Over five million spat of the king scallop, Pecten maximus (L.) were collected accidentally in the North Water of Mulroy Bay in County Donegal, Ireland in the summer of 1979. This large natural settlement, by far the greatest number obtained at the time in any European trial, led to research investigations in 1980 and 1981 to support the development of this site as a scallop spat collection center. A combination of gonad monitoring, plankton sampling, spat settlement and spat collection trials were used to develop a technique for predicting the date of the scallop spatfall to maximize the yield of scallop spat. A technique for forecasting the date of peak spatfall involving installation of spat collectors when the mean shell length of scallop larvae was 180 μm and 50% of the larval cohort exceeded this size was developed. Unlike other sites studied, peak spat collection occurred at 4 m beneath the water surface. Since its development, this technique for prediction of the date of the peak collection has been used commercially, and for illustrative purposes data from 2002 have been provided. The development and application of this forecasting technique has assisted in the collection of millions of scallop spat for ongrowing trials by the scallop culture industry.

Heterosis between two stocks (A and B) of the bay scallop Argopecten irradians irradians (Lamarck, 1819) was studied by comparing performance in hatching success, larval survival, larval, spat and adult growth of reciprocal hybrid crosses (AB and BA) and that of two parental groups (AA and BB). Stock A is derived from the initial 1982 introduction from Connecticut, USA and expected to be highly inbred because of the small founder population (26 individuals) and the long breeding history (20 generations). Stock B is the fourth generation from a 1999 introduction from Virginia and Massachusetts, USA, which is expected to have higher heterozygosity caused by a larger founder population (200 wild and 206 first generation cultured individuals) and a short breeding history. Both hybrid crosses demonstrated positive heterosis for all traits studied, although the magnitude of heterosis varied among traits and life history stages. Midparent heterosis was 7.9% for hatching success, 10.8% and 3.0% for larval survival and growth and 8.4% and 10.9% for juvenile and adult growth. Single-parent heterosis also varied among traits. For fitness related traits such as hatching success and larval survival, single-parent heterosis was positive for both parental stocks. Single-parent heterosis for growth, a morphological trait, was positive in stock A and negative in stock B.

We examined sediment selection by juvenile sea scallops (Placopecten magellanicus) and their predators, sea stars (Asterias vulgaris) and rock crabs (Cancer irroratus). In laboratory trials, groups of scallops (~30 mm shell height) were simultaneously offered four sediment types in the presence and absence of a sea star or a rock crab: (1) glass representing a homogeneous, hard bottom; (2) sand; (3) granule and (4) pebble. As well, individual predators were offered the four sediment types without scallops. The number of scallops and the proportion of time predators spent on each sediment type were monitored over time. When compared with the expected distribution, scallops avoided glass and tended to select granule and pebble sediments when alone. In the presence of a rock crab, scallops also avoided glass. However, scallop distribution was similar to the expected distribution when a sea star was present, because sea star encounters are an important trigger of scallop swimming, leading to frequent redistribution of scallops. Sea stars spent less time than expected on glass, whereas crabs spent more time than expected on sand. For both predators, distribution did not change significantly in the presence or absence of scallops. In sum, scallop distribution appears more dependent on predator distribution than the reverse. Predation of scallops by sea stars and rock crabs was not influenced by sediment type. Our results have implications for the bottom culture of scallops. Because scallops select heterogeneous sediments over homogeneous ones, dispersal of scallops may be important on unsuitable sediments. Also, dispersal may be higher when sea stars are present at an aquaculture site.

Argopecten nucleus and Nodipecten nodosus are two Caribbean scallops occurring in Colombia, which have recently been selected for artificial culture based on their high commercial value. As part of an effort to develop culture technology for these species, we studied the effects of food concentration and temperature on feeding rates (filtration, ingestion, and absorption), oxygen consumption, ammonium excretion and scope for growth in adults of the two scallop species. We tested the effects of four concentrations of the microalga Isochrysis galbana (10, 20, 40 and 60 cells μL⁻¹) at three water temperatures (20, 25 and 28°C), at a constant salinity of 36‰. The results showed that increases in food concentration induced increases in feeding rate, oxygen consumption and growth potential, but at values of 60 cells μL⁻¹ these variables decreased, indicating saturation of the digestive tract. The excretion rate increased at low food concentrations, particularly at the middle (25°C) and/or at the highest temperature tested (28°C). This suggested utilization of endogenous proteins as a supplementary energy source under these conditions. The increase in temperature had no significant effect on the feeding variables or on the scope for growth of A. nucleus, but raised the N. nodosus ones. All the physiological rates for the two species were similar except for oxygen consumption, which was greater in N. nodosus than in A. nucleus. Using values obtained for the algae concentrations, which produced the greatest growth potential, the optimal value for I. galbana for both the scallops was 40 cells μL⁻¹, whereas the optimal temperature for N. nodosus was 25°C. There was no single optimal temperature for A. nucleus, which functioned equally well at between 20°C and 28°C.

The first and second internal transcribed spacer (ITS1 and ITS2) regions of the ribosomal DNA from six species, Meretrix meretrix, Cyclina sinensis, Mercenaria mercenaria, Protothaca jedoensis, Dosinia corrugata and Ruditapes philippinarum, in the family Veneridae were PCR amplified and sequenced. The size of the ITS1 sequence ranged from 522–900 bp, which was the largest range so far reported for a bivalve species, with GC contents from 57.66% to 65.62%. The size of the ITS2 sequence ranged from 281–412 bp, with GC contents from 65.21% to 67.87%. Extensive sequence variation and obvious length polymorphisms were noted for both regions in these species, and ITS2 sequence similarity was higher than that of ITS1 across species. The complete sequences of 5.8S ribosomal RNA gene were obtained by assembling ITS1 and ITS2 sequences, and the sequence length in all species was 157 bp. The phylogenetic tree of Veneridae clams was reconstructed by using ITS2 containing partial sequences of both 5.8S and 28S rDNA, and corresponding sequence information in Arctica islandica (Dahlgren et al. 2000) as an outgroup species. Tree topologies indicated that P. jedoensis has a closer relationship with M. mercenaria than with other species.

