Natural marine pearls were a rare and valuable by-product of a fishery targeting pearl oyster shells for their mother-of-pearl (MOP). This fishery developed around the world throughout the 18th century and increased significantly through the 19th century in Australia and the Pacific islands. Overfishing of the MOP resource led to the development of pearl oyster spat (juvenile) collection techniques to assist stock replenishment. Although the MOP industry eventually ceased in the 20th century, spat collection provided a basis for pearl culture industries in the Pacific, that used nucleated pearl culture techniques developed in Japan. Today, French Polynesia is the largest producer of cultured round pearls in the South Pacific using the endemic black-lip pearl oyster Pinctada margaritifera. The successful French Polynesian pearl industry was a catalyst for development of pearl culture in other Pacific island countries such as the Cook Islands and Fiji. As well as significant export income, pearl culture offers livelihood opportunities (upstream and downstream) to coastal communities at a number of levels, including collection of pearl oyster spat (juveniles) for on-selling to pearl farms, and jewelry and MOP shell craft production. Despite being compatible with local lifestyles, round pearl culture has significant barriers to entry, including high initial investment, high operational costs, and requirement for a high level of technical skills. Alternatively, significant opportunities for coastal communities exist from production of mabé pearls (half pearls) because although not as valuable as high-grade round pearls, they are cheaper to produce, demand fewer technical skills, and pearls can be produced by local people with minimum training. Diversification of round pearl farms into mabé pearl production, or the establishment of stand-alone mabé pearl farms, is increasingly prevalent in Pacific pearl-producing nations, motivated by risk minimization, a broader market base, and a much simpler and less costly industry entry pathway.

Molluscs mineralize carbon as calcium carbonate in shells within a protein matrix that is a small portion of the total shell mass. In parts of Florida, the northern quahog Mercenaria mercenaria is cultured in mesh bags in shallow coastal marine habitats. These habitats were selected by the State of Florida for their pre-existing lack of large molluscan populations, so most of the shell material harvested by aquaculture operations would not otherwise exist. The carbonate content of shell material was quantified by coulometry, and shell production was estimated per harvested clam, and per unit area per year. The majority of the shell material harvested (about 91%) was M. mercenaria, and the remainder came from other species of molluscs that grew in or on the mesh bags. Of the non-Mercenaria shell material, most (8.5% of total percentage) came from oysters (Crassostrea virginica and Ostrea stentina), and the rest from at least 37 other species of molluscs and other shelled taxa. Each harvested market-size clam represented approximately 2.93 g of mineralized carbon, including shell material that was not part of the marketed clams. Clam leases in full production produced about 1.0 × 10³ g of mineralized carbon per square meter per year, including nonclam shell material, and the Florida northern quahog industry produced about 534 metric tons of mineralized carbon in 2008. This mineralization resulted in an estimated atmospheric efflux of 374 tons of metabolic-independent carbon in the form of carbon dioxide, from the Florida northern quahog industry in 2008.

This study determined the biochemical composition of the adductor muscle and mantle of two species of the giant clams Tridacna crocea and Tridacna squamosa harvested from the lagoon of South China Sea. Moisture, crude protein, crude lipid, and ash contents of the giant clams (% wet weight) ranged 77.01%–81.47%, 10.90%–15.59%, 0.39%–1.02%, and 2.25%–3.23%, respectively, with some significant differences between species and tissues (P < 0.05). The total amino acid and essential amino acid contents of the adductor muscle were 62.20–61.07 g/100 g and 24.89–24.80 g/100 g, respectively, significantly higher than those in the mantle (52.80–55.98 g/100 g and 17.85–19.73 g/100 g, respectively) (P < 0.05). Total saturated fatty acids (SFA) were found to be higher than total monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), accounting for 41.53%–55.40% for SFA, 25.83%–27.31% for MUFA, and 18.63%–31.25% for PUFA. There was no difference between the MUFA profiles of T. crocea and T. squamosa, whereas the PUFA profiles in T. squamosa were significantly higher than those in T. crocea (P < 0.05). The ratios of total n-3 PUFA to n-6 PUFA were the highest in the mantle of T. squamosa (6.60), followed by the mantle of T. crocea (2.54), and finally, the adductor muscle of T. crocea (1.82) and T. squamosa (1.09). Therefore, these two giant clam species, T. crocea and T. squamosa, are excellent sources of several nutrients that could be beneficial for the health of consumers.

The softshell Mya arenaria is an ecologically and commercially important bivalve mollusc that develops a fatal cancer known as disseminated neoplasia or hemocyte leukemia. This cancer, like many human cancers, involves the master control gene of apoptosis, p53. This gene is also known to interact with retrotransposons, and a growing body of evidence suggests that p53 actually controls retrotransposon expression and subsequently oncogenesis. The recent description of a retrotransposon (i.e., Steamer) in adult M. arenaria and its potential involvement in the oncogenesis of hemocyte leukemia has been suggested. Juvenile clams, previously shown not to develop hemocyte leukemia, were exposed to climate-related changes in seawater temperature and pH predicted for the year 2100. All juvenile softshells do express the retrotransposon Steamer. When juvenile clams are exposed to predicted climate-related changes in temperature and pH in the Gulf of Maine, it significantly induces Steamer expression, specifically in treatments where clams were exposed to low pH. For juvenile individuals of M. arenaria and potentially other bivalves, Steamer may be a candidate biomarker for exposure to ocean acidification conditions.

