The infaunal, suspension-feeding softshell clam (Mya arenaria L.) is a conspicuous member of the intertidal macrofauna in numerous northern temperate and boreal soft-bottom communities. Recruitment variability can affect the magnitude and scope of various ecosystem services provided by M. arenaria, including its role as a source of food and energy for organisms at higher trophic levels. Manipulative field experiments were conducted in the intertidal zone in 2014 and 2015 at three tidal estuaries in southern Maine, to investigate the importance of post-settlement processes in determining the strength of the annual 0-y class cohort across predator-exclusion treatments within and between tidal heights. Four short-term (4–5 mo), small-scale studies over both years in the Webhannet River (Wells, ME) and Fore River (Portland, ME), the two southernmost estuaries, demonstrated that clam recruits were up to 118× more abundant when predators were deterred versus controls. In a 7-mo study conducted in the Harraseeket River (HR; Freeport, ME) during 2014, recruits of Mya attained densities 899× greater in large-scale plots designed to exclude large (>6 mm) predators than in ambient, adjacent sediments where predators were undeterred. A novel, epibenthic settlement trap (0.15 m²), initially containing no sediments and designed to deter both infaunal and epibenthic predators larger than 1.9 mm, was used to examine spatial variability in clam recruitment over a 6-mo period in 2015 in the HR. Traps showed a 60-fold difference in mean number of clam recruits between sides of the river only 600 m apart. Collectively, results suggest that post-settlement mortality rates of 0-y class individuals of Mya exceed 99% at these locations, severely limiting ecosystem services they would otherwise provide, and that these early losses are primarily responsible for explaining distribution and abundance patterns of ≥1-y class individuals.

High-intensity infection with the protozoan parasite Perkinsus olseni is lethal to the Manila clam Ruditapes philippinarum, especially to juvenile clams; however, how this parasite impacts its host remains unclear. This study was carried out to investigate the effects of P. olseni on the growth, condition index, burrowing behavior, and filtration activity of the Manila clam to elucidate mechanisms by which the infection causes death of the clams. Juvenile Manila clams (5–9 mm in shell length) were challenged with parasitic zoospores and were then reared in seawater for 52 days. Growth and condition index were frequently, but not always, significantly lower in the challenged group compared with the unchallenged group during the challenge experiment. Fewer individuals from the challenged groups compared with the unchallenged groups exhibited lower burrowing activity, when they were placed on sand in wells of 24-well plates. Furthermore, to compare filtration activity, clams from both groups were maintained in separate suspensions of diatoms. Diatom density remained higher in the challenged clams compared with the unchallenged clams, indicating that challenged clams exhibited lower levels of filtration activity. Decreased burrowing activity may cause higher predation rates and make the clams vulnerable to turbulent water and periodic tidal air exposure, resulting in death of Manila clams under natural conditions. In addition, suppression of filtration activity by infection may cause decrease in food and oxygen intake, leading to mortality induced by nutrient loss and hypoxia.

Several species of harmful algal blooms (HAB) exert inimical effects on bivalve molluscs, with mass mortalities and pathologies reported worldwide. Information on the effects of HAB on the reproduction of bivalve molluscs, however, remains very limited. The Japanese pearl oyster Pinctada fucata martensii is an important economic species cultured in Japan. In previous studies, harmful dinoflagellates and raphidophytes were shown to affect embryos and larvae of Japanese pearl oyster. In the present study, quantitative deleterious effects of Alexandrium catenella, Alexandrium affine, Heterosigma akashiwo, and Chattonella marina on egg viability and spermatozoa swimming velocity are reported. All four HAB species significantly reduced the swimming velocity of spermatozoa. Egg viability was affected only after exposure to A. catenella and A. affine. An additional cytotoxicity test using Vero cells showed that bioactive exudates are associated with the deleterious effects and these effects are more prominent during the death phase of the algal culture. The results of the present study warrant further research on the effects of HAB species on gamete quality of bivalves, further characterization of bioactive compounds secreted by Alexadnrium spp., and highlight the role of physical activation of the toxic mechanism of harmful raphidophytes suggested in a previous study and confirmed in the present study.

