Distribution of the giant clam Tridacna elongatissima in the Western Indian Ocean
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PROVIDER: PRJEB47863 | ENA |
REPOSITORIES: ENA
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Project description:Western Indian Ocean giant tortoises
| PRJEB51299 | ENA
Project description:The Oman upwelling zone (OUZ) creates an unfavorable environment and a major biogeographic barrier for many coral reef species, such as giant clams, thus promoting and maintaining faunal differences among reefs on the east and west side of the Arabian Peninsula. We record the former existence of Tridacna in the Gulf of Oman and review its stratigraphic distribution in the Persian Gulf to provide new insights on the connectivity of coral reef habitats around southern Arabia under changing climate and ocean conditions. Fossil shells were carbon-14 dated and employed as sclerochronological proxy archives. This reveals that the Omani population represents a last glacial colonization event during the Marine Isotope Stage 3 interstadial under colder-than-present temperatures and variable upwelling intensity linked to Dansgaard-Oeschger climate oscillations. It was favored by temperatures just above the lower threshold for the habitat-forming reef coral communities and instability of the upwelling barrier. We conclude that the distribution of Tridacna in the northern Arabian Sea is generally limited by either strong upwelling or cool sea surface temperature under gradually changing climate conditions at the interglacial-glacial scale. Opportunities for dispersal and temporary colonization existed only when there was a simultaneous attenuation of both limiting factors due to high-frequency climate variability. The OUZ will unlikely become a future climate change refuge for giant clams because they will be exposed either to thermal stress by rapid anthropogenic Indian Ocean warming or to unfavorable upwelling conditions.
| S-EPMC9529976 | biostudies-literature
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.
| S-EPMC7175534 | biostudies-literature
Project description:The complete mitochondrial genome of the giant clam Tridacna derasa was completely sequenced by high-throughput sequencing method. The total length of the complete mitogenome was 20,760bp, including 13 protein-coding genes, 23 transfer RNA genes, 2 ribosomal RNA genes and a non-coding control region. The base composition of the genome is 28.41% A, 36.92% G, 21.94% G and 12.74% C with a total GC content of 34.68%. Phylogenetic tree based on complete mitogenome sequences revealed that T.derasa was closely related to T.squamosa, both belonging to the Tridacna genus.
| S-EPMC7799873 | biostudies-literature
Project description:Giant clams (genus Tridacna) are iconic coral reef animals of the Indian and Pacific Oceans, easily recognizable by their massive shells and vibrantly colored mantle tissue. Most Tridacna species are listed by CITES and the IUCN Redlist, as their populations have been extensively harvested and depleted in many regions. Here, we survey Tridacna crocea and Tridacna maxima from the eastern Indian and western Pacific Oceans for mitochondrial (COI and 16S) and nuclear (ITS) sequence variation and consolidate these data with previous published results using phylogenetic analyses. We find deep intraspecific differentiation within both T. crocea and T. maxima. In T. crocea we describe a previously undocumented phylogeographic division to the east of Cenderawasih Bay (northwest New Guinea), whereas for T. maxima the previously described, distinctive lineage of Cenderawasih Bay can be seen to also typify western Pacific populations. Furthermore, we find an undescribed, monophyletic group that is evolutionarily distinct from named Tridacna species at both mitochondrial and nuclear loci. This cryptic taxon is geographically widespread with a range extent that minimally includes much of the central Indo-Pacific region. Our results reinforce the emerging paradigm that cryptic species are common among marine invertebrates, even for conspicuous and culturally significant taxa. Additionally, our results add to identified locations of genetic differentiation across the central Indo-Pacific and highlight how phylogeographic patterns may differ even between closely related and co-distributed species.
| S-EPMC3835327 | biostudies-literature
Project description:In this study, we present the first complete mitochondrial genome sequence of the giant clam Tridacna gigas. The total length of the mitogenome is 19,558 bp. It contains the typical mitochondrial genomic structure, including 13 protein-coding genes, 23 transfer RNA genes, two ribosomal RNA genes, and one control region (D-loop). Mitogenome base composition is biased toward A + T content, at 57.6%. A phylogenetic tree based on complete mitogenome sequences revealed that, within the genus Tridacna, T. gigas is closely related to T. derasa.
| S-EPMC7594740 | biostudies-literature
Project description:The giant clam Tridacna crocea, native to Indo-Pacific coral reefs, is noted for its unique ability to bore fully into coral rock and is a major agent of reef bioerosion. However, T. crocea's mechanism of boring has remained a mystery despite decades of research. By exploiting a new, two-dimensional pH-sensing technology and manipulating clams to press their presumptive boring tissue (the pedal mantle) against pH-sensing foils, we show that this tissue lowers the pH of surfaces it contacts by greater than or equal to 2 pH units below seawater pH day and night. Acid secretion is likely mediated by vacuolar-type H+-ATPase, which we demonstrate (by immunofluorescence) is abundant in the pedal mantle outer epithelium. Our discovery of acid secretion solves this decades-old mystery and reveals that, during bioerosion, T. crocea can liberate reef constituents directly to the soluble phase, rather than producing sediment alone as earlier assumed.
