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Carinaria cristata forma cristata (Linnaeus, 1766)

Overview

This is a very large shelled pelagic snail, up to 50 cm long, with an almost completely transparent body (Carinaria c. cristata 2). The body can never withdraw into the shell. The shell is high conical. Only the broad triangular visceral nucleus is darkly pigmented. The large eyes, with black retina, and the mouth organs are clearly seen. The intestine is frequently full and visible. The body is long and cylindrical with one swimming fin. It hunts large prey such as fish, shelled pteropods and other heteropods. It lives in upper layers of the warm waters of the Indo-Pacific Ocean.

Taxonomic Description

The largest planktonic mollusc belong to this taxon, they may reach half a meter long (Carinaria c. cristata 1). The short stalked nucleus and shell lay in a depression between the high trunk and high tail crest. The shell is pyramidal, slightly curved with a top angle >60° (Carinaria c. cristata). The tail crest is semi-circular instead of slightly triangular as in Carinaria l. lamarcki and it tapers into a whip-like prolongation which is triangular in cross-section and ends in a dark coloured thