate the dynamics of fatty acids during embryogenesis. The long chain PUFA 20:4n-6, 22:4n-6, 20:5n-3 and 22:5n-3 increased or remained stable during embryogenesis in both species whereas palmitoleic acid (16:1n-7) in B. columbina and 16:0, 17:0, 18:0 and 18:1n-9 in P. aurantiomarginata decreased. The major n-3 PUFA, 22:6n-3, marked decreased in B. columbina but remained unchanged in P. aurantiomarginata. These data indicate that fatty acids play different roles during embryogenesis and that in both nudibranchs the embryo requirements are not the same.

Experiments were conducted to examine the effects of salinity fluctuation pattern on the intermolt period and growth of Fenneropenaeus chinensis with initial body weight of 1.4510 ± 0.0040 g. The salinity of the control treatment (S0) was 30 ppt throughout the experiment, whereas Treatments S2, S4, S7 and S10 were subjected to different salinity fluctuation pattern with the ranges of ±2, ±4, ±7 and ±10 (ppt), respectively. After the 32-day feeding trial, there were no significant differences in the intermolt periods (P > 0.05); the special growth rates (SGR) under 5 treatments were ranked as S4 > S7 > S2 > S10 > S0, and SGR under treatment S4 was significantly higher than those under treatments S0 and S10 by 58.94% and 37.52%, respectively (P < 0.05). There were no significant differences in feed intake (FI) among all the treatments (P > 0.05). The maximal food conversion efficiency (FCE) occurred in treatment S4, which was significantly higher than those under treatments S0 and S10 by 46.07% and 34.24%, respectively (P < 0.05). Energy budget is also discussed in this article.

The effect of salinity and pH on the immune response of the white shrimp Litopenaeus vannamei was studied over a period of 12–15 days. The results indicate that salinities between 5‰ to 30‰ and pH of approximately 7.0–9.5 affect hemocyte count, phenoloxidase activity, bacteriolytic activity and antibacterial activity. Phenoloxidase activity peaked at the 12th hour, whereas bacteriolytic activity and antibacterial activity were lowest. By the 6th day of exposure, every parameter returned to the values observed in controls except hemocyte count, which remained low with a decrease in salinity. From the 6th to the 15th day of the salinity test, the hemocyte count at every salinity were constant but significantly lower than control; significant changes in phenoloxidase activity, bacteriolytic activity and antibacterial activity were observed over the same period. During the first 3 days exposure to variable pH, hemocyte count and antibacterial activity decreased gradually as time elapsed at pH 7.0, 7.5, 9.0 and 9.5. Phenoloxidase activity peaked at the 12th hour, but the bacteriolytic activity fell. During the third to the 12^th day of the pH test, every immune parameter was stable. The hemocyte count, bacteriolytic activity and antibacterial activity decreased, whereas the phenoloxidase activity increased in response to a change in pH.

Penaeid shrimp are important resources for worldwide fisheries and aquaculture. In Brazil, Farfantepenaeus brasiliensis, is an important commercially exploited species and an ideal animal for studying the impairment caused by the effects of heavy metals that are often detected in coastal areas. The main purpose of this study is to detect the acute toxicity of mercury to F. brasiliensis larvae, and to investigate its effects on oxygen consumption and ammonium excretion, which have not been carried out in this species before. We examined the acute toxicity Hg to F. brasiliensis larvae revealed at 24, 48, 72 and 96-h of exposure and the medium lethal concentration (LC₅₀) values obtained were of 0.13 mg L⁻¹; 0.054 mg L⁻¹; 0.047 mg L⁻¹ and 0.045 mg L⁻¹, respectively. Furthermore, we also found that exposure of shrimp to Hg caused an inhibition in oxygen consumption of 53.42% lower than that of the control. However, after separate exposure to Hg, elevations in ammonium excretion were obtained, which were 217.64%, higher than the control.

