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Diacavolinia robusta Van der Spoel, Bleeker and Kobayasi, 1993

Overview

This is a medium sized, uncoiled thecosomatous pteropod, 0.5 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 small. Shell sculpture consists of faint growth lines and faint transverse striation. The dorsal lip has no notch, no constriction but a gutter is present. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in the Atlantic Ocean at shallow depths (Diacavolinia robusta).

Taxonomic Description

The hyaline shell is slightly triangular; has a brown colour especially along the aperture rim, the joint, and the ventral side except for its borders. The depressed dorsal lip has no notch in the rostrum and no constriction, but a gutter is present and a faint indication of a nose is present. The slender rostrum is not very long. The moderate ventral lip has a small median depression. The lateral spines are not bent, they have sharp little hooks; the gutter corners are small. The 19 clear but thin ventral ribs are line-shaped. The lateral lines are convex and the flanks are well developed. The dorsal side is somewhat flattened, with weak central and latero-dorsal ribs; the lock ribs are weak. The lock area is well developed with small main, lunar and minor tubercles and link. A second lock system is absent. The growth lines are typical. The hump is very small or absent as in the paratypes; an inner hump is absent. The protoconch II area is project far. In the holotype, the convex caudal joint is 0.96 mm; the caudal fold, 0.72 mm long, is slightly moon-shaped. There are no lip flaps; strong lip bellies and strong lip shoulders are developed. The aperture is narrow. In the holotype the lip angle is 126°, the lock angle is 76°, and the side angle is 85°. The holotype has a shell length of 3.84 mm, the width is 3.04 mm.
The shell length range is 5.36-3.84 mm and the width range is 4.48-3.04 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 robusta has only been recorded from the NW-Atlantic Ocean, see the Diacavolinia robusta map).

Types

Diacavolinia robusta Van der Spoel, Bleeker and Kobayasi, 1993: 137, fig. 10.
Holotype (ZMUC. gas 157) and 1 paratype (ZMUC. gas 158) in ZMUC, 2 paratypes (ZMA. moll3.92.010) in ZMAN.
Type locality: 2°52'N 87°38'W, 0-50 m depth, CDAE Stat. 3556 viii, 14 September 1928.
Etymology: Named for its square robust shape without any projecting spines or rostrum.

Diacavolinia robusta