Bentharca cf. asperula (Dall, 1881)

Wiklund, Helena, Taylor, John D., Dahlgren, Thomas G., Todt, Christiane, Ikebe, Chiho, Rabone, Muriel & Glover, Adrian G., 2017, Abyssal fauna of the UK- 1 polymetallic nodule exploration area, Clarion-Clipperton Zone, central Pacific Ocean: Mollusca, ZooKeys 707, pp. 1-46 : 14-16

Bentharca cf. asperula (Dall, 1881)

Material examined.

NHM_108 NHMUK 20170061, collected 2013-10-11, 13.79335 -116.70308, 4081 m. http://data.nhm.ac.uk/object/9d29d7ec-55cd-4b41-929a-2379be221263

NHM_150 NHMUK 20170062.1-2, collected 2013-10-11, 13.75833 -116.69852, 4080 m. http://data.nhm.ac.uk/object/96bfe548-f511-49c4-b2a3-0a9a45f9154b

NHM_170 NHMUK 20170063, collected 2013-10-11, 13.7936 -116.70308, 4078 m. http://data.nhm.ac.uk/object/8d9beefd-2fbc-4204-9bf8-90551419ac1c

NHM_282 NHMUK 20170064, collected 2013-10-17, 13.75583 -116.48667, 4076 m. http://data.nhm.ac.uk/object/ccdd114d-c8a8-47da-ba84-8b8ca5125a6a

NHM_427 NHMUK 20170065, collected 2013-10-20, 13.86367 -116.54432, 4050 m. http://data.nhm.ac.uk/object/1d462c2a-bb98-4369-afc3-63a7c33a4bdd

NHM _454 NHMUK 20170066, collected 2013-10-21, 13.90165 -116.59, 4163 m. http://data.nhm.ac.uk/object/a30eab51-5f52-4fec-89d7-d47152895c92

Description.

Shell elongate, trapezoidal, strongly inequilateral, anteriorly attentuated and posteriorly expanded, umbones small, low, dorsal edge straight. Byssal sinus in ventral margin. Sculpture of irregular commarginal lamellae and low radial ribs but covered by a thick, shaggy, brown periostracum with projecting scales. Two pre- and post- umbonal hinge teeth with each tooth crossed by transverse grooves giving a lobate appearance (Fig. 13E, F). Inner shell margin smooth. DNA voucher NHM_150 shell length 3.2 mm shell width 1.9 mm.

Genetic data.

GenBank NHM_108 18S-MF157470, COI-MF157502; NHM_150 18S-MF157476; NHM_170 18S-MF157477; NHM_282 18S-MF157490, COI-MF157513; NHM_427 18S-MF157496; NHM_454 18S-MF157499.

Remarks.

Bentharca asperula has been regarded as a cosmopolitan deep-water species with a considerable recorded depth range of 430-5005 m ( Knudsen 1967, 1970, Coan and Valentich-Scott 2012) from Atlantic, Indian and Pacific Oceans. The lectotype and paralectotypes (USNM 63174, 887339, 94363) originated from the Gulf of Mexico, off Yucatan, 2868 m (Blake stn 33). Because of its epifaunal, byssate life habit B. asperula shows considerable shape variation and Knudsen (1967) synonymised several nominal species and described how the number of hinge teeth increases with shell size (age). Without supporting genetic evidence from samples from different oceans it is impossible to test whether the species is truly cosmopolitan. Perhaps significantly, no shell has been described with as few hinge teeth as the present sample and none with the transverse grooves (Fig. 13F). No genetic matches on GenBank.

Ecology.

Quite abundant. Found in polymetallic nodule province.