This study investigates for the first time the reproduction biology of Uroteuthis duvauceli in the northern Red Sea, Egypt, over 4 seasons. The sexual maturity was analyzed using the gonad condition in both sexes and by the color of the accessory nidamental glands in females. Spawning season was determined by calculating the gonadosomatic index (GSI) in both sexes as well as the nidamental gland—somatic index in females. Results showed that the spawning season is in winter and early spring. Lastly, the biochemical composition of the mantle in males and females was estimated in the 4 seasons. Lipids, protein, and carbohydrates had a significant difference between the 2 sexes (P < 0.05); however, only protein differed significantly between the 4 seasons (P < 0.05). The seasonal fluctuation of GSI showed a similar trend to the seasonal variation in various biochemical components. In addition to the total lipids and proteins, detailed profiles of each biochemical component are discussed in relation to the sexual maturity of the animal. Also, the morphometric characteristics of males and females of the squid U. duvauceli were investigated. Various body parts were found to have significant difference between the 2 sexes over the 4 seasons (P < 0.01). The analysis also showed that total length has a significant difference in relation to the mantle length between the 2 sexes (P = 0.016). The analysis of length frequency of male and female samples revealed the presence of 2 modes that are assumed to be 2 y classes.

The aim of this study was to evaluate the performance of Patagonian octopus fed with moist diets formulated with several local feed ingredients. All formulated diets were based on crab paste (70%) and the experimental feed ingredient (30%). Experiment 1 assayed salmon meal, prime sardine meal, and wheat gluten, using fresh fish as a control; experiment 2 assayed prime fish meal and macroalgal meal against crab paste alone as a control. The ingestion rate was lower than expected for all diets except those of fresh fish, crab paste alone, and crab paste plus prime sardine meal. No significant differences were found in the observed digestibility of the diets, indicating, in general, low digestibility, even for fresh fish. The highest protease values were observed for crab paste plus prime sardine meal in both experiments. The better growth of Enteroctopus. megalocyathus was obtained when these were fed fresh fish, which was associated with the greater consumption observed in this diet, as neither the digestibility nor the enzymatic activities of the hepatopancreas were related to this greater growth.

The surfclam taxon Spisula solidissima similis, known as the “southern” surfclam and as Raveneli's surfelam, was recently shown to be reproductively isolated and genetically distinct from S. s. solidissima, the commercially harvested Atlantic surfclam, at the level of species. The reported distribution for S. s. similis includes shallow nearshore marine habitats south of Cape Hatteras as well as in the Gulf of Mexico. In contrast, S. s. solidissima is larger, has a longer life span, and is found in cooler waters north of Cape Hatteras both nearshore and offshore. The current study used molecular markers to test for S. s. similis in Long Island Sound (LIS), New York, at latitude 41°N, well north of its typical range. After analyzing a diagnostic mitochondrial DNA marker in 90 surfclam specimens from 3 locations in LIS, all samples were identified as S. s. similis. The LIS sample was also significantly different in both shell shape and in the shape of the cardinal tooth than comparably sized offshore S. s. solidissima. However, these shell differences are not adequate for differentiating between these taxa in the field. The documented history of Spisula in LIS is reviewed to address hypotheses about its origin there. In addition, the fishery management implications of our findings are discussed.

Many studies have indicated that annual spawning of bay scallops (Argopecten irradians) peaks during discrete and limited periods each year. Spawning in most Florida bay scallop subpopulations has been shown to occur in fall, whereas more northerly U.S. populations typically spawn in late spring or summer. In this article we describe our efforts to expand our understanding of the seasonality of bay scallop recruitment dynamics in Florida. Visual surveys were conducted by divers each spring from 1994 to 2009 to estimate adult scallop abundance. Adult abundance was low (6.1 scallops/600 m²) during the first 3 y of the study (1994 to 1996), prompting a 7-y restoration effort intended to enhance the number of spawning adults and thereby enhance the local production of larval scallops. Adult abundances increased to an average of 21.9 scallops/600 m² in 1997 to 2006, and then rose dramatically to an average density of 154.8 scallops/600 m² in the most recent years (2007 to 2009). Artificial recruit collectors (n = 12) were deployed monthly near the Anclote River estuary beginning in 1997 and were allowed to soak for 2 mo at a time. Each collector's deployment period overlapped with the preceding and following trap's deployment period by 1 mo. The project is ongoing, but only data collected through December 2009 is included here (bay scallops recruited to the collectors during 163 of the 185 deployment periods). For the entire study period, the average recruitment rate was 0.3 scallops/collector/day, the maximum average for a single deployment period was 5.5 scallops/collector/day during November 2001 to January 2002, and the highest rate for a single collector was 19.6 scallops/collector/day during November 2001 to January 2002. In most years, the collectors retrieved in late fall and early winter had the highest settlement rate; a secondary recruitment peak was observed in the spring. A period of protracted recruitment (December 2005 to December 2009) occurred, during which scallops recruited to at least 1 of the 12 deployed collectors deployed during 53 consecutive deployment periods. The average recruitment rate for this protracted period was 0.4 scallops/collector/day; the maximum recruitment rate for a single deployment period (3.5 scallops/collector/day) and individual collector (17.7 scallops/day) occurred during December 2008 to February 2009. Early in our study, scallops were detected in a majority of our recruit collectors, and a protracted period of recruitment (October 2001 to February 2004) coincided with the multiyear restoration effort. However, the recent high adult densities and protracted period of recruitment occurred in the absence of any active restoration in this subpopulation, suggesting that, at least within the Anclote River estuary, the population has stabilized for the short term.

