Dataset Information

Predatory blue crabs induce stronger nonconsumptive effects in eastern oysters Crassostrea virginica than scavenging blue crabs.

ABSTRACT: By influencing critical prey traits such as foraging or habitat selection, predators can affect entire ecosystems, but the nature of cues that trigger prey reactions to predators are not well understood. Predators may scavenge to supplement their energetic needs and scavenging frequency may vary among individuals within a species due to preferences and prey availability. Yet prey reactions to consumers that are primarily scavengers versus those that are active foragers have not been investigated, even though variation in prey reactions to scavengers or predators might influence cascading nonconsumptive effects in food webs. Oysters Crassostrea virginica react to crab predators by growing stronger shells. We exposed oysters to exudates from crabs fed live oysters or fed aged oyster tissue to simulate scavenging, and to controls without crab cues. Oysters grew stronger shells when exposed to either crab exudate, but their shells were significantly stronger when crabs were fed live oysters. The stronger response to predators than scavengers could be due to inherent differences in diet cues representative of reduced risk in the presence of scavengers or to degradation of conspecific alarm cues in aged treatments, which may mask risk from potential predators subsisting by scavenging.

SUBMITTER: Scherer AE

PROVIDER: S-EPMC5333538 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Predatory blue crabs induce stronger nonconsumptive effects in eastern oysters <i>Crassostrea virginica</i> than scavenging blue crabs.

Scherer Avery E AE Garcia Miranda M MM Smee Delbert L DL

PeerJ 20170228

By influencing critical prey traits such as foraging or habitat selection, predators can affect entire ecosystems, but the nature of cues that trigger prey reactions to predators are not well understood. Predators may scavenge to supplement their energetic needs and scavenging frequency may vary among individuals within a species due to preferences and prey availability. Yet prey reactions to consumers that are primarily scavengers versus those that are active foragers have not been investigated ...[more]

PMID: 28265512

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Project description:BackgroundThe eastern oyster, Crassostrea virginica, is a euryhaline species that can thrive across a wide range of salinities (5-35). As with all estuarine species, individual oysters must be able to regulate their osmotic balance in response to constant temporal variation in salinity. At the population level, recurrent viability selection may be an additional mechanism shaping adaptive osmoregulatory phenotypes at the margins of oyster salinity tolerance. To identify candidate genes for osmoregulation, we sequenced, assembled, and annotated the transcriptome of wild juvenile eastern oysters from 'high' and 'low' salinity regimes. Annotations and candidates were mostly based on the Pacific oyster (Crassostrea gigas) genome sequence so osmoregulatory relevance in C. virginica was explored by testing functional enrichment of genes showing spatially discrete patterns of expression and by quantifying coding sequence divergence.ResultsThe assembly of sequence reads and permissive clustering of potentially oversplit alleles resulted in 98,729 reftigs (contigs and singletons). Of these, 50,736 were annotated with 9,307 belonging to a set of candidate osmoregulatory genes identified from the C. gigas genome. A total of 218,777 SNPs (0.0185 SNPs/bp) were identified in annotated reftigs of C. virginica. Amino acid divergence between translations of C. virginica annotated reftigs and C. gigas coding sequence averaged 23.2 % with an average dN/dS ratio of 0.074, suggesting purifying selection on protein sequences. The high and low salinity source oysters each expressed a subset of genes unique to that group, and the functions for these annotated genes were consistent with known molecular mechanisms for osmotic regulation in molluscs.ConclusionsMost of the osmoregulatory gene candidates experimentally identified in C. gigas are present in this C. virginica transcriptome. In general these congeners show coding sequence divergence too high to make the C. gigas genome a useful reference for C. virginica bioinformatics. However, strong purifying selection is characteristic of the osmoregulatory candidates so functional annotations are likely to correspond. An initial examination of C. virginica presence/absence expression patterns across the salinity gradient in a single estuary suggests that many of these candidates have expression patterns that co-vary with salinity, consistent with osmoregulatory function in C. virginica.

Project description:BackgroundDeclines of the Eastern oyster, Crassostrea virginica, and its numerous ecological benefits have spurred oyster restoration initiatives. Successful restoration of a self-sustaining oyster population requires evaluating the temporal and spatial patterns of recruitment (settlement and survival) of oyster larvae in the target waterbody. Restoration of the Eastern oyster population in the Maryland Coastal Bays (MCBs), USA, a shallow lagoonal estuary, is of interest to federal, state, and non-governmental, but the location and timing of natural recruitment is not known.MethodsWe assessed the spatial and temporal variation in oyster larval recruitment throughout the MCBs using horizontal ceramic tiles and PVC plates. Newly settled oyster larvae (recruits) were monitored biweekly from June to September 2019 and 2020 at 12 sites in the MCBs and a comparison site in Wachapreague, Virginia. Water quality measurements collected included temperature, salinity, dissolved oxygen, pH, and turbidity. The objectives of this study were to determine (1) the most effective substrate and design for monitoring oyster recruitment, (2) the spatial and temporal distribution of oyster larval recruitment in the MCBs, and (3) patterns in oyster larval recruitment that would be applicable to other lagoonal estuaries.Results(1) Ceramic tiles were more effective than PVC plates for recruiting oyster larvae. (2) Peak settlement began during the period from late June through July, and oyster recruitment was greatest at sites closest to the Ocean City and Chincoteague inlets. (3) Areas near broodstock that have slow flushing rates to retain larvae may provide the best environments for recruitment of oysters to lagoonal estuaries.DiscussionAs the first study on oyster larval recruitment in the MCBs, our results provide insight into their spatial and temporal distribution, methods that can serve as a foundation for future recruitment studies in other lagoonal estuaries, and baseline data that can be used to inform stakeholders and evaluate the success of oyster restoration projects in MCBs.

Dataset Information

Predatory blue crabs induce stronger nonconsumptive effects in eastern oysters Crassostrea virginica than scavenging blue crabs.

Publications

Predatory blue crabs induce stronger nonconsumptive effects in eastern oysters <i>Crassostrea virginica</i> than scavenging blue crabs.

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