Hypselodoris apolegma (Yonow, 2001)

Location: Horse Shoes, Okinawa Island (Onna and Yomitan area), Okinawa, Japan
Date: 2015/12/21
Length: 80mm
Depth: 30.0m
Water temperature: 23.0℃

Description

A large chromodorid reaching about 100 mm in body length. In life the ground colour is an almost luminescent deep magenta-pink to violet. The colour of the mantle is connected to an opaque white margin by a region of violet stippling combined with white reticulations, so that the boundary between the violet mantle and the white edge is diffuse. The mantle is elongate, fairly spatulate anteriorly, with a crinkled edge. The body is high and fleshy but firm, with a definite but reduced mantle overlap. The foot is large and firm, extending beyond the mantle posteriorly. The rhinophores are deep orange-yellow with purple peduncles; the holotype has 25 lamellae on the club, while one extended rhinophore of an FMMME specimen had 27 and 29 lamellae on the two sides. The five tripinnate gills are yellow with violet stalks, located far back on the dorsum and held very high. The rhinophores and gills issue from pockets with a raised rim, the rim being the same colour as the mantle. The gill pocket is very high in life, almost tubular, with a pimpled surface. The foot is uniformly coloured, a shade more purple than the mantle, with no banding around the edge. The foot is bilaminate; neither lamina is notched but the edges are crumpled. In all three preserved specimens the sides of the foot bear characteristic folds, with a main fold just beyond the head and smaller undulating folds posteriorly. The oral tentacles are just visible on each side of the head. The radula bears rows of hooked and serrated teeth, all similar along the row, increasing rapidly in size for the first 5–6 teeth and remaining more or less constant to the last few laterals, which have reduced cusps. There is no central rachidian or thickening visible. The first lateral bears 4–5 denticles on the outer side, as do the remaining laterals; there are no denticles medially. Each cusp has 4–6 serrations (rarely 7 or 8) along the bottom of the cuspar. The radular formula of the 80 mm specimen (Mal. 23) is 90 (+6) × min. 121.0.121.

Distribution

Western Pacific to western Australia. Type locality: Het Suikerbroodje, Hitu, Ambon, Maluku, Indonesia, 4–5 m depth, based on the holotype (RBE Stn 39, 46 × 22 mm preserved) collected by W. Kolvoort on 9 December 1990. Paratypes from the same station and from Cape Nusanive, Leitimur, 24 m depth, collected by B.W. Hoeksema on 21 November 1996 (80 mm). Subsequently widely recorded from Malaysia, the Philippines, Japan and other tropical and sub-tropical western Pacific localities.

Etymology

The original Etymology section (Yonow, 2001, p.43) reads: "Apolegma is Greek for the hem of a robe, referring to the white margin which is not sharply distinct from the violet mantle." The specific epithet apolegma derives from the Ancient Greek word for the hem or border of a garment, in reference to the diffuse white edge of the violet mantle.

Remarks

In the original description Yonow placed the species in Risbecia. The species had previously been confused with Hypselodoris bullocki in Wells & Bryce 1993, Strack 1998, Allen & Steene 1994, Debelius 1996, Colin & Arneson 1995 and Gosliner et al. 1996. Risbecia was subsequently synonymised with Hypselodoris Stimpson, 1855, and this species was transferred to Hypselodoris; the parentheses in the author citation reflect this generic transfer. The Japanese name "シンデレラウミウシ" ("Cinderella slug") refers to the bright violet colour evoking a princess's dress and glass slippers.

Photographed by 今川郁

Description

Distribution

Etymology

Remarks

References

A Kindle field guide by the site author

Seasonality

Shooting Locations

Photos of Hypselodoris apolegma

Same Genus Nudibranchs

Similar Colors Nudibranchs

Academic Database