The reproductive cycle, sex distribution, and gonadal characteristics of the flame scallop, Ctenoides scaber, formerly Lima scabra scabra (Born 1778), collected from Boca Chica Key, FL, were investigated over the 21-mo period from January 1998 through September 1999. Gametogenic cycles were examined using qualitative and quantitative methods, and the relationships between those observations and environmental conditions (e.g., water temperature, salinity and phytoplankton concentrations) were analyzed. The relationships between sex, gonad color and shell height were also examined. Gamete development in both sexes was initiated in winter and was associated with small oocytes and follicles, cool water temperatures and moderate concentrations of food. Growth of gametes occurred throughout spring, as temperature and chlorophyll-a concentrations increased. A partial synchronous spawn occurred in early summer but did not seem to be related to environmental conditions. Maximum gamete ripeness and size occurred in late summer, when water temperatures were at maximum values and food densities were increasing. Decreases in female gamete and follicle sizes and increases in occurrence of partially spawned, spent and early growth gonads in autumn were suggestive of synchronous spawning, which coincided with a rapid decrease in water temperature and maximum measured chlorophyll-a concentrations. Decreases in oocyte size in February coincided with annual water temperature minimums and may represent the conversion of energy from reproduction to survival, and not spawning. The presence throughout the year of juveniles, ripe and partially spawned flame scallops and chlorophyll-a concentrations sufficient to support gamete development suggest a reproductive strategy of continuous spawning, common in tropical marine invertebrates. No relationship was detected between salinity and gonad condition. Flame scallops collected for this study ranged in size from 21–68 mm shell height (SH) and those >25 mm SH had gamete development. The smallest animals were found principally in summer, which suggests a massive synchronous spawning event. Analyzing sex distribution by SH showed that flame scallops are protandric sequential hermaphrodites. Flame scallops <40 mm SH were predominantly male (83%), those ≥40 mm SH were mostly female (71%), and 4% were in sexual transition near 40 mm SH. The sex ratio for the sampled population was 0.63M:1F. Histologic examination of fresh gonadal tissues revealed that female gonads were predominantly purple (96%) and male gonads were predominantly cream-colored (91%). Other gonad colors observed were not reliable indicators of sex nor was there a clearly defined association between color and those animals in sexual transition. Documenting the reproductive cycle of Ctenoides scaber in the existing Florida fishery is the first logical step to understanding its life history. Because flame scallops are important to the marine aquarium industry in the United States and are a potential food source for humans, it is important that we understand the reproductive cycle of this species to ensure proper management policies. This study provides basic information applicable to mariculture of flame scallops for commercial production to supplement the harvest of wild stock for the marine aquarium industry.

Salinity tolerance and resistance of the Pacific lion's paw scallop Nodipecten subnodosus, using the median lethal concentration method (LC₅₀) and a gradual change method were measured. We also attempted to demonstrate whether salinity and temperature, pH, dissolved oxygen and turbidity control the distribution and densities of species within a coastal lagoon (Laguna Ojo de Liebre, Mexico). The upper and lower LC₅₀ of this scallop were determined in the laboratory at predetermined times over 4 days (96 h) when exposing specimens to salinities of 15, 20, 25, 30, 37, 42, 47, 50 and 60 ppt. The upper and lower salinity resistances were studied by subjecting the specimens to either increases or decreases of salinity by 3 ppt every 3 days, departing from a normal salinity of 37 ppt. Salinity, temperature, pH, dissolved oxygen, and turbidity of the water close to the bottom were measured once a month from January 2001 to March 2004 at 20 stations located along the shore of the lagoon. Results showed no statistical differences at the upper or lower LC₅₀, at 24, 48, 72 and 96 h, and the species salinity tolerance varied from 23.5–24.2 to 50.4–53.8 ppt. Salinity resistance, measured by the gradual change method showed no mortality in the 22–52 ppt range, but abrupt mortality occurred with exposure beyond this range. Comparing these results with field data, we concluded that our results provide evidence that salinity is not a limiting factor regulating distribution and density of adult Pacific lion's paw scallop in the lagoon. Food quality and availability, water currents and substrate could be limiting factors.

The employment of different types of spat collectors and their orientation were investigated, as well as the effect of light and depth on larval settlement, with the aim of optimizing hatchery production of C. varia spat. Competent larvae were seeded in tanks with and without collectors, and were maintained for 3 wk. The larvae showed preference for settling on the internal shaded surface of the collectors placed horizontally. Settlement was significantly higher in deeper than shallower situated collectors. The absence of light reduced the settlement significantly. The mean settlement on the walls of the tanks without collectors was 17.7 ± 0.59%, whereas settlement on the walls of the tanks with collectors was 13.7 ± 2.62% and increased an additional 18.6 ± 3.93 when collectors were in place (i.e., a final settlement of 32.3%). The results suggest that the presence of an attachment substrate improves the yield obtained during hatchery production of C. varia spat.

It is expected that in triploid organisms the energy normally used for reproduction would be allocated to growth. However, not all triploid molluscs are completely sterile, and in some cases even gametes are produced. The aim of this study is to assess the gonadal development in the native scallop Argopecten purpuratus induced to triploidy. Argopecten purpuratus Lamarck 1819, is a functional hermaphrodite, the male portion of the gonad being creamy-white, located proximal to the foot, and the distal female gonadal portion is bright orange-red. They were induced to triploidy with 6-dimethylaminopurine (6-DMAP). Treated (=induced) and control scallops were processed for histology using routine methods. At the age of 11 mo, when the control scallops were mature, some treated scallops had a gonad, which showed a uniform brown color. These were true triploids, assessed by chromosome counts. They showed the tendency of reducing the “ripeness” of the female gonad, only few acini with oocytes were observed, associated to hemocytes, presumably phagocytosing them. Female acini were mostly empty. The male gonad was relatively more developed, but the spermatocytes, spermatids and spermatozoan-like cells showed a highly abnormal morphology. This evidence strongly suggests that these gametes are incapable of viable fertilization. Triploid A. purpuratus did not lose their hermaphroditic condition, which was different from another functional hermaphrodite scallop, Argopecten ventricosus, whose triploid gonad turned into only female.