Oceanographic fronts and their associated physical processes create strong spatial patterns of food availability that may influence the metabolic processes of bivalves located within these areas. To investigate this prediction, we used mass-size relationships, condition indices, and carbon (C) and nitrogen (N) stable isotopes to evaluate how the biological characteristics of the Patagonian scallop (Zygochlamys patagonica) are influenced by the Shelf Break Front (SBF) and the surrounding chlorophyll a concentration (CSAT). Scallops from 2 transects across the front (38–39°S, 55–56°W, southwest Atlantic Ocean) were sampled with a nonselective dredge in October 2005. The results show that the SBF position, estimated from satellite-derived sea surface temperature, was more stable than the CSAT maximum concentrations. If muscle tissue is considered a better indicator of food shifts as previous studies indicate, scallops located far from the front have lower C isotopic signatures and C/N ratios than scallops located near the front. However, the lack of a shift in scallop organ conditions suggest that spatial differences in food supply are not strong enough during the time of year we sampled to impact scallop development, as may happen at a seasonal scale. Our results show that complicated interactions exist between oceanographic structures, food supply, and scallop life history characteristics.

Artificial collectors deployed in May and early June obtained higher numbers of Aequipecten opercularis spat than when collectors were deployed in late June and July in both 2007 and 2008. Different recruitment patterns were found in the 2 y studied. Four successive cohorts settled in both 2007 and 2008; however, in 2007 the 4 cohorts settled over short periods of time, whereas in 2008 a single cohort settled for an extended period of time and produced most of the spat of the year. The effectiveness of collectors for spat settlement decreased after 2 mo. Spat showed a fast growth rate that was density dependent. In general, the survival rate was high, mainly because there were very few predators.

In this work we describe a simple methodology to assess the availability of quality gametes throughout the year to perform technological assays. This methodology was applied to the evaluation of the reproductive seasonality of Crassostrea gigas from October 2007 to November 2008 in the western Mediterranean coast (Burriana, Spain). Gonad maturation degree and sex were assessed. When both gametes were present, fertilization assays were performed. The percentage of differentiated males increased from January to February (1%) to July to August (62%). Females presented the same tendency, also reaching maximum values in July to August (32%). Both males and females showed a significant degree of maximum gonad maturation in July to August. Both gamete types could only be obtained from March to October, normal larvae being observed only from July to October. Breeding periods established in this work coincided with those reported by other authors in different Mediterranean and Atlantic coastal regions. These results indicate that oysters from different origins and maintained in natural conditions are an alternative to performing laboratory studies or assays, but only in the months from July to October.

Spat of Pacific oysters (Crassostrea gigas) were collected from Gamakman Bay, Korea, and raised in a spat hardening facility located in the low intertidal zone of the bay for a “hardening/stunting” period of 10 mo. Seasonal changes in growth, reproductive condition, and digestive tubule atrophy (DTA) of these “hardened/stunted” oysters were monitored for more than a year after transplanting to a suspended longline system in a grow-out area in the bay. After transplantation, the hardened/stunted oysters showed a logarithmic increase in shell size for the first 4 mo, from June to October, and growth remained stable from late fall to early spring. During the 12 mo of the grow-out, the shell size of the hardened/stunted oysters increased from 15.4–74.2 mm, and tissue weight increased from 0.49–12.85 g. Histological analysis revealed that gametogenesis of hardened/stunted oysters commenced as early as February when water temperature remained at 10°C, and spawning occurred from July to September when water temperature reached 25–27°C. DTA assessed from histological analysis was higher from September to February, when the chlorophyll a level in the bay was lower. These data suggest that seasonal fluctuations in water temperature and food availability in the water column are the 2 main environmental parameters governing reproduction and growth of oyster in Gamakman Bay, and DTA could be a useful biomarker for monitoring the nutritional condition of oysters.

This study reports mortality under laboratory conditions in unselected controls and 2 lines of juvenile Pacific oysters Crassostrea gigas previously selected for their high or low survival in the field during the summer period. Oysters were also deployed in field conditions, and mortality between both conditions was then compared. In the laboratory, mortality was observed in all experiments and it always lasted for a week, indicating that mortality under laboratory conditions was a short-term event. It was also shown that mortality could be repeated for a batch in several experiments using oysters that never experienced any abnormal mortality. This approach could facilitate further studies to investigate the causes of mortality by allowing repeated trials during a summer. Differences in mortality between the resistant and the susceptible selected lines confirmed the positive response to selection under laboratory conditions. Batches that performed well in the laboratory also showed high survival in the field, and the results of those exhibiting low survival in the laboratory trials were also mirrored in the field. Finally, challenging oysters with heat stress is proposed as a useful method for estimating the survival capacity of hatchery-produced and wild-caught spat used by the oyster industry.

