Calloarca (Barbarca) tenella ( Reeve, 1844 )

Raines, Bret & Huber, Markus, 2012, 3217, Zootaxa 3217, pp. 1-106 : 19

Calloarca (Barbarca) tenella ( Reeve, 1844)

Figures 8 A–C

Arca tenella Reeve, 1844 : sp. 91, pl. 14, fig. 91.

Calloarca (Barbarca) hua Dall et al., 1938: p. 24 , pl. 4, figs. 5–8.

Barbatia tenella ( Reeve, 1844) — Tröndlé & Boutet, 2009: p. 5; Kay, 1979: p. 504, figs. 162 C–D.

Barbatia (Barbarca) tenella ( Reeve, 1844) — Oliver, 1992: p. 36, pl. 2.

Calloarca (Barbarca) tenella ( Reeve, 1844) — Huber, 2010: p. 131, fig. 7; Severns, 2011: p. 430, pl. 196, fig. 5.

Material examined. Over one hundred single valves (4.1 to 6.2 mm) from EI and SyG (BK), plus specimens from the Hawaiian and Marquesas Islands ( MHU).

Diagnosis. Shell small, elongated ovate, equivalve, inflated, not fragile. Umbones elevated. Posterior and anterior ends rounded. Ventral margin sinuous. Exterior surface of fine radial riblets and commarginal threads. Hinge consisting of numerous teeth separated under the umbones, slanted, and larger distally. Color creamy white.

Remarks. All the EI specimens are exceedingly small, so it cannot be completely excluded that the current EI population may represent a distinct species. However, without strong genetic data to support it, there is no way to separate them. As with most families the EI material consists of smaller examples overall, which is probably due in part to a combination of the insular isolation, harsh environment and a scarce food supply.

Habitat. Commonly found at many locations around EI and SyG, in sand, from 10–80 m.

Distribution. Calloarca (Barbarca) tenella is a widely distributed species from eastern Africa to Marquesas Islands, Tuamotu Archipelago, Austral Islands and the Hawaiian Islands. However, it is not known from New Zealand or the Kermadec Islands. Easter and Salas y Gómez Islands are now considered a range extension— E5.