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

Overview

This is a large thecosomatous pteropod, 1.6 cm long, living at moderate depths. It has a flat dorsal side with moderately developed ribs. There are no keels along the lateral sides. The caudal spine is straight and relatively long. The ventral side is moderately vaulted. The shell sculpture consists of faint growth lines and faint transverse striation. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in the Indian Ocean (Cavolinia t. danae dorsal).

Taxonomic Description

The shell is hyaline or opaque with a flat dorsal surface, having nearly invisible longitudinal ribs. The dorsal lip is separated from the dorsal side by a flat but distinct arch-shaped rib. The lateral sides have no keel, the tops of the lateral spines are directed caudad. The dorsal aperture lip is truncated with a straight upper margin, about 4 mm long. The relatively long caudal spine is straight and the shell margin, between caudal and lateral spines, is concave. The ventral side is moderately vaulted (Cavolinia t. danae, Cavolinia t. danae dorsal 2). The growth lines and transverse ribs are not distinct ventrally. The aperture is trapezoid. The shell colour is irregularly distributed yellowish-brown.
Shell length varies between 12.0 and 16.0 mm and width varies between 8.0 and 10.5 mm, with averages of 14.8 and 9.5 mm respectively.

Juveniles

A special description is not available.

Reproduction

This forms is a protandric hermaphrodite.

Ecology

The form is phytophagous.

Distribution

This forma is restricted to the Indian Ocean north of 25°S, see the Cavolinia t. danae map.

Types

Cavolinia tridentata forma danae Van der Spoel, 1974: 107, fig 5f, 6e.
The holotype is kept in alcohol in the ZMUC, two paratypes are preserved in alcohol in the ZMAN.
Type locality: 14°16'S 41°48' E, CDAE stat. 3951iv.

Kingdom Animalia
Phylum Mollusca
Class Gastropoda
Subclass Euthyneura
Order Thecosomata
Suborder Euthecosomata
Family Cavoliniidae
Subfamily Cavoliniinae
Genus Cavolinia
Species Cavolinia tridentata
Forma danae

Status in World Register of Marine Species

Not included in WoRMS database

Scientific synonyms and common names

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

Synonyms

Hyalaea affinis (non d'Orbigny, 1836; non Sowerby, 1878) Fryer, 1869: 266
Cavolinia tridentata forma danae n. forma Van der Spoel, 1974: 107

This forma is usually named Cavolinia tridentata in previous works and Tesch (1948) probably used "var. platea " for part of this taxon.

Fryer, G. E., 1869. A contribution to our knowledge of pelagic Mollusca. J. asiatic Soc. Bengal. 38: 259-268, pl. 21.

Rampal, J., 1975. Les thécosomes (mollusques pélagiques). Systématique et évolution écologie et biogéographie méditerranéennes. Aix-Marseille (Thesis Univ. Provence CNRS AO 11932): 1-485, 15 tabs, 99 figs.

Sakthivel, M., 1976a. Geographical and seasonal distribution of Euthecosomata (Pteropoda, Gastropoda) in the Indian Ocean. Meteor Forsch. Ergebniss D23: 1-22.

Stubbings, H. G., 1938. Pteropoda. Sci. Rep. John Murray Expedition 1933-1934, 5(2): 3-33, 2 figs.

Tesch, J. J., 1948. The thecosomatous pteropods, 2. The Indo-Pacific. Dana Report 30: 1-45, 34 figs, 3 pls.

Spoel, S. van der and Heyman, R. P., 1983. A comparative atlas of zooplankton. Biological patterns in the oceans. Bunge, Utrecht; Springer Verl., Berlin: 1-186.

Spoel, S. van der, 1974. Geographic variation in Cavolinia tridentata (Mollusca, Pteropoda). Bijdr. Dierk. 44 (1): 100-112.

Spoel, S. van der, 1976c. Pseudothecosomata, Gymnosomata and Heteropoda. Bohn, Scheltema & Holkema, Utrecht. 484 pp. 246 figs.

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