Molluscan Larvae Research Articles

Coastal Ecosystem Effects of Increased Summer Temperature and Contamination by the Flame Retardant HBCDD

The combined effects of ocean warming and contaminants on marine ecosystems are poorly understood. In this study, we exposed model ecosystems comprising typical shallow coastal Baltic Sea communities to elevated temperature (+5 °C) and the flame retardant hexabromocyclododecane (HBCDD), both singly and in combination, for 13 days. Higher temperatures caused the release of PO4 from the sediment, which in turn stimulated the growth of the cyanobacteria Dolichospermum sp. This in turn led to an increase in the copepod Acartia bifilosa and other indirect effects in the plankton, interpreted as being caused by changes in predation, grazing, and competition. Elevated temperatures also stimulated benthic primary production and increased production of benthic mollusk larvae. Although increased temperature was the dominant driver of effects in these systems, HBCDD also appeared to have some effects, mainly in the zooplankton (both direct and indirect effects) and benthic meiofauna (an interactive effect with temperature). Although the study used model ecosystems, which are an approximation of field conditions, it highlights that interactive ecosystem effects between two stressors are possible and demonstrates the ecological and temporal complexity of such responses. Such unpredictable responses to warming and contaminants are a major challenge for ecosystem management to deal with multistressor situations in the Baltic Sea.

Transcriptomic analysis of oyster Crassostrea gigas larvae illustrates the response patterns regulated by catecholaminergic system upon acute heat and bacterial stress

Bacterial infection and heat stress, as two major environmental threats of marine molluscs, could affect larval development and dramatically promote mortality of oysters. In the present study, next-generation sequencing, together with determinations of mRNA expression and measurements of enzyme activities, were employed to understand the response patterns of oyster larvae under acute heat and bacterial stress. After RNA-seq, a total of 9472 differentially expressed genes including 4895 significantly up-regulated ones and 4577 significantly down-regulated ones were obtained from 12 transcriptome libraries. GO overrepresentation analysis of the up-regulated genes revealed that the neuroendocrine immunomodulation pathway was activated after acute heat and bacterial stimulation, in which the catecholaminergic regulation played an important role. GO overrepresentation analysis of the down-regulated genes suggested that the immune capacity of Crassostrea gigas larvae was suppressed under stress, which was further validated since superoxide dismutase (SOD) and phenoloxidase (PO) activities in the total protein extract of larvae decreased dramatically after stress. Moreover, the shell formation of trochophore was inhibited and severe mortality was caused after acute heat and bacterial stress. These results collectively indicated that acute heat and bacterial stress could significantly inhibit larval development and suppress immune response of oyster C. gigas larvae. And the neuroendocrine immunomodulation, especially the catecholaminergic regulation, played an indispensable role in the stress response of molluscan larvae.

A simplified, economical, and robust light trap for capturing benthic and pelagic zooplankton

Most of the commonly used light traps for plankton studies are often large, heavy and expensive, and cannot be easily used for pelagic sampling. Although many small, and simple light traps have been designed, most of them are fragile and have weak light sources, allowing only limited collection. In the present study, a new simplified light trap design was described, which is small, lightweight, robust, inexpensive ($70 USD) and easy to construct. The main body of the trap is constructed from a 6L commercial mineral water PET bottle, and the lighting component consists of four 3W white LED bulbs. Pelagic deployment of the new simplified trap and the commonly-used modified Doherty trap was conducted in the same location and compared the composition of the catches including larval fishes and invertebrates. The taxonomic composition of larval fishes collected between the two traps was similar, but it appears that the Doherty trap can collect larger sized larval fishes. Catch composition, wet weights and total number of marine invertebrates collected between the two types of traps are comparable. Ten taxa (copepods, amphipods, crab larvae and juveniles, Cumacea, Euphausiacea, molluscan larvae, isopods, mysids, ostracods and Polychaetes) accounted for over 98% of the total catch of individuals by both trap models. Copepods and crabs larvae were the two most abundant taxa, accounting for more than 55% of the catch. The new and simplified traps therefore represent a robust and comparable design that can be manufactured in large quantities (even in developing countries) and easier in transportation for spatial and temporal studies of plankton dynamics.