Field surveys in southeastern Raritan Bay and laboratory studies from 1999 to 2005 were conducted to compare the characteristics of mud and sand habitats in relation to the abundance of the northern quahog (Mercenaria mercenaria). In 2000, the population density of quahogs was about 15 times higher in the mud habitat than in the sand habitat. In addition, the mud habitat also had a dense population of the amphipod Ampelisca abdita (about 24,000 m⁻²) associated with it. This species produces mats of tubes over the bottom. The sediment surface of the mud was comprised mostly of fecal pellets, the majority of which was produced by A. abdita. In contrast, the sand habitat did not have A. abdita tubes or much erect surface structure; its sediments were comprised of medium grain sand (φ = 1.17–1.4). In southeastern Raritan Bay, the principal quahog predators are the longwrist hermit crab (Pagurus longicarpus), Atlantic oyster drill (Urosalpinx cinerea), and xanthid mud crabs. Collectively, they were >7 times more abundant in the sand habitat than in the mud habitat. We suggest that quahogs are abundant in the mud habitat because the presence of the tube mats probably reduces water siltation, encourages settlement of larval quahogs and deters predation on the quahogs.

The annual reproductive cycle of the squalid callista Megapitaria squalida living in the Ojo de Liebre lagoon was analyzed from January to December 2001. The reproductive activity was analyzed qualitatively (through histological analysis), defining five gonad development stages (undifferentiated, developing, ripe, spawning and spent). A quantitative analysis was also conducted (through the gonadic index and oocyte diameter) to correlate the reproductive activity with water temperature and salinity. Male and female gonads developed and spawned in parallel through time. M. squalida displays a clearly seasonal reproductive cycle in the Ojo de Liebre lagoon, with a long reproductive activity period (January to August) that coincides with the rise in temperature, plus a well defined inactivity period (September to December) with 100% of undifferentiated or spent organisms and the onset of which coincides with the temperature decrease. M. squalida's reproductive cycle does not seem to be influenced by salinity variations in the Ojo de Liebre lagoon. The spawning size of M. squalida was determined at 92 mm SL at an approximate age of 2.2 y. However, some individuals started spawning at 64 mm SL. Marked differences were found in some aspects of the reproductive pattern of M. squalida compared with studies conducted in other sites, and the likely causes are discussed here.

Reliable banding techniques are a major necessity for the genetic research in marine bivalves. Restriction enzyme banding (HaeIII) was performed, in this study, on chromosomes of two commercially important species of veneroid bivalves: the clam Ruditapes decussatus (Adams and Reeve) and the cockle Cerastoderma edule. Identification of the nineteen individual chromosome pairs was obtained for both species. The cytogenetic studies made in marine molluscs have recently experienced a very fast development caused by the introduction of new molecular techniques mainly fluorescence in situ hybridization (FISH). Recently it has been shown in mammalian chromosomes that restriction enzyme banding is compatible with FISH, allowing simultaneous banding, and consequent accurate identification of the localization of the probes and unambiguously identification of the chromosome(s) carrier(s). As far as we know this is the first RE-banding obtained in karyotypes of veneroid species. The application of restriction enzyme chromosome banding in veneroids are diverse and this study can constitute a fundamental step for future gene mapping on this commercially important group of bivalves and could offer a new approach to specific problems in veneroid taxonomy and genetics.

Examination of the hypoxic tolerance of Nucula sulcata determined that the mean survival time under hypoxia was 9.57 d with a maximum longevity of 30 d. Comparison between the three species, N. sulcata, N. nitidosa, and N. nucleus reveals that N. sulcata is the most tolerant of hypoxia followed by N. nucleus and N. nitidosa. It is suggested that the hypoxic tolerance of the species is a reflection of the normal habitat they occupy.

The reproductive cycle of the razor clam Solen marginatus (Pulteney 1799) was studied in three different locations of Spain. Sampling was performed in the natural beds of: Eo Estuary (NW Spain) in 1994 to 1995, Santander Bay (N Spain) in 1998 to 1999 and Terrón Estuary (SW Spain) in 1999. In Eo, Santander and Terrón, respectively: phase 0 (resting stage) occurred in July to August, September to October and August to September, phase I (proliferation of gonias) happened in: August to October, October to December and September to November, phase II (gametogenesis) was developed in November to April, January to May and December to April and phase III (reproduction) took place in: May to June, June to August and May to July. Two new approaches oriented to the fast monitoring of the gametogenic cycle of the species based on sequential mean drained soft parts weights obtained by simulation and on the macroscopic observation of the gonad are presented.

This work describes the parasites and their respective pathologies in the stout razor clam, Tagelus plebeius (Lightfoot, 1786) (Psammobiidae) from Argentinean coasts. It represents the first report about a histopathological survey for these species in the Southwestern Atlantic. Specimens of T. plebeius were collected at Mar Chiquita coastal lagoon (37°46′S, 57°27′W) (n = 104 dissected under stereomicroscope, n = 28 histologically sectioned and microscopically examined) and from the mouth of the Quequén Salado River (38°56′S, 60°33′W) (n = 14 dissected under stereomicroscope). Tagelus plebeius was found housing two ciliate species without apparent host reaction and acting as first intermediate host for two digenetic trematode species of the families Fellodistomidae and Gymnophallidae, by hosting sporocysts (mainly in gonad and digestive gland that results in the replacement of host tissues) and as second intermediate host by housing a gymnophallid metacercaria. Likewise, T. plebeius was found parasitized by a larval spirurinae nematode encapsulated by hemocytes. The finding of two ciliate species, the gymnophallid cercaria and metacercaria, and the larval nematode represents the first record for the host. The Southwestern Atlantic populations of this clam seem to be devoid of serious pathogens in the study area.

