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Diacavolinia vanutrechti Van der Spoel, Bleeker and Kobayasi, 1993 forma vanutrechti 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 but pronounced usually hook-shaped. Shell sculpture consists of growth lines and faint transverse striation. The dorsal lip does not have a notch, a constriction, or an inner hump but a gutter is present. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in the Indian and W-Pacific Ocean at shallow depths (Diacavolinia v. vanutrechti 2).

Taxonomic Description

The hyaline brown shell is slightly triangular. The dorsal lip usually does not have a notch in the slender rostrum; there is no constriction, a gutter is present. In a few specimens and in one paratype, a notch is found (Diacavolinia v. vanutrechti). The ventral lip is moderately sized and has a clear median depression. The lateral spines are strongly bent, the spines are hook-shaped; the gutter corners are small. The 14 thin ventral ribs are slightly comb-shaped. The lateral lines are convex and the flanks are well developed. The dorsal side is convex, with a weak central rib, latero-dorsal ribs and lock ribs. The lock area is small, showing a small main tubercle and link, the lunar and minor tubercle are of equal size. A second lock mechanism is present midway between the lateral spine and the normal lock area. The growth lines are typical. A hump is absent. The protoconch II area projects moderately. In the holotype the small caudal joint is 1.08 mm; the caudal fold, 1.00 mm long, is straight or even convex in some specimens and the left and right fold form an angle. There are no lip flaps; weak lip bellies and very small lip shoulders are present. The aperture is wide. In the holotype the lip angle is 150°, the lock angle is 76°, and the side angle is 73° (Diacavolinia v. vanutrechti 1). The holotype has a shell length of 4.36 mm, the width is 3.64 mm.
The shell length ranges from 4.88 to 3.76 mm and width from 3.64 to 2.40 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 vanutrechti forma vanutrechti is an Indo-West Pacific taxon found in the W-Pacific and N-Indian Oceans, see the Diacavolinia v. vanutrechti map.

Others

Representatives of this taxon without a notch resemble Diacavolinia elegans, but the present species differs in having larger lip shoulder and a prominent second lock.

Types

Diacavolinia vanutrechti forma vanutrechti Van der Spoel, Bleeker and Kobayasi, 1993; 135, fig. 7.
Holotype (ZMUC. gas 153) and 5 paratypes (ZMUC. gas 154) in ZMUC, 3 paratypes (ZMA. moll. 3.92.008) in ZMAN.
Type locality: 14°37'N 119°52'W, 0-100 m depth, CDAE. Stat. 3731 iv.
Etymology: The name is given in honour to our friend and colleague Dr. W. L. van Utrecht, who kindly assisted the first author during many expeditions and research projects.

Diacavolinia vanutrechti vanutrechti