Temperature controls the toxicity of the ichthyotoxic dinoflagellate Cochlodinium polykrikoides

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 545:63-76 (2016) - DOI: https://doi.org/10.3354/meps11590 Temperature controls the toxicity of the ichthyotoxic dinoflagellate Cochlodinium polykrikoides Andrew W. Griffith, Christopher J. Gobler* School of Marine and Atmospheric Sciences, Stony Brook University-Southampton, 239 Montauk Highway, Southampton, NY 11968, USA *Corresponding author: christopher.gobler@stonybrook.edu ABSTRACT: Blooms of the harmful dinoflagellate Cochlodinium polykrikoides occur across temperate and tropical zones of the Northern Hemisphere and have lethal impacts on marine life, including fish, coral, and shellfish. We report a series of laboratory- and ecosystem-based experiments examining the effects of temperature on the growth and lethal effects of C. polykrikoides. Growth rates of this alga were positive from 15 to 30°C and were maximal at 24 to 27°C, with cultures cultivated at warmer temperatures (>20°C) yielding significantly higher percentages of cells in chains. In contrast to growth, lethality of clonal isolates and bloom populations of C. poly-krikoides to both larval fish and larval shellfish significantly decreased as temperatures progressively increased from 16 to 28°C. Clonal populations comprising primarily single cells were significantly more toxic than cell-equivalent densities of populations in chains at the same temperature, suggesting temperature-induced changes in cell concatenation influenced lethal effects. The enzyme catalase was capable of mitigating the lethality of C. polykrikoides to fish at higher, but not lower, temperatures, suggesting that higher rates of enzyme activity by the alga and/or target organisms at higher temperatures may mitigate toxicity associated with reactive oxygen species. Collectively, these findings suggest that (1) as blooms in temperate zones progress from summer to fall, their lethality may increase, (2) blooms occurring at tropical latitudes may be less toxic than those in temperate regions, and (3) as global temperatures increase, Cochlodinium spp. blooms may expand into new, higher-latitude regions, where they may be highly lethal. KEY WORDS: Cochlodinium polykrikoides · Climate change · Reactive oxygen species · Harmful algal blooms · Mercenaria mercenaria · Argopecten irradians · Menidia beryllina · Cyprinodon variegatus Full text in pdf format PreviousNextCite this article as: Griffith AW, Gobler CJ (2016) Temperature controls the toxicity of the ichthyotoxic dinoflagellate Cochlodinium polykrikoides. Mar Ecol Prog Ser 545:63-76. https://doi.org/10.3354/meps11590 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 545. Online publication date: March 08, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Transgenerational responses of molluscs and echinoderms to changing ocean conditions

AbstractWe are beginning to understand how the larvae of molluscs and echinoderms with complex life cycles will be affected by climate change. Early experiments using short-term exposures suggested that larvae in oceans predicted to increase in acidification and temperature will be smaller in size, take longer to develop, and have a greater incidence of abnormal development. More realistic experiments which factored in the complex life cycles of molluscs and echinoderms found impacts not as severe as predicted. This is because the performance of one life history stage led to a significant carryover effect on the subsequent life history stage. Carryover effects that arise within a generation, for example, embryonic and larval stages, can influence juvenile and adult success. Carryover effects can also arise across a generation, known as transgenerational plasticity (TGP). A transgenerational response or TGP can be defined as a phenotypic change in offspring in response to the environmental stress experienced by a parent before fertilization. In the small number of experiments which have measured the transgenerational response of molluscs and echinoderms to elevated CO2, TGP has been observed in the larval offspring. If we are to safeguard ecological and economically significant mollusc and echinoderm species against climate change then we require more knowledge of the impacts that carryover effects have within and across generations as well as an understanding of the underlying mechanisms responsible for such adaptation.

