Flexibility in Red Sea Tridacna maxima ‐Symbiodiniaceae associations supports environmental niche adaptation

Giant clams are an important ecological component of coral reefs in the Red Sea, as they enhance the reef’s productivity and provide habitat that can increase diversity. Three species of giant clams, namely Tridacna maxima, T. squamosa, and T. squamosina have been described within the Red Sea. However, due to its scarcity, information about the distribution and ecology of T. squamosina in the Saudi Arabian Red Sea is still lacking. This study used DNA barcoding to confirm the identity of the rare T. squamosina in the Farasan Banks. Six mtCOI fragments (500 bp) of T. squamosina were successfully amplified using the SQUA-primers for the first time. We used our data along with 18 reference sequences (16S) from the online database to assess the genetic diversity and population structure of T. squamosina. Low genetic diversity among the T. squamosina populations inferred from the 16S sequences implies a recent bottleneck for this species, which is supported by their historically higher diversity based on the coalescent-based estimator. Given the small population abundance and limited genetic variation of T. squamosina, it may warrant immediate local protections such as biobanking and fertility preservation programs as well as effective integrated coastal zone management plans.

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Large dendrinids meet giant clam: the bioerosion trace fossil Neodendrina carnelia igen. et isp. n. in a Tridacna shell from Pleistocene–Holocene coral reef deposits, Red Sea, Egypt

Fossil Record ◽

10.5194/fr-21-1-2018 ◽

2018 ◽

Vol 21 (1) ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Max Wisshak ◽

Christian Neumann

Keyword(s):

Coral Reef ◽

Red Sea ◽

Trace Fossil ◽

Giant Clam ◽

Shallow Marine ◽

Tropical Coral ◽

Tropical Coral Reef ◽

Tridacna Maxima ◽

Large Representative ◽

Sea Coast

Abstract. The rosette-shaped microboring trace fossil Neodendrina carnelia igen. et isp. n. – a large representative of the ichnofamily Dendrinidae – is identified on the inner side of the giant clam Tridacna maxima from Pleistocene to Holocene coral reef deposits of the El Quseir district at the Egyptian Red Sea coast. The new dendritic bioerosion trace fossil is diagnosed as a radial rosette comprised of a prostrate system of roofless canals that ramify in a strictly dichotomous fashion forming intermittent branches of uniform width and rounded terminations. The trace appears to be rare, although in the type material it occurs in a cluster of more than a hundred specimens. The location of traces on the interior surface of the shell suggests that boring occurred post-mortem to the host. Its record is presently restricted to shallow marine, euphotic, tropical coral reef settings in the Western Indo-Pacific (Red Sea and Madagascar). The biological identity of the trace maker cannot be resolved yet, but several lines of reasoning allow speculations directed towards a complex attachment scar, perhaps produced by a benthic foraminiferan or a macrophyte.

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