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Diacavolinia striata Van der Spoel, Bleeker and Kobayasi, 1993

Overview

This is a medium sized, uncoiled thecosomatous pteropod, 0.6 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 or absent. Shell sculpture consists of pronounced narrow spaced growth lines or transverse striation. The dorsal lip has a notch, a gutter but no constriction or 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 striata)

Taxonomic Description

The hyaline shell is triangular and colourless. The dorsal lip has a notch in the rostrum; there is a shallow gutter but no constriction. The ventral lip is normal sized and shows a clear median depression. The reduced, rounded, lateral spines do not bent dorsally. The dorsal side is flattened, the central dorsal rib is well developed and the latero-dorsal ribs and lock ribs are moderately developed. The 19 ventral ribs are strongly developed thin lines; the same type of ribs covers the dorsal side. This constitutes a striking difference with D. aspina. The flanks are slightly developed and the lateral lines are nearly straight. The lock area is small. Main, lunar and minor tubercle are typical. A second lock system is, though also small, present. The growth line pattern is taken over by the ribs on ventral and dorsal sides. There is a vague indication of a hump. The protoconch II area distinctly projects. In the holotype the caudal joint is 1.04 mm; the caudal fold is 1.04 mm and nearly straight, the left and right fold form in ventral view an angle. There are no lip flaps; the lip bellies are moderately developed and the lip shoulders are very small. The aperture is wide. In the holotype the lip angle is 149°, the side angle is 80 to 90°, and the lock angle is 74°. The dorsal aperture rim is sharp and the ventral rim is slightly thickened. The holotype has a shell length of 4.56 mm and width of 3.12 mm.
The shell length ranges from 5.60 to 3.92 mm and width from 4.24 to 2.88 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 striata is an Indian Ocean species described here from the NE-Indian Ocean, see the Diacavolinia striata map.

Types

Diacavolinia striata Van der Spoel, Bleeker and Kobayasi, 1993: 140, fig. 14.
Holotype (ZMUC. gas 161) and 6 paratypes (ZMUC. gas 162) in ZMUC, 8 paratypes (ZMA. moll. 3.92.015) in ZMAN.
Type locality: 2°57'S 99°36'E, 0-400 m depth, CDAE Stat. 3860 xi-xv, 20 October 1929.
Etymology: The name is given as the shell looks entirely striated by the extremely strong rib pattern.

Diacavolinia striata