Taringa luteola (Kelaart, 1858)

Yonow, Nathalie, Anderson, R. Charles & Buttress, Susan G., 2002, Opisthobranch molluscs from the Chagos Archipelago, Central Indian Ocean, Journal of Natural History 36 (7), pp. 831-882 : 848-849

Taringa luteola (Kelaart, 1858)

(®gures 4e, 9A±C, 10a)

Doris luteola Kelaart, 1858: 103 ; 1859: 299.

? (sic.) Thordisa caudata Farran, 1905: 340 , pl. 2, ®gures 18, 19.

Trippa luteola: Eliot, 1906b: 658 , pl. 42, ®gure 4.

Taringa luteola: Gosliner and Behrens, 1998: 286 , ®gures 1B, 4, 5.

Material. Chag96/69: 253 8 mm; inner reef of Ile Diamant, Peros Banhos Atoll; 27 February 1996; at 6 m depth.

Description. The body was roughly rectangular in shape, covered with numerous tiny pustules; the ground colour was cream with several yellow patches and streaks forming a ring around gill pocket and two lines running from the rhinophores to the gills. The mantle margin was deep yellow (®gure 4e). Rhinophores sparsely lamellate, very long in comparison to body size; very dark brown but fading at the base. Six long gills, with pale grey rachides, brown pinnae and yellow pinnules. The oral tentacles and foot were white.

The preserved specimen is soft and translucent pinkish white. The long stalks of the rhinophores retain an ochre hue, while the 18 ±19 lamellae are speckled with black. The six gill rachides also retain black specks. The tubercles on the mantle skirt are spiculose; the spicules stick out of the sides and tops of most tubercles. The rhinophore pocket margins appear undulated. Ventrally the sole is smooth. The anterior edge is bilaminate and the upper one notched centrally; the short digitiform oral tentacles are visible behind the notched lamina (®gure 10a). The radular formula is 30 (1 2±3)3 30.0.30 with a median thickening. The teeth are simply hooked with a small denticle on the cusp on all teeth and a groove or ¯ange on the large broad base which forms a hump or peg on the top of the teeth (®gure 9A±C). There is a rapid increase in size in the ®rst dozen teeth, then a gradual increase to the last-buttwo or three. All the teeth have denticles and a ¯ange, which might have been di cult to see without SEM; the very reduced outermost two or three teeth are still very di cult to distinguish unless greatly magni®ed. The three outermost laterals have long bristles instead of denticles on the cusps.

Geographic distribution. Western Indian Ocean; this is the ®fth record of this unusual species, also known from Sri Lanka (Kelaart, 1858; Farran, 1905), Madagascar ( Gosliner and Behrens, 1998) and Tanzania ( Eliot, 1906b).

Remarks. In his original description from Sri Lanka, Kelaart (1858) implied that he found it frequently in shallow water, and described the egg ribbon as`light green in two narrow tape-like convolutions’. However, we have only a single specimen, as did Farran; Eliot just had two specimens, as did Gosliner and Behrens (1998). Both Eliot and Farran gave identical radular formulae, 38 (1 2)3 39.0.39, and descriptions of the teeth: 1±10 were smaller with a small denticle on the top and a ridge or ¯ange on the base. The outermost two or three teeth were very reduced, with a tuft of bristles at their tips. Gosliner and Behrens’ (1998) two specimens were 15 and 22 mm preserved, one of which had a radular formula of