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Diacria schmidti Van der Spoel, 1971a subsp. schmidti Van der Spoel, 1971a

Overview

This is a small, uncoiled, shelled thecosomatous pteropod, 0.5 cm long, but relatively large for the group. It is globular with rounded ventral and dorsal sides and strongly developed ribs. The lateral spines are small. The caudal spine is absent, as in juveniles, the protoconch is broken off, leaving only a mark. The shell sculpture consists of faint growth lines and 2 or 3 dorsal striae. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in the E-Pacific Ocean (Diacria s. schmidti ventral).

Taxonomic Description

The rather globular shell is red-brown and semi-transparent. The dorsal lip is arch-shaped and borders a very narrow shell aperture. The ventral and dorsal sides are both heavily vaulted, and show striae near the aperture lips. The caudal spine mark is oval. Between the small lateral spines and the corners of the spine mark the curved lateral sides are thickened. Usually a faint median depression is found on the ventral side and lip. The aperture lips are thickened. A pair of closing mechanisms, less developed than in Cavolinia, are found in the aperture. The radula formula is 1-1-1. The dorsal ribs are moderately developed, transverse striae on ventral and dorsal surface is weakly developed. The ventral surface is regularly rounded and in some specimens this side is seen in dorsal view. (Diacria s. schmidti, Diacria s. schmidti drawing). The lateral spines are well developed and bent dorsally. The imbricate dorsal ribs are 2 or 3 in number.
Shell length 4.00-4.60 mm, width 2.6-3.8, diameter of caudal spine mark 0.96-1.36 mm.

Juveniles

The juvenile has a long dorso-lateral flattened needle-like shell with lateral sides diverging only anteriorly. The protoconch I is rounded, slightly egg-shaped. There is no sculpture on protoconch I or II. The lateral sides of protoconch II are thickened.

Reproduction

This form is a protandric hermaphrodite.

Ecology

This form is phytophagous.

Distribution

This form is found in the tropical E-Pacific, see the Diacria s. schmidti map.

Types

Diacria quadridentata subsp. quadridentata forma schmidti Van der Spoel, 1971: 8, fig. 8.
Holotype: ZMUC (alcohol collection). Paratypes: ZMUC 15 specimens, ZMAN 5 specimens (alcohol collection).
Type locality: 4°20'S 116°46'W Coll. CDAE stat. 3561x.

Diacria schmidti schmidti