In this study, a length-structured population model was implemented to describe changes in the abundance of Panopea globosa over time, given parameters for growth and natural mortality rate. The following modules described population dynamics: stochastic individual model growth, survival, selectivity, recruitment, and estimates of initial numbers. In addition, the harvest rate, total biomass, and vulnerable biomass (VB) were calculated to advise management quantities. Spatial serial depletion patterns were detected for P. globosa and evident from the expansion of the fishing grounds over time. These patterns of geographic expansion are common in developing fisheries and are a problem for stock assessment. The densest patches available are usually harvested or even depleted, with fishers switching to new beds and potentially rotating back over time. If the changes in the harvestable area are ignored, the increases in VB and recruitment may mask the population dynamics of several beds, including those that are depleted and have low yield.

Texas Parks and Wildlife Department restricts movement of eastern oysters Crassostrea virginica among Texas bay systems because of potential disease transfer and genetic differences in natural oyster stocks. Oyster diseases, such as bonamiosis, which was found serendipitously in 2007 in Florida waters, and MSX (Haplosporidium nelsoni) have not been characterized in Texas bays. Therefore, it is prudent to periodically examine C. virginica and other bivalve species (e.g., Ostrea equestris and Isognomon sp.) from Texas bays for the presence of the causative agents of these diseases, that is, Bonamia spp. and H. nelsoni, as well as known diseases such as dermo (Perkinsus marinus). Eastern oysters (n = 30/bay) were collected from October to December 2016 from five Texas bays and analyzed for the presence of these parasites. In addition, 89 historical oyster tissue samples collected from two Texas bays in 2010 and 2011 and 37 flat tree oysters Isognomon alatus collected from a single Texas bay in December 2017 were examined. All specimens collected in 2016/2017 were assessed by PCR and histology for the presence of Bonamia spp., H. nelsoni, and P. marinus, whereas 2010/2011 samples were only assessed by PCR. Neither Bonamia spp. nor H. nelsoni were detected in any collected samples. Although 15% of the 2016 eastern oyster samples and 29% of the 2010 to 2011 eastern oyster samples contained P. marinus, the parasite was not found in any flat tree oyster. Sanger sequencing of isolated DNA was performed on samples that were positive for dermo as well as the positive controls for Bonamia sp. and H. nelsoni, which confirmed results. These results serve as a point reference that indicate Bonamia spp. and H. nelsoni are not currently present in Texas bays, but continued biennial monitoring is suggested.

Thirteen aerobic, mesophilic marine bacterial strains were isolated from the pallial (mantle) cavity fluids and associated mucus of the eastern oyster Crassostrea virginica Gmelin. All strains were Gram-negative and identified to genus using 16S RNA gene sequence analysis. Each isolated strain was tested for its ability to inhibit growth of six Gram-negative and five Gram-positive bacterial tester strains, as well as the yeast Candida albicans, using an in vitro agar diffusion screening method to detect antimicrobial activity (Romenenko et al. 2008). All of the marine bacteria isolated from the oyster pallial cavity fluids showed some ability to inhibit tester strains. Two isolates, F (red) and M, inhibited the greatest variety of indicator strains and produced the largest zones of inhibition. Gram-negative indicator strains were more susceptible to antimicrobial activity of pallial fluid isolates than Gram-positive strains. None of the isolated bacteria was shown to inhibit C. albicans. In addition, targeted 16S metagenome libraries from the Chesapeake Bay were screened for the presence of bacteria isolated from this study. Results indicate that there are commonalities between bacteria associated with oysters from Long Island Sound and the Chesapeake Bay systems.