Genetic by environment (GxE) interactions were estimated for harvest traits of Pacific oysters Crassostrea gigas based on data collected over a period of 20 y from farm trials conducted by the Molluscan Broodstock Program, a family-based selective breeding program aimed at improving yields of Pacific oysters on the West Coast, USA. Genetic by environmental interactions were estimated for oyster families planted at subtidal and intertidal sites, as well as at coastal and Puget Sound (PS) sites in the Pacific Northwest. Covariance components were obtained using a multiple-trait mixed model, treating one type of trait in different environments as two different but correlated traits. A total of 9,970 records were analyzed for five generations of selectively bred oysters. Heritability estimates for yield and average individual weight at harvest (total weight of all living oysters in a container divided by the number of live oysters) were similar in both inter- and subtidal environments, ranging from 0.42 ± 0.02 to 0.45 ± 0.02; however, the heritability for survival was higher (0.45 ± 0.02) in intertidal than in subtidal environments (0.31 ± 0.02). Genetic correlations among harvest traits within environments ranged from small-negative (-0.05 ± 0.06) to high-positive (0.77 ± 0.02) values. Genetic by environmental correlations were moderate to high between inter- and subtidal environments (0.66 ± 0.04, 0.81 ± 0.05, and 0.64 ± 0.06 for yield, survival, and average individual harvest weight, respectively), whereas correlations between coastal and PS environments were moderate (0.46 ± 0.06, 0.69 ± 0.05, and 0.52 ± 0.06 for yield, survival, and average individual harvest weight, respectively), indicating that GxE interactions were stronger between the coastal and PS sites. Indirect responses to selection were mostly lower compared with direct selection. Stronger GxE effects and low indirect responses to selection for yield between coastal and PS sites suggest that developing separate breeding programs, rather than a single breeding program, would be more effective in improving harvest-related traits of Pacific oysters farmed in these two different geographic regions.

Many of the features that make estuaries among the most productive natural systems on earth also make them prone to acidification. Understanding the effects of estuarine acidification on different components of an ecological community is an important step in identifying indicators of ecosystem degradation. This study examined the impact of estuarine acidification, as a result of acid sulfate soil runoff, on wild Sydney rock oysters Saccostrea glomerata and their associated epifaunal communities in estuaries experiencing acid sulfate soil runoff in New South Wales, Australia. The responses of oysters and their invertebrate epifaunal communities to chronic acidification (greater than 6 mo; represented by oyster source site conditions) were assessed by examining the differences in oyster communities associated with moderate acidification (3.5 km from the source of acidification) or low acidification (8.2 km from the source). Oysters from moderate- or low-acidification sites were transplanted to a site with high exposure to acidification (less than 3 km from the source) or back to their original source sites (control) to mimic episodic acidification (2 wk). Epifaunal mussels Xenostrobus securis and limpets Patelloida mimula showed a negative association with oyster mortality, suggesting that these communities are closely tied to oyster survival. Oyster-associated epifaunal communities exposed to both chronic and episodic acidification were significantly different from communities with low exposure. Epifaunal communities exposed to episodic acidification were significantly less diverse than the control. Spionid and syllid worms were significantly less abundant and the mussel X. securis was significantly more abundant on oysters with moderate exposure or chronic exposure to acidification, as compared with communities from areas with low exposure to acidification. The mussel X. securis and the snail Bembicium auratum were significantly less abundant in oyster communities that were exposed to episodic acidification, as compared with the control. In systems where community composition depends on a single habitat-forming species, maintaining resistance may rely on the ability of that species to persist in the face of environmental stress.