To resolve the taxonomic status of a small cupped oyster from southern China, we collected and sequenced oysters from 20 sites in China along with sister species from other parts of the world. A total of 187 oysters were sequenced for 2 fragments belonging to the mitochondrial 16S rRNA and cytochrome oxidase I (COI) genes. Sequence analyses of both gene fragments indicate that the small cupped oyster from southern China is the same species as Crassostrea angulata from Portugal. C. angulata has a wide distribution in southern China, ranging from Zhejiang to Hainan, with the Yangtze River separating it from Crassostrea gigas in northern China. The wide distribution and high gene diversity in China support the suggestion of a historical transfer of C. angulata from China to Europe. Sequence divergence between C. angulata and C. gigas, 1.05–1.32% in 16S and 2.22–3.37% in COI, is higher than that between the most divergent populations of a Crassostrea species (C. virginica, 0.51% in 16S and 2.04–2.22% in COI), but considerably lower than that observed between two closely related sister species (2.11–2.37% in 16S and 9.32–10.11 % in COI, between C. gigas and Crassostrea sikamea). This finding and the fact that the two oysters live in the same region with slightly different biological characters but can hybridize without any difficulties suggest that C. angulata should be considered a subspecies of C. gigas.

The Piankatank River is a trap-type estuary on the western shore of Chesapeake Bay that has been managed for seed oyster production since 1963. Market oyster production in the river is minimal. Repletion efforts include shell planting and seed removal. We describe sequential changes in population demographics and habitat in relation to repletion activities on eight Piankatank River public oyster reefs from 1998 through 2009. Two reef groups (northern and southern) may be distinguished by density (oysters/m²), biomass (g dry tissue weight), and shell volume (L/m²) data. Age-at-length relationships were estimated from demographic data using a quadratic model. Observed mortality rates were high, and age 3 oysters were essentially absent. A strong recruitment signal was observed in 1999 and 2002. Between 1998 and 2009, about 30% of the live oysters in the river were harvested as seed, corresponding to ∼7.5% of the total shell base in an average year. Typically, for every 5 bushels of shell planted, 1 bushel of seed was harvested (20% return). Even with shell planting (∼10 L/m²/y), the river shell budget showed a deficit with respect to the accretion rate required to balance sea level rise and natural degradation processes. During the study period, the mean river recruit-to-stock ratio was ∼4. The unusual and consistently high recruit-to-stock ratios suggest that management for modest continuous seed removal may be accomplished without shell planting. Annual stock assessment to identify low recruitment years is recommended as a method to adjust annual seed harvest quotas.

The substantial decline of eastern oyster (Crassostrea virginica) stocks along the east coast of the United States has prompted the growth of many types of restoration and enhancement efforts. One of the most recent types is oyster gardening. Oysters grown in floating structures are subsequently planted in bays, where they continue to live, grow, and spawn; filter the water; contribute to the larval pool; and provide habitat. Our study is one of the first evaluations of habitat value provided by floating oyster gardens in a degraded mid-Atlantic estuary. Oyster growth and survival within the floats was monitored in a eutrophic, turbid, periodically hypoxic, soft-bottom coastal lagoon system. We examined the abundance and diversity of fishes and invertebrates with respect to 3 replicated treatments: live oyster clusters, disarticulated oyster shell, and a float with no shells or oysters. We also studied the effects of 2 cleaning frequencies (biweekly and monthly) on species assemblages, and the growth and survival of oysters, and monitored basic water quality parameters. The species assemblages in floats with oyster clusters were very similar to those with loose shell but considerably different than that of empty floats. Cleaning frequency (biweekly and monthly) did not affect the growth or survival of oysters. Location of floats within the canal system, however, was a large determinant of oyster vital rates as well as community structure. Forty-nine species of fishes and invertebrates, and 8 species of macroalgae were collected from floating oyster gardens, including 9 commercial or recreational fishery species, many of which are likely habitat limited in the Inland Bays because of the loss of tidal wetlands, oyster reefs, and seagrass beds. Newly settled juvenile oysters have been found for the first time within the floating oyster gear in the manmade, residential canal systems. Our results will be used to gauge the success of enhancement efforts and to improve our understanding of the effects oyster gardens on the Inland Bays ecosystem.

The boring sponge Cliona celata poses an ongoing threat to the quality of eastern oysters Crassostrea virginica cultured in Baie St-Simon, Shippagan, New Brunswick, Canada. Although grown primarily off-bottom, 25–30% of cultured oysters develop severe sponge infections, leading to the culling of otherwise marketable individuals. The main objectives of the current study were to identify the areas with the highest prevalence of infected oysters, determine the primary mode of sponge infection, document the rate of shell bioerosion, and develop an effective treatment for eliminating the sponge without harming the oysters. A bottom survey of wild oysters throughout the bay indicated a high prevalence of sponge infection in certain areas, possibly related to seasonal salinity patterns. No evidence of sponge infection via shell-to-shell contact, or proximity to wild oysters, was detected during the winter months when oyster shells were deployed in bags lying on the bottom. Histological sectioning of sponge tissues in severely infected wild oysters revealed the presence of developing gametes in early June, mature eggs and sperm from mid June to mid July, and empty follicles in late July. Larvae were never successfully identified in plankton tows, but the sequential deployment and retrieval of experimental shells corroborated that June/July was the peak infection period. By the end of October, single infections measured approximately 0.05–0.10 cm², with evidence of shell bioerosion and papillae development. Monitoring of sponge growth in 70–90-mm shells (upper valve) indicated that a 5-cm² infection will grow at a rate of approximately 15 cm²/y, rapidly occupying the 21-cm² valve of a marketable oyster (64-mm shell length). Comparison of various treatment strategies indicated that a 6-min brine dip (>90% NaCl saturation) was completely effective at eliminating the boring sponge without harming the oysters. A program of brine dipping every second year appears to be sufficient to control the development of this pest organism in cultured oysters.

