Olivella (Anasser) careorugula, Absalão & Pimenta, 2003

Absalão, Ricardo S. & Pimenta, Alexandre D., 2003, A new subgenus and three new species of Brazilian deep water Olivella Swainson, 1831 (Mollusca, Gastropoda, Olivellidae) collected by the RV Marion Dufresne in 1987, Zoosystema 25 (2), pp. 177-185 : 182-183

Olivella (Anasser) careorugula n. sp.

( Fig. 1 G-I)

TYPE MATERIAL. — Holotype: MNHN; paratypes (two shells in each lot): MNRJ 8913 , 8915 ; IBUFRJ 11074 ; MORG 41036; MZSP 35529; ANSP 410280. All type material from the type locality.

TYPE LOCALITY. — South of Cabo Frio, Rio de Janeiro State, Brazil , MD-55, stn CB105, 23°47’S, 042°10’W, 610 m.

OTHER MATERIAL EXAMINED. — MD-55, stn CB105, 23°47’S, 42°10’W, 610 m, 2.VI.1987, 41 spec. ( MNHN) ; MD-55, stn CB105, 23°47’S, 42°10’W, 610 m, V.1987, 2 shells ( MNHN) ; MD-55, stn CB97, 21°34’S, 40°08’W, 600 m, V.1987, 1 spec.

ETYMOLOGY.— From careo (Latin):not; and rugula (Latin): fold, referring to the absence of folds or pillar structure.

DESCRIPTION

Shell medium sized (maximum length about 6.0 mm), white, semi-translucent, glossy of about 3.5 whorls. Spire of 2.5 whorls moderately tapering, comprising about 16-19% the total length. Protoconch small, rounded, not projecting above the outline of shell. The sutures are narrow and channeled visible as a spiral line due to shell translucence. In fresh specimens, there is usually an opaque white subsutural belt. Body whorl sub-cylindrical; spire whorls quite convex and very slightly stepped. Apex blunt and convex. Fasciole simple and sometimes hardly discernible. Low, light parietal callus, a bit more opaque than the shell and extending only to the end of the aperture. Pillar structure absent. Columella strongly concave at anterior end, the remainder almost straight. Yellowish chitinous operculum present.

REMARKS

Olivella careorugula n. sp. ( Fig. 1 G-I) is less inflated and much smaller than O. amblya ( Fig. 1 A-C). Olivella ephamilla ( Fig. 1 D-F) shares with O. careorugula n. sp. the oblong outline but the spire profile of O. ephamilla is almost straight, giving a stepping tapering appearance, while in O. careorugula n. sp. it is strongly convex. Besides that, O. careorugula n. sp. bears a large subsutural white band, which is not present in the types of O. ephamilla .

The only species from western Atlantic with shells similar to O. careorugula n. sp. are O. (Minioliva) acteocina Olsson, 1956 and O. (Minioliva) perplexa Olsson, 1956 ( Olsson 1956: pl. 12, fig. 6 and pl. 16, fig. 7 respectively) from Florida and Bahamas-Panamá respectively. Both these Minioliva have higher spires and less convex whorls than O. (Anasser) careorugula n. sp. Furthermore, they have a typical Minioliva pillar structure (sensu Olsson 1956), absent in all Anasser n. subgen. species.

Additionally, Anasser n. subgen. seems to be a deep water southern Atlantic group while O. acteocina and O. perplexa inhabit shallow, more northernly coastal waters.

We failed to find radulae in dried specimens. Despite rehydration, careful dissection and, ultimately, KOH digestion. Olivella careorugula n. sp. may lack this structure.

Figures

FIG. 1. — Subgenus Anasser n. subgen.; A-C, Olivella amblia Watson, 1882; A, syntype, 5.9 mm length (BMNH 1887.2.9.771-3); B, syntype, 5.2 mm length (BMNH 1887.2.9.771-3); C, specimen from MD-55, stn 95, 8.2 mm length (MNHN); D-F, Olivella ephamilla Watson, 1882; D, syntype, 3.6 mm length (BMNH 1887.2.9.774); E, syntype, 4.2 mm length (BMNH 1887.2.9.771-3); F, specimen from MD-55, stn DC73, 4.7 mm length (MNHN); G-I, Olivella careorugula n. sp., holotype (MNHN); G, optical photography, 4.5 mm length; H, SEM photography, 4.5 mm length; I, apex detail. Scale bar: I, 500 µm.