Isolation and Characterization of Vibrio Species from Shrimp and Artemia Culture and Evaluation of the Potential Virulence Factor

The intensive cultivation conditions for marine shellfish larvae may easily cause microbial problems. Vibrio species are commonly present in disease affected shrimp farms, seawater and sediments. Vibriosis has resulted in severe economic losses to aquaculture worldwide and affects many farm-raised fishes, shrimps, crustaceans and Artemia. V. harveyi and closely related bacterial species are commonly found in estuarine and coastal marine habitats and can readily be isolated from different environmental sources. The lethal toxicity of extracellular products (ECPs) produced by V. harveyi V. anguillarum and V. parahaemolyticus isolated from shrimp and Artemia culture. Also the virulence factors such as protease, proteolytic activity, and phospholipase and lipase activity and haemolytic activity was studied the virulence strains compared with the non-virulent Vibrio strains. This paper addresses the virulence and epidemiology of vibrio pathogen; pathogenesis of its disease

Draft Genome Sequence of the Shellfish Larval Probiotic Bacillus pumilus RI06-95.

Bacillus pumilus RI06-95 is a marine bacterium isolated in Narragansett, Rhode Island, which has shown probiotic activity against marine pathogens in larval shellfish. We report the genome of B. pumilus RI06-95, which provides insight into the microbe’s probiotic ability and may be used in future studies of the probiotic mechanism.

Directional flow sensing by passively stable larvae.

Mollusk larvae have a stable, velum-up orientation that may influence how they sense and react to hydrodynamic signals applied in different directions. Directional sensing abilities and responses could affect how a larva interacts with anisotropic fluid motions, including those in feeding currents and in boundary layers encountered during settlement. Oyster larvae (Crassostrea virginica) were exposed to simple shear in a Couette device and to solid-body rotation in a single rotating cylinder. Both devices were operated in two different orientations, one with the axis of rotation parallel to the gravity vector, and one with the axis perpendicular. Larvae and flow were observed simultaneously with near-infrared particle-image velocimetry, and behavior was quantified as a response to strain rate, vorticity and centripetal acceleration. Only flows rotating about a horizontal axis elicited the diving response observed previously for oyster larvae in turbulence. The results provide strong evidence that the turbulence-sensing mechanism relies on gravity-detecting organs (statocysts) rather than mechanosensors (cilia). Flow sensing with statocysts sets oyster larvae apart from zooplankters such as copepods and protists that use external mechanosensors in sensing spatial velocity gradients generated by prey or predators. Sensing flow-induced changes in orientation, rather than flow deformation, would enable more efficient control of vertical movements. Statocysts provide larvae with a mechanism of maintaining their upward swimming when rotated by vortices and initiating dives toward the seabed in response to the strong turbulence associated with adult habitats.

Directional flow sensing by passively stable larvae.

Mollusc larvae have a stable, velum-up orientation that may influence how they sense and react to hydrodynamic signals applied in different directions. Directional sensing abilities and responses could affect how a larva interacts with anisotropic fluid motions, including those in feeding currents and in boundary layers encountered during settlement. Oyster larvae (Crassostrea virginica) were exposed to simple shear in a Couette device and to solid-body rotation in a single rotating cylinder. Both devices were operated in two different orientations, one with the axis of rotation parallel to the gravity vector, and one with the axis perpendicular. Larvae and flow were observed simultaneously with near-infrared particle-image velocimetry, and behaviors were quantified as a response to strain rate, vorticity, and centripetal acceleration. Only flows rotating about a horizontal axis elicited the diving response observed previously for oyster larvae in turbulence. The results provide strong evidence that the turbulence-sensing mechanism relies on gravity-detecting organs (statocysts) rather than mechanosensors (cilia). Flow sensing with statocysts sets oyster larvae apart from zooplankters such as copepods and protists that use external mechanosensors in sensing spatial velocity gradients generated by prey or predators. Sensing flow-induced changes in orientation, rather than flow deformation, would enable more efficient control of vertical movements. Statocysts provide larvae with a mechanism of maintaining their upward swimming when rotated by vortices and initiating dives toward the seabed in response to the strong turbulence associated with adult habitats.