The black-lip rock oyster, Saccostrea echinata, has considerable potential for aquaculture in tropical Australia and the Indo-Pacific region because of its large size, rapid growth rates, and established market acceptance. This article is the first to report on embryonic and larval development of this species reared under hatchery conditions. Developmental biology was examined across three larval cultures over a 21-day period. Newly fertilized eggs had a mean (±SE) diameter of 50 ± 0.4 µm, and postfertilization, the first polar body formed within 20 min. The earliest actively swimming trochophore appeared from 12.5 h postfertiliszation (hpf) and D-stage larvae appeared by 18 hpf. Rapid shell growth resulted in the presence of early umbo larvae at 5–7 days post fertilization (dpf). Pediveliger larvae were present from 18 dpf and the larvae settled with induction by epinephrine bitartrate from 21 dpf when they had reached an anteroposterior shell measurement of approximately 280 µm and could be retained on a 200-µm nylon mesh screen. Despite minor differences, overall, the early ontogeny of S. echinata is consistent with that of other members of the genus. This study fills an important knowledge gap in the literature and will aid the advancement of hatchery protocols for this developing aquaculture species.

Round pearl culture is an increasingly important industry in Fiji. Significant barriers to entry include high capital outlay and technical requirements, and a high turnover of small to medium size farms has limited industry growth. This study developed a viable-scale farm model for round pearl culture in Fiji to assist new or potential entrants understand costs, risks, and production levels required for success. Major production costs were labor (51%), oyster stock (18%), and pearl nuclei (10%). At steady state, median annual profitability was determined to be $156,362, but inclusion of price and production risk factors reduced annual profitability to $29,463. The model farm achieved an internal rate of return of 36% with a benefit-cost ratio of 1.8 and payback period of 5 y. Farms holding 100,000 oysters and producing more than 8,000 pearls are deemed of viable scale. At this scale, farms can attract overseas pearl seeding technicians, apply economies of scale, and invest profits into future development. Given the average rural household income in Fiji is $5,800, round pearl culture offers significant economic opportunity and delivers socioeconomic benefits for rural communities in upstream (oyster stock supply) and downstream (handicrafts, jewelry, and tourism) activities.

Blooms of toxic microalgae and the accumulation of their toxic compounds in bivalve molluscs are a regular worldwide problem to both consumers and producers. To select populations that accumulate a less amount of toxins is very important to understand the metabolism of biotoxins. The study of gene expression patterns by real-time quantitative polymerase chain reaction (RT-qPCR) may provide insights into the genes involved in detoxification metabolic pathways. One of the critical steps using RT-qPCR is that the expression results have to be normalized using internal reference genes. A systematic evaluation of reference genes in mussels has not been done yet and genes are frequently used as reference genes without validation. In this study, eight commonly used candidate reference genes have been tested as suitable in the mussel Mytilus galloprovincialis and their expression in mussels exposed to a toxic tide was studied by RT-qPCR. Their expression stabilities were evaluated using three different Excel applets (geNorm, NormFinder, and BestKeeper) which produced highly comparable results. The most suitable combination of reference genes for the normalization was glyceraldehyde-3-phosphate dehydrogenase (gapdh), 40S ribosomal protein S4 (rps4), and cytochrome c oxidase subunit 1 in digestive gland and gill and gapdh, rps4, and 40S ribosomal protein S27 in mantle. The M. galloprovincialis mrp1 and mrp2 genes were used to assess the quality of these reference genes. Our results show that some of the most widely used reference genes are not always suitable. This work underlies the importance of the validation of reference genes for each experimental situation and will be useful for the identification of genes involved in detoxification pathways in M. galloprovincialis.

Genetic and morphometric variability in mussels are the important issues that attract the attention of numerous researchers with special emphasis in recent years on hybrid occurrence and genetic introgression. Here, the genetic and multidimensional discriminant function analysis (DFA) that included morphometric traits (MT) were performed on mussels, Mytilus trossulus and Mytilus galloprovincialis, taken from the northwestern Sea of Japan (NWSJ). The analysis, based on eight polymorphic enzyme loci and two nuclear DNA markers, used samples from eight settlements in 2011 and samples from six settlements in 2012 to 2013 for a smaller set of loci but jointly with MT analysis. If the average generation length is taken as three years, the number of immigrants (Nm) per generation was estimated approximately as Nm = 5. Assuming that interspecific gene flow is from the offspring of generations such as F₂, F₃, and F_b rather than F₁, the fraction of interspecific migrants estimated as F_b F₂ etc. are equal to 0.9% ± 0.7%. The data suggest a continuing invasion of M. galloprovincialis into NWSJ. Judging from the occurrence of hybrids of all types, it is clear that rate of genetic introgression between two taxa is at a low level, varying across 14 y in the sampled Vostok Bay area from 0% in 2012 to 2013 (this study) to 8.95% ± 1.68% back in 1999. The data support the concept of a bimodal hybrid zone, with the contact zone showing a limited degree of hybridization of two species. Analysis by DFA, using GLU-5 genotypes as a diagnostic grouping variable, allows the determination of the extent to which indigenous phenotypes and hybrids differ; M. trossulus and F1 offsprings in the 2012 to 2013 data were detected correctly with a high accuracy, near 94%. Despite that, DFA showed generally weak differentiation of settlements even with the use of a combined set of traits and indices.

