Giant Clams (Bivalvia: Cardiidae: Tridacninae): A Comprehensive Update of Species and their Distribution, Current Threats and Conservation Status

Neo, Mei Lin; Wabnitz, Colette C.C.; Braley, Richard D.; Heslinga, G.A.; Fauvelot, Cécile; Wynsberge, Simon Van; Andréfouët, Ser.G.E.; Waters, Charles G.; Tan, Aileen Shau-Hwai; Gomez, Edgardo D.; Costello, Mark J.; Todd, Peter A.

doi:10.1201/b21944-5

Cited by 92 publications

(117 citation statements)

References 99 publications

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“…; Neo et al. ). Unlike the cold and nutrient‐rich waters of higher latitudes, the warm tropical waters lack overturn which stirs up bottom sediments and brings nutrients to the surface waters to trigger plankton growth (Horn ).…”

Section: Introductionmentioning

confidence: 98%

Carbonic anhydrase 2‐like in the giant clam, Tridacna squamosa : characterization, localization, response to light, and possible role in the transport of inorganic carbon from the host to its symbionts

Koh

Hiong

et al. 2017

Physiol Rep

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The fluted giant clam, Tridacna squamosa, lives in symbiosis with zooxanthellae which reside extracellularly inside a tubular system. Zooxanthellae fix inorganic carbon (Ci) during insolation and donate photosynthate to the host. Carbonic anhydrases catalyze the interconversion of CO 2 and HCO3−, of which carbonic anhydrase 2 (CA2) is the most ubiquitous and involved in many biological processes. This study aimed to clone a CA2 homolog (CA2‐like) from the fleshy and colorful outer mantle as well as the thin and whitish inner mantle of T. squamosa, to determine its cellular and subcellular localization, and to examine the effects of light exposure on its gene and protein expression levels. The cDNA coding sequence of CA2‐like from T. squamosa comprised 789 bp, encoding 263 amino acids with an estimated molecular mass of 29.6 kDa. A phenogramic analysis of the deduced CA2‐like sequence denoted an animal origin. CA2‐like was not detectable in the shell‐facing epithelium of the inner mantle adjacent to the extrapallial fluid. Hence, CA2‐like is unlikely to participate directly in light‐enhanced calcification. By contrast, the outer mantle, which contains the highest density of tertiary tubules and zooxanthellae, displayed high level of CA2‐like expression, and CA2‐like was localized to the tubule epithelial cells. More importantly, exposure to light induced significant increases in the protein abundance of CA2‐like in the outer mantle. Hence, CA2‐like could probably take part in the increased supply of inorganic carbon (Ci) from the host clam to the symbiotic zooxanthellae when the latter conduct photosynthesis to fix Ci during light exposure.

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Section: Introductionmentioning

confidence: 98%

Carbonic anhydrase 2‐like in the giant clam, Tridacna squamosa : characterization, localization, response to light, and possible role in the transport of inorganic carbon from the host to its symbionts

Koh

Hiong

et al. 2017

Physiol Rep

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“…Giant clams (Cardiidae: Tridacninae) are iconic mollusks of Indo‐Pacific coral reefs, distributed from the Red Sea and eastern Africa to the central Pacific Ocean, inhabiting shallow lagoons and reef slopes down to approximately 30 m deep (Neo et al, ). They are of high ecological importance, playing multiple roles in the framework of coral reef communities (Neo, Eckman, Vicentuan, Teo, & Todd, ).…”

Section: Introductionmentioning

confidence: 99%

“…They also are of subsistence, commercial and cultural importance for local communities (Wabnitz, Taylors, Green, & Razak, ). Ravaged by overexploitation, wild stocks of most giant clam species are depleted worldwide, with some species locally extinct in several countries (Neo et al, ; Wells, ; van Wynsberge et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…Three of these Tridacna species are endemic to the Red Sea and WIO region ( T. lorenzi , T. rosewateri and T. squamosina ) (Neo et al, ). Tridacna squamosina has been only recently reappraised as a species distinct from its two congeners in the Red Sea, T. maxima and T. squamosa , based on molecular genetics (Richter, Roa‐Quiaoit, Jantzen, Al‐Zibdah, & Kochzius, ).…”

Section: Introductionmentioning

confidence: 99%

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Phylogeographical patterns and a cryptic species provide new insights into Western Indian Ocean giant clams phylogenetic relationships and colonization history