Size selectivity curves were estimated for two commercial dredge configurations used in the United States Atlantic sea scallop (Placopecten magellanicus) fishery. Traditionally, the New Bedford Style dredge (New Bedford dredge) has been used by the commercial fleet; however, since 2013, the Coonamessett Farm Turtle Deflector Dredge (turtle dredge) has been required seasonally in the Mid-Atlantic region to minimize the capture of sea turtles. This analysis provides estimates of selectivity and relative efficiency for the turtle dredge and the New Bedford dredge. Selectivity information for the turtle dredge is currently unknown, and selectivity for the New Bedford dredge was originally assessed in 2008. The Share Each Lengths Catch Total method was used to model scallop catch-at-length data for each commercial dredge with data collected during the Virginia Institute of Marine Science fishery-independent surveys in 2015 to 2017, conducted onboard commercial fishing vessels. The surveys were conducted in the Mid-Atlantic and Georges Bank regions of the resource in three distinct areas. A paired study design was used, where a nonselective National Marine Fisheries Service sea scallop survey dredge and either the turtle dredge or New Bedford dredge were towed simultaneously at each survey station. To assess for time-varying changes in selectivity, results were compared with the 2008 New Bedford dredge analysis. Results indicated the 50% retention length was 98.2 mm, with a selection range of 28.2 mm and a relative efficiency of 0.83 for the turtle dredge. New Bedford dredge results estimated a 50% retention length of 107.4 mm, selection range of 50.5 mm and relative efficiency of 0.81. Comparing selectivity profiles for the turtle dredge and New Bedford dredge with the 2008 results indicated a shift toward increased retention probability for smaller size classes of scallops.

A 49-day rearing trial was conducted to investigate the effects of Pseudoalteromonas espejiana W115 on digestive and immune–related enzyme activities in larval and juvenile Yesso scallop Patinopecten yessoensis. Larvae (day 2 post-fertilization) (day 2 PF) were distributed into three groups and provided with a diet only of microalgae (control group) and supplemented with W115 at final concentrations of 1 × 10⁴ and 1 × 10⁶ cells/mL, respectively. Results showed that umbo larvae (day 13 PF) and/or crawling-pediveliger larvae (day 28 PF) and/or juveniles (day 51 PF) fed with W115 supplementation diet at 10⁴ cells/mL showed a significant increase in pepsin, amylase and cellulase activities compared to those fed the diet of microalgae, however, no significant difference was observed between the 10⁶ cells/mL supplementation and control groups at days 13, 28 and 51 PF. The lysozyme and superoxide dismutase activities of umbo larvae and/or crawling-pediveliger larvae and juveniles treated with 10⁴ and/or 10⁶ cells/mL W115 supplementations were significantly higher than those in the control group, while there were no significant differences in enzyme activities in larvae and juveniles treated with two doses of W115 at days 13, 28 and 51 PF. No significant difference in catalase activity was observed among the three groups at days 13, 28 and 51 PF. In addition, there was increased survival in W115-amended treatments after juveniles were challenged with Vibrio splendidus. The results suggest that a 10⁴ cells/mL supplementation of W115 can be useful in Yesso scallop larviculture.

The biogeochemistry of the Gulf of Maine (GOM) is rapidly changing in response to the changing climate, including rising temperatures, acidification, and declining primary productivity. These impacts are projected to worsen over the next 100 y and will apply selective pressure on populations of marine calcifiers. This study investigates the transcriptome expression response to these changes in ecologically and economically important marine calcifiers, blue mussels. Wild mussels (Mytilus edulis and Mytilus trossulus) were sampled from sites spanning the GOM and exposed to two different biogeochemical water conditions: (1) present-day conditions in the GOM and (2) simulated future conditions, which included elevated temperature, increased acidity, and decreased food supply. Patterns of gene expression were measured using RNA sequencing from 24 mussel samples and contrasted between ambient and future conditions. The net calcification rate, a trait predicted to be under climate-induced stress, was measured for each individual over a 2-wk exposure period and used as a covariate along with gene expression patterns. Generalized linear models, with and without the calcification rate, were used to identify differentially expressed transcripts between ambient and future conditions. The comparison revealed transcripts that likely comprise a core stress response characterized by the induction of molecular chaperones, genes involved in aerobic metabolism, and indicators of cellular stress. Furthermore, the model contrasts revealed transcripts that may be associated with individual variation in calcification rate and suggest possible biological processes that may have downstream effects on calcification phenotypes, such as zinc-ion binding and protein degradation. Overall, these findings contribute to the understanding of blue mussel adaptive responses to imminent climate change and suggest metabolic pathways are resilient in variable environments.

In an effort to elucidate the causes of early life stage mortality, the histological characteristics of oocyte atresia were examined biweekly in the European common cockle Cerastoderma edule (Linnaeus, 1758) over an 11-mo-period (January–November 2018), at a farmed site on the French Atlantic coast. Gametogenesis was continuous at the population level, with no apparent interindividual synchronicity. Atresia was observed throughout the year, at all stages of oogenesis, characterized by loss of the nucleolus, nuclear and chromatin degradation, and angular cell shape. Both atresic and nonatresic oocytes were observed in the same gonad acini, suggesting that the process was either not propagated or not synchronized. Stereological counts showed that atresic oocytes occupied an annual mean of 30% (range 12%–47%) of the oocyte volume. Estimation of the minimum atresic impact showed that more than 50% of the oocytes, whose fate can be determined from histological sections, were or would become atresic, reducing the fecundity accordingly. Together with previously reported results in other bivalve species, this underscores the need for better recognition, documentation, and integration of this process into models of fecundity, reproductive effort, population dynamics, and production.