The populations of freshwater mussels belonging to the family Unionidae have been facing drastic changes in terms of diversity and numbers caused by constant aggressions on their natural habitat. Nevertheless, bivalves are capable of developing strategies of defense to overcome potential aggressors. The present work aimed to assess the potential antibacterial capacity of different species of unionid mussels from the north of Portugal. For this purpose, circulating cells (hemocytes), fluids, and mucus were obtained by nonlethal methods from the species Anodonta anatina (Linnaeus), Anodonta cygnea (Linnaeus), Potomida littoralis (Cuvier), and Unio delphinus (Spengler), and tested against bacterial reference strains and multidrug-resistant isolates. The cellular fraction of A. anatina, A. cygnea, and P. littoralis showed antibacterial activity, detected by the agar disc diffusion method, against Bacillus subtilis ATCC 6683, Pseudomonas aeruginosa ATCC 27853 and Acinetobacter baumannii ATCC 19606. Circulating cells from P. littoralis and A. anatina also inhibited Listeria monocytogenes ATCC 19111 and A. cygnea has also inhibited a multidrug-resistant isolate of Pseudomonas putida. The plasma of all mentioned freshwater mussels, used directly or diluted, showed great ability to hamper or inhibit the biofilm formation of Staphylococcus aureus ATCC 25923, P. aeruginosa ATCC 27853, and Escherichia coli ATCC 25922. Anodonta cygnea hampered the biofilm formation by Enterococcus faecalis ATCC 29212 as well. Overall, these results showed that not only cells play a relevant role in the immune system of these species but also the plasma, which likely contains antibiofilm substances. Anodonta cygnea stood out by presenting the best antibacterial inhibition potential.

The hermaphorodic clam Corbicula fluminea has the unusual reproduction mode of androgenesis. In fertilized eggs, all maternal chromosomes and centrosomes are simultaneously extruded as two polar bodies. To reveal the process of this unusual polar body formation, the process was observed by confocal microscopy. In particular, actin organization of oocytes labeled with anti-α- and γ-tubulin antibodies and rhodamine phalloidin were observed. The meiotic spindle was organized near the animal pole and was parallel to the oocyte surface at metaphase of the first meiosis. A thin actin layer was uniformly distributed across the oocyte membrane at metaphase. At anaphase of the first meiosis, two circular, actin-poor regions appeared where the meiotic half spindles docked. All chromosomes and centrosomes were located within the two bulges formed at anaphase in the actin-poor regions. No overlapping of microtubules was observed from either centrosome at anaphase. The centrosomes were located at the apical region of the bulges. Microtubules radiated for the bulge base. At late anaphase, around the actin-poor regions, actin accumulated and two actin rings became distinct. The diameter of these rings gradually decreased and cytokinesis occurred at the base of the bulges. Thus, all centrosomes and chromosomes were extruded together with the polar body. The present study suggests that centrosomes at the first meiosis could have the equal ability to approach and attach to the membrane and induce polar body formation.