Fauvelot

Zuccon

Borsa

et al. 2020

Journal of Biogeography

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Aim: The unique biodiversity in the Red Sea is the result of complex ecological and evolutionary processes driven by Pleistocene climatic change. Here we investigate the species diversity, phylogenetic relationships and phylogeographical patterns of giant clams in the Western Indian Ocean (WIO) and the Red Sea to explore scenarios of marine speciation in this under-studied region. Location: Mozambique Channel, Madagascar, and the Mascarene Islands (WIO); the Farasan Islands (Red Sea). Taxon: Giant clams of the genus Tridacna (Cardiidae: Tridacninae). Methods: Giant clams were sampled as complete organisms or through underwater biopsies. Nuclear (28S) and mitochondrial (16S and COI) DNA sequences were subjected to Bayesian and maximum likelihood analyses to generate a phylogenetic hypothesis for all known species within the genus Tridacna. Bayesian inference with molecular and fossil calibration was used to infer their colonization history. Results: From the 10 genetically distinct clades recovered from the analyses of 253 sequenced specimens, five distinct Tridacna lineages were sampled, three of which were endemics of the WIO and the Red Sea. Each lineage corresponded to a distinct species, except one grouping the two formerly known WIO endemics, T. lorenzi and T. rosewateri. This lineage clustered with two other well-supported lineages: the Red Sea endemic T. squamosina, and a previously unrecognized lineage, restricted to the WIO, for which we resurrect the long-forgotten name T. elongatissima Bianconi, 1856. For the two other species sampled (T. maxima and T. squamosa), contrasting phylogeographical patterns were observed. Main conclusions: Our data confirm the validity of the species T. rosewateri, a WIO endemic genetically indistinguishable from T. lorenzi, which should be considered a junior synonym. The phylogenetic placement of the newly resurrected T. elongatissima provides insights into the probable origin of T. squamosina, which split from its sister species no later than 2 Ma, likely during Middle Pleistocene glacial periods. Two | 1087 FAUVELOT ET AL.

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“…Resource extraction, sediment pollution and habitat modification are important drivers of marine biodiversity declines globally (Sala and Knowlton 2006), and there are many examples from the literature of reduced species richness and altered community composition at heavily urbanized sites (Pearson and Rosenberg 1978, Long et al 1995, Lindegarth and Hoskin 2001, Lotze et al 2006, Airoldi and Beck 2007, Poquita-Du 2019. Even though the diversity of marine assemblages in some regions is negatively correlated with human population density (Scherner et al 2013, Neo et al 2017), this pattern is not universal, and varies considerably between regions, cities, the taxa and type of diversity considered, and the methods used. For instance, using eDNA from water samples, Kelly et al (2016) found that species richness was positively correlated with land-based urbanization in intertidal seagrass beds.…”

Section: Changes In Biodiversity and Productivitymentioning

confidence: 99%

Towards an urban marine ecology: characterizing the drivers, patterns and processes of marine ecosystems in coastal cities

Todd

Heery

Loke

et al. 2019

Oikos

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Human population density within 100 km of the sea is approximately three times higher than the global average. People in this zone are concentrated in coastal cities that are hubs for transport and trade – which transform the marine environment. Here, we review the impacts of three interacting drivers of marine urbanization (resource exploitation, pollution pathways and ocean sprawl) and discuss key characteristics that are symptomatic of urban marine ecosystems. Current evidence suggests these systems comprise spatially heterogeneous mosaics with respect to artificial structures, pollutants and community composition, while also undergoing biotic homogenization over time. Urban marine ecosystem dynamics are often influenced by several commonly observed patterns and processes, including the loss of foundation species, changes in biodiversity and productivity, and the establishment of ruderal species, synanthropes and novel assemblages. We discuss potential urban acclimatization and adaptation among marine taxa, interactive effects of climate change and marine urbanization, and ecological engineering strategies for enhancing urban marine ecosystems. By assimilating research findings across disparate disciplines, we aim to build the groundwork for urban marine ecology – a nascent field; we also discuss research challenges and future directions for this new field as it advances and matures. Ultimately, all sides of coastal city design: architecture, urban planning and civil and municipal engineering, will need to prioritize the marine environment if negative effects of urbanization are to be minimized. In particular, planning strategies that account for the interactive effects of urban drivers and accommodate complex system dynamics could enhance the ecological and human functions of future urban marine ecosystems.

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Giant Clams (Bivalvia: Cardiidae: Tridacninae): A Comprehensive Update of Species and their Distribution, Current Threats and Conservation Status

Cited by 92 publications

References 99 publications

Carbonic anhydrase 2‐like in the giant clam, Tridacna squamosa : characterization, localization, response to light, and possible role in the transport of inorganic carbon from the host to its symbionts

Carbonic anhydrase 2‐like in the giant clam, Tridacna squamosa : characterization, localization, response to light, and possible role in the transport of inorganic carbon from the host to its symbionts

Phylogeographical patterns and a cryptic species provide new insights into Western Indian Ocean giant clams phylogenetic relationships and colonization history

Towards an urban marine ecology: characterizing the drivers, patterns and processes of marine ecosystems in coastal cities

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