Heat shock protein 60 (HSP60) is evolutionarily highly conserved, and it assists with protein folding in the mitochondria and serves as a molecular chaperone, increasing cell survival under various conditions. Studies of HSP60 in molluscs under stress conditions remain limited. Here, this study first characterize a full-length HSP60 cDNA from the ark shell Scapharca broughtonii (termed SbHSP60) containing a 1,725-bp open reading frame corresponding to a deduced protein of 574 amino acid residues with a predicted molecular mass of approximately 61.4 kDa. The deduced protein has 72.3%–80.3% amino acid identity with homologs from invertebrates and vertebrates. Phylogenetic analysis showed that SbHSP60 grouped with proteins from other molluscs, forming a sister cluster to the HSP60 proteins from vertebrates. The expression pattern of SbHSP60 as examined by quantitative real-time PCR suggested that these mRNA transcripts were distributed across all examined tissues. The highest levels of expression were found in the hepatopancreas and gill, with decreasing levels of expression in the mantle, foot, hemocytes, and adductor muscle. Expression of SbHSP60 after challenge with Vibrio anguillarum showed similar upregulation profiles in the hepatopancreas and gill, indicating that SbHSP60 is involved in the bacterial defense process as an acute-phase protein. Levels of SbHSP60 in the hepatopancreas and gill were higher in cadmium-exposed individuals than in controls. SbHSP60 was significantly upregulated by Cd stress in the gill, but expression was less affected in the hepatopancreas, implying different roles in cellular Cd stress protection. The effects of heat stress on SbHSP60 mRNA expression were duration- and tissue-specific. The induction of SbHSP60 in the heat-stressed group occurred predominantly in the hepatopancreas, suggesting that protein damage and the consequent requirement for the HSP60 protein are increased during the heat shock process.

The Patagonian red octopus Enteroctopus megalocyathus (Gould, 1852) is one of the most important octopus fishing resources in Patagonian Atlantic and Patagonian Pacific coasts, but there is no information available regarding the biological aspects of the species in intertidal environments. In this work, maturity condition of E. megalocyathus and composition of the capture obtained by a small-scale fishery on intertidal rocky shores in the north of San Jorge Gulf (Patagonian Atlantic coast) were investigated, together with the fishing capacity of the fishermen who operate in the area. Throughout each of the three fishing seasons analyzed, a progressive increase in sexual maturity stages was observed for both sexes. Mature-spawning and spent females were not registered in the catches, whereas mature males constituted only 7.5% of the total catches. Females were heavier than males at a given mantle length. Weight composition of catches revealed the presence of middle-weight animals in all fishing months and an increase in mean weights along the fishing season. Toward the end of the fishing period, the proportion of mature males increased and females outnumbered males. At that time, lighter and immature octopuses recruited to fishing areas, mean weight of the catches decreased, and most fishermen stopped fishing. The mean individual catch was 18.1 kg/fisherman-day, but it was highly variable. Results suggest that females reach maturity, become able to copulate, and spawn in the following months away from fishing grounds, whereas the reproductive stock remains little affected.

The English Channel population of the common cuttlefish Sepia officinalis is the northernmost stock among the entire family Sepiidae. It is characterized by the largest eggs among the species (8.5–12.2 mm in length and 221–533 mg in weight). The potential fecundity is of 3,200–13,000 eggs and actual fecundity up to 3,000 eggs. Size of postovulatory follicles in June was similar to those in March, indicating similar spawning history of sampled animals. Females that lay eggs during the entire reproductive season from the beginning to the end probably are very rare. Despite cold climate and shorter “window” available for reproduction, the female cuttlefish still exhibits the same intermittent spawning as in more southern areas, although individuals release eggs in relatively short periods of time.

The shrimp Pleoticus muelleri (Bate, 1888) is an important fishing product from the Southwest Atlantic waters which is frequently captured as a bycatch and discarded. Wastes and by-products of shrimp are an excellent source of protein and enzymes. This review highlights the biochemical and catalytic properties of proteases from shrimp. Previous studies on P. muelleri enzymes have found different activities of alkaline proteases ranging from 0.01 to 0.78 Abs/min/mg of protein. These changeful results might be explained by the great influence that several biological and experimental factors, such as molting and developmental stages, type of diet, and culture conditions, have on the enzyme function. Regarding acid protease, it has been demonstrated that they have activities between 0.3 and 0.4 Abs/min/mg of protein. Processing Argentine red shrimp waste could offer many higher value products without increasing wild catch volumes; therefore, it is essential to conduct further studies that allow the development of more value-added products derived from the practical usage of shrimp processing waste.