A simple procedure for transporting live calico scallop, Argopecten gibbus (Linnaeus, 1758), juveniles for grow-out culture is described. The effects of 4 simulated transport periods (9, 16, 20 and 24 h), and subsequent recovery were examined. Success was assessed by survival rate and growth during 2-wk recovery. Survival rate was of 100% for all tested transport periods immediately following transport and following 2-wk recovery. Shell growth averaged 1.76–2.31 mm over the 2-wk period, yielding a growth rate 0.88–1.2 mm.week⁻¹; comparable to average growth rate at same site. There was no significant difference in growth among transport exposure time. Monitored levels of heat shock protein 70 (HSP 70) during manipulation did not indicate any physiologic stress. Successful application of this procedure to a real life 14 h airway transport of another subtropical/tropical scallop species, demonstrates its use for transport of two scallop species juveniles ranging in size from 8–40 mm, without detriment to subsequent survival or growth.

Three recent range extensions for the Chesapeake Bay, Virginia, veined rapa whelk (Rapana venosa) population are described. These extensions into Tangier Sound, the mid James River estuary, and to Cape Henry at the Bay mouth extend respectively, the northern, western, and southeastern boundaries of the occupied rapa whelk range in Virginia waters. Salinity and tidal circulation mediate the distribution of adults and larvae of this animal. During dry years (e.g., 2001 and 2002) adult rapa whelks may move up-estuary in western tributaries like the James River, given increased salinity and available habitat and food resources. Declines in salinities (or return to normal salinities) will either kill the rapa whelks in the upriver habitats or force a return to downstream habitats.

Decoupling emigration from mortality is critical for accurately estimating mortality in recapture surveys. However, open-population models often suffer from their inability to distinguish between these two parameters. A model is presented here that separates emigration from mortality based on movements of a tagged population of 42 hatchery-reared queen conch, Strombus gigas, released into a 20 m × 20 m plot in the nearshore waters of the Florida Keys. The model was constructed in a 4-step process. Recapture sampling of uniquely tagged individuals was used to derive a frequency distribution based on the movements of these individuals over a given time period. A probability density function was then fit to the frequency distribution. A probability of emigration was assigned to each cell in the plot. This value represented the probability of an individual located in that cell emigrating from the plot. Missing tagged individuals were assigned emigration probabilities (survival) based on the distance between their last observed location and the distance to the periphery of the plot. The overall survival of the population was estimated by constructing a survivorship table to estimate survival within and external to the plot for each sampling interval. After 3 mo, 14 conch were recaptured alive and another eight survivors were estimated to be present outside the plot representing an overall survival of 52.7%.

We investigated evidence for bias in estimates of abalone density from the point-nearest-neighbor (PNN) diver survey method wherein divers measure distances between abalone and from random points to nearest abalone. Field and simulation tests of the PNN survey method were undertaken. In two plots of a lightly exploited abalone population in South Australia, all the greenlip abalone (Haliotis laevigata Donovan) were enumerated by divers, providing the true density in both study regions. Clustering of abalone was visually evident and quantified by a Hopkins test. The study areas were gridded into 1-m² quadrats. Divers measured distances from randomly selected grid points to the nearest abalone, and from that nearest abalone to its nearest neighbor. A second set of inter-abalone distances from every fifth tagged abalone were also measured. Two PNN estimator formulas, of Byth (1982) and Diggle (1975), were used to estimate abalone density. The resulting estimates from both PNN estimators were biased, underestimating true (enumerated) density by 18% to 29% and 18% to 55% in the two sites respectively. The Byth estimator showed less underestimation. Clustering of abalone is a likely cause of density underestimation in the two study areas. Simulated PNN surveys in simulated clustered populations quantified both overestimation and underestimation bias. Randomly interspersed individuals (“loners”) reduced density underestimation, and centrally (rather than uniformly) distributed clusters worsened it. Because the spatial distributions of abalone and other invertebrates are often clustered, this strong bias is problematic for the use of PNN as a survey method for estimating density in these populations.

Benthic diatoms are the main food source for abalone postlarvae and juveniles. To feed abalone postlarvae, seawater is enriched with nutrients to increase natural microalgae populations. Another common method is to feed abalone with a monospecific culture of benthic diatoms. The objective of this work was to evaluate the growth of red abalone postlarvae (Haliotis rufescens) (2.85 ± 0.89 mm shell length; 3.93 ± 2.95 mg weight), fed with Navicula incerta, Amphiprora paludosa var. hyalina and a mixture of both species (1:1 dry weight). Cultures of benthic diatoms were maintained monospecific or mixed in 18-L plastic buckets with f/2 medium. Monospecific and mixed cultures were used to feed abalone postlarvae. The highest protein content (44.87 ±g 10⁶ cells⁻¹) was obtained for the monospecific culture of N. incerta. The highest growth rate (89.71 & plusmn;m d⁻¹) was found in the abalone postlarvae fed with N. incerta. No significant differences (P > 0.05) were found in the growth rate of abalone postlarvae fed with A. paludosa var. hyalina (52.94 μm d⁻¹) or with the mixed culture (53.22 μm d⁻¹). Postlarvae fed with the mixed culture had greater preference for A. paludosa var. hyalina than N. incerta and the lower nutritional value of A. paludosa var. hyalina explained the low growth rate for postlarvae.

A factorial experiment, in which blacklip (Haliotis rubra; Leach, 1814) and greenlip abalone eggs (H. laevigata; Donovan, 1808) were exposed to a range of conspecific sperm densities (ca. 10⁴–10⁷ sperm mL⁻¹) for different time intervals (7–2,400 s), showed there was a significant interaction between these factors in both species. Prolonged exposure (i.e., 1,200–2,400 s for blacklips and 480–2,400 s for greenlips) to concentrated sperm (i.e., 10⁷ sperm mL⁻¹) resulted in lysis of the egg membrane and polyspermy. Analysis of CoVariance of F₅₀ values (i.e., the sperm concentration required for 50% fertilization, derived from the linear regression of logit (proportion of eggs fertilized) versus sperm density) between species across a range of contact times demonstrated that contact time had a significant effect (P < 0.001) whereas species did not (P = 0.22). The lack of a species effect suggests that the fertilization potential of blacklip and greenlip abalone eggs are similar, at least across the range of sperm densities and contact times used. An examination of sperm morphology using scanning electron microscopy of both species revealed similarities in sperm length (i.e., 42–46 μm) and differences in the shape of acrosome, the tip of which was blunt in blacklip sperm and V-shaped in greenlip sperm. Morphological differences in haliotid sperm are discussed in relation to species differences in fertilization kinetics.

