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Diacavolinia grayi Van der Spoel, Bleeker and Kobayasi, 1993

Overview

This is a medium sized, uncoiled thecosomatous pteropod, 0.4 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 broad dorsal lip is without notch or constriction but the gutter is present. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in the Indian Ocean and Indo-Malayan waters, at shallow depths (Diacavolinia grayi).

Taxonomic Description

The hyaline shell is triangular; it has a brown hue over the entire surface, especially along the dorsal ribs and there are dark spots marking the closing apparatus in the aperture. The dorsal lip does not have a notch in the broad rostrum and no constriction; a gutter is present and the inner hump is strongly developed. A nose comparable to that found in Diacavolinia angulosa is present. The ventral lip is large and shows a clear median depression. The lateral spines are not bent; they are short, sharp, and hooked; the gutter corners are moderately developed. The 16 well-developed ventral ribs are thin, line-shaped. The lateral lines are straight; flanks are present. The dorsal side is flattened, with a strong central rib and weak latero-dorsal ribs; the lock ribs are weak. The lock area, the main tubercle and the link are small. The lunar tubercle is normal and the minor tubercle is absent. There is no second lock system. The growth lines are well developed and on the dorsal side some ribs also are found. A hump is present with a strong inner hump. The protoconch II area is broad, with a caudal joint not projecting far. In the holotype it is 1.20 mm; the caudal fold, 1.00 mm long, is nearly straight. There are no lip flaps but pronounced lip bellies; the lip shoulders are large. The aperture is narrow. In the holotype the lip angle is 140°, the lock angle is 70°, and the side angle is 75°. Both ventral and dorsal rims are thick.
The shell length ranges from 5.36 to 3.16 mm and width from 5.28 to 2.40 mm.

Juveniles

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

Reproduction

This species is a protandric hermaphrodite.

Ecology

This species is phytophagous.

Distribution

Diacavolinia grayi is an Indo-Malayan and Indian Ocean species found so far in the Banda Sea and N-Indian Ocean, see the Diacavolinia grayi map.

Others

As in Diacavolinia angulosa both long spines and short-spined shells occur. This is probably only due to growth and no special taxa are described for these different populations.

Types

Diacavolinia grayi Van der Spoel, Bleeker and Kobayasi, 1993: 142, fig. 17.
Holotype (ZMA. moll. 3.92.019) and 8 paratypes (ZMA. moll. 3.92.020) in ZMAN.
Type locality: Banda Sea, 5°22.8'S 130°05'E, 90-196 m depth, Snellius II Exped., Stat. C trawl 2, 28 August 1984.
Etymology: The name is given in honour of Dr. J. E. Gray, author of species in this group.

Diacavolinia grayi