The genetic mechanisms of osmoregulation accompanied by salinity changes in aquatic crustaceans are still unclear. In this study, two different salinity transition experiments were conducted, and the gene expression profiles of gill tissues between the two salinity transition processes were compared to unveil the genetic basis of osmoregulation and high/low salinity acclimation for Eriocheir sinensis. A total of 910 genes were significantly differentially expressed within the two salinity transition processes. Genes associated with ion transport, signal transduction, immune response, and DNA repair generally showed fluctuated expressions in the two salinity transition processes. Genes associated with the nitrogen compound metabolic process, sexual reproduction system, and ammonium transport, such as AASS, HDAC4, VG, MARF1, VMO1, and RHBG, were upregulated in a high salinity environment. Genes associated with lipid metabolism processes, such as OXCT1, TEX2, DIB, and CHKB, were upregulated in a low salinity environment. Results revealed the common and specific responsive mechanism of osmoregulation and different levels of salinity acclimation within the two salinity transition processes of E. sinensis. This study provides valuable genetic resources and novel insights into the osmoregulation research of crustaceans.

The Atlantic horseshoe crab (Limulus polyphemus), a long-lived marine arthropod, is a prime example of a common-pool resource across its native range from Maine to the Yucatan Peninsula, being both a vital ecological food source and a valuable commercial commodity. Genetic differentiation and diversity of horseshoe crabs have been assessed on a regional level, but no fine-scale examinations of these measures had been conducted in South Carolina. A suite of 12 microsatellite loci was used to evaluate the population structure and genetic diversity of spawning adult horseshoe crabs (n = 740) collected from seven sites along the coast of South Carolina from the Georgia/South Carolina border to Bulls Bay. No significant genetic differentiation was detected among the sites, indicating that some degree of gene flow is occurring along the South Carolina coast and that spawning adult horseshoe crabs in South Carolina form a single, unified stock. The horseshoe crab stock in South Carolina contains moderately high levels of genetic diversity (H_o = 0.775_,H_e = 0.778) and fairly low levels of inbreeding (F_IS = 0.005). The effective population size is on the order of several thousand individuals and within the values recommended to maintain evolutionary potential. The information generated here will be useful for management purposes to aid in the regulation and preservation of the horseshoe crab stock and fishery in South Carolina.

Telomeres are evolutionarily conserved sequences capping the ends of linear eukaryotic chromosomes that usually shorten at each cell division, as well as under stressful living conditions. For this reason, telomere length (TL) has been considered as a proxy of age and stress for decades. Globally, most ecological and biology researches have used TL to assess the impact of specific life history traits on organisms life expectancies and persistence of populations. Nevertheless, to our knowledge, ecological studies that consider TL as an approximation of temporal cohorts are rare. In many population monitoring studies, however, knowledge about temporal cohorts are lacking, although they would provide comprehensive information on the natural processes underlying population dynamics. With this in mind, a quantitative PCR approach was used to measure the relative length of telomere sequences of DNA extracted from Paracentrotus lividus sea urchin. The species undergoes intensive harvesting, and some populations are under surveillance in the Mediterranean basin. The results showed that P. lividus experiences a shortening of telomeres with age, suggesting that according to this hypothesis, TL would probably be a relevant biomarker, which could reveal population differences based on their demographic structure, and differential susceptibility to pollution according to size. Future studies are still needed to define the accuracy of TL in detecting specific temporal cohorts in this species and to determine whether the TL should be considered locally in population surveillance studies.

Suppressors of cytokine signaling (SOCS) family members can inhibit multiple biological functions of cytokines, hormones, and growth factors. In this study, a SOCS6 gene homolog from triangle sail mussel Hyriopsis cumingii (HcSOCS6) was cloned and characterized. The full-length cDNA of HcSOCS6 was 1,823 bp and encoded 458 amino acid residues. No introns were found in the genomic sequence. The deduced HcSOCS6 protein possesses highly conserved functional domains, including the Src homology 2 domain and the SOCS box. Phylogenetic analysis showed that HcSOCS6 was clustered with other molluscan genes. Transcripts of HcSOCS6 were constitutively expressed in all examined tissues, at high levels in the hepatopancreas and gills and low levels in hemocytes. Transcription of HcSOCS6 was significantly upregulated in hemocytes and the hepatopancreas after injecting with lipopolysaccharide, but it was only upregulated in hemocytes after Aeromonas hydrophila stimulation. The expression of HcSOCS6 in mantle significantly increased during wound healing, especially on the third day. These results suggested that HcSOCS6 was involved in the immune response and wound healing in the triangle sail mussel.