The false mussel, Mytilopsis leucophaeata originating from the Atlantic coast and Gulf of Mexico in North America invaded brackish water systems in Europe. Seasonal sessile population structure is determined by spat fall, growth, and mortality. Juvenile and adult M. leucophaeata were kept in cages in a brackish water canal to study their mortality and to estimate annual and seasonal shell growth rate in relation to shell size and water temperature. Mortality increased with increasing temperature with the strongest effect on the 4–6 mm and 8–10 mm size classes. The average mortality of all size classes of M. leucophaeata in cage experiments was lowest in winter, increased from April to July, and peaked in July and August. Between a water temperature of 18 and 23°C, a strong growth was observed for mussels of size classes 2–14 mm, whereas mussels of size class 14–16 mm showed only a slight growth (<20 µm day^-1) and size classes 16–18 mm and 18–22 mm showed no growth at all. When water temperature was between 9 and 18°C, there was no or slight growth, and at lower than 9°C, hardly any growth. Especially for the small mussels, the influence of the water temperature on shell growth is strong. Polynomial regression showed a mean summer growth rate of 94 µm day^-1 for the 2–4 mm class, 37 µm day^-1 for the 10–12 mm class, and no growth for the 18–22mmclass. Analysis of all available (literature) data yielded mean summer and annual growth rates of M. leucophaeata collected in brackish western European harbors and canals ranging from 30 to 133 µm day^-1 and 8 to 49 µm day^-1, respectively. Increase of water temperature by climate change or thermal discharges will increase growth rates and mortality of this mussel.

Severe outbreaks of black gill (BG), heavily melanized gills of crustaceans, have been reported in white (Litopenaeus setiferus) and brown shrimp (Farfantepenaeus aztecus) from coastal Georgia and South Carolina during late summer and fall since the mid-1990s. The cause of this condition is an apostome ciliate that elicits the innate immune response of the shrimp, resulting in the formation of melanized nodules in shrimp gill tissue. In the absence of a definitive identification, the causative ciliate is referred to as the shrimp black gill (sBG) ciliate. During outbreaks, necrosis of gill tissue was often seen in microscopic sections; in some cases, there appeared to be penetration of the ciliate into gill tissue. Shrimp with BG exhibited reduced physical endurance and escape responses compared with shrimp without symptomatic BG. Physical impairment due to BG may contribute to higher predation rates and increased vulnerability to environmental conditions. The infection transmission rate of the sBG ciliate appears to be atypically low for apostome ciliates, raising the question of how epidemic levels of BG reoccur annually. Asymptomatic shrimp placed in direct contact with carcasses (heads) from BG symptomatic shrimp exhibited a significant increase in the development of BG symptoms after 7 days (P = 0.028), but waterborne transmission was not detected. A preliminary survey of sympatric crustacean species, including syntopic species of grass shrimp (Palaemonetes spp.), indicated the possible presence of the sBG ciliate, suggesting that other crustacean species may serve as infection reservoirs. These studies support the conclusion that BG is negatively impacting the penaeid shrimp fishery and highlight the challenges that remain in understanding and managing the ongoing sBG epidemic in the southeastern United States.

Common antigens and analyzed the hemocytes of the lady crab (Charybdis japonica) were studied. Chinese mitten crab (Eriocheir sinensis), Dungeness crab (Cancer magister), and red king crab (Paralithodes camtschaticus) using a laser scanning confocal microscope (LSCM), flow cytometry (FCM), Western blotting (WB), and transmission electron microscopy. In this paper analyzed hemocyte classification and immunological characteristics of the whole proteins in these species and their antisera. Four antisera positively cross-reacted, to varying degrees, with hemocytes of the four species. Two subpopulations were classified in C. japonica, P. camtschaticus, and E. sinensis and three in C. magister. The LSCM results showed that four antisera were positive with the hemocytes of the four crustacean species, respectively. Dot fluorescent signals on the hemocyte membranes show a cricoid intensive distribution. FCM analysis showed a positive rate of cross-reaction, in which the reaction of the antisera with its own hemocytes was higher than that with other species' hemocytes. The positive rate of granulocytes was always higher than that of hyalinocytes. Western blotting results showed that the four antisera mainly recognized antigens with molecular weights of about 75 or 80 kDa in the hemocytes of C. japonica, 80 or 90 kDa in the hemocytes of P. camtschaticus, 30 and 82 kDa in the hemocytes of E. sinensis, and 43 or 70 kDa in the hemocytes of C. magister. More lanes reacted between hemocytes of E. sinensis and C. magister and their antisera. The results indicate antigenic similarities among the hemocytes of the four crustacean species.