The greenshell mussel Perna canaliculus is the most important species in aquaculture in New Zealand. Mussel energetics and growth rates are subject to the natural variability in phytoplankton biomass and species composition and thus understanding the influence of food type on assimilation efficiency is fundamental to the prediction of mussel production and planning farm management. In this study pulse-chase feeding techniques were used to assess the effect of diet on assimilation efficiencies for nine phytoplankton species including three diatoms Chaetoceros calcitrans, Skeletonema costatum and Thalassiosira sp., and three flagellates Eutreptiella sp., Pyramimonas sp. and Isochrysis galbana, and three dinoflagellates Akashiwo sanguineum, Alexandrium minutum and Gymnodinium catenatum. Assimilation efficiency varied with algal species, but it was significantly higher when mussels were fed dinoflagellates (84.5%) compared with diatoms (61.7%) and flagellates (77.9%). Assimilation efficiency of dinoflagellates and flagellates increased with gut passage time, whereas with a diatom diet, a negative correlation was evident. This finding has implications in understanding and predicting growth rates of mussels (and hence commercial yield) in tandem with natural variability in phytoplankton species composition.

The aim of this study is to elucidate the impact of age and temperature on metabolic key parameters (respiration rate and mitochondrial marker enzymes) controlling maximal size and longevity in the blue mussel Mytilus edulis L. from geographically separated populations of Northern European seas. Mussels from the Barents Sea attain similar maximal sizes as animals from the warmer North Sea. Young animals (<5 y) grow faster in the North Sea, however, inshore Barents Sea mussels grow rapidly even at advanced age. The slowest growth rates were found in a population exposed to strong wave action in the Barents Sea. Respiration rates followed the same age dependent pattern in mussels from all studied populations with low respiration rates in the youngest specimens followed by a rapid increase and then a gradual decline to nearly constant values in the oldest animals. When compared at a common temperature, metabolic rates only of young blue mussels (<7–8 y) are cold compensated with maximal respiration in the most Northern populations. Cold compensated metabolic activities in mussels from Northern populations may support similar patterns of maximal body size and longevity as in the more temperate Southern population.

Many physiological processes in bivalves are influenced by the valve opening sate and thus the valve opening-closing response times of the experimental animals. Controlled laboratory studies using underwater video camera recording of valve-gape responses of mussels (Mytilus edulis) to presence or absence of algal cells in the ambient water have revealed that valve opening and closing responses are strongly influenced by the preceding feeding conditions. The observations indicate that the period during which mussels may “learn” or “forget” to respond to the presence or absence of algal cells can last for weeks in the laboratory. Further, the critical algal concentration below which mussels close their valves has been identified to be about 700 Rhodomonas sp. cells mL⁻¹, or 0.9 μg chl a L⁻¹. Such knowledge is essential for making allowance for possible deviation from natural-response times in mussels kept in the laboratory previous to experimental physiological studies. In situ simultaneous registrations of water flow, chl a and valve-opening degree of mussels were made within a dense mussel bed in a shallow, tidally dominated inlet to a Danish fjord. Phases of strong tidal flow brought ample supply of phytoplankton to the mussel bed, and it was observed that concentrations higher than about 1 μg chl a L⁻¹ in the near-bed layer stimulated the mussels to keep their valves wide open, whereas tidal slack with slow flow resulting in near-bed concentrations below 1 μg chl a L⁻¹ caused by grazing by the mussels, after some time led to shell closure, or reduced valve gapes of the mussels. The valve opening time from opening degree 50% to 100% and the valve closing time from opening degree 100% to 50% in response to variation in near-bed chl a concentration were on average 59 ± 22 and 50 ± 19 min, respectively, which is considerably faster than observed in unfed mussels in the laboratory.

The study was conducted to determine the feasibility for growing-out of the spotted babylon juveniles (Babylonia areolata) to marketable sizes with the large-scale operation of 20.0 × 20.0 × 1.5 m earthen ponds at Petchaburi province, Thailand. The production and economic analysis for monoculture of spotted Babylon were compared with the polyculture with sea bass (Lates calcarifer). Each pond was stocked with juveniles of 0.3 g initial weight at a density of 200 snails m⁻². This study provides good results in growth and production of spotted babylon in earthen ponds. The average growth rates in body weight were 0.67 and 0.51 g mo⁻¹ for snails held in the monoculture and polyculture with sea bass, respectively. At the end of the experiment, total yield of spotted babylon held in the monoculture and polyculture with sea bass was 10,520 and 10,450 kg ha⁻¹, respectively. Based on farm data, stocking data and harvest data used in this study, total cost per production cycle of the monoculture and polyculture with sea bass were $19,184 and $23,245, respectively. The cost of producing spotted babylon marketable sizes in this grow-out farm design was $5.69 per kg and $6.95 per kg for the monoculture and polyculture trials, respectively. At a farm gate price in 2003 of $9.00 per kg resulted in a net return of $11,124 and $14,691 for the monoculture and polyculture with sea bass, respectively. The present study indicated the technically feasible, and economically attractive for monoculture and polyculture of B. areolata to marketable sizes in earthen ponds.