Microhabitat availability resulting from spatial complexity on oyster reef allows niche overlap and enhances benthic-pelagic coupling within a localized area; however, in Georgia, little is known regarding the temporal succession patterns of resident species on constructed reef. The purpose of this research is to evaluate the development and relative habitat value of man-made oyster habitat by monitoring oyster growth and the colonization by structurally important and resident oyster reef community species. Sixteen sampling units of commercial spat sticks in densities of 81/m² were deployed prior to the oyster reproductive season during April 2004. Two sampling units were extracted every 3 mo starting July 2004 and assessed for biomass; oyster shell height and growth rate; oyster, barnacle, and mussel density per 0.01 m²; and species and phyla richness. Maximum oyster growth rate (0.39 mm/day) occurred during January 2005, with mean oyster shell height peaking at 83.56 ± 1.31 mm by May 2005. Oysters, barnacles, and scorched mussels appeared concurrently on sampling units during July 2004, and ribbed mussels appeared in October 2004. There were significant positive relationships between oyster and mussel (ribbed and scorched) densities (P < 0.0001), but none were detected between oyster and barnacle densities. Reef species rapidly colonized sampling units (24 of 31 species by October 2004), and a significant correlation between biomass and species (R² = 0.91) and phyla (R² = 0.96) richness was observed. Settlement and optimal growth of structurally important species on vertically elevated man-made oyster reef enhanced habitat availability and supported rapid colonization of reef-associated species.

Comparisons of historical surveys and fishery data have led to the popular belief that during the past century, more than 90% of oyster habitat has been lost through overfishing, disease, storms, and alterations to water quality and natural flow in the state of Georgia. Using handheld GPS computers, we conducted an on-the-ground inventory of living intertidal oyster reefs at four separate locations, and have concluded that previous surveys were not comprehensive or accurate enough to facilitate a reliable quantitative assessment of habitat loss. Alternatively, we have shown that intertidal oyster reefs are remarkably resilient and may occur in greater abundance today than when first documented in 1891. Rather than a collapse of oyster stocks, declining trends in fishery landings reflect the social and economic challenges associated with an unsustainable canning industry during the early 20th century. In addition, we challenge the axiom that the condition of existing intertidal reef habitat has deteriorated. Areas of shell deposits attributed to exhausted beds in historical assessments may in fact represent naturally occurring coastal features. Nonetheless, enhancement and conservation efforts are worthy efforts, because intertidal oyster habitat increases the health and resiliency of coastal Georgia by providing essential fish habitat, flood control, erosion abatement, and pollution reduction services. We propose that detailed GIS inventories like the ones conducted in this study can establish accurate baseline data to document reliably future changes in distribution, abundance, and condition, particularly with respect to the growing threats from development, sea level rise, and ocean acidification.

Although the top shell Turbo (Batillus) cornutus (Turbinidae) is a well-known and industrially important shellfish species in Japan, the diploid chromosome number and karyotype of this species have not been previously elucidated. In this study we investigated the diploid chromosome number and performed karyotype and fluorescence in situ hybridization (FISH) analyses of the telomere sequence on chromosomes of T. cornutus. A diploid chromosome number of 36 was identified in larval somatic cells, and the karyotype comprised 16 pairs of metacentric and 2 pairs of metacentric/submetacentric chromosomes. In the telomere FISH analysis using a vertebrate telomere probe, fluorescein isothiocyanate-positive hybridization signals were clearly observed on the telomeric regions of the chromosomes. This result suggests that the FISH technique is appropriate for other Turbinidae species and that the telomere sequence of T. cornutus is (TTAGGG)n, which is the same as that of vertebrates.

This study identified the most suitable fluorochrome to mark prodissoeonch of larval Siphonaria australis, a common pulmonate gastropod commonly found on rocky shores throughout New Zealand. The pulmonate habit of laying attached larval egg masses makes them an excellent candidate for studies of larval connectivity using chemical staining methods. Larval S. australis egg masses were immersed in 200 mg/L of either alizarin red S (ARS), calcein, or Oxytetracycline (OTC) for 24 h before viewing under ultraviolet light to allow quantification of mark brightness using image analysis software. Counts of pre- and postimmersion mortality were also made to identify any fluorochrome toxicity to S. australis larvae. Calcein was found to be the most suitable fluorochrome to use when fluorescently marking larval S. australis, because average brightness was significantly greater than either ARS or OTC, with negligible mortality levels recorded for calcein. The results show that fluorochromes can penetrate the gelatinous egg matrix and the larval capsules, thus providing an opportunity for staining large numbers of these species for alongshore connectivity studies.