Bacteria in the genus Vibrio can be opportunistic pathogens for organisms in marine and estuarine systems. Consumption of seagrass by the blue crab Callinectes sapidus or macroalgal kelp by the lobster Homarus americanus reduced epibiotic bacteria in the Vibrio genus. Bacterial Vibrio spp. densities were estimated by colony growth on thiosulfate citrate bile sucrose agar. Nonspecific epibiotic bacterial densities were estimated by colony growth on nonselective agar or by direct counting under a fluorescence microscope. Consumption of the seagrass Ruppia maritima, but not the aquatic plant Stukenia pectinata or a control diet, reduced Vibrio spp. densities on blue crabs. A diet containing the kelp Saccharina latissima reduced Vibrio spp. densities on lobsters compared with a control diet. Results for nonspecific bacterial densities were mixed. A reduction was observed when cultured colonies were counted but not when cells were counted directly. The results suggest that diets containing seagrass or kelp can reduce epibiotic bacterial densities of some but not all bacterial species. This reduction may involve the utilization of antibacterial compounds obtained through diet and could enhance animal health by inhibiting growth of potential pathogens.

Summer mortality impacts the productivity of greenlip abalone, Haliotis laevigata, on land-based farms in South Australia. It is associated with high water temperature (greater than 23°C), low dissolved oxygen levels, increased bacterial loads, and immune system suppression during summer months. This study aimed to alleviate mortality rates of greenlip abalone by dietary intervention using vitamin K₁ to support the innate immune system and oxidative status. Dietary vitamin K₁ at 0.0, 0.5, 1.0, and 5.0 mg kg^-1 was added to a commercially formulated diet mash. An additional diet containing 0.5 mg kg^-1 of K₃ was also used for comparison. Diets were fed to 3-y-old abalone (71.51 g; 79.91 mm) at 22 and 25°C water temperatures for 39 days. No mortalities were observed at 22°C; however, high mortalities were observed in all dietary treatments at the water temperature of 25°C. Compared with the negative control diet (0.0 mg additional inclusion ofK₁ or K₃ kg^-1) at 25°C, the inclusion of vitaminK₁ orK₃ did not improve survival of greenlip abalone (P > 0.05). VitaminK₁ inclusion level resulted in significant increases in vitamin K₁ concentration of visceral organ and muscle tissues (P < 0.05). Steady-state levels of vitamin K₁ were not reached. Steady-state levels of K₂-MK-4 in visceral organ and muscle were reached when analyzed levels of dietary vitamin K₁ reached 0.02 mg kg^-1. This was also true for K₂-MK-7, but in the visceral organ only. Vitamin K₁ inclusion level did not significantly affect total hemocyte count, phagocytic activity, or phagocytic index (P > 0.05). Increasing water temperature to 25°C resulted in significant increases in serum catalase activity (22 < 25°C) and vitaminK₁ concentration in muscle tissue (22 < 25°C). Comparison of vitamin K₁ or K₃ at 0.5 mg kg^-1 resulted in significant changes to serum catalase activity (K₁ > K₃) and vitamin K₁ concentration in visceral organ (K₁ >K₃). In conclusion, vitaminK₁ at the doses tested, resulted in significant increases in vitaminK₁ concentration in visceral organ and muscle tissues, but failed to improve immune function, oxidative status, or survival of greenlip abalone at high summer water temperatures.