Abalone culture, a developing industry in Baja California, Mexico, would benefit from genetic improvement and controlled breeding. The use of cryopreserved sperm would allow germplasm availability, and this study was designed to develop sperm cryopreservation protocols for red abalone Haliotis rufescens. The acute toxic effects of the cryoprotectants dimethyl sulfoxide (DMSO), propylene glycol (PG), and glycerol (GLY) were assessed after suspending sperm in different concentrations, whereby cryoprotectant treatments of 10% DMSO and 10% GLY equilibrated for 10 min yielded the highest range of motile sperm in preliminary freezing trials and were used for cryopreservation studies. To determine effective cooling rates, three freezing chambers were tested. Replicate samples of sperm from 4 males were placed in 0.5-mL French straws and frozen using a commercial freezing chamber (CFC) used for bull sperm, a programmable rate chamber (PRC), and a manually controlled styrofoam chamber (MCC). For the CFC, the cooling rate was 16°C/min, from 4°C to −140°C. For the PRC and MCC, it was 1°C/min, from −20°C to −30°C. The samples were held at −30°C for 5 min before being plunged into liquid nitrogen (−196°C) for storage, and each sample was thawed in a water bath at 45°C for 8 s. The quality of thawed sperm was determined by estimating percent motility, evaluating membrane integrity using a dual-staining technique and flow cytometry, and estimating fertilization rate. Statistical analyses were performed using 2-way ANOVA where chamber and treatment were the independent variables. Sperm quality parameters were independent. For motilities, a significant interaction was noted between the cryoprotective treatment and the chamber type, whereby motilities for DMSO and GLY were higher (P = 0.0055) using MCC. Membrane integrities were significantly lower after using the PRC than the CFC or the MCC (P = 0.0167). The highest post-thaw motility (48 ± 7%) was found using sperm suspended in 10% glycerol and frozen in the MCC. The highest percent of intact membranes (56 ± 11%) was for sperm suspended in 10% glycerol and frozen in the CFC. The highest fertilization rate (29 ± 10%) was with samples frozen with 10% glycerol in the CFC. The use of cryopreserved sperm from red abalone provides an alternative breeding option for culture and the protocols delineated are the first developed for this species.

The hypobranchial gland of the muricid Plicopurpura pansa (Gould, 1853) is so active that the snails can be stimulated periodically without harming them to expulse the secretion. This property is a great advantage in the study about its biologic and chemical characteristics. No statistical difference could be determined between the incidence of expulsion and the sex of the animals. Also the test on whether the size of the animals had an influence on the frequency of expulsion showed no relation. The incidence of expulsions is the same between the different size classes. From between September 2003 and February 2005 collected snails (total number 3,577) 1,724 (48.2%) expulsed secretion. The proportion of snails that expulsed or not varied from month to month, however no clear seasonal trend could be observed. We determined in the laboratory the amount of the total organic compounds in the “milk” and found great variations (from 34.2 mg/100 animals to 337.8 mg/100 animals). We determined from 11 samples collected during different months an average of 148.9 mg organic compounds/100 animals. The “milk” expulsed from the hypobranchial gland of P. pansa contains 6.15% (±1.07 SD n = 3) total solids, 21.3 mg/ml (±17.8 SD n = 38) soluble proteins, and 6.01 mg/ml (±3.2 SD n = 38) carbohydrates. In organic extracts from the secretion of the hypobranchial gland we determined in a microwell assay a 50% lethal dose (LD₅₀) of 81.72 μg/mL (SD 35.78 n = 5) against Artemia nauplii. In assays to determine possible antibacterial activities in organic extracts we found two inhibition zones against Staphylococcus aureus. To quantify the microbial activity we determined a lowest inhibitory concentration of 125 μg/disk. By thin layer- and column chromatography, as well as by IR spectroscopy, we could preliminary identify some of the organic compounds in the “milk” and in organic extracts. By comparing previously reported front reference values (Rf-values) we could identify the dye precursor tyrindolinone, tyriverdin and bromoisatin. By column chromatography the extract was separated with different mixtures of organic solvents. In a first step gradient fractionation we obtained three fractions, which were unstable in light and turned immediately purple, and one yellow, light stable fraction. Two light stable brownish-colored fractions turned purple after acid hydrolysis. They were united and subjected to further fractionation, where four fractions and the green insoluble tyriverdin were obtained. By IR spectrophotometry and comparison with reported spectra it could be shown that one fractionated compound was a salt of probably 6-bromo-2-methylsulfonylindoxylsulfate and the other 6-bromoisatin. In organic extracts of the secretion free radical scavenging activities were determined by the 2,2-diphenyl-1-picrylhydrazyl radical method (DPPH). We observed two yellow patches above a purple background. By IR spectroscopy of the organic extract used we could determine the chromogen IV, probably 6-bromo-2 methylsulfonylindoxylsulfate, as a substance responsible for the free radical scavenging activity.