To investigate a unionid mussel die-off that began in 2016 in the Clinch River, organ tissues from 10 pheasantshells Actinonaias pectorosa (Conrad, 1834) were collected from Kyles Ford, TN, on October 6, 2016. Histological evaluations quantified abundances of tissue lesions in gills, digestive glands, and kidneys; gamete production and resorption levels in reproductive acini; and percentages of mussels infested with parasites. Atrophy and necrosis of digestive gland tissues were prevalent in most mussels, and pervasive necrosis in vesicular connective tissues (VCT) also was observed. Nine of the 10 mussels were infested with parasites. One mussel stained Gram positive, and examination revealed the presence of unidentified streptococci-like bacteria. Nine mussels stained Gram negative, and the stained spherical structures resembled cocci. High fractions of kidney cells containing lipofuscin were observed in the study mussels, indicating high levels of oxidative stress and probable impairment of important organ functions. It is likely that oxidative stress and consequent lipofuscin abundances in the kidney cells resulted from the combined effects of lesions (tissue damage, parasitic infestations, and presumptive bacterial infections) and the low-concentration contaminant array in the Clinch River. Necrosis in digestive glands and VCT decreased the available somatic energy (i.e., lipids and carbohydrates), although energy demands were high because of parasitic infestation, presumptive bacterial infection, altered physiological functions, and needed tissue repair. Although the results of this study could not determine the actual causes of mortality during the mussel die-off, they revealed numerous pervasive tissue lesions in the mussels, which led to starvation-like conditions due to unidentified environmental stressors.

The color of pearl, one of the important quality traits, is determined by the shell nacre color of host mussel; however, the effective method to evaluate the effect of genetic breeding on the purity and uniformity of the nacre color was still limited to the freshwater mussel Hyriopsis cumingii. In this study, the characteristics of the υ₁ band of polyene pigments in the colorful shell nacre and pearl samples from different selective generations of H. cumingii were detected by Raman spectroscopy. The results of this study showed that the number of peaks at the υ₁ band of polyene pigments decreased gradually from 6–8 in the shell nacre and pearls with the color scheme of purple for wild mussels to 1 in those from the mussels of the F4 generation by genetic breeding. Similar results were also found in the samples with the color scheme of orange. But, no obvious peak of the υ₁ band was detected in the samples with white color after four generations of selective breeding. Thus, it could be speculated that the single peak of the υ₁ band in the Raman spectroscopy of shell nacre could be used as the sign of color uniformity to reflect the degree of purification in shell nacre color by genetic breeding. Meanwhile, the results showed that the samples with the same color scheme have a similar main peak at the υ₁ band (ca. 1,508 cm^–1 for the purple color scheme and ca. 1,528 cm^–1 for the orange color scheme), suggesting that the polyene pigments in shell nacre and pearl with the same color scheme have the same length of C = C double bond. The length of C = C double bond were 12 and 9 in purple and orange samples, respectively. In summary, the results of this study support the conclusion that Raman spectroscopy is an efficient method to evaluate the genetic breeding for nacre color in H. cumingii.

Quantifying the physiological impact of environmental stressors on living organisms is critical to predicting the response of any given species to future climate scenarios. Oxygen consumption rates (μmol/g/min) were measured to examine the physiological response of the juvenile blue crab Callinectes sapidus from the Chesapeake Bay (Patuxent River, Maryland) to elevated temperature and dissolved carbon dioxide in water (pCO₂) reflective of projected future climate scenarios. Treatment levels were selected to represent current conditions in the Chesapeake Bay (26°C and 800 μatm) and conditions predicted to occur by the year 2100 (31°C and 8,000 μatm). Crabs were exposed in a factorial design to these conditions throughout two successive molts (approximately 30 days). At the end of the exposure, the oxygen consumption rates of individual crabs were determined over at least a 10-h period using a flow-through respiration chamber equipped with optical oxygen electrodes. No significant effect of temperature or pCO₂ on oxygen consumption was observed, suggesting the absence of a respiratory impact of these two climate stressors on juvenile blue crabs. Oxygen consumption rates were also determined for crabs that experienced a rapid increase in temperature without prior acclimation. The oxygen consumption rate of crabs may have acclimated to increased temperature during the 30-day exposure period before respiratory measurement. This potential acclimation, combined with high individual variability, and a relatively small difference in temperature treatments are likely the cause for the lack of a statistically significant difference in mean oxygen consumption rates by temperature in the core experiment. The results of this study suggest that the blue crab may be quite resilient to future climate stressors and underscore the need for species-specific studies to quantify the effects of climate change on estuarine crustaceans.

Biological interactions between predators and prey constitute a key component of the ecology and evolution of marine systems, and animal behavior can affect the outcome of predator–prey interactions. It has been recently demonstrated that CO₂-induced ocean acidification can alter the behavior of marine organisms and potentially alter predator–prey dynamics. This study combines both quantitative (meta-analysis) and qualitative approaches to review the effects of ocean acidification on behavioral prey defenses in marine invertebrates. A systematic literature search identified 34 studies that experimentally assessed behavioral defenses under elevated pCO₂ spanning three phyla: crustaceans, echinoderms, and molluscs. A meta-analysis suggested that exposure to elevated seawater pCO₂ can negatively affect behavioral defenses in bivalve molluscs and malacostracan crustaceans. By contrast, defenses of cephalopod molluscs seem to be positively impacted by elevated pCO₂, whereas gastropods and echinoids appear unaffected. A qualitative assessment of studies on combined effects of ocean acidification and warming revealed that combined effects typically differ from ocean acidification–only effects. Based on a qualitative assessment of three studies to date, neurological interference of GABA_A receptors under elevated pCO₂ may play a major role in ocean acidification effects on prey defense behaviors; however, more research is needed, and other mechanistic underpinnings are also important to consider. Ultimately, the results of this study suggest that behavioral prey defenses in some shellfish taxa may be vulnerable to ocean acidification, that the effects of ocean acidification are often different under warming scenarios than under present-day temperature scenarios, and that GABA_A interference may be an important mechanism underpinning behavioral responses of shellfish prey under ocean acidification. Despite the importance of shellfish behavioral defenses in the ecology and evolution of marine biological communities, however, research to date has only scraped the surface in understanding ocean acidification effects. Increased research efforts on the effects of multiple stressors, acclimation and adaptation, environmental variability, and complex situational and ecological contexts are needed. Studies of fish behavioral defenses under ocean acidification can help streamline hypotheses and experimental approaches, particularly given the similar effects of elevated pCO₂ on GABA_A function.

