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Cavolinia tridentata (Niebuhr, 1775) forma teschi Van der Spoel, 1974

Overview

This is a shelled thecosomatous pteropod, 1.9 cm long. Ventral surface moderately vaulted, dorsal side with three moderately developed central and two faintly developed lateral dorsal ribs. The caudal spine is straight and relatively long. Upper aperture lip rounded, no keel along the lateral sides. Aperture triangular lunar-shaped. Shell sculpture consists of faint growth lines. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in the Indian Ocean, living at moderate depth(Cavolinia t. teschi dorsal).

Taxonomic Description

The hyaline or opaque shell has a flat dorsal surface with slightly developed longitudinal ribs (Cavolinia t. teschi early adult, Cavolinia t. teschi vent aperture area). The dorsal aperture lip is separated by a moderately developed rib forming an arch between the closing mechanisms of the aperture. This dorsal aperture lip is rounded. In some of the older specimens there is a small additional portion which gives rise to a truncated part with a straight margin of only about 3 mm (Cavolinia t. teschi lateral aperture slit). The lateral sides have no keel, the tops of the lateral spins are directed caudad. The caudal spine is straight and the shell margin, between this spine and the lateral spines, is concave. The ventral side is moderately vaulted (Cavolinia t. teschi dorsal 2, Cavolinia t. teschi lateral, Cavolinia t. teschi, Cavolinia t. teschi dorsal 3). The wide shell aperture has a lunar shape. Growth lines are extremely faint and the transverse striae on the ventral side are thin, and do not disturb the smooth character of the shell. The shell colour consists of a yellowish-brown hue, the central parts of ventral and dorsal side are usually lighter.
The shell length varies between 10.0 and 19.0 mm, the width varies between 7.5 and 12.0 mm, with averages of 13.7 and 8.9 mm respectively.

Juveniles

A special description is not available. Development through a minute stage as normal for cavoliniids (Cavolinia t. teschi juv.dorsal, Cavolinia t. teschi minute stage dorsal).

Reproduction

This form is a protandric hermaphrodite.

Ecology

This form is phytophagous.

Distribution

This forma is restricted to the Indian Ocean north of 25°S, Indo-Malayan, equatorial and tropical Pacific (Cavolinia t. teschi map).

Types

Cavolinia tridentata forma teschi Van der Spoel, 1974: 107,figs. 5g, k, 6d.
The holotype and three paratypes are kept dry in the ZMAN.
Type locality: 5°40.7'S 120°45.5'E,Siboga stat. 211.
Etymology: Tesch (1948) did not publish a description, as he did not indicate type material the name "platea" is in fact a nomen nudum.
Etymology: the name teschi is proposed in honour of the late Dr. J. J. Tesch.

Cavolinia tridentata teschi