Voltage-gated potassium ion channel may play a major role in the settlement of Pacific oyster (Crassostrea gigas) larvae

Abstract While the effects of potassium ion (K + ) on the settlement and metamorphosis of mollusc larvae have been studied in some species, little of this research has focused on the Pacific oyster ( Crassostrea gigas ). It is still unclear which of the potassium channels, the voltage-gated channel or the inward rectifier channel, plays the more important role in the settlement and metamorphosis of mollusc larvae. In this study, the effects of K + and K + channel inhibitors on the settlement and metamorphosis of Pacific oyster larvae were examined. After 24, 48, or 72 h, the highest oyster larval settlement rate was observed at 19 mM K + . The relative metamorphosis rate (number of larvae at metamorphosis ∕ number of larvae at settlement) decreased with increasing K + concentration, however, the highest total metamorphosis rate (number of larvae at metamorphosis ∕ total number of larvae) was observed at 19 mM K + as a result of the very high settlement rate at this concentration. Treatment with tetraethyl-ammonium, the voltage-gated potassium channel inhibitor, resulted in a more obvious suppression of K + -induced oyster larval settlement than Glyburide (Glib), an inhibitor of the inward rectifier potassium channel. These results suggest that the voltage-gated potassium channel may play a more important role than the inward rectifier potassium channel in the settlement of oyster larvae.

Isolation and Characterization of Potential Probiotic Bacteria Suitable for Mollusk Larvae Cultures

Isolation and Characterization of Potential Probiotic Bacteria Suitable for Mollusk Larvae Cultures

Identification of candidate biomarkers for quality assessment of hatchery-reared mussel larvae via GC/MS-based metabolomics

To ensure environmental and economic sustainability of future aquaculture growth, large-scale hatchery production of mollusc larvae is required. However, variation in larval quality currently limits potential maximum yields. Identification of biomarkers which reflect the immediate physiological condition of larvae during hatchery production could help monitor and determine causes of variation. Metabolomics is well-suited to this task due to its capacity for providing an instantaneous snapshot of the physiology of an organism through analysis of its metabolite profile. As a test, we applied GC/MS-based metabolomics for this purpose. Using a variety of univariate and multivariate feature selection methods, we identified four metabolite–metabolite ratios involving levels of succinate, glycine, alanine, pyroglutamate and myristic acid as candidate biomarkers for assessing mussel larval quality. These metabolites are known to have roles in energy metabolism, osmotic regulation, immune function and cell–cell communication. We anticipate that further investigation of these metabolites and their associated biochemical pathways will yield a more complete understanding of the factors responsible for larval production variability.

Complete Genome Sequence for the Shellfish Pathogen Vibrio coralliilyticus RE98 Isolated from a Shellfish Hatchery.

Vibrio coralliilyticus is a pathogen of corals and larval shellfish. Publications on strain RE98 list it as a Vibrio tubiashii; however, whole genome sequencing confirms RE98 as V. coralliilyticus containing a total of 6,037,824 bp consisting of two chromosomes (3,420,228 and 1,917,482 bp) and two megaplasmids (380,714 and 319,400 bp).

Complete Genome Sequence of the Larval Shellfish Pathogen Vibrio tubiashii Type Strain ATCC 19109.

Vibrio tubiashii is a larval shellfish pathogen. Here, we report the first closed genome sequence for this species (ATCC type strain 19109), which consists of two chromosomes (3,294,490 and 1,766,582 bp), two megaplasmids (251,408 and 122,808 bp), and two plasmids (57,076 and 47,973 bp).

Cytochemical characterization of yolk granule acid phosphatase during early development of the oyster Crassostrea gigas (Thunberg)

In this study, a cytochemical method and transmission electron microscopy was used to examine acid phosphatase activities of yolk granules throughout the early developmental stages of the Pacific oyster Crassostrea gigas. This study aimed to investigate the dynamic change of yolk granule acid phosphatase, and the mechanisms underlying its involvement in yolk degradation during the early developmental stages of molluscs. Three types of yolk granules (YGI, YGII, and YGIII) that differed in electron density and acid phosphatase reaction were identified in early cleavage, morula, blastula, gastrula, trochophore, and veliger stages. The morphological heterogeneities of the yolk granules were related to acid phosphatase activity and degrees of yolk degradation, indicating the association of acid phosphatase with yolk degradation in embryos and larvae of molluscs. Fusion of yolk granules was observed during embryogenesis and larval development of C. gigas. The fusion of YGI (free of acid phosphatase reaction) with YGII (rich in acid phosphatase reaction) could be the way by which yolk degradation is triggered.

