Volvulella onoae, Valdés, 2008

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 751-752

Volvulella onoae n. sp.

Figs 81B, 83

TYPE MATERIAL. — Holotype MNHN 20430 and 11 paratypes MNHN 20431-20434 , 4 paratypes LACM 3006 . TYPE LOCALITY. — North of New Caledonia, 19°07’S, 163°22’E, 110 m [MUSORSTOM 4: stn DW 150 ].

MATERIAL EXAMINED. — North of New Caledonia. MUSORS- 655 , 21°17’S, 165°57’E, 375 m, 2 dd, paratypes; stn DE 700, Passe TOM 4 : stn DW 149 , 19°08’S, 163°23’E, 155 m, 3 dd, 1 lv des- du Cap Baye, 20°57’S, 165°35’E, 160-222 m, 1 dd; stn DE 705, troyed to dissect the gizzard plates, paratypes ( MNHN 20432 ); 21°02’S, 165°38’E, 350-400 m, 3 dd, paratypes ( MNHN 20433 ); stn DW 150 , 19°07’S, 163°22’E, 110 m, 2 dd, holotype ( MNHN stn DW 706 , Passe SE de Ngoe, 21°42’S, 166°34’E, 247-252 m, 3 20430; Fig. 81B) and paratype ( MNHN 20431 ). dd, paratypes ( MNHN 20434 ) . — BATHUS 2 : stn DW 717 , Ile des New Caledonia proper. VAUBAN: stn 40, 22°30’S, 166°24’E, 250- Pins, 22°44’S, 167°17’E, 350-393 m, 1 dd .

350 m, 4 dd, paratypes ( LACM 3006 ) . — BATHUS 1 : stn DW 654 , Fiji. MUSORSTOM 10: stn DW 1380 , S of Viti Levu, 18°19’S, Passe de Canala , 21°17’S, 165°57’E, 237-298 m, 1 dd; stn DW 177°59’E, 321 m, 1 dd .

DISTRIBUTION. — Known from Fiji and New Caledonia (Fig. 83), in 100-375 m, live in 155 m.

DESCRIPTION. — Shell morphology. Length 3 mm, width 1.5 mm (holotype). Shell solid, oval, slightly narrower anteriorly (Fig. 81B). Only 1 whorl visible, forming the entire shell. Anterior end of the shell rounded. Umbilicus narrow. Aperture long, wide anteriorly, narrowing at about 1/3 of its length. At its apical end, the aperture bends over the apex of the shell and the parietal wall forms a short spine that completely covers the apex. Columellar margin thickened, with a small protuberance. Sculpture of 8 simple and wide spiral grooves at the posterior end and 10 thin and irregular grooves at the anterior end, which are not clearly visible in all specimens. The rest of the shell is covered with faint spiral grooves. There are also numerous fine growth lines all over its surface. Colour uniformly shiny whitish.

Anatomy. Digestive system without radula, jaws or gizzard plates.

REMARKS. — Volvulella onoae is characterized and distinguishable from other members of the genus from the tropical Indo-Pacific by having a series of 8-10 simple spiral grooves at each end of the shell, an oval general shape, and a short apical spine. Another western Pacific species with an oval shell and spiral grooves near the two ends of the shell is Volvulella eburnea A. Adams in Sowerby, 1850 (see Hori 2000c). However, the holotype of V. eburnea , figured by Higo et al. (2001), has a rounded apex, with no spine, lacks an umbilicus, and the spiral grooves are not visible. Kuroda & Habe (1954) figured a specimen supposedly seen by A. Adams that resembles the redescription by Hori (2000c), but the photograph is not detailed enough to allow a comparison.

Volvulella fortis (Thiele, 1925) , originally described from Indonesia in 132 m, also has spiral grooves near the two ends of the shell but is more elongate than V. onoae .

Volvulella onoae is distinguished from Volvulella ovulina (A. Adams in Sowerby, 1850) by having spiral grooves at both ends of the shell and a shorter and thinner apical spine.

ETYMOLOGY. — Dedicated to Emiko Ono (LACM), who was instrumental in obtaining volunteer support for the completion of this manuscript.