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Diacavolinia atlantica Van der Spoel, Bleeker and Kobayasi, 1993

Overview

This is a large uncoiled thecosomatous pteropod, 1 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 when the ventral and dorsal sides grow together. The lateral spines are well developed. Shell sculpture consists of faint growth lines and a extremely faint transverse striation. The dorsal lip has a notch, a gutter and constriction. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in E-Atlantic Ocean at shallow depths (Diacavolinia atlantica2).

Taxonomic Description

The hyaline shell is triangular; it has a brown hue over the entire surface; the central part of the wings is intensively brown. The dorsal lip has a notch and constriction in the broad gutter-shaped rostrum (Diacavolinia atlantica swimming, Diacavolinia atlantica). The relatively small ventral lip has a distinct median depression. The lateral spines are slightly bent, relatively long, the spine itself is sharp, and hooked; the gutter corners are large. The 39 thick ventral ribs are comb-shaped. The flanks are not pronounced. The upper part of the ventral side is flat in profile. The dorsal side is slightly convex, with well-developed central and lateral ribs; the lock ribs are small although strongly developed. The lateral lines are convex; the lock area is well developed, with large main, lunar and small minor tubercle and link. A second lock system is found at the upper level of the attachment of the spines to the lateral lines. The growth lines are typical. A hump is absent. The protoconch II area projects slightly. In the holotype the caudal joint is 1.44 mm; the caudal fold is 2.21 mm long and straight. There are no lip flaps; the low lip bellies are well developed, the lip shoulders are moderately developed. The aperture is rather narrow. In the holotype the lip angle is 136°, the lock angle is 74°, and the side angle is 75°.
The shell length ranges from 10.88 to 8.33 mm and the width ranges from 9.60 to 7.14 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 atlantica is endemic to the NE-Atlantic and lives within and outside outside the upwelling area, see the Diacavolinia atlantica map. It is frequently sympatric with D. limbata.

Others

This species is close to Diacavolinia limbata forma limbata, and differs only by having a narrower aperture and a bend dorsal shell lip. The discovery of colour differences in the soft parts of this species and Diacavolinia limbata initiated the present study.

Types

Diacavolinia atlantica Van der Spoel, Bleeker and Kobayasi, 1993; 134, fig. 6.
The holotype (ZMAN. moll3.92.006) and 12 paratypes (ZMAN. moll3.92.007) are preserved in the ZMAN.
Type locality. 28°23.5'N 29°55.9'W, 40-100 m depth, AMNAPE. Stat. 25, trawl 7, 30 April 1980, RMT 8.
Etymology: The occurrence of this species in the Atlantic Ocean is expressed in its name.

Diacavolinia atlantica