Recent range extensions of the invasive rapa whelk Rapana venosa, biological data of the population and possible ecological impacts on the food webs of the Río de la Plata estuary are presented. A total of 41 rapa whelks and 21 egg capsules were collected between February 2004 and March 2006. Specimens were found all over the mixohaline waters of the estuary, with records off Montevideo, Samborombón Bay and off Punta Rasa. Specimens ranged between 28 and 120 mm shell length. Almost all R. venosa presented epibionts all over the shell, suggesting an exposed lifestyle. Egg-masses were attached to specimens of R. venosa, debris and plastic garbage. The spatial distribution of R. venosa within the estuary was coupled with the spatial distribution of Mactra isabelleana, a typical subtidal bivalve of mixohaline waters. The implications for the food webs of the estuary, including possible predators, are discussed. The presence of R. venosa in muddy sediments together with the finding of egg-capsules over the specimens, and the low salinity values at which it is found in the Río de la Plata estuary, confirmed the high plasticity of R. venosa and the potential capability of successfully invading novel environments.

The reproductive cycle of purple snail, Plicopurpura pansa (Gould 1853), sampled randomly monthly over a period of 20 mo at Playa Cerritos at the Pacific, and Punta Perico at the Gulf of California, Baja California Sur, Mexico, was examined by histological observations of the gonadal development. At both sites year-round copulations were observed, whereas egg capsules could be found only during February to May. During nearly the whole period, male and female gonads were found in the developing stage. From January to July and August most female gonads were found in the ripe, and from January to June and August in the spawning stage. Male gonads in the spawning stage were observed from December to September. The recovering stage was found in male and female gonads between September and October. Synchronism of gonadal development between both sexes was evident. Spawning could be observed in females with a total shell length of more than 18 mm, whereas smaller animals had gonads in the developing stage. In gonads of males signs of spawning could be observed in animals larger than 18 mm. No relationship was found between the water temperature and the spawning period. The sex ratio was 1:1 at Playa Cerritos, whereas at Punta Perico more males than females were counted.

Neutral red retention (NRR) assay was used to evaluate the effect of changes in water temperature on lysosomal membrane integrity in the hemolymph of blacklip abalone, Haliotis rubra. Results from gradual temperature changes between 7°C and 16°C and between 16°C and 25°C showed that water temperatures within the range of 15°C to 17°C were optimal for maintaining lysosomal membrane integrity in this species. The rapid temperature changes between the ranges used in the gradual temperature change experiments indicated that when abalone were transferred directly between these temperatures their NRR time gradually increased or decreased to the level corresponding with the new temperature. However, when abalone were transferred directly between 7°C and 25°C or between 11.5°C and 20.5°C their NRR times initially decreased significantly, and then gradually increased to the levels corresponding with the new temperatures, indicating that different ranges of water temperature change can affect the lysosomal membrane integrity differently. The NRR times of blacklip abalone at 7°C, 16°C and 25°C were 40.0 ± 2.89 min, 113.33 ± 3.85 min and 35.0 ± 2.89 min, respectively.

Planktonic larvae of benthic fauna that can grow quickly in the plankton and reduce their larval period duration lessen their exposure to pelagic predators and reduce the potential for advection away from suitable habitats. Veined rapa whelks (Rapana venosa, Muricidae) lay egg masses that release planktonic veliger larvae from May through August in Chesapeake Bay, USA. Two groups of veliger larvae hatched from egg masses during June and August 2000 were cultured in the laboratory. Egg mass incubation time (time from deposition to hatch) ranged from 18–26 d at water temperatures between 22°C and 27°C. Four stages of rapa whelk veliger development along a time series from hatch to settlement were described using external morphological features. Rapa whelk veligers were measured at three-day intervals from hatching through the onset of spontaneous settlement. A four-parameter Gompertz growth model was used with length at age data from cultures of rapa whelk veligers to estimate maximum growth rates for June and August hatched groups. Larval rapa whelks settled at shell lengths of 1.18–1.24 mm after planktonic larval periods ranging from 24–42 d. Maximum larval growth rates observed in August (0.03 mm d⁻¹) are 50% lower than maximum larval growth rates observed for June hatched rapa whelk veligers (0.071 mm d⁻¹). Daily larval growth rates from hatch to first spontaneous settlement for rapa whelk veligers ranged from 0.002–0.099 mm d⁻¹ with maximum growth rates occurring between 12–18 d post hatch in June. Larval period duration, or the time from hatch to first spontaneous settlement, was 12 days shorter for June hatched larvae than for August hatched larvae. Water temperature was not significantly correlated with larval growth rates (mm d⁻¹) in either June or August. Plasticity in larval period duration may enhance survival and dispersal opportunities for planktonic rapa whelk veligers.

Molluscs, both gastropods and bivalves, appear to disproportionately influence the dynamics of salt marsh habitats. Bivalves typically are facilitators positively affecting the growth and survival of marshes, but gastropods may have unanticipated top-down effects through direct consumption of the predominant marsh vegetation, Spartina alterniflora. Natural, elevational differences in S. alterniflora density and morphology also may exert an influence on the spatial distributions of marsh snails. We examined the abundance of both plants and snails across an elevation gradient to determine if similarities or differences existed in the observed distribution patterns. Plant, mainly S. alterniflora, and snail, Littoraria irrorata (Say) and Melampus bidentatus Say, densities were measured along tidal creek to forest transects within the intertidal marshes of three marine-dominated South Carolina inlets. Significant differences in S. alterniflora density among marsh zones were paralleled by similar L. irrorata density differences. A consistent, unimodal pattern with peak L. irrorata density in the “short,” dense S. alterniflora mid marsh occurred within each inlet. In contrast, M. bidentatus was restricted almost entirely to the high marsh across all transects and inlets. Densities of L. irrorata and S. alterniflora were positively correlated in the low marsh consistent with the potential importance of culms as a food source and refuge from predators. Littoraria irrorata biomass was significantly different among zones in only one inlet and increased in a shoreward direction in two inlets. Although biomass patterns previously have not been reported for Southeastern US marshes, amounts were consistently greater than expected within the high-marsh zone. In SC, L. irrorata appears to be a conspicuous resident across the entire vegetated marsh and our results suggest previous studies focusing on the marsh near tidal creeks could underestimate appreciably the total population and overall significance of L. irrorata within coastal marshes.