Morphology and morphometry of buccopharyngeal cavity and pharyngeal dental apparatus of Chagunius chagunio (Hamilton 1822)

Abstract Introduction: Adaptation in morphological and functional aspects of feeding organs is one ofthe key features in the process of biological evolution. Chagunius chagunio represent remarkable specialization and generalization in their buccopharyngeal cavity. Materials and Methods: The samples ranging from 125-190 mm to study the general shape and size of different subdivisions of buccopharyngeal cavity. Results: Buccopharyngeal cavity measures 32.34± 2.95 mm in length and 15.3±2.96 mm in width. Sickle shaped pharyngeal arch measures 14.52±1.2mm in length and 3.52±0.74 mm in width with dental formula 5,3 2-2, 3,5. Conclusion: The minor carp, Chagunius chagunio has been poorly described in literature. It inhabits fast flowing water, have buccopharyngeal cavity with filter feeding modification as in H. molitrix and H. nobilis with spoon shaped pharyngeal teeth However, It has been described in literature that this fish feed on molluscan larvae.

Pelagic larvae of bivalve mollusks of Amursky Bay, Sea of Japan

Larvae of 63 Bivalvia taxa were found in Amursky Bay. Of these, 47 were identified to the species level. Larvae of 55 taxa were found throughout the bay. The highest species diversity was recorded in the northeastern part and in the center of the southern part of the bay, as well as at the exit from it. Larvae of Mactra chinensis, Mytilus coruscus, Crassostrea gigas, Teredo navalis, Mya japonica, and Mysella ventricosa were widely distributed in the bay. The maximum numbers of species were observed in July and September. A comparison of species lists using the set-theory method showed that the species complexes typical of different parts of Amursky Bay are formed under the influence of the Razdolnaya River runoff flow from the north and marine waters coming from the south. The mean density of larvae during the observation period was 1100 specimens/m3 in the northern and 735 specimens/m3 in the southern part of the bay. The highest density of larvae in Amursky Bay was observed at the end of June, the beginning of July, and in September; the minimal larval density occurred in April, May, and August. While the species diversity was similarly high, the density of larvae was significantly higher in Amursky Bay than in the nearby Ussuriisky Bay.

Mechanisms underlying dual effects of serotonin during development of Helisoma trivolvis(Mollusca)

BackgroundSerotonin (5-HT) is well known as widely distributed modulator of developmental processes in both vertebrates and invertebrates. It is also the earliest neurotransmitter to appear during neuronal development. In aquatic invertebrates, which have larvae in their life cycle, 5-HT is involved in regulation of stages transition including larval metamorphosis and settlement. However, molecular and cellular mechanisms underlying developmental transition in aquatic invertebrate species are yet poorly understood. Earlier we demonstrated that in larvae of freshwater molluscs and marine polychaetes, endogenous 5-HT released from the neurons of the apical sensory organ (ASO) in response to external stimuli retarded larval development at premetamorphic stages, and accelerated it at metamorphic stages. Here we used a freshwater snail Helisoma trivolvis to study molecular mechanisms underlying these dual developmental effects of 5-HT.ResultsLarval development of H. trivolvis includes transition from premetamorphic to metamorphic stages and shares the main features of metamorphosis with free-swimming aquatic larvae. Three types of 5-HT receptors (5-HT1-, 5-HT4- and 5-HT7-like) are functionally active at premetamorphic (trochophore, veliger) and metamorphic (veliconcha) stages, and expression patterns of these receptors and respective G proteins undergo coordinated changes during development. Stimulation of these receptors modulated cAMP-dependent regulation of cell divisions. Expression of 5-HT4- and 5-HT7-like receptors and their downstream Gs protein was down-regulated during the transition of pre- to metamorphic stage, while expression of 5-HT1 -like receptor and its downstream Gi protein was upregulated. In accordance with relative amount of these receptors, stimulation of 5-HTRs at premetamorphic stages induces developmental retardation, while their stimulation at metamorphic stages induces developmental acceleration.ConclusionsWe present a novel molecular mechanism that underlies stage-specific changes in developmental tempo of H. trivolvis larvae in response to endogenous 5-HT produced by the neurons of the ASO. We suggest that consecutive changes in expression patterns of different receptors and their downstream partners in the course of larval development represent the molecular base of larval transition from premetamorphic (non-competent) to metamorphic (competent) state.