An international community of biologists presents the Pacific oyster Crassostrea gigas as a candidate for genome sequencing. This oyster has global distribution and for the past several years the highest annual production of any freshwater or marine organism (4.2 million metric tons, worth $3.5 billion US). Economic and cultural importance of oysters motivates a great deal of biologic research, which provides a compelling rationale for sequencing an oyster genome. Strong rationales for sequencing the oyster genome also come from contrasts to other genomes: membership in the Lophotrochozoa, an understudied branch of the Eukaryotes and high fecundity, with concomitantly high DNA sequence polymorphism and a population biology that is more like plants than any of the model animals whose genomes have been sequenced to date. Finally, oysters play an important, sentinel role in the estuarine and coastal marine habitats, where most humans live, environmental degradation is substantial, and oysters suffer intense fishing pressures and natural mortalities from disease and stress. Consumption of contaminated oysters can pose risks to human health from infectious diseases. The genome of the Pacific oyster, at 1C = 0.89 pg or ~824 Mb, ranks in the bottom 12% of genome sizes for the Phylum Mollusca. The biologic and genomic resources available for the Pacific oyster are unparalleled by resources for any other bivalve mollusc or marine invertebrate. Inbred lines have been developed for experimental crosses and genetics research. Use of DNA from inbred lines is proposed as a strategy for reducing the high nucleotide polymorphism, which can interfere with shotgun sequencing approaches. We have moderately dense linkage maps and various genomic and expressed DNA libraries. The value of these existing resources for a broad range of evolutionary and environmental sciences will be greatly leveraged by having a draft genome sequence.

The Japanese oyster Crassostrea gigas forms the mainstay of the South African oyster farming industry. Despite having been cultured along the South African coast for 30 years, this is the first record of naturalized populations of this well known global invader from the region. DNA sequence data confirmed the presence of C. gigas in the Breede and Goukou estuaries. Populations of 184,206 ± 21 058.9 (SE), 876 ± 604.2 (SE) and 1 228 ± 841.8 (S.E.) individuals were recorded in the Breede, Goukou and Knysna estuaries respectively. No C. gigas were recorded from the open coast. The condition index of oysters in the Goukou and Knysna estuaries differed significantly from those in the Breede Estuary (Kruskal-Wallis ANOVA H = 48.249, P < 0.01) but no difference was found between the Goukou and Knysna estuaries (Kruskal-Wallis ANOVA H = 48.249, P > 0.05). The lower condition index recorded in the Breede Estuary is believed to reflect decreased food supply as a result of the large C. gigas population present in the estuary.

To investigate the effect of varying concentrations of PAHs and laboratory holding on hemocyte characteristics, Pacific oysters, Crassostrea gigas, were exposed to varying concentrations of polycyclic aromatic hydrocarbons for 40 days. The circulating hemocyte count (HC) was significantly decreased over the experimental day for all treatments including controls, by day 20; after 10 days, there were no differences among treatments. Similar pattern of decrease was observed over the experimental day in phagocytic index (PI) with relatively constant PI after 20 days. Statistical significance observed only at 10 days. Percent of mobile hemocyte (PMH) also exhibited significant decrease with an association of PAH concentrations without effect of laboratory holding. Lysosomal membrane destabilization (LD) increased continuously over the experimental day with exposed level-dependent differences. Our result indicate that PMH and LD are useful tools for biomarker with sensitivity to toxicant regardless of the effect of laboratory holding, however, HC and PI are significantly influenced by laboratory holding and exposure effect is negligible at the end of the experiment.

Variations in biochemical composition and lipid classes in relations to the gametogenic cycle were studied in digestive gland, labial palps and gonad in the Pacific oyster Crassostrea gigas from the Western Atlantic coast of France over 1 y. Variations in the weight of the soft body parts, gonad development and spawning depended on environmental conditions, mainly on nutrients availability. The main energy reserve is the glycogen, showing a marked seasonal variability in all tissues studied this component increased in the digestive gland during the phytoplankton blooms and was rapidly transferred and accumulated in labial palps and gonad during stages IIID-0; glycogen was then mobilized during the final stage of somatic growth and during the beginning of the gametogenic cycle (stage IA). Glycogen is consumed almost totally at the beginning of spring, coinciding with an important increase of phospholipids in males and triacylglycerols in females. This fact seems to indicate that the glycogen reserves were used in the synthesis of lipids and in supporting the high energy demand existing during the active vitellogenesis and spermatogenesis. The digestive gland, besides playing an intermediary role in transferring the ingested lipids to other organs, seems to constitute an important organ of reserve of lipids, mobilizing phospholipids in winter towards palps and gonad during the somatic growth, but also during the initial gametogenesis and sexual maturation (triacylglicerols). There is depletion in the reserves of glycogen and triacylglicerols of the labial palps during the last stage of gonadal maturation. Simultaneously, an increase in triacylglicerols in gonad occurs, suggesting that the labial palps were an organ of reserve to sustain the most advanced stages of gonadal ripeness. The changes of sterol esters of gonad are discussed with regard to gametogenic cycle of Crassostrea gigas.

We randomly sampled the landings of oyster boats fishing on the New Jersey oyster beds of Delaware Bay during the 2004 fishing season (April to mid November) to determine (a) the viability of a simple conversion between the numbers-based stock assessment and the bushel-based quota-setting process and (b) the degree to which undersized oysters are taken during the fishing process because of imperfect culling. Rarely were more than 3% of the chosen (unattached) animals less than 2.5″ in length: fisherman choice is a knife-edge process. Most smaller oysters were attached to chosen oysters. Incidental catch caused by imperfect culling contributed 9.9% to fishing mortality. Season influenced landings size frequency more than did bed of harvest. Oysters chosen for market were larger in the Fall; consequently the number per bushel was lower in the Fall. Attached oysters were more numerous in the Fall, so that the total number of oysters per bushel did not differ significantly over the year. Trends in the uniformity of sizes harvested were dominantly related to within-bed variations in size frequency. Trends in the average size of oysters harvested were partly determined by fisherman choice. For the purposes of management, a single average conversion is adequate: 272 oysters per bushel. Regulations furthering an increase in culling efficiency are unnecessary.