Temporal variation in abundance of spat of the blacklip pearl oyster (Pinctada margaritifera) was determined over an eight-year period at two sites, Gizo and Noro, in the Western Province of Solomon Islands. Spat were collected by deploying shade mesh substrata at a depth of 3 m for near-sequential two-month period. Overall, spatfall at the two sites was similar, with summer maximum of 4.9 (Gizo) and 4.7 collector⁻¹ (Noro). At both sites, significantly fewer spat were collected in late winter than in summer. Abundance of spat varied among years, although there was no consistency between the two sites regarding years of highest recruitment. Maximum settlement of spat at Gizo was 10.2 collector⁻¹ in January 2002, whereas at Noro it was 19.6 collector⁻¹ in March 2000. Mean size of spat did not vary over time, but spat at Gizo were significantly smaller (geometric mean 7.6 mm) than those at Noro (mean 8.4 mm). Predators of spat settled on the collectors throughout the year; there were significantly more gastropod predators at Noro than at Gizo. Gizo and Noro in the Western Province of Solomon Islands are reliable places for collection of blacklip pearl oyster spat. Spat can be caught all year round, although collections will be most effective between November and March.

As with most cultivated bivalves, culture of the Tahitian pearl oyster Pinctada margaritifera is particularly dependent on the natural environment, especially for spat supply. The ability to track in real time the abundance and the development of pearl oyster larvae in the plankton would help optimize spat collection in atolls of French Polynesia. However no identification criteria are available for the larvae of several bivalves species present in the lagoons and it is not yet possible to specifically monitor pearl oyster larvae. The aim of this study is to determine the most pertinent morphological identification criteria, to specifically identify the larvae of P. margaritifera and differentiate them from those of three other abundant species: Pinctada maculata, Crassostrea cuculata and Chama sp. The method of image analysis after photon microscopy was assessed. It allowed automatic measurement of numerous morphometric features that were tested alone or in combination and identification threshold for P. margaritifera larvae were determined by statistical analyses. These results led to a key that allowed correct identification for 77% of P. margaritifera larvae. The hinge diagnosis method under scanning electron microscopy, a prime method for the identification of specific criteria on bivalve larva shells, was also used on larvae of both Pinctada species. The two species could be differentiated precisely because of specific differences in the thickness of their hinge provinculum and the number of denticles it bears. However this approach is too time-consuming and technically demanding to use in real time field studies. This study showed the limitations of image analysis as an identification tool of the P. margaritifera larvae, but proper statistical analyses and especially the decision tree approach could be used to evaluate and efficiently prioritize the choice of the species identification criteria.

Over the period from June 2002 to June 2003, we examined the relationship of seasonal changes in the mass of the gonad and somatic tissues to environmental factors for four size groups of the zebra ark shell Arca zebra at Chacopata, in northeastern Venezuela. The gonads of A. zebra began to increase in size when individuals attained 18–20 mm in shell length, but maximum gonad mass relative to somatic mass was only attained at 55–60 mm in length. Large individuals (>50 mm) showed a distinct annual reproductive cycle with a marked increase in gonad mass from July to late September 2002, coinciding with the increase in temperatures related to stratification of the water column. A decrease in gonad size occurred during October 2002 through January 2003 and coincided with a temperature decline related to renewed upwelling. The mass of somatic tissues was highest between late August to late December 2002, coinciding with the reproductive period and elevated temperatures. Other environmental factors showed little seasonal variation, although chlorophyll a concentration was lowest during the major period of increase in the gonad and somatic tissues (July to late September 2002), suggesting that the animals were not limited by the abundance of phytoplankton food. A. zebra seemed to be well adapted to the high loads of inorganic seston found in the Chacopata region.

To determine whether DNA could be isolated from tissues obtained by brush-swabbing the mantle, viscera and foot, mantle-clips and swabbed cells were obtained from eight Quadrula pustulosa (Lea, 1831). DNA yields from clips and swabbings were 447.0 and 975.3 ηg/μL, respectively. Furthermore, comparisons of sequences from the ND-1 mitochondrial gene region showed a 100% sequence agreement of DNA from cells obtained by clips and swabs. To determine the number of swabs needed to obtain adequate yields of DNA for analyses, the visceras and feet of 5 Q. pustulosa each were successively swabbed 2, 4 and 6 times. DNA yields from the 2, 4 and 6 swabbed mussel groups were 399.4, 833.8 and 852.6 ng/μL, respectively. ND-1 sequences from the lowest yield still provided 846–901 bp for the ND-1 region. Nevertheless, to ensure adequate DNA yield from cell samples obtained by swabbing, we recommend that 4 swab-strokes of the viscera and foot be obtained. The use of integumental swabbing for collection of cells for determination of genetic relationships among freshwater mussels is noninvasive, when compared with tissue collection by mantle-clipping. Therefore, its use is recommended for freshwater mussels, especially state-protected or federally listed mussel species.