Previous research has shown that gut-bacterial populations in farmed abalone are shaped by ontogeny, their macroalgal diet substrates, bacteria present in the environment, and other environmental factors. It has been suggested that weaning postsettlement diatom-fed abalone onto artificial feed may alter the natural succession of bacterial establishment in their guts. The gut-bacterial composition of Haliotis midae (5–9 mm) weaned onto either a commercial formulated feed (Abfeed-S34), fresh kelp (Ecklonia maxima), or a commercial formulated feed containing kelp (E. maxima) (Abfeed-S34K) was compared. The gut microbiota of postsettlement diatom-fed abalone was dominated by Planctomycetes. Weaning to kelp or formulated feed resulted in a significant difference in the gut-bacterial communities, with the Firmicutes becoming dominant in the kelp-fed treatment and the Proteobacteria dominating in the two formulated feed treatments (analysis of similarities: R = 0.77, P = 0.02). The gut microbiota of kelp-fed abalone displayed a relatively low diversity compared with that of abalone fed formulated feeds and was dominated by fermentative Clostridia bacteria. There was no difference in gut-bacterial communities of the abalone fed commercial formulated feed with or without kelp inclusion. The dominance of the Clostridia in the kelp-fed abalone guts is explained by the large volume of fermentable polysaccharides present in macroalgae, whereas the energy-rich formulated feeds appeared to reduce the selectivity of the gut environment resulting in a relatively higher bacterial diversity.

RNA isolation from the hepatopancreas of adult abalone is challenging, as indicated by the variable results of reverse transcription-polymerase chain reaction (RT-PCR) amplification. In this study, three RNA isolation methods were tested to evaluate their usefulness in RNA isolation from various abalone tissues. Unlike the conventional method (method I), methods II and III included additional centrifugation and lithium chloride precipitation steps, respectively. RNA quality assessment based on the RT-PCR amplification of ribosomal protein L3 (RPL3) showed little difference in the quality of RNA isolated from muscle, regardless of the isolation method used. While RNA isolated from the hepatopancreas using methods I and II resulted in lower levels of RPL3 amplification, method III was found to be a more effective method of RNA extraction from the hepatopancreas, as indicated by a 30–60-fold increase in the RPL3 level. Competitive inhibition experiments using mixtures of RNA prepared by each method were performed to investigate which RT-PCR step was inhibited by materials present in the RNA preparation. An almost complete absence of RPL3 amplification was observed in RT-PCR with a cDNA template prepared from a mixture of RNAs containing a small amount of hepatopancreatic RNA isolated using method I. A drastic decrease in the incorporation of a fluorescence-labeled nucleotide into cDNA was also evident in the reverse transcription containing hepatopancreatic RNA isolated using method I. These results indicate a distinct inhibition of cDNA synthesis by materials present in the hepatopancreatic RNA preparation isolated using method I, but not present when method III is used. A competitive inhibition experiment was performed using mixtures of cDNA prepared from RNA isolated by each method to investigate whether the materials used in the preparation inhibited the polymerase chain reaction (PCR) step. The level of RPL3 amplification was proportional to the amount of cDNA prepared from hepatopancreatic RNA isolated using method III. The comparable degree of amplification regardless of the amount of cDNA prepared from RNA isolated using method I, together with the low cDNA synthesis in the latter, indicated that it had little, if any, inhibitory effect on the PCR step. This study reports an RNA isolation method that is applicable to the hepatopancreas and other abalone tissues with similar efficacy.

A total of 840 channeled (female, n = 388; male, n = 452) and 405 knobbed (female, n = 239; male, n = 166) whelks were measured for shell length (SL) and shell width (SW), with age estimates made from corresponding operculum annual growth striae readings. Gonads (ovary and testis) and reproductive structures [nidamental gland (females) and vas deferens (males)] were assessed macroscopically for maturity stage. All whelks used in this study were collected from Rhode Island state waters within Narragansett Bay, Mount Hope Bay, and Little Narragansett Bay (Pawcatuck River). Data were aggregated by species and sex, with each species treated as a single population within the study area. Age at size (growth rates) and age and size at 50% and 95% maturity were estimated for both species by sex. Female channeled whelk had the highest mean annual growth rates and reached minimum legal size quickest [minimum shell length (MSL) = 136.53 mm, minimum shell width (MSW) = 76.20 mm] and at the youngest age. Male channeled and female knobbed had similar growth rates and were the next quickest to reach MSL and MSW. Male knobbed grew slowest and were the last to enter the fishery and at the oldest age. Estimated age at 50% maturity (A₅₀) for female channeled and female knobbed was nearly the same at 8.46 and 8.35 y, respectively. Male channeled had an estimated A₅₀ of 7.35 y and that of male knobbed was 5.65 y. Estimated size at 50% maturity (SL₅₀ and SW₅₀) for female channeled was 136.8 mm SL and 77.5 mm SW; female knobbed was 124.0 mm SL and 68.4 mm SW; male channeled was 116.0 mm SL and 64.9 mm SW; and male knobbed was 89.4 mm SL and 47.7 mm SW. No instances of protandrous hermaphroditism, pseudohermaphroditism, or imposex were observed. A total of 231 newly hatched (age 0) knobbed whelks were measured for SL and SW, with mean SL and SW at age 0 included in age-at-size (growth rate) analyses.