The enzyme phenoloxidase is believed to be a component of internal defense in invertebrates. We detected phenoloxidase activity in the membrane fraction of hemocytes from the eastern oyster, Crassostrea virginica. The activity is associated with a protein with a molecular weight of 133 kDa. That the enzyme is a phenoloxidase and not a peroxidase was shown by inhibition of the activity by diethyldithiocarbamic acid. The phenoloxidase displayed a preference for diphenol substrates and was inactivated by incubation at temperatures above 70°C. The activity was highest in a pH range of 6.0–7.5. The oyster pathogen P. marinus causes serious disease in the commercial oyster, Crassostrea virginica, but not the mussel Geukensia demissa. We measured the effect of P. marinus cells on the phenoloxidase activity in hemolymph from C. virginica and G. demissa over a 6-h time course. The presence of P. marinus significantly suppressed the phenoloxidase activity of both species at the 2-h time interval. The phenoloxidase activity seemed to increase at the 4-hr and 6-h time intervals. These data suggest that a transient inhibition of host phenoloxidase may play a role in the study of P. marinus infection.

Field studies were conducted to compare quartzitic sandstone to siliceous limestone in its ability to collect oyster spat, and to determine if sandstone is a suitable cultch for oysters. Thirty bags of sandstone and 30 bags of limestone were placed on each of 3 sites in Terrebonne Parish, Louisiana–South Sister Lake (SSL), North Sister Lake (NSL), and Bay Junop. The bags were deployed in late May and retrieved in early to mid July. (The Bay Junop bags were missing upon retrieval.) All recruits to the substrate (live spat, articulated dead shells and single shells) were counted as spat. South Sister Lake had higher salinities and higher spatfall than did NSL. The mean number of oyster spat per bag at SSL was 2156.5 for limestone and 338.5 for sandstone; at NSL mean number of spat per bag was 315.3 for limestone and 16.8 for sandstone. The difference between sandstone and limestone was highly significant (P < 0.0001) at both sites. There was thus a clear preference of oyster larvae for limestone at high salinity and high-larval abundance, and at low salinity and low-larval abundance. Sandstone does not appear to be a suitable alternative to limestone as a cultch for oysters.

The eastern oyster is an economically and ecologically important species whose vitality is threatened by the protozoal parasite Perkinsus marinus. To better understand which cellular defense mechanisms impart resistance to P. marinus, resistant (Crassostrea gigas) and susceptible (Crassostrea virginica) oyster species were challenged by an experimental infection with P. marinus and their cellular responses were quantified and compared. Both in vivo and in vitro infection trials measured hemocyte phagocytosis, respiratory burst, apoptosis at 1, 3 and 7 days postinfection (in vivo) or 1-h postco-incubation (in vitro). Total parasite body burden concentrations were also measured at the end of in vivo infections. Infections were significantly more severe in C. virginica than C. gigas at 3 and 7 days postinfection confirming the resistance of C. gigas and validating the experimental model. There was more phagocytosis in infected C. virginica than infected C. gigas three days postinfection. In vitro, C. virginica granulocytes phagocytized significantly more parasites and fluorescent latex beads than C. gigas granulocytes, and infection increased bead phagocytosis in both species, equally in cells with or without intracellular parasites. Neither in vivo nor in vitro infections significantly increased respiratory burst activity. While in vitro infections suppressed hemocyte apoptosis in both species, in vivo infections increased hemocyte apoptosis frequency in C. gigas at 3 days postinfection. In vivo infection increased hemocyte apoptosis in C. virginica at 7 days postinfection but not at three days postinfection. From those experiments, we concluded that the increased phagocytosis without concomitant increase in respiratory burst activity seen in infected C. virginica might exacerbate infections. Also, while in vitro P. marinus infection suppresses hemocyte apoptosis in both species, C. gigas appeared to overcome that suppression faster than C. virginica upon in vivo infection, suggesting that hemocyte apoptosis may be an effective oyster defense response against P. marinus infection. The combination in vitro and in vivo infections in P. marinus disease resistant and susceptible oyster species with multiple time points and assays allowed the identification of apoptosis as the cellular defense mechanism most likely to play an important role in defense against P. marinus. This information may provide more accurate predictive criteria for disease resistance, allowing for the testing and selection of more disease resistant oysters.

The Suminoe oyster, Crassostrea ariakensis, is currently under consideration for introduction to the Chesapeake Bay for aquaculture and to restore lost fishery resources once provided by the native Eastern oyster. To assess the suitability of the Suminoe oyster for substitution into native oyster markets, we provided whole triploid oysters for home cooking to consumers in coastal North Carolina and asked them to complete a survey on qualities of the Suminoe oyster. Participants reported the frequency with which they would consume the oyster inside and outside of the existing oyster season, how they would consume the oyster and the price they might be prepared to pay for the Suminoe oyster relative to the native oyster. Because participants prepared the Suminoe oysters themselves, consumer evaluations incorporated not only attributes of the oyster meat but also the ease with which the oysters could be shucked and prepared. Consumers rated the Suminoe oyster's aroma, appearance, texture and flavor as likeable. As a result of the oyster's tissue quality and the ease with which it could be shucked, 81% indicated that they would purchase the Suminoe oyster if it is introduced. Only 19% of survey participants said they would pay more for Suminoe than Eastern oysters when both are available. This contrasts sharply with the 45% that would be prepared to pay a higher price for the Suminoe oyster than they would normally pay for Eastern oysters at times when the Eastern oyster is not available. Consumers generally indicated that they would prepare the non-native oyster in similar ways to the native oyster. Thus, our study indicates that the Suminoe oyster is considered by consumers in eastern North Carolina to be a close substitute for the native oyster. Consequently, the Suminoe oyster might serve as a successful substitute for the lost fishery resource of the native oyster.