The effects of temperature (10°C and 15°C), sexual maturity (immature and mature) and sex on instantaneous growth rates, daily feeding rates and gross growth efficiency were studied in the “Pulpito,” Octopus tehuelchus (d'Orbigny, 1834), under laboratory conditions. At 15°C, immature octopus showed higher instantaneous growth and daily feeding rates than individuals maintained at 10°C (P < 0.01). At 10°C, immature individuals showed higher daily feeding rates than mature specimens (P < 0.01). Aside from a lack of measurable growth observed in mature males, sex appears to have had no effect on either instantaneous growth or daily feeding rates in either maturity stage or temperature treatment (P > 0.05). An alternative method to compare gross growth efficiencies (GGE) among 6 treatments, based on the relationship between growth and food intake, is proposed. Immature octopuses at 10°C showed a higher GGE value than at 15°C (P < 0.05). Mature individuals at 10°C were less efficient in using food in growth than immature ones. GGE value (52%) found for immature octopus at 10°C is among the highest reported in the literature. This could have important implications for a possible rearing activity of this species. Mature males and females at 10°C showed a lower GGE (35.5%) than immature individuals held at 10°C (GGE = 52%) and 15°C (GGE = 44%). Food intake, growth and food conversion are linked processes, which in O. tehuelchus are influenced by temperature and sexual maturity. In addition, whereas classic statistical tests failed to detect any of these effects on GGE, the alternative method here proposed based on the relationship of growth versus food intake was successful.

The subcellular fractionation of the digestive gland cells of the common cuttlefish Sepia officinalis was performed to investigate the distribution of metals between organelles and cytosol and the different cytosolic fractions separated by gel-filtration chromatography. Total metal concentrations vary over 3 orders of magnitude, ranging from dwt for Pb to dwt for Zn. With the exception of Cd, Co, and Cu, metals were mostly bound to the organelles. Whereas no specific organelle compartment was found for Mn, Pb, and Zn, Fe was mainly associated with nucleus, brown body, and “boule” fraction (i.e., 52%) and 44% of the total Ag was contained in the lysosomal and mitochondria enriched fraction. The link of metals with hydrosoluble proteins in the cytosolic fraction was investigated at 254 and 280 nm. Direct relationship between cytosolic metal and metallothioneins could only be established for Ag and Cu, whereas Cd and Zn seem to mainly bind high (>70 kDa) and low (<4 kDa) molecular weight proteins.

Fifty-two ovigerous females of Cancer johngarthi were caught from the Baja California Peninsula's western coast, Mexico. Carapace length, carapace width and total weight of each specimen were registered. Fecundity estimates were obtained from the wet weight of eggs in each organism. Mean fecundity was 765,227 eggs, corresponding to a mean carapace width of 117 mm, and the mean relative fecundity was 4,305 eggs per gram of female body weight. Fecundity data (F) were fitted in relation to carapace width (CW) to the power model F = 0.84CW^2.87, R² = 0.52. C. johngarthi has a high population renewal capacity compared with other larger species like Maiopsis panamensis, which produces between 351,000 and 1,162,668 eggs, and Stenocionops ovata, which produces between 35,187 and 180,057 eggs; in both species, the relative fecundity is lower than 1,000 eggs per gram of female body weight.

Ten strains of Artemia parthenogenetica have been collected from inland salt lakes and coastal salterns in China. Ten diploid clones were selected from each Artemia parthenogenetica strain for analysis of the population genetic structure and genetic differentiation using inter simple sequence repeats (ISSR). One hundred and seventy fragments (100–2200 bp) were generated using 20 ISSR primers. A high level of genetic variation was found, with 96.47% polymorphic loci in total loci. The number of alleles (Na), effective number of alleles (Ne) and Shannon information index (SI), the mean Nei's gene diversity (H), the average values of Ht, Hs, Gst for pairwise subpopulations and mean value of all 100 clones from 10 Chinese Artemia parthenogenesis strains were analyzed. The results showed that genetic structure of populations of A. parthenogenetica from China were complicated with high genetic diversity among the populations. Cluster analysis was then performed to create a dendrogram using the UPGMA method based on the Nei' genetic identity. The UPGMA dendrogram showed that 10 Chinese Artemia parthenogenetica strains can be significantly divided into three major groups (subpopulation): Liaoning, (PK and YK); Shandong and Hebei, (HH, TG, LN, WD, WZ and FC) and Qinghai and Xinjiang (GH and BLK).

The growth, food consumption, food conversion efficiency and apparent digestibility coefficient of juvenile Chinese shrimp, Fenneropenaeus chinensis Osbeck (body weight 0.36 ± 0.04 g) were examined under different temperature regimes. The animals were subjected to 6 constant temperatures of 18°C, 22°C, 25°C, 28°C, 31°C and 34°C and diel fluctuating temperatures of 22 ± 2°C, 25 ± 2°C, 28 ± 2°C and 31 ± 2°C. The results showed that the growth rate of Chinese shrimp at the constant temperature regimes increased from 18°C to 31°C, whereas decreased significantly at 34°C. The growth rates of shrimp at 22 ± 2°C, 25 ± 2°C and 28 ± 2°C were significantly greater than those at the corresponding constant temperatures of 22°C, 25°C and 28°C, respectively, whereas no significant difference was found between 31 ± 2°C and 31°C. As compared with those at constant temperature, the mean temperature at which maximum growth rate of shrimp occurred shifted to cooler temperature at diel fluctuating temperatures. The shrimp consumed more food at 25 ± 2°C, 28 ± 2°C and 31 ± 2°C than those at 25°C, 28°C and 31°CC, respectively, but no significant difference in apparent digestibility coefficient was found between the fluctuating and corresponding constant temperatures. The food conversion efficiency and energy assimilated into growth as percentage of energy from food for shrimp at 22 ± 2°C, 25 ± 2°C and 28 ± 2°C were significantly higher than at the corresponding constant temperatures. Therefore, more food consumption, high food conversion efficiency and more energy partitioned into growth might contribute to the enhanced growth rate at the fluctuating temperatures.