As negative effects of ocean acidification are experienced by coastal ecosystems, there is a growing trend to investigate the effect ocean acidification has on multiple generations. Parental exposure to ocean acidification has been shown to induce larval carryover effects, but whether acute exposure to a stressor as an adult can influence the larval generation long after the stress has been removed has yet to be tested. To assess how a temporary exposure to experimental ocean acidification affects the ecologically and commercially relevant Pacific oyster Crassostrea gigas, adult oysters were exposed to either low pH (7.31 ± 0.02) or ambient pH (7.82 ± 0.02) conditions for 7 wk. Oysters were then held for 8 wk in ambient conditions, and subsequently reproductively conditioned for 4 wk at ambient pH. After conditioning, the oysters were strip-spawned to create four families based on maternal and paternal ocean acidification exposure. The number of D-hinge larvae was counted 18 h postfertilization. A sex-specific brood stock response was observed, where female exposure to low pH conditions resulted in fewer D-hinge larvae. This study demonstrates that the effects of ocean acidification can last beyond the time from when the environmental perturbation is experienced. Broadening the understanding of environmental memory will be valuable when considering organismal ability to persist in the face of environmental change.

As oceans and many estuaries become more acidic, identifying adaptable or nonadaptable species (“winners” or “losers”) will enable better predictions of community and ecosystem function alterations due to climate change. Marine bivalves are frequently subjects of ocean acidification (OA) research because of their perceived vulnerability, which also threatens loss of their valuable ecosystem services. Studies indicate that larvae of many broadcast spawning oyster and mussel species are physiologically sensitive to alterations in carbonate chemistry. Running counter to this trend are recent investigations of brooding oyster species (genus Ostrea) that suggest their offspring may be considerably more resistant to OA stress. Although the precise mechanism conferring OA resistance to Ostrea larvae is unknown, a strong candidate appears to be exaptation of traits developing embryos that require to cope with adverse carbonate conditions they typically encounter in the brood chamber. New and previously reported data on Ostrea brood chamber conditions are discussed in the context of OA. Novel technical and experimental approaches are offered to address current knowledge gaps in future studies.

Increasing anthropogenic carbon dioxide is predicted to cause declines in ocean pH and calcium carbonate saturation state over the coming centuries, making it potentially harder for marine calcifiers to build their shells and skeletons. One mechanism of resilience to ocean acidification is an organism's ability to regulate pH and, thus, calcium carbonate saturation state, at its site of calcification. This mechanism has received detailed study in scleractinian corals but is relatively understudied in other taxonomic groups that are vulnerable to ocean acidification, such as bivalves. Here, the results of a 74-day controlled laboratory experiment investigating the impact of ocean acidification on the extrapallial fluid (EPF; the bivalve calcifying fluid) pH, calcification rate, and condition factor of the king scallop Pecten maximus at their average spring and summer temperatures (362 ppm/9.0°C, 454 ppm/12.3°C; 860 ppm/9.0°C, 946 ppm/12.3°C; 2,639 ppm/8.9°C, 2,750 ppm/12.1°C) are presented. Scallop EPF pH was lower than seawater pH in all treatments and declined with increasing pCO₂ under the spring temperature (9°C) but was uncorrelated with pCO₂ under the summer temperature (12°C). Furthermore, king scallop calcification rate and EPF pH were inversely correlated at 9°C and uncorrelated at 12°C. This inverse correlation between EPF pH and scallop calcification rate, combined with the observation that scallop EPF pH is consistently lower than seawater pH, suggests that pH regulation is not the sole mechanism by which scallops concentrate carbonate ions for calcification within their EPF. Calcification trends contrasted most other published studies on bivalves, increasing with ocean acidification under spring temperature and exhibiting no response to ocean acidification under summer temperature. Scallop condition factor exhibited no response to ocean acidification under spring temperature but increased with ocean acidification under summer temperature—exactly the opposite of their calcification response to ocean acidification. These results suggest that king scallops are relatively resilient to CO₂-induced ocean acidification, but that their allocation of resources between tissue and shell production in response to this stressor varies seasonally.