The genome size of the abalone Haliotis midae was determined using flow cytometry and calculated relative to the known genome size of the rainbow trout (Oncorhynchus mykiss). The C value for H. midae was estimated to be 1.43 pg, which is smaller in comparison with other abalone species with the same number of chromosomes (2n = 36), namely H. corrugata, 2.14 pg; H. rufescens, 1.82 pg; and H. fulgens, 1.71 pg. In these Californian abalone species, a positive correlation between C value and the number of metacentric/submetacentric chromosomes with a subsequent loss of submetacentric/subtelocentric chromosomes was observed. Karyotypic analysis in H. midae indicates 6M 10SM 2 ST (metacentric submetacentric subtelocentric) chromosome pairs, the lowest number of metacentric and the highest number of subtelocentric chromosomes when compared with the Californian species. This pattern, in the light of recent phylogenetic and cytogenetic evidence, leads us to hypothesize that during the evolution of the genus, there were some preferential karyotypic rearrangements. Research on the genome size of other abalone species in general and specifically South African species, combined with chromosome banding techniques, could provide more insight into the evolution of this genus.

In abalone farms and laboratories of the Baja California peninsula in Mexico, young and postlarval abalone feed on benthic diatoms that grow on the artificial surfaces of the culture tanks, or on epiphytic diatoms growing on kelp (Macrocystis pyrifera) blades provided when a change in their diet is estimated. It is not known whether grazing selectivity occurs by postlarvae and young abalones at this time. Thus, experiments were conducted to determine whether discrimination by juveniles of red abalone (Haliotis rufescens) occurs while grazing on diatoms that grow on the rocks and kelp blades extracted from their habitat, and to determine whether the ingested diatoms are, indeed, digested. Our hypothesis was that juveniles of H. rufescens would feed nonselectively on the diatom films; thus, the characteristics of the diatom assemblages (species composition, diversity) from their gut contents should be similar to those upon which they feed. We also expected that the smaller forms of diatoms would pass through the digestive tract intact. Overall, 171 diatom taxa were identified: 123 in the tank walls, 35 on the rocks, 143 in the gut contents, and 38 in the feces. Only Amphora pediculus appeared in all the gut contents examined; however, 12 taxa accounted for 80% of the relative abundance (n = 500). Highest diversity ( = 4.46) was measured in the walls of a tank where M. pyrifera was included, but abalone specimens from this tank showed the lowest H' value in their gut contents. The hypothesis that grazing by young H. rufescens is nonselective is supported, as well as the importance of the structure of the diatom assemblage grazed upon (as in H. fulgens), which is reflected in their gut contents. Moreover, feces analysis showed that many small diatoms that are ingested are not digested, and are able to reproduce and grow after passing through the digestive tract.

The abalone, Haliotis tuberculata coccinea has been considered in the Canary Islands as a potential candidate species for aquaculture to restock its natural ecosystem. Because the study and development of artificial culture techniques require as much information as possible on natural populations, 20 monthly H. tuberculata coccinea samples were collected in the island of Gran Canaria between June 2005 and May 2007. Reproductive biology was assessed by histological techniques, and von Bertalanffy growth parameters were also estimated. Ovarian morphology of H. tuberculata coccinea showed 6 sexual cell stages during the oogenetic process and a group synchronous ovarian development. Its reproductive cycle is characterized by an annual spawning period throughout the entire year, although the maximum reproductive activity of this population was observed between August and February. Batch fecundity ranged from 85,749 (shell length (SL), 39 mm)-691,456 (SL, 62 mm), and a significantly higher fecundity rate was observed in individuals with an SL larger than 55 mm, suggesting that, to optimize egg production, this is the minimum broodstock size to be used in hatcheries. With regard to the population structure, the overall maleto-female ratio was 1:1.02 and the data of the size class analysis did not show any tendency. The von Bertalanffy growth parameters estimated for females and males were 72.5 and 78.8 mm in SL of asymptotic length, and 0.43 year^-1 and 0.37 year^-1 of growth rate.

The shell microstructure of freshwater bivalve Anodonta cygnea was observed from the ventral margin toward the intrapallial regions by scanning electronic microscopy during the spring/summer period. The three main structures—the periostracum, prismatic, and nacreous layers—were visualized in a sequential path from the ventral margin toward the intrapallial regions. Although with always the same calcium carbonate polymorph (aragonite), A. cygnea presented composites of aragonite crystals embedded within an organic matrix displaying varied morphologies and structural arrangements. The prisms of the prismatic shell layer are composed of single-crystal fibers radiating from spheruliths, whereas in the nacreous layer the structure is similar to that of a brick wall, with tablets in each layer offset with respect to those in the layers above and below them. From the shell ventral margin, the last nacreous lamina formed exhibit crystals with rounded forms, followed by rhombic and hexagonal shapes toward the interior with irregular microstructure. There are gradual intermediate forms between these distinct shapes. This study offers a description of the inner calcareous mineralized layers of A. cygnea and will be useful for future comparative studies in several research areas such as phylogenetic evolution, ecotoxicology, and the influence of environmental and physicochemical factors on the shell formation process in freshwater bivalves.