| S-EPMC6030592 | biostudies-literature
Project description:Vibrio coralliilyticus is a pathogen of coral and mollusk, contributing to dramatic losses worldwide. In our study, we found that V. coralliilyticus challenge could directly affect adult Tridacna crocea survival; there were dead individuals appearing at 6 h post infection, and there were 45.56% and 56.78% mortality rates in challenged groups after 36 h of infection. The apoptosis rate of hemocytes was significantly increased by 1.8-fold at 6 h after V. coralliilyticus injection. To shed light on the mechanistic molecular responses of T. crocea to V. coralliilyticus infection, we used transcriptome sequencing analysis and other relevant techniques to analyze T. crocea hemocytes at 0 h, 6 h, 12 h and 24 h after V. coralliilyticus challenge. Our results revealed that the total numbers of unigenes and DEGs were 195651 and 3446, respectively. Additional details were found by KEGG pathway enrichment analysis, where DEGs were significantly enriched in immune-related signaling pathways, such as the TLR signaling pathway, and some were associated with signaling related to apoptosis. Quantitative validation results illustrated that with exposure to V. coralliilyticus, the expression of TLR pathway members, TLR, MyD88, IRAK4, TRAF6, and IкB-α, were significantly upregulated (by 22.9-, 9.6-, 4.0-, 3.6-, and 3.9-fold, respectively) at 6 h. The cytokine-related gene IL-17 exhibited an increase of 6.3-fold and 10.5-fold at 3 h and 6 h, respectively. The apoptosis-related gene IAP1 was dramatically increased by 2.99-fold at 6 h. These results indicate that adult T. crocea could initiate the TLR pathway to resist V. coralliilyticus, which promotes the release of inflammatory factors such as IL-17 and leads to the activation of a series of outcomes, such as apoptosis. The response mechanism is related to the T. crocea immunoreaction stimulated by V. coralliilyticus, providing a theoretical basis for understanding T. crocea immune response mechanisms.
| S-EPMC7148125 | biostudies-literature
Project description:Giant clams (subfamily Tridacninae) are prevalent members of coral reef communities and engage in symbioses with algal photosymbionts of the family Symbiodiniaceae, similar to their scleractinian coral counterparts. However, we know little about their associated bacterial microbiome members. Here, we explored bacterial community diversity of digestive system, gill, and mantle tissues associated with the giant clam Tridacna maxima across a cross-shelf gradient (inshore, midshore, and offshore reef sites) in the central Red Sea using 16S rRNA gene amplicon sequencing. Different tissues harbor spatially stable and distinct microbial communities. Notably, diverse assemblages of bacteria affiliated to the family Endozoicomonadaceae were prevalent in all tissues, but particularly abundant in gills and to a lesser extent in digestive tissues. Besides Endozoicomonadaceae, bacteria in the families Pasteurellaceae, Alteromonadaceae, and Comamonadaceae were common associates, depending on the tissue queried. Taxonomy-based functional inference identified processes related to nitrogen cycling (among others) to be enriched in giant clam tissues and contributed by Endozoicomonadaceae. Our study highlights the tissue-specificity and broad taxonomic range of Endozoicomonadaceae associates, similar to other marine invertebrates, and suggests their contribution to nitrogen-related pathways. The investigation of bivalve-associated microbiome communities provides an important addition to the pathogen-focused studies for commercially important bivalves (e.g., oysters).
| S-EPMC6901920 | biostudies-literature
Project description:Temperature can modify membrane fluidity and thus affects cellular functions and physiological activities. This study examines lipid remodelling in the marine symbiotic organism, Tridacna maxima, during a time series of induced thermal stress, with an emphasis on the morphology of their symbiont Symbiodinium First, we show that the French Polynesian giant clams harbour an important proportion of saturated fatty acids (SFA), which reflects their tropical location. Second, in contrast to most marine organisms, the total lipid content in giant clams remained constant under stress, though some changes in their composition were shown. Third, the stress-induced changes in fatty acid (FA) diversity were accompanied by an upregulation of genes involved in lipids and ROS pathways. Finally, our microscopic analysis revealed that for the giant clam's symbiont, Symbiodinium, thermal stress led to two sequential cell death processes. Our data suggests that the degradation of Symbiodinium cells could provide an additional source of energy to T maxima in response to heat stress.
| S-EPMC5087672 | biostudies-literature