The major cultured mussel species Perna canaliculus is now supported by hatchery production, providing the opportunity to explore and optimize environmental parameters to enhance production. Other cultured bivalve larvae have demonstrated performance that is directly correlated to the aragonite saturation state (Ω_ar) of their tank water, with low or undersaturated water being detrimental and artificially elevated Ω_ar enhancing productivity. Trials were, therefore, designed to specifically explore Ω_ar sensitivity in preveliger (0–2 days old, prodissoconch I = “PD1″) and veliger (2–21 days old, prodissoconch II = “PD2″) stages of P. canaliculus separately. For the PD1 experiment, commercial incubation tanks (control Ω_ar 1.9) were modified to target Ω_ar 0.5 or 0.8 by elevating pCO₂, or 2.9, 4.5, and ∼7 by the addition of sodium carbonate. In the control environment, 72.8% ± 2.9% of fertilized eggs formed viable “D” veligers within two days; an increased yield of 82.6% ± 3.8% in Ω_ar 4.5 was found to be nonsignificant. In comparison, only 12.7% of the Ω_ar ∼7 and <1% of the Ω_ar 0.5 and 0.8 eggs attained the veliger stage, with the remaining underdeveloped or malformed. By 2 days postfertilization, reactive oxygen species were significantly elevated in the undersaturated treatments, whereas DNA damage, lipid hydroperoxides, and protein carbonyls were significantly higher in the Ω_ar 0.5 and ∼7 treatments. Antioxidant enzyme levels were significantly lower in these extreme treatments, whereas Ω_ar 4.5 larvae showed elevated superoxide dismutase, glutathione reductase, and peroxidase levels. Carry-over effects persisted when veligers were transferred to control conditions, with no net recruitment from undersaturated Ω_ar, 29.4% of eggs surviving to pediveliger under control conditions, compared with 33.2% following Ω_ar 4.5 exposure or 1.9% from Ω_ar ∼7. In the PD2 veliger trial, linear shell growth halved in undersaturated water, but was unaffected by elevation of Ω_ar. Mortality rate was consistent across all treatments, suggesting relative resilience to different Ω_ar. It is recommended that hatcheries trial Ω_ar 4–4.5 enrichment in preveliger incubation water to improve yield and minimize oxidative stress. Preveliger stages present a potential survival bottleneck, and focused research exploring sensitivity to near-future ocean acidification is, therefore, needed.

Mussel mariculture uses the natural attachment strategy of marine mussels by allowing them to aggregate on submerged rope lines that are then pulled to the surface and harvested. Mussels attach to ropes using a network of byssal threads, proteinaceous fibers that adhere to surfaces underwater using a powerful biological glue (adhesive plaque). Plaques use the surrounding seawater as a molecular trigger during adhesive curing, a process that requires a pH greater than 7.0 and an abundance of dissolved oxygen to progress. To ascertain whether mussels experience seawater conditions that are potentially harmful to mussel attachment, this study measured the conditions within mussel aggregations at a mussel farm in Washington state and, then, applied those conditions to plaques to determine whether such conditions are sufficient to weaken attachment. Seawater monitoring demonstrated that mussels infrequently experience acidic (pH <5.0) and hypoxic excursions (O₂ <2 mg L^–1) in the summer, especially near the seafloor. When reproduced in laboratory assays, the most extreme pH excursions observed delayed plaque strengthening when applied early in the plaque-curing process, whereas extreme excursions in hypoxia decreased adhesion strength after the adhesive had fully matured. In either case, adhesion strength was rescued after reimmersion in open-ocean seawater conditions, highlighting the resilience of the mussel holdfast to stresses other than mechanical strain. The window of susceptibility to changes in environmental conditions during and after curing could contribute to fall-off events at mussel farms, especially in the late summer months.

Although ocean acidification studies related to marine animal behavior have increased in recent years, the behavioral effects of ocean acidification on shellfish are relatively understudied, even though marine shellfish exhibit a wealth of behaviors that can modify organismal interactions and biological community functioning. Furthermore, detecting acute behavioral changes may provide a biological indicator of ecosystem stress and/or an early warning system for aquaculture operations. This article highlights a new and emerging technology—high-frequency noninvasive (HFNI) electromagnetic biosensors—that can be used to document acute and long-term effects of elevated CO₂ on the valve-gaping behavior of marine bivalves. An overview of the technology is presented, and the current and potential uses of these biosensors in ocean acidification research are highlighted, along with current limitations and next steps. Although a handful of studies have used these biosensors to test for effects of acidification on bivalve valve-gaping behavior, their potential for testing critical and novel hypotheses regarding ocean acidification effects in a broader range of shellfish taxa is currently underused. Ultimately, this article provides a basis for expanding ocean acidification research on shellfish behavior through the use of HFNI electromagnetic biosensors.