Vibrio vulnificus is an important human pathogen, which occurs naturally in estuarine waters and in large numbers in oysters. The levels of V. vulnificus in shellfish vary greatly, and the causes of this variation are not well understood. A protozoan parasite, Perkinsus marinus, is a pathogen of oysters, which was earlier suggested to increase susceptibility of oysters to bacterial infections. A goal of our study is to determine whether the presence of P. marinus plays a role in determining the incidence or magnitude of V. vulnificus infection in oysters. We also used fluctuating asymmetry (FA) of shell weight as an indicator of developmental instability and thus of microbially-induced physiological stress in oysters. We harvested 155 adult oysters (Crassostrea virginica) from a small environmentally homogeneous site in North Carolina, and examined them for V. vulnificus and P. marinus infections. V. vulnificus and P. marinus were detected in 88% and 73% of the oysters, respectively. The incidence of the two pathogens in these oysters was independent, with no greater tendency to infection by V. vulnificus in oysters infected by P. marinus and vice versa. V. vulnificus loads per g tissue weight varied by over four orders of magnitude in oysters of the same size, weight and age, which were harvested from this single habitat. V. vulnificus loads were found to be unaffected by age of oysters (and thus by the length of exposure to this pathogen). On the contrary, there was a significant decrease in both incidence of V. vulnificus infection and tissue loads of this bacterium with the host weight, possibly indicating growth dilution. Infection with V. vulnificus or P. marinus did not affect FA of shell weight in oysters. Overall, our findings suggest that infection by P. marinus does not predict V. vulnificus loads in C. virginica, nor did oysters infected with either of these pathogens exhibit physiological stress that results in developmental instability.

Recent (2001–2002) surveys of hard clam Mercenaria mercenaria density and distribution, using patent tongs in a stratified random design (n = 7,358 stations) in lower Chesapeake Bay are not consistent with historic descriptions of clam habitats and densities. The highest average densities observed, up to 3.1 clams m⁻², were in the lower James River. The highest modern average density observed is half that of clam densities commonly observed in these same habitats during the early 1970s. Current distribution is significantly affected by water depth and substrate composition. Hard clam density in Chesapeake Bay is positively associated with increasing sediment grain size; 78% of all clams collected were found in shell or sand habitats. However, 44% of sand habitats and 54% of shell habitats were unoccupied suggesting that even habitat types that typically support higher clam densities may currently be underused.

We report results of a survey explicitly focused on ocean quahog recruitment in the Mid-Atlantic Bight. The recruitment survey resampled all NMFS survey sites south of Hudson Canyon and a selection of sites north and east of Hudson Canyon off the Long Island coast over the entire depth range of this species with the exception of the most inshore reaches off Long Island. More ocean quahogs were encountered, on a per tow basis, in the vicinity of and north of Hudson Canyon. The proportion of recruits in the size-frequency distribution was higher in the south and the most recent recruitment events were concentrated there. Analysis of the 104 size-frequency distributions delineated regions of recent recruitment, areas that have not seen significant recruitment for many decades and areas that received heavy recruitment some decades previously but not recently. Overall, the survey suggests that three regionally distinctive processes determine the size-frequency distributions of ocean quahog assemblages and recruitment therein. The area northeast of Hudson Canyon is unique in the regionally extensive uniformity of size-frequency distributions among sampled assemblages, the near absence of recent recruitment and the presence of large numbers of older recruits, 65–80 mm in size. The inshore (by ocean quahog standards) area off New Jersey is unique in the dominant presence of the largest size classes of ocean quahogs and the remarkable absence of significant recruitment over an extraordinary time span. The area south of 39°N is unique in the widespread presence of relatively young recruits, including some animals with ages within the time span of the present fishery. Recruitment events in ocean quahog populations, although rare in the sense of occurring only once in a score or two of years, are frequent in the context of the 200-year life span of this species, yet also rare in the context of stock survey timing and fishery dynamics. This study strongly supports the assumption that long-lived species recruit successfully only rarely when at carrying capacity. This study also suggests that the history of recruitment over the last perhaps two-score years, revealed by this survey, may be a poor measure of the recruitment dynamics to be anticipated over the next two-score years when the population abundance is reduced to what is anticipated to approximate the biomass at maximum sustainable yield. Given the long time span required for ocean quahogs to grow to fishable size, a substantive disequilibrium may exist between the recruitment anticipated from the relationship of adult biomass to carrying capacity and the contemporaneous number of recruits for minimally 20 y after adult abundance is reduced from circa-1980 carrying capacity to biomass, maximum sustainable yield.

The Mytilus gonadal cycle in Vigo Estuary follows the histological pattern proposed by Lubet (1957, 1959). We show details not previously described, due to sexual differences, environmental characteristics and high periodicity samplings: an out of phase between reserve tissue and gonadal cycles; a “bridge stage” determined by intermediate characteristics among the last spawnings, gonad resorption and regeneration of the reserve tissue; a moving forward of the initial stages and different duration by sexes; and clear-cut differences between spawnings and restorings: in winter, they are a slow and less intense process, with abundant reserve tissue, high atresia and they do not end in effective spawnings, whereas in spring are very rapid and intense processes causing massive spawnings. The atresia present two phases: cytoplasmatic structures self-lysis and digestion by hemocytes. Winter atresia is related to unfavorable conditions to stimulate spawning. Temperature and food availability determine the temporal evolution of the gametogenic cycle in male and female differently. The mantle tissue index varies depending on the number of gametes and is suitable as a gonadal index in this species.

Considering that the analysis of total gut contents in large sized bivalve species is extremely time-consuming, the aim of the present study is to give a statistically tested methodology that permits quantitative assessment of gut contents in bivalves from selected subsamples. Thirty Patagonian scallops Zygochlamys patagonica (35–55 mm total height) from Reclutas bed (39° S to 55° W) were dissected. The complex “gut digestive gland” was extracted for the analysis of approximately 1/6 of the total content. This procedure was analyzed using the results of the 2-stage sampling theory. The error in the estimation of the mean number of particles per gut was estimated between 15% and 16% using this methodology.

Mytilus edulis and M. trossulus are the two molluscan species co-occurring along the Gaspé coast, eastern Canada. Few studies examine the effects of environmental factors (temperature, salinity, tidal height and wave action) on the local or regional distribution of these two species in areas where they co-occur. This study is designed precisely to examine the niche of each of the two species, particularly in relation to environmental factors in the northeastern part of the Gulf of St. Lawrence, Canada. Mussels were sampled on rocky shores according to a factorial design including six locations, 3 degrees of wave exposure (exposed, semi exposed and sheltered) and 2 intertidal levels (mid and low). Species were distinguished with polymerase chain reaction amplification using a diagnostic DNA marker (Glu-5). Relative frequencies of each species showed no clear patterns of distribution with wave exposure or tidal height. A pattern of distribution at the regional scale does occur, but this pattern could not be related to salinity or temperature gradients observed.

