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Diacavolinia ovalis 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 well developed. Shell sculpture consists of faint growth lines and faint transverse striation. The dorsal lip has a notch, a constriction and a gutter. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in Atlantic Ocean at shallow depths (Diacavolinia ovalis).

Taxonomic Description

The hyaline shell is colourless and triangular. The dorsal lip has a notch in the rather broad rostrum; there is a shallow gutter and a strong constriction. The ventral lip is normal sized and has a median depression. A small nose is present at the base of the rostrum. The long hooked lateral spines bend dorsally. The dorsal side is convex, the central rib and latero-dorsal ribs are well developed, and the lock ribs are well developed, though small. The ventral ribs, 19 to 23 in number, are strongly developed and comb-shaped. The flanks are present; the lateral lines are convex. The lock area is small with moderately developed main and lunar tubercle and small minor tubercle. The second lock system is present. The growth line pattern is typical. There is a vague indication of a hump but an inner hump is absent. The protoconch II area does not project far. In the holotype the caudal joint is 1.12 mm; the slightly moon-shaped caudal fold is 1.20 mm. There is an indication of lip flaps; the lip bellies are strong and low and the lip shoulders are well developed. The aperture is narrow. In the holotype the lip angle is 138°, the side angle is 71°, and the lock angle is 72°. The dorsal aperture rim is sharp and the ventral rim is slightly thickened. The holotype has a shell length of 5.25 mm and width of 4.64 mm.
The shell length ranges from 6.08 to 4.00 mm and width from 5.04 to 3.12 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 ovalis is found in the N-Atlantic Ocean, see the Diacavolinia ovalis map.

Types

Diacavolinia ovalis Van der Spoel, Bleeker and Kobayasi, 1993: 144, fig. 9c, 20.
Holotype (ZMA. moll. 3.92.023) in ZMAN.
Type locality: 38°50'N 72°25'W, 0-100 m depth, July 1975, Deepwater Dumpsite 106 project cruise 2, Stat. 67-M.
Etymology: The ventral shell side, the constriction and the aperture are all oval, hence the name ovalis.

Diacavolinia ovalis