This study addresses effects of handling and air exposure during harvest and transport on mortality and gonad growth of Strongylocentrotus droebachiensis in a proceeding roe enhancement trial. Two experimental factors: (1) handling (gentle and rough) and (2) degree of air exposure (wet and dry) were combined to form 4 different treatments; gentle/dry (GD), rough/dry (RD), gentle/wet (GW) and rough/wet (RW). In the proceeding roe enhancement trial, the highest mortality, exceeding 25%, was observed in the GD treatment. Mortality was 1.5% in RW and RD treatments, whereas no mortality was observed in the GW treatment. Mortality only occurred during the first 4 weeks after harvest. Desiccation appears to be the main cause of mortality. There was a significant increase in gonad index for all treatments during the roe enhancement trial; from 7.6% (median) at the beginning of the trial to 15.7, 14.5, 13.5 and 11.2% (median) at the end for GW, RW, GD and RD respectively. However, the increase in gonad index was significantly lower in the RD compared with the others. The lower gonad growth in RD was probably caused by the high frequency of individuals with visual injuries, a frequency that was an order of magnitude higher than in the other treatments. Overall, there was a clear relationship between visual injuries and gonad index, where individuals with injuries had a significantly lower gonad index at the end of the experiment (median; 10.4%) compared individuals without visual injuries (median; 14.5%). The lower feed consumption and higher feed conversion factor observed in RD indicate that individuals with injuries have a reduced gonad growth caused by a combination of reduced appetite and lower feed conversion efficiency. Regeneration of spines and lesions may have resulted in less resources allocated to gonad growth.

Urbanization poses a particular threat to the coastal areas of the southeastern United States where uplands surrounding wetlands are still relatively undeveloped compared with other regions. Predictive models, which would correlate information on land use change and development, would be useful so that downgrades in water quality can be predicted before they occur to allow effective land management decisions to be made. The approach used for this study involved a historical comparison of land use change and fecal coliform bacterial densities on Murrells Inlet (MI) (urbanized site) (n = 2026 samples) and North Inlet (NI) (pristine site) (n =1656 samples), both bar-built estuaries located on the northern coast of South Carolina south of Myrtle Beach. The microbiological and water quality data used in this research covered the period of 1967–1995 and the following parameters were used: date of sampling, most probable number (MPN) of fecal coliform bacteria, salinity, rainfall and water temperature. The regression models used the above parameters and a change in trend term that accounted for both instantaneous and gradual changes in water quality that may arise from a particular environmental intervention. For MI, the 1980 environmental intervention consisted of the construction of a jetty and the conversion from septic tanks to a main sewer line of approximately 92% of all residences. For NI, the 1973 and 1977 interventions were the construction of Baruch Laboratory and urban development of Debidue Island, respectively. For MI, the intervention, controlling for other environmental parameters, was found to be significant at the alpha = 0.05 level. There was a significant decrease in the increasing trend of fecal coliform bacteria for MI and the conversion to the sewage collection system had a beneficial effect on water quality and probably dominated the jetty effect. For NI, the laboratory construction had no overall impact on water quality so background natural sources of bacteria probably masked any small increases from human sources.

We published an article (Elston et al. 2005) in Volume 24 of the Journal of Shellfish Research demonstrating substantial contamination of St. Louis Bay, Mississippi with dioxins and heavy metals, including chromium, nickel and arsenic that occurred in close proximity to a large titanium dioxide plant that has operated near the Bay since the early 1980s. We conducted an exhaustive evaluation of potential sources of contamination and concluded that the plant was the most likely source of contaminants. We were aided in this analysis by a variety of data including a preplant baseline study (Lytle & Lytle 1982) and a study of dioxin contamination in oysters harvested from Southern Mississippi conducted in 1997 (Fiedler et al. 1997). In this addendum we publish new information that further implicates the plant as the source of dioxin contamination, corrects minor underestimates from our original report in some of the WHO-TEQ (World Health Organization Toxic Equivalencies) for dioxins in St. Louis Bay and Mississippi Sound shellfish and also corrects the estimated magnitude of increase of dioxins in Southern Mississippi since 1997. These corrections do not change the conclusions of our original study. In fact, the increases in WHO-TEQs for shellfish and the new data obtained since publication of that article provide additional and substantial support for our conclusion that the plant is the primary source of dioxin contamination. In addition, these new data call into question the reliability and utility of data reported by the plant to the United States Environmental Protection Agency Toxic Release Inventory for use in assessing the public health risk of releases from the plant. This new information demonstrates 2,3,7,8 TCDD, the most toxic dioxin congener and one recognized as a carcinogen by the International Agency for Research on Cancer, is in fact present on the plant site, a fact previously unknown and unreported, although we reported this congener in the two sediment samples adjacent to the plant outfall in our original report.

No Abstract available.