A database containing 1,234 records of Corbicula fluminea in Texas was created based on published literature accounts, survey reports by Texas Parks and Wildlife Department, unpublished records from university and museum collections, personal communications and author's data. This invasive, exotic bivalve was first collected in Texas in the Neches River in 1958 and was next found in El Paso in 1964. Initial presence on opposite sides of the state supports invasion occurring from the west and east. Corbicula fluminea has since colonized all major drainage basins in Texas. By 2005, it was known from 162 lotic and 174 lentic waterbodies located in 180 of 257 Texas counties. There was a positive significant correlation between the percentage of invaded waterbodies by reservoir size (Pearson r² = 0.78) and stream order (Spearman R = 0.65). Corbicula populations were found more often in larger reservoirs and higher-order streams and were usually rare to absent in the smallest. Unless precluded by lack of permanent water or inadequate physicochemical parameters, C. fluminea may colonize most of Texas streams greater than second order and all but the smallest impoundments.

Bivalve veligers are difficult to identify morphologically, and when it comes to strait hinge (~90 μm) or small velichoncha veligers (>90–300 μm) it is practically impossible. However, the use of new molecular based methods allows the identification of individual larvae, in a size independent manner (Larsen et al. 2005). In this contribution we show small-scale spatial variations among species of velichoncha veligers, in the size range of 120–135-μm shell length. Larvae were sampled quasi-simultaneously in a squared matrix at Løgstør Broad, Limfjorden, Denmark. The matrix consisted of 46 sampling sites, situated within 500–750 m apart. Velichoncha larvae were enumerated and sized. Larval concentrations ranged from <50 to >350 Ind. per liter, and found not to be coupled to any environmental parameter recorded. At 25 of the sampling sites larvae were identified to species/genera level by Singe Step Nested Multiplex PCR (SSNM-PCR). The bulk of the velichoncha was Mytilus edulis/Musculus marmoratus (52% to 91%), which was found to be present in all samples tested. In contrast Ensis spp. was observed in 24 of the tested samples, making up between 4% to 31%, whereas species of the order Myoida and species belonging to the Cardiidae family only was observed occasionally in low relative abundance. At a few sampling sites a difference in the vertical distribution among the composition of velichoncha assemblages was suggested. Hence, SSNM-PCR was useful for identifying evidence for spatial scale differences in species composition within bivalve larval assemblages. Because of the ecologic and economic importance of some species, there are significant perspectives in identifying bivalve veligers in large scale studies.

The identification of effective, nontoxic means for physically marking and tracking marine invertebrate larvae is a necessary step towards meeting a major goal of modern marine population biology, the direct measurement of larval dispersal. An inexpensive, rapid and effective means for marking bivalve larvae would be particularly useful because, as a taxonomic group, bivalves contain many commercially important and exploited species. Likewise, bivalves produce large numbers of propagules for experimental procedures and, for many species, methods for rearing larvae have been well established. Calcein has been used as a marker in numerous studies of adults and juveniles of calcium-carbonate-containing marine organisms, but its effects on small and sensitive life history stages such as embryos and larvae can be detrimental. We show that calcein can be used to rapidly and effectively mark large numbers of larvae from two bivalve species, Argopecten irradians concentricus (Say, 1822) (the Bay Scallop) and Mytilus trossulus Gould, 1850 (the Bay Mussel). Calcein had no detectable negative effects on growth or survivorship of larvae of either species; therefore, this fluorescent mark should serve as a useful tool for directly tracking dispersal of these species in the field. Our marking method is simple and inexpensive and can easily be used to determine the effectiveness and potential toxicity of the calcein mark for other bivalves.

Furunculosis, caused by the bacterium Aeromonas salmonicida, was artificially induced in brook trout (Salvelinus fontinalis) in an experimental tank. Ebonyshells (Fusconaia ebena) were placed to cohabit with these fish to acquire the pathogen through siphoning. After 2 wk of cohabitation, 10 of the mussels were assayed by bacterial culture and all were found to harbor A. salmonicida. The mean cell count from soft tissue homogenates was 1.84 × 10⁵ cfu/g, which comprised an average 14.41% of the total bacteria isolated from tissues. From the fluids, a mean of 2.84 × 10⁵ A. salmonicida cfu/mL was isolated, which comprised an average of 17.29% of the total bacterial flora. The mussels were removed from the cohabitation tank and distributed equally among five previously disinfected tanks, 35 per tank. The F. ebena in each tank were allowed to depurate A. salmonicida for various durations: 1, 5, 10, 15 or 30 days. After each group had depurated for their assigned time, 10 were assayed for bacteria, tank water was tested, and 20 pathogen-free bioindicator brook trout were added to cohabit with the remaining mussels. Depuration was considered successful if A. salmonicida was not isolated from tank water or the mussels, and there was no infection or mortality to bioindicator fish. After 1 day of depuration, A. salmonicida was not isolated from the soft tissues; however, it was isolated from one of the paired fluids (10% prevalence). The tank water tested positive, and the bioindicator fish became infected and died. From the 5-day depuration group, A. salmonicida was not isolated from soft tissues, but was isolated from three fluids (30%; mean = 1.56 × 10² cfu/mL). Tank water from the 5-day group was negative, and there was no mortality among the bioindicator fish. However, A. salmonicida was isolated from 2 of 20 fish at the end of the 14-day observation period. One F. ebena fluid sample was positive for A. salmonicida from the 10-day depuration group, but none of the soft tissue homogenates. The pathogen was not isolated from 10-day tank water, but there was a 30% cumulative mortality to the bioindicator fish. Aeromonas salmonicida was not isolated from any of the soft tissue homogenates, fluids or tank water from the 15 day or 30 day depuration groups, and the bioindicator fish remained pathogen- and disease-free. Study results showed that the F. ebena were harboring a high A. salmonicida cell load going into depuration, but at 15 days and beyond, the pathogen had been depurated to the extent that the mussels did not serve as pathogen vectors.