In this study, for the first time, using similar methods, we compared the population density and distribution across different substrate types of Limnoperna fortunei and Dreissena polymorpha, as well as their impacts on the composition of benthic communities. Data on L. fortunei were obtained in Rio Tercero Reservoir, Argentina, whereas studies on D. polymorpha were conducted in North America and Europe. We found that, similar to the zebra mussel, L. fortunei creates high densities on hard substrates in the littoral zone, and avoids soft substrates in the profundal zone; however, the overall population density of L. fortunei in a water body seems to be higher than that of zebra mussels. Additional studies on Limnoperna are needed to confirm this hypothesis. The effect of L. fortunei on macrobenthos is very similar to the effect of D. polymorpha and is associated with an increase in the overall diversity, density, and biomass of native macroinvertebrates in druses compared with bare sediments. The presence of L. fortunei druses in the littoral zones of Río Tercero has increased the average species richness of native benthic invertebrates per sample by almost 70% and their density and biomass by threefold, positively affecting epifaunal organisms and negatively burrowing invertebrates and unionids. In the near future, the freshwaters of North America may be colonized by L. fortunei, resulting in strong impacts on entire invaded ecosystems and devastating impacts on native unionids, especially in the southern regions of the United States, which are not colonized with dreissenids.

In the current study, bacteria were identified in zebra mussel samples collected from the Huron River, Crystal Lake, and Vineyard Lake, Michigan. Bacteria were identified by sequencing the 16S ribosomal RNA gene of amplified community bacterial DNA extracted from mussel homogenate samples. More than 170 zebra mussel bacterial 16S gene sequences were checked for similarity to 16S sequences contained in the Ribosomal Database Project and BLAST public databases. Analysis demonstrated the presence of 27 bacterial genera belonging to 12 subdivisions in tissues of zebra mussels collected from the 3 locations. Potentially pathogenic bacteria for aquatic and terrestrial animals, like Aeromonas spp., Flavobacterium spp., Pseudomonas fluorescens, Shewanella putrefaciens, and Shigella sp. were also detected in mussel homogenates raising concerns that this invading mussel may play a role in disease ecology. Data generated in this pilot study constitute the first account of bacterial community composition in the zebra mussel in Michigan waters and underscore the need to understand better the bacteria-host relationship in invading dreissenids in their new environment in the Laurentian Great Lakes.

The gonadal organization and cytological characteristics of gametogenesis in a population of the freshwater clam Musculium argentinum (d'Orbigny, 1835) are described. Sections of the rather small gonad demonstrate the existence of hermaphroditic specimens, and is composed of hermaphrodite follicles among the intestine coils in the posterior dorsal region of the body. Follicles contain male and female germ cells at different stages of maturation, which can be recognized by their shape, size, and nuclear features. Male germ cells are organized in cysts, and spermatocytes do carry out meiosis. Within follicles, male and female germ cells occupy different regions. Gonad activity throughout the year is coincident with the life cycle pattern of the M. argentinum population studied previously.

Blue crabs (Callinectes sapidus, Rathbun 1896) were sampled with commercial crab pots on Shell Bar oyster reef in the Great Wicomico River, VA, from May through October during 2006 and 2007. Weekly catch per unit effort (CPUE), sex ratio, and size (carapace width, measured in millimeters) were evaluated in the context of water temperature (measured in degrees Celsius), salinity, and daylength (measured in hours) conditions on the reef. The total number of crabs collected in 2006 and 2007 was 5,221 and 3,303, respectively. Blue crab CPUE was highest from mid-June through mid-September at water temperatures at or more than 26°C, with maximum CPUEs observed in late July. The overall annual ratio of females to males was 0.47 in 2006 and 0.60 in 2007. Males made up more than 50% of the catch at Shell Bar reef from May through August. The observed sex ratio shifted from male dominated to female dominated as salinity increased, whereas water temperature and daylength decreased seasonally. Female crabs (median carapace width (CW), 142–144 mm) were approximately 20 mm in CW larger than males (median CW, 125 mm) in both years. Annual average CPUE (13.42 crabs per pot; SE = 1.57) and maximum CPUE (32.06 crabs per pot) was twice as high in 2006 as it was in 2007. The observed interannual differences in crab CPUEs may be the result of an enhanced forage base on the reef in 2006 relative to 2007. Approximately 9 million cultchless oysters (40–80 mm in shell height) were planted on Shell Bar reef between May and October 2006 as part of a concurrent oyster rehabilitation program.

Laboratory experiments were conducted to evaluate how water temperature mediates the cannibalistic relationship between age 0 and age 1 red king crab (RKC) (Paralithodes camtschaticus), and the role of habitat structure in providing refuge for prey. We also observed the activity levels of age 1 crabs under light and dark conditions, and predator avoidance behavior by the age 0 crabs. Age 1 crabs (15–20 mm in carapace length (CL)) were active 24 h/day, but motion was about 33% higher in light than in dark conditions, and increased in direct proportion with water temperature (2–10°C). Feeding rate was also directly related with temperature for age 1 crabs, which consumed 7% of body weight per day at 2°C, and 20% at 10°C. Both temperature and habitat complexity had significant effects on survival of age 0 RKC (CW, 2.2–2.6 mm) when exposed to age 1 crabs (CL, 17–19 mm), with no significant interaction. Survival diminished 31% in a linear relationship from 2–10°C, and was twice as high in a complex structural environment compared with bare sand habitat. Predator avoidance behavior by age 0 RKC improved from juvenile molt stage 2 to stage 4. Increasing water temperature may serve to increase mortality by cannibalism in RKC, both in aquaculture and in the field, but survival will increase substantially in structurally complex environments.