Molluscan Larvae from the Carboniferous Ichinotani Formation, Fukuji, Gifu Prefecture, Central Japan

Molluscan larval shells are described from the upper Carboniferous (Moscovian) Ichinotani Formation at Fukuji, Okuhida-onsen-gou, Takayama City, Gifu Prefecture, Japan. The vast majority of these larval shells are isolated and not metamorphosed. The larvae appear to represent species with planktotrophic larval development representing pseudozygopleurid, streptacidid and indeterminate gastropods and pteriomorph and anomalodesmacean bivalves. This is the first report of isolated molluscan larval shells from Palaeozoic deposits in Japan.

069 Advances in shellfish germplasm cryopreservation: Current status and future directions

Cryopreservation can be a powerful tool in shellfish aquaculture for selective breeding programmes and hatchery production. Most species that are commercially farmed are broadcast spawners, releasing sperm and eggs into the environment where they fertilize and develop. However, some species are brooders (e.g. flat oysters (Ostrea chilensis) ), which retain and rear embryos until they reach later developmental stages. Sperm cryopreservation has been successfully achieved for several farmed species including the Pacific oyster ( Crassostrea gigas ), greenshell™ mussel ( Perna canaliculus ) and abalone ( Haliotis iris ). In general, dimethyl sulphoxide and trehalose are the preferred cryoprotectants (CPAs) and simple methods to control cooling rate (e.g. floating rack on liquid nitrogen; methanol/dry ice bath) have worked well for our main species of interest (Pacific oyster, greenshell™ mussel and abalone). Interestingly, sperm perform better in CPAs that are prepared in Milli-Q water as opposed to seawater, indicating that a lower salt concentration during freezing is beneficial. Recent studies with flat oysters and geoducks ( Panopea zelandica ) have also resulted in successful sperm cryopreservation. Shellfish oocyte and larvae cryopreservation has proven more challenging, however, successful cryopreservation of Pacific oyster oocytes has been achieved. Pacific oyster oocytes are able to be fertilized and develop to normal spat post-thawing. However, for other species (e.g. greenshell™ mussel) and for larvae, cryo-injuries are not always immediately apparent post-thawing but manifest during development and are often lethal. greenshell™ mussel oocytes are irretrievably damaged when they reach -6 to -8°C and attempts to overcome this sub-zero chilling injury by vitrification have been unsuccessful. Towards understanding these injuries and their effects, we investigated the effect of cryopreservation on the meiotic spindle of greenshell™ mussel oocytes. Results show that the meiotic spindle undergoes major changes during both CPA addition and cooling. However, the spindle is able to re-form normally in most instances given sufficient time post thawing. For a proportion of oocytes, cryopreservation appears to trigger oocyte activation. The effect of cryopreservation on oxidative stress in greenshell™ mussel oocytes has also been investigated. Although, there are changes in oxidative stress parameters as a result of cryopreservation and strong correlations between fertilization, development and oxidative stress parameters (lipid hydroperoxides, superoxide dismutase, protein carbonyls, total glutathione and glutathione state), preliminary attempts to mitigate oxidative stress using antioxidants have so far failed to enable normal development following cooling, suggesting that oxidative stress may be a secondary rather than primary stress event. Research on shellfish larval cryopreservation utilizing SEM and confocal microscopy has also been carried out for greenshell™ mussel. Later larval stages (D-larvae) appear more resilient to cryopreservation than trochophore larvae, but abnormalities are still apparent (e.g.shell abnormalities and delayed organogenesis). Future studies are aimed toward elucidating mechanisms of injury using new tools such as proteomics and then targeting susceptible cellular processes for protection during cryopreservation. Source of funding: This research was funded by the New Zealand Ministry of Business Innovation and Employment (CAWX0802). Conflict of interest: None declared. serean.adams@cawthron.org.nz