The octopus fishery in Mexico is supported by two species, Octopus maya and an Octopus vulgaris-like species that teuthologists have named O. vulgaris type I. The main fishery species off the Yucatan Peninsula is O. maya, whereas the O. vulgaris-like species historically has supported the octopus fishery off the Mexican east coast. Management policies protect this species in the Veracruz Reef System (VRS) in the Gulf of Mexico, where artisanal fisherman catches it; however, specimens of O. vulgaris type I harvested in this reef system share haplotypes with Octopus insularis, and they cluster together in a strongly supported monophyletic clade. The species O. insularis does not belong to the O. vulgaris complex, as it was previously believed; it is related to the American octopuses, O. maya and Octopus mimus. The results indicate that O. insularis is distributed from the Gulf of Mexico to the coastal waters off southern Brazil and imply that the octopus fishery in the VRS is based on a misidentified species.

The impacts of non-native species on native ecosystems can be substantial, and effective management strategies often require a comprehensive understanding of species biology and ecology within the invaded range. The island apple snail Pomacea maculata is an invasive species known to alter the structure and function of wetland habitats. Researchers first reported island apple snails in the United States in Tallahassee, FL, in 2002 and subsequently observed this species in South Carolina (SC) in 2008. The objectives of this study were to document the spatial distribution, phenology and life history, and habitat preference of island apple snails, as well as its association with co-occurring gastropods in SC. Populations were surveyed in stormwater retention ponds throughout coastal SC, where surveyors documented the numbers of live specimens, sex ratios, and the substrate types on which island apple snails deposited egg clutches. The high abundances and year-round presence of egg clutches observed in this study indicate that these populations are successfully reproducing throughout the year, although egg clutch abundance was positively correlated with air temperature. Overall, this study found higher numbers of female P. maculata than males, and that females preferred to lay egg clutches on culverts as opposed to other available substrates. In addition to P. maculata, four other non-native gastropods were documented in stormwater retention ponds. Among these, Melanoides tuberculata and Pyrgophorus parvulus are potential vectors for multiple human diseases and had never before been reported in SC. Understanding the current distribution and life history traits of P. maculata is important for determining the potential for further spread and providing opportunities to protect healthy, natural ecosystems from the impacts of non-native species.

The marine gastropod Nassariidae is a group of edible mud snails that are distributed worldwide. Some of the nassarid species could accumulate algal toxins that cause paralytic shellfish poisoning when being consumed. Therefore, efficient classification of nassarids is important for seafood safety, yet quite challenging because of their complex morphological diversity. In this study, an approach based on cytochrome c oxidase subunit 1—restriction fragment length polymorphism was developed to discriminate six common nassarid species, including Nassarius nodifer, Nassarius conoidalis, Nassarius sinarus, Nassarius succinctus, Nassarius variciferus, and Reticunassa festiva. Specific 709-bp fragments were polymerase chain reaction—amplified, which yielded differential digestion patterns after MspI restriction, allowing unambiguous discrimination of all six targeted species. Compared with a previously published approach for determination of nassarids using DNA barcodes, the approach developed here is much more efficient and cost saving, and will be an effective way to detect paralytic shellfish toxins—accumulating nassarids in seafood market.