The prey and size-class preferences of four marine epibenthic predators was examined in a laboratory study by determining the mortality rates of four commercial bivalve species in 4-d trials where predators were present or absent. Bivalve species used were quahogs (Mercenaria mercenaria), eastern oysters (Crassostrea virginica), blue mussels (Mytilus edulis) and soft-shell clams (Mya arenaria). Prey size-classes investigated were 0–15, 15–25 and 25–40 mm. A first set of experiments compared the mortality rates of prey in the presence of the invasive green crab (Carcinus maenas) and the native rock crab (Cancer irroratus). The second set of experiments compared the predation behavior of the green crab, the common starfish (Asterias vulgaris) and the moon snail (Euspira heros). Single- and multiple-choice experiments were carried out in relation to the prey species being challenged by the predator. Results from the first set of experiments showed that green crabs preyed on all prey species from all size-classes in single and multiple-choice trials. Mussels and clams were the preferred prey species. Rock crabs preyed on mussels in single- and multiple-choice trials. Rock crabs preyed heavily on soft-shell clams in single-choice trials, whereas no clams were eaten in multiple-choice trials. Rock crabs did not prey on quahogs in single- and multiple-choice trials. In both trials, small individuals were preyed on more often by both crab species. The second set of experiments confirmed results observed for the green crab in the first set of experiments. The common starfish was a very active predator as well. Blue mussels were the preferred prey species of the starfish. Moon snails displayed a much lower predation activity than the other predators. The multiple-choice experiment showed different results in that predation rates were lower than in cases where predators were facing one prey species at a time. Overall, our results showed that the two crab species and the common starfish displayed a generalist feeding behavior. Results also showed that the invasive green crab might represent a new predation threat to commercial bivalves as well as a competing threat to the native rock crab.

Ovigerous blue crabs, Callinectes sapidus Rathbun, undergo ebb-tide transport (ETT) during the spawning migration from estuaries to coastal areas where they release larvae. An initial field study found that only females with mature embryos underwent the spawning migration and that postspawned females switched to flood-tide transport for movement back into and up estuaries. Alternatively, a more recent field study found ETT occurred in females throughout embryo development and continued after larval release. An endogenous rhythm in vertical migration underlies ETT during the spawning migration. A past study found the circatidal rhythm was only present in females with mature embryos but not in females with immature embryos or after larval release. The present study reinvestigates this rhythm in vertical migration. Both females with early embryos and postlarval release females entrained in the field have circatidal rhythms, in which they swim vertically at the time of consecutive ebb tides at the collection site or on alternate ebb tides. These results support the field study that ovigerous females undergo ETT throughout embryo development and after larval release. Thus, females will be transported seaward and release subsequent larval clutches in coastal areas that increase the likelihood that larvae will be transported to offshore developmental areas.

The Asian shore crab, Hemigrapsus sanguineus, is an invasive species along the Atlantic coast of North America. It has spread rapidly since its discovery in the USA in 1988 and has become the dominant crab species in rocky intertidal habitats at many locations in the Middle Atlantic Bight and in the southern Gulf of Maine. The reproductive biology of H. sanguineus has received only cursory study in native east-Asian waters. Available information consists mainly of descriptions of the larval stages and general characterizations of the natural history of the species. This study examined the periodicity of larval release in an invasive population of H. sanguineus near its original site of introduction at the mouth of Delaware Bay. We investigated larval release at diel and tidal frequencies. Analysis of laboratory data showed that larval release always occurs near the time of nocturnal high tide. Field sampling confirmed the presence of stage I zoeae in waters near adult habitat at the expected time of larval release. This pattern of release minimizes the impact of visual predators on newly hatched zoeae and takes advantage of circulation at tidal frequency to transport zoeae away from intertidal habitats where conditions may not be favorable for larval development. However, H. sanguineus is not unique among intertidal crabs in releasing larvae near the time of nocturnal high tide. This pattern has been reported for a large number of species with wide representation among families. Thus, the pattern of release observed in H. sanguineus does not provide any special competitive advantages over co-occurring native species, and the remarkable success of the species in North American habitats may be attributable to competitive interactions occurring after settlement and metamorphosis.

The reproductive period of the blue shrimp Litopenaeus stylirostris off the Gulf of California coast of Sonora and Sinaloa in Mexico has been determined with the percentage of mature females as index. The objective is to determine the reproductive period and output of this species near Agiabampo, Sonora-Sinaloa by combining three indices of mature females; fecundity of size, abundance and size of mature females into a single index, the egg production index (EPI). Monthly samples from January through December 2002 were collected. During five continuous days around the full moon (full moon ± 2 days), trawl nets were used at depths from 1–9 m with a 2 km north and south of the mouth of the Agiabampo lagoon. The proportion of mature females to all sampled females, was highest (66%) in May, mature females were more abundant (13 ± 4 org. ha⁻¹) in July, and the average total length of mature female was significantly smaller (F_(2,291) = 79, P < 0.05) in July than in the others months. Length at maturity was 172 mm. I concluded that it is more important to determine the reproductive processes than only the reproductive period. Particularly off Agiabampo, blue shrimp has a well-defined reproductive output of about 6 × 10⁶ eggs ha⁻¹ with just one massive spawning peak (May to July).

Body size, sex ratio and timing of reproduction of the sand shrimp, Crangon septemspinosa Say (1818), and the distribution of larvae and adults with respect to temperature and salinity, were studied in the estuary of the Kouchibouguac River, New Brunswick. Contrary to predictions, body size was not related to latitude or biogeographic zone. Reproduction in May and June by a cohort of large females, followed in summer and early fall by a cohort of smaller reproductive females, was consistent with previous reports of estuarine populations. Reproduction was continuous throughout the spring and summer, in contrast to the two distinct spawning seasons reported for other northerly populations. Larvae were most abundant in July. At least part of the adult population remained in shallow waters of the estuary throughout the summer, at temperatures up to 28°C, unlike the offshore migrations reported for most other populations during periods of warm water conditions.

No Abstract available.

No Abstract available.