Clinical biochemistry is the measurement of body fluid constituents, and is considered an integral component of disease diagnosis in human and veterinary medicine. Biochemical reference intervals are the ranges of values of specific analytes at the population level that are expected to encompass 95% of “normal” individuals. However, how do we define a “normal” lobster? Homarus americanus (H. Milne Edwards, 1837) is a sublittoral ectotherm with a limited homeostatic ability to adapt to rapid environmental changes. An experiment was designed to measure the changes that may occur in selected analytes as wild lobsters “acclimate” to captivity. Biological variation was minimized by the maintenance of strict environmental conditions, uniform life stages, nutrition, and molt status. The results of this experiment suggest that elevations in hemolymph levels of glucose, L-lactate, crustacean hyperglycemic hormone, ammonia, ionic calcium, and a decrease in ionic potassium may be indicative of the stress associated with capture, handling, and emersion hypoxia. Although the data demonstrate a considerable intraspecific variation in most analytes during the acclimation process, these reference intervals may be useful in the interpretation of clinical findings in lobsters held in captivity for research or exhibition in public aquaria.

We investigated a noninvasive sampling technique that estimates fecundity for ovigerous American lobster based on field measurement and live release. These estimates were compared with fecundity estimates obtained from the widely used traditional invasive technique involving the removal, drying, and weighing of the entire egg mass. The noninvasive technique, which requires the removal of only 10 eggs per female, produced fecundity estimates that were within 4% of those obtained using the traditional invasive method. Applications of this technique may be carried out in an experimental setting where the effects of conservation measures such as v-notching or the establishment of closed areas, aimed at increasing egg production, can be quantified without the use of destructive sampling techniques.

This study examined the effects of ration and temperature on the molt of male adolescent snow crab Chionoecetes opilio (O. Fabricius, 1788). In one experiment, crabs were exposed to 1 of 4 treatments, 2 levels of ration and 2 levels of temperature. In a second experiment, all crabs were fed and a 4-level factor was addressed in which temperature was held constant as in experiment 1 (2 levels) or switched from one level to the other. Food consumption declined significantly and at a similar rate over time at both temperatures, several weeks before molt took place. Larger crabs molted to morphometric maturity in a greater proportion with no influence of ration or temperature. Smaller crabs also molted earlier than larger crabs. Temperature had a marked effect on the timing of molt, with crabs kept at a higher temperature molting 1 mo earlier and crabs exposed to shifted temperatures, molting midway between the two other groups. Body density decreased markedly at ecdysis, but was also influenced by ration and temperature particularly in nonmolters; the effect of ration on body density in nonmolters was highly significant. Ration also had a major effect on the size of muscle and digestive gland and their moisture content. Unfed nonmolters were in poor condition, particularly at a higher temperature, whereas molted crabs had large digestive glands associated with high moisture contents, irrespective of treatment. Timing of the migration of snow crabs to shallow and potentially warmer waters in the spring in the Gulf of St. Lawrence might be determined in part by molt requirements. Cold temperatures provide an energetic advantage during the premolt period, when food consumption decreases, but high temperatures result in an earlier molt and a fast recovery during the early postmolt period.

A 4 × 4 factorial experiment was conducted to determine the effects of low salinity (0.2, 3, and 6; and the control salinity, 21) and low temperature (7°C, 9°C, and 11°C; and the control temperature, 25°C) on survival, growth, and energy budget of juvenile shrimp Exopalaemon carinicauda. The duration of the experiment was 60 days. Results showed that E. carinicauda juveniles have a greater ability to survive extreme salinity conditions at temperatures of 11–25°C, and their capability to withstand temperature extremes was greater at salinities of 3–21. The specific growth rate, food consumption, feed efficiency, and apparent digestibility coefficient of E. carinicauda showed remarkable increase paralleled with salinity elevation. Similarly, the specific growth rate, food consumption, and apparent digestibility coefficient of E. carinicauda also exhibited significant increasing tendency as the temperature rises. However, feed efficiency is found to be decreased with elevated temperature. In general, the shrimp maintained at the control salinity (21) and control temperature (25°C) had a significantly higher specific growth rate, whereas those maintained at a salinity of 0.2 and a temperature of 7°C exhibited a significantly lower value. The pattern of energy allocation is found to be varied in accordance with salinity and temperature, inasmuch as 68.46–78.98% of consumed energy was lost through respiration, 5.37–13.70% was invested in growth, 8.02–13.28% was for feces production, 4.55–5.83% was for excretion, and only 0.62–0.73% was for exuviae. The current study also reveals that there is an increased tendency for percentage of intake energy invested in growth (the energy value expressed as the percentage of intake energy, %C), whereas that lost in excretion and feces (%C) exhibited a remarkable decrease with increase of salinity. The percentage of intake energy invested in growth and lost in feces (%C) showed decreased trends, whereas that lost in respiration and excretion (%C) is found to be decreased as the temperature is elevated. As far as the pattern of intake energy allocation is concerned, it was apparent that salinity affects the growth of E. carinicauda juveniles mainly by influencing energy conversion efficiency, whereas temperature affects primarily food consumption and energy conversion efficiency as well. The interaction of low salinity and low temperature on survival and growth of E. carinicauda were also discussed.

