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Diacavolinia souleyeti Van der Spoel, Bleeker and Kobayasi, 1993

Overview

This is a medium sized, uncoiled thecosomatous pteropod, 0.7 cm long. It has a flat dorsal side with moderately developed ribs. The ventral side is vaulted. The caudal spine is absent and a caudal spine mark is not left as the ventral and dorsal sides grow together. The lateral spines are well developed. Shell sculpture consists of faint growth lines and faint transverse striation. The slender dorsal lip has a notch, there is no pronounced gutter or constriction and no inner hump. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in the Indian Ocean at shallow depths (Diacavolinia souleyeti).

Taxonomic Description

The colourless, hyaline shell is triangular and may have a purple hue. The dorsal lip has a small notch in a slender rostrum; there is no pronounced gutter and no constriction in the rostrum. The ventral lip is normal sized and shows a clear median depression. The lateral spines, bending dorsally, are sharp and hooked. The dorsal side is convex, the central- and latero-dorsal ribs are well developed and the lock ribs are small. The ventral ribs, 28 in number, are pronounced thin lines, with regularly arranged tubercles. The flanks are not pronounced and the lateral lines are concave. The lock area is clearly visible; the lock mechanism is medium sized and the main tubercle is not pointed but forms a broad fold. Due to lack of material no data is available on the second lock system. The growth lines are typical. There is no hump. The protoconch II area is project moderately. In the holotype the caudal joint is 1.12 mm and the caudal fold is 1.12 mm and is nearly straight. There are no lip flaps; the lip bellies are weak; the lip shoulders are extremely small or absent. The aperture is wide. The lip angle is 158°, the side angle is 76°, and the lock angle is 69°. The aperture rims are sharp. The lateral corners of the posterior footlobe are light purple-brown, the rest of the wings is colourless. The holotype has a shell length of 6.00 mm and width of 4.72 mm.
The shell length ranges from 6.64 to 6.00 mm and width from 4.96 to 3.92 mm.

Juveniles

A special description for this forma is not available, see Diacavolinia longirostris.

Reproduction

This species is a protandric hermaphrodite.

Ecology

This species is phytophagous.

Distribution

Diacavolinia souleyeti is described from the NE-Indian Ocean and seems to be restricted in distribution, see the Diacavolinia souleyeti map.

Types

Diacavolinia souleyeti Van der Spoel, Bleeker and Kobayasi, 1993: 139, fig. 13.
Holotype (ZMUC. gas 160) in ZMUC and one paratype (ZMA. moll. 3.92.014) in ZMAN.
Type locality: 2°57'S 99°36'E, 0-100 m depth, Dana Stat. 3860 xi-xv, 20 October 1929.
Etymology: The name is given in honour of Dr. F. L. A. Souleyet who described many pteropod species.

Diacavolinia souleyeti