The sonic scattering layer (SSL) or deep scattering layer (DSL) of the eastern Arabian Sea of India is found in depths between surfaces to 750 m with varying thicknesses and in multiple layers. There is a distinct resident community of pelagic shrimps that is widely distributed in the DSL biocomposition. Pelagic shrimps formed 19% of the total biomass and 47% of the micronekton biomass of the DSL. Many of them serve as important food resources to several pelagic/mesopelagic organisms. Pelagic shrimps concentrate in the deep scattering layer and diurnally migrate in the water column. The estimated average abundance pelagic shrimps ranged between 0.04–106/1000 m³. Shrimp catches were higher during night at 50–200 m depth than day. The dominant families encountered in the catches were Thalassocarididae, Pasiphaeidae, Sergestidae and Oplophoridae. Dominant genera of pelagic shrimps present were Gennadas, Sergestes, Sergia, Lucifer, Oplophorus, Acanthephyra, Nematocarcinus, Leptochela, and Thalassocaris. Species Sergestes seminuds, Thallassocaris crinata and Leptochela robusta were present in swarms

A commercial fishery for shrimp Palaemon serratus occurs on the south and west coasts of Ireland. Two temporal phases were identified: expansion from the mid 1970s to the late 1980s when maximum national landings were less than 150 t annually; and a second phase since 1990 when most years yielded more than 200 t. Maximum landings of 548 tons were reached in 1999. Three indicators of fishery performance are examined: total annual landings, weight landed per vessel per day and the average weights of individual shrimp in October and December, reconstructed from processors' records of graded shrimp. Total landings and daily landings weights correlated positively, whereas both correlated negatively with average individual shrimp weight in October and December over a 13-year period. Periodic and possibly cyclical recruitment events are identified as a contributor to improved yield.

Distribution of the sea urchin Hemicentrotus pulcherrimus was monitored monthly or bimonthly from April 1998 to May 1999 at a 100 m² permanent site in intertidal to subtidal zones at depths of up to 2.8 m in Onagawa Bay, northern Honshu, Japan. Factors causing seasonal demographic changes were analyzed from vertical algal vegetation, sea urchin size, gonad development, and gut content. The highest density of H. pulcherrimus was found on algal turf on boulders at the depth of 0–0.3 m. Migration of adult sea urchins on crustose corallines at the depth of 0.3–2.8 m to the algal turf and subsequent inhabitation in more suitable boulder habitat are suggested from November to March, when Acrosorium polyneurum, which is their main food, grew dominantly. As the high gut content of crustose coralline of the sea urchins on crustose corallines resulted in significantly lower gonad indices, it is likely that migration is caused by their high foraging activity for A. polyneurum to ensure gonad development. The growth of the sea urchins on algal turf was ensured by Chondrus spp. as main food.

The parasites Perkinsus spp. are relatively easily and inexpensively detected in host tissues, but available methods to detect free-living planktonic stages are technologically complex and expensive. As a result, few studies have been conducted to detect and quantify free-living stages during transmission. Here, we describe an adaptation of Ray fluid thioglycollate medium (RFTM) assay to detect and enumerate Perkinsus spp. parasites in environmental water samples. Recovery of in vitro cultured P. marinus was successful, but recovery rates were low. Filtration of water samples captured significantly more cultured P. marinus cells than centrifugation. Lipid supplementation during RFTM incubation enhanced recovery of cultured P. marinus, but not of naturally occurring Perkinsus spp. parasites. Comparisons between the modified RFTM filtration method and a more complex immunoassay revealed that the two methodologies were equally sensitive, indicating that the RFTM filtration method may be confidently applied to environmental water samples to determine relative concentrations of Perkinsus spp. parasites.

The bacterium, Vibrio tapetis, is the aetiological agent of Brown Ring Disease (BRD), which affects the Manila clam, Venerupis (Ruditapes) philippinarum. Two PCR assays for detection of V. tapetis were applied to a sample of 52 Manila clams, and evaluated in comparison with the more traditional V. tapetis detection method of microbiological isolation and characterization, as well as the traditional BRD diagnostic technique of shell valve analysis. The pathogen was detected in 15.4% of the sample using the PCR assay of Rodríguez et al. (2003, 2006) in 50% of the sample using the PCR assay of Paillard et al. (2006) and in 36.5% of the sample by microbiological methods. Whereas shell valve analysis was the least sensitive technique, detecting BRD in 7.7% of the sample, it was an essential diagnostic tool because it was the only technique that identified the disease, rather than the aetiological agent. None of the four techniques was sufficient on its own for effective BRD diagnosis; rather various combinations of two techniques were the minimum required. The combination of shell valve analysis with the assay of Paillard et al. (2006) proved to be the most sensitive and rapid of those tested. Shell valve analysis was the most time-efficient and cost-effective technique, whereas microbiological characterization was the most time-consuming, and PCR detection, using either set of primers, the most expensive. These results may need to be considered in light of diagnosis and management of BRD.

The stimulation of hemocytes during phagocytosis leads to the generation of a series of oxygen radicals known as reactive oxygen species (ROS). Among these, hydrogen peroxide plays an important microbicidal role by directly killing microorganisms or by serving as an intermediate for other antimicrobial radicals. In this study, we adapted a technique using 2′,7′-dichlorofluorescein-diacetate (DCFH-DA) to measure H₂O₂ production in lobster hemocytes. After oxidation by hydrogen peroxide, this molecule produces a fluorescent product that can be easily detected. The respiratory burst was successfully activated in lobster hemocytes by the addition of zymosan particles, but not with phorbol myristate acetate. After optimization, we used the technique to investigate the effect of different bacterial strains, including lobster pathogens, on the oxidative burst. Results demonstrate that Aureococcus viridans, a bacterial pathogen that is able to survive phagocytosis by lobster hemocytes, quenches ROS production. The comparison of ROS production in lobsters collected from field sites submitted to different levels of dissolved oxygen suggests that this technique provides a good indicator of lobster physiological status and immunocompetency.

