Dataset Information

Growth, Survival and Reproduction of the Giant Clam Tridacna maxima (Roding 1798, Bivalvia) in Two Contrasting Lagoons in French Polynesia.

ABSTRACT: Shell growth, reproduction, and natural mortality of the giant clam Tridacna maxima were characterized over a two-year-period in the lagoon of the high island of Tubuai (Austral Archipelago) and in the semi-closed lagoon of Tatakoto (Tuamotu Archipelago) in French Polynesia. We also recorded temperature, water level, tidal slope, tidal range, and mean wave height in both lagoons. Lower lagoon aperture and exposure to oceanic swells at Tatakoto than at Tubuai was responsible for lower lagoon water renewal, as well as higher variability in temperature and water level at Tatakoto across the studied period. These different environmental conditions had an impact on giant clams. Firstly, spawning events in the lagoon of Tatakoto, detected by gonad maturity indices in June and July 2014, were timed with high oceanic water inflow and a decrease in lagoon water temperature. Secondly, temperature explained differences in shell growth rates between seasons and lagoons, generating different growth curves for the two sites. Thirdly, local mortality rates were also found to likely be related to water renewal patterns. In conclusion, our study suggests that reef aperture and lagoon water renewal rates play an integral role in giant clam life history, with significant differences in rates of shell growth, mortality and fertility found between open versus semi-closed atoll lagoons in coral reef ecosystems.

SUBMITTER: Van Wynsberge S

PROVIDER: S-EPMC5261826 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Publications

Growth, Survival and Reproduction of the Giant Clam Tridacna maxima (Röding 1798, Bivalvia) in Two Contrasting Lagoons in French Polynesia.

Van Wynsberge Simon S Andréfouët Serge S Gaertner-Mazouni Nabila N Wabnitz Colette C C CC Menoud Mathilde M Le Moullac Gilles G Levy Peva P Gilbert Antoine A Remoissenet Georges G

PloS one 20170124 1

Shell growth, reproduction, and natural mortality of the giant clam Tridacna maxima were characterized over a two-year-period in the lagoon of the high island of Tubuai (Austral Archipelago) and in the semi-closed lagoon of Tatakoto (Tuamotu Archipelago) in French Polynesia. We also recorded temperature, water level, tidal slope, tidal range, and mean wave height in both lagoons. Lower lagoon aperture and exposure to oceanic swells at Tatakoto than at Tubuai was responsible for lower lagoon wate ...[more]

PMID: 28118406

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Project description:BACKGROUND:Giant clams and scleractinian (reef-building) corals are keystone species of coral reef ecosystems. The basis of their ecological success is a complex and fine-tuned symbiotic relationship with microbes. While the effect of environmental change on the composition of the coral microbiome has been heavily studied, we know very little about the composition and sensitivity of the microbiome associated with clams. Here, we explore the influence of increasing temperature on the microbial community (bacteria and dinoflagellates from the family Symbiodiniaceae) harbored by giant clams, maintained either in isolation or exposed to other reef species. We created artificial benthic assemblages using two coral species (Pocillopora damicornis and Acropora cytherea) and one giant clam species (Tridacna maxima) and studied the microbial community in the latter using metagenomics. RESULTS:Our results led to three major conclusions. First, the health status of giant clams depended on the composition of the benthic species assemblages. Second, we discovered distinct microbiotypes in the studied T. maxima population, one of which was disproportionately dominated by Vibrionaceae and directly linked to clam mortality. Third, neither the increase in water temperature nor the composition of the benthic assemblage had a significant effect on the composition of the Symbiodiniaceae and bacterial communities of T. maxima. CONCLUSIONS:Altogether, our results suggest that at least three microbiotypes naturally exist in the studied clam populations, regardless of water temperature. These microbiotypes plausibly provide similar functions to the clam host via alternate molecular pathways as well as microbiotype-specific functions. This redundancy in functions among microbiotypes together with their specificities provides hope that giant clam populations can tolerate some levels of environmental variation such as increased temperature. Importantly, the composition of the benthic assemblage could make clams susceptible to infections by Vibrionaceae, especially when water temperature increases. Video abstract.

Project description:1. A beta-galactosyl-binding lectin was purified from the haemolymph of the clam Tridacna maxima by affinity chromatography using polylecyl larch galactan, D-galactosamine coupled to epoxy-activated Sepharose or acid-treated Sepharose. Elution with N-acetyl-D-galactosamine or lactose displaced the bound lectin, which appeared homogeneous by sedimentation analysis. On immunoelectrophoresis at pH8.6 and against rabbit antisera to crude T. maxima haemolymph, the lectin gave one precipitin arc in the alpha-region. 2. On a alkaline polyacrylamide disc gels, one lightly stained band and a broad diffuse band were seen close to the cathode. Ioselectric focusing in solution revealed two peaks of pI4.05 and 4.25 and a shoulder, pI4.0, whereas at least three bands close together (pI3.9-4.3) were seen after electrofusing in gel. 3. The agglutinin is a glycoprotein with a mol.wt. of 470300 +/- 20000. Amino acid analysis revealed no methionine and a significant amount of half-cystine residues. 4. Tridacna lectin is a metalloprotein requiring Ca2+ for its haemagglutinating and precipitating activities. 5. In haemagglutination studies the agglutinin exhibited a broad pH optimum (4.8-10.6). 6. Polysaccharides and glycoproteins with terminal non-reducing beta-D-galactosyl residues reacted with the lectin to form precipitates both in gel and in solution. Inhibition experiments showed that N-acetyl-D-galactosamine was the best inhibitor of the agglutinin combining sites, followed by p-nitrophenyl beta-D-galactoside, methyl beta-D-galactoside, D-galactosamine and 60O-beta-D-galactopyranosyl-D-galactopyranose. On a molar basis, N-acetyl-D-galactosamine was 20-fold more active than D-galactose and nearly 10-fold more inhibitory than D-galactosamine. 7. Circular-dichroism studies showed that the lectin contains a relatively high proportion of beta-structure. 8. Mercaptoethanol treatment of the agglutinin followed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed subunits with approx. mol.wts. of 10000, 20000 and 40000.

Dataset Information

Growth, Survival and Reproduction of the Giant Clam Tridacna maxima (Roding 1798, Bivalvia) in Two Contrasting Lagoons in French Polynesia.

Publications

Growth, Survival and Reproduction of the Giant Clam Tridacna maxima (Röding 1798, Bivalvia) in Two Contrasting Lagoons in French Polynesia.

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