Ledella knudseni Taylor & Wiklund

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 : 8-9

Ledella knudseni Taylor & Wiklund sp. n.

Material examined.

Paratype NHM_288A NHMUK 20170047.1-2, collected 2013-10-17, 13.75583 -116.48667, 4076 m. http://data.nhm.ac.uk/object/8aec47f4-dcec-4668-8398-9e4b0c28ecb8

Holotype NHM_288C NHMUK 20170048, collected 2013-10-17, 13.75583 -116.48667, 4076 m. http://data.nhm.ac.uk/object/f1886d78-22bf-403e-bdb2-784b91c0eb12

Description.

Shell relatively thick, robust. Ovoid with short rostrum, umbones broad, prominent; postero ventral margin sinuous; broad, shallow sulcus extending from umbones to posteroventral margin. Sculpture of low, relatively broad, closely spaced, commarginal lamellae; fine radial striations on rostrum and juvenile shell. Ligament internal, situated on broad resilium beneath umbones. Hinge robust, with 8-9 chevron shaped, blunt teeth to either side of ligament. Inner shell margin smooth. Prodissoconch large, ellipsoidal 0.3 mm long, with sharp rim, surface irregularly pitted. Holotype NHM_288C shell length 2.2 mm, width 1.5 mm; paratype NHM_288A shell length 2.1 mm, height 1.5 mm. (Figure 7).

Genetic data.

GenBank NHM_288A COI-MF157515; NHM_288C 18S-MF157491, COI-MF157516.

Remarks.

Similar in form to Ledella ultima (Smith, 1885) widespread in the abyssal Atlantic ( Allen 2008), but has a less massive hinge with more teeth, 8-9 compared with 6-8 in L. ultima . Also similar is the species identified by Knudsen (1970) as L. ultima from the Sunda Trench in Indian Ocean at 3810 m. The only species recorded from the deep eastern Pacific is Ledella dicella (Dall, 1908) from 734-1200 m off Ecuador but this lacks the short rostrum and has 12-13 hinge teeth on each side of the ligament ( Coan and Valentich-Scott 2012 pl. 26). No genetic matches on GenBank. Ledella knudseni groups in a small subclade with but is distinct from the Atlantic species L. ultima and Ledella jamesi Allen & Hannah, 1989, as well as another Ledella species from this study in the Pacific, Ledella sp. (NHM_381) (Figure 12). The new species can be confused with juveniles of B. calcar (see above), but shell is less shiny and iridescent, and ribs are more pronounced. DNA may be required to confirm identification.

Etymology.

Named for Jørgen Knudsen (1918-2009), deep-sea bivalve systematist and author of the Galathea Report on abyssal and hadal Bivalvia.

Ecology.

Found in polymetallic nodule province.