An improved and rapid biochemical identification of the culturable aerobic bacteria species associated with Galician oyster production was performed by the combination of numerical taxonomy and sequencing of 16S rRNA gene. The 16S rRNA sequences of 23 representative bacterial isolates from different growing stages of Ostrea edulis, surrounding water, and phytoplankton were compared with related sequences from the EMBL database. These results were used to identify the phenetic clusters obtained by numerical taxonomy using the S_J/UPGMA with a similarity level of 74%. The combination of the two techniques was a useful tool for identifying 40 out of 75 representative aerobic Gram negative isolates comprising the bacterial community studied and for improving the phenotypical description of each identified species. It was mostly facultative psycrophilic α-Proteobacteria showing a great diversity. No specifity of bacteria, according to the geographical area studied was found. Almost all of the identified species were associated, for the first time, with different growing stages of oyster. Some could have a probiotic effect (Roseobacter gallaeciensis, Shewanella schlegeliana) or could be a potential risk for oyster cultures (Pseudoalteromonas piscicida, Pseudomonas anguilliseptica) or for humans by consumption (Acinetobacter johnsonii, Pseudoalteromonas tetraodonis).

Outbreaks of lipophilic toxins have been recorded in the north Atlantic coast of Morocco since 1999, but are rare in the Mediterranean coast. Samples of mussels from the Atlantic coast where toxicity was detected by mouse bioassay were stored for further research. Chemical analysis by LC-MS conducted in mussels harvested from this region showed, in addition to the presence of okadaic acid (OA) and dinophysistoxin-2 (DTX2), the presence of azaspiracid-2 (AZA2) as the dominant form of the azaspiracid's (AZAs) family, followed by AZA1 (13% to 26%). AZA3 was rarely detected, and maximal concentrations found were between 3% and 8% of total AZA1/3. The presence of AZA2 and AZA1 was confirmed by mass spectra. Time series corresponding to the summer of 2004 and 2005 showed maximal concentration of AZAs appeared in July in both years. Correlation with occurrence of OA and DTX2, showed both toxin families could appear simultaneously in Moroccan mussels, but maximal concentrations found were always separated in time. This is the first report of azaspiracids in Morocco (NW Africa) and the first report outside of European coastlines.

Foot structures of the spiny top shell, Batillus cornutus were investigated by light and transmission electron microscopy. The foot was composed of epithelial layer, connective tissue layer, and muscular layer from outside inward. The epithelial layer was multiple-folded and simple and was composed mostly of columnar and mucous cells. Epithelial layer thickness was approximately 40 μm in the pedal body and approximately 30 μm in the opercular zone. Distribution of mucous cells in the epithelial layer was found to be higher in the opercular zone than those in the pedal body. Mucous cells contained acidic material abundant in sulfate and carboxylate group, from the results of AF-AB reaction. From TEM observation, the epithelial layer is composed of epithelial cell, ciliated cell, absorptive cell, and secretory cell. Secretory cells can be classified into six types (A, B, C, D, E, F) in accordance with the shapes and ultrastructural characteristics of secretory granule. Type A secretory cell is the most abundant cell of the six types of secretory cells. The type of muscle fibers was mostly smooth muscle fibers. Muscle fibers can be divided into two types, one that is composed only of thin microfilaments and the other composed of thin and thick microfilaments.

Our research focused on determining the diversity and abundance of sessile and motile macrofauna that use intertidal reefs of the eastern oyster Crassostrea virginica for feeding, settlement space or refuge in Mosquito Lagoon, Florida. Five replicate lift nets were deployed at six sites (three impacted reefs with seaward margins of disarticulated shells, three reference reefs without dead margins) to determine the species composition and numbers present on these reef types. All nets were deployed intertidally on backreef areas on living oyster reefs, just above mean low water. One and a half liters of live oysters and oyster shells were placed in each net (1m²) on deployment. Nets were surveyed for all fauna monthly for one year. Metrics used to evaluate habitat use were species richness (total number of different species found) and density (total number of organisms per net). Comparisons were also made between community assemblages found on the two different types of reefs in the area (with and without dead margins) and for sessile species, recruitment on living oysters versus disarticulated shells. Forty sessile and 64 motile species of macroorganisms were found utilizing the oyster reefs in Mosquito Lagoon. However, recruitment on live oysters was twice that on disarticulated shells. Significant temporal variations were documented. When the two reef types were compared, however, no differences were found.

The Eastern oyster (Crassostrea virginica) is an economically important fisheries resource along the US Gulf Coast and the eastern seaboard. In the past few years, Mississippi has ranked second in the country in shellfish production, harvesting an average of 350,000 sacks (~15.8 million kg of oysters) per year. A GIS-based decision support tool was developed to aid the Mississippi Department of Marine Resources in managing shellfish in the state. The tool was designed using the ESRI ArcGis 8.3 Arcview software, which enabled us to integrate GIS data layers (e.g., oyster reef sites) with a program that automatically obtains Pearl River stage (gage height) and rainfall amount data from the USGS and NOAA websites, respectively. The program then compares the data with established area-specific standards and makes recommendations to the shellfish manager on the area(s) that should be closed or opened. The decision support tool is the first tool developed for shellfish management in the US Gulf Coast area. Although it was developed for use in Mississippi, it can be modified for use in other states. It simplifies the shellfish management process and maintains a database of the water quality data and the management actions that have been taken, thereby facilitating data analyses and preparation of reports.

A sample of Australian oyster consumers evaluated the sensory quality of diploid and triploid Pacific oysters subjected to high pressure (HP) treatment with and without salt. Triploid and diploid oysters received comparable hedonic ratings despite having dissimilar condition indices at the time of testing. The HP treatment did not adversely affect the sensory quality of Pacific oysters because the test products received similar ratings of sensory quality to the control (unprocessed) products. Moreover, oysters subject to HP received higher ratings for liking of appearance and were judged to have lower levels of perceived saltiness compared with the control. The use of HP in extending the shelf life of farmed Australian oysters should be investigated.