Copper is an essential micronutrient in the diets of animals. It is a component of many enzymes involved in energy production, participates in immune function, and protects cells from free radicals. However, excessive levels in the diet can be toxic. Small (∼13 g wet weight) Lytechinus variegatus were fed formulated feeds with 12, 36, or 114 mg Cu/kg for 12 wk (levels based on established dietary levels for other marine invertebrates, supplemented as CuSO₄·5H₂O). Under these experimental conditions, wet weights of individuals fed a 36-mg Cu/kg diet were slightly higher (43.2 ± 1.2 g (SEM); P = 0.069) than those fed a 12mg Cu/kg and 114-mg Cu/kg diet (39.9 ± 1.2 and 40.3 ± 1.7 g wet weight, respectively). Ovary and gut wet weights were significantly lower (P < 0.003) in the 114-mg Cu/kg diet than the 12-mg Cu/kg and 36-mg Cu/kg diets (7.24 ± 0.75 g, 8.11 ± 0.55 g, and 4.99 ± 0.32 g ovary wet weight and 0.97 ± 0.04 g, 1.07 ± 0.06 g, and 0.83 ± 0.04 g gut wet weight for the 12-, 36-, and 114-mg Cu/kg diets, respectively). Mature gamete formation in ovary and testis was inversely correlated with dietary copper level. Acini from the ovaries and testis of urchins in the 36-mg Cu/kg and 114-mg Cu/kg diet treatments had a greater area occupied by nutrient phagocytes than urchins on the 12-mg Cu/kg diet. In diets containing low dietary copper (12 mg Cu/kg), survivorship decreased from 100% to 87%. These data suggest that dietary copper is essential for normal physiological function but can be detrimental for certain physiological processes at high levels. This information will help in the development of formulated feeds for sea urchin aquaculture.

A 4-wk rearing trial of the sea urchin Paracentrotus lividus was carried out in a closed-circuit system in the presence and absence of food supply to evaluate the short-term response of gametogenesis to different feeding conditions. At the end of the trial, the gonad index (GI) was calculated, histological analyses of the gonads were performed, gamete fertilization ability was evaluated, and sperm motility was assessed by computerized motility analysis. Starvation significantly affected gametogenesis, whereas developing gametes were always observed in fed animals, whose GI had doubled by the end of the 4-wk trial. No differences were recorded between gametes from reared (fed) urchins and wild-collected ones. Although spent gonads frequently contained unspawned motile spermatozoa or morphologically intact eggs, the fertilization ability of gametes from starved urchins was significantly lower. It may be concluded that, although they were at the end of the reproductive season, the specimens fed ad libitum were able to reactivate the gamete maturation process immediately. This ability can be used in short-term procedures for roe enhancement and gamete production, particularly for specimens from areas in which environmental conditions determine slow gametogenesis and a consequently short reproductive season.

Lipophilic shellfish toxins (LSTs) produced by dinoflagellates, including Dinophysis spp., can accumulate in bivalves. The seasonal variability of LSTs in bivalves and waters, and the abundance of Dinophysis spp. were investigated in Jinhae Bay, Republic of Korea, in 2007. Diarrhetic shellfish poisoning (DSP) such as okadaic acid and dinophysistoxin-1, and other lipophilic toxins such as pectenotoxin-2 (PTX2) and yessotoxin were analyzed by liquid chromatography—tandem mass spectrometry (LC-MS/MS). The toxin concentration in size-fractionated plankton material (20–100 µm in size) concentrated from a specific volume of water was converted into the toxin contents per unit volume of water. Among the genus Dinophysis, only D. acuminata was observed. The seasonal variability of okadaic acid, dinophysistoxin-1, and PTX2 per unit volume of water paralleled that of the abundance of D. acuminata. The cellular content and profile of toxins in D. acuminata varied, but PTX2 was mostly the dominant toxin. The toxins in the hepatopancreas of mussels (Mytilus galloprovincialis) were found from spring to autumn, and relatively high levels of toxins were detected in summer (June to August). Variation of the toxins in the hepatopancreas of mussels was remarkably consistent with both abundance of D. acuminata and toxin concentration in the water. Our results suggest that LC-MS/MS analysis of toxin in plankton concentrates has the possibility of becoming an alternative to or complement of the conventional microscopic method in toxic phytoplankton monitoring.

Although spirochetes were first detected in crystalline styles of bivalves more than 100 years ago, little is known about the characteristics of these consortia (commensalism or parasitism). The presence of spirochetes in bivalves can so far not be generalized. The purpose of this study was the detection and phylogenetic identification of spirochetes associated with crystalline styles of different marine bivalve species collected in temperate regions and Antarctica. Polymerase chain reaction amplification of spirochete 16S ribosomal gene sequences was performed. 16S ribosomal gene clones were identified by phylogenetic analysis, and the variability within each bivalve species was determined. The spirochetes were mainly related to yet uncultured or potentially pathogenic spirochetes from the marine environment. All identified spirochete clones fell into 2 families: the Spirochaetaceae with 2 genera, Cristispira and Spirochaeta, and the Brachyspiraceae, with the genus Braehyspira. The diversity of spirochetes in the crystalline style of each bivalve species was low. All clone sequences from crystalline styles of the oyster Crassostrea gigas clustered into the group of Cristispira species. Interestingly, these Cristispira spirochetes were previously found in Crassostrea virginica, another oyster species. The spirochete clones of each bivalve species formed distinct clusters. We therefore assume that the investigated bivalve species harbor distinct populations of spirochetes. Although spirochetes were not found in all the investigated samples, the occurrence of spirochetes was not random and implies a closer association between the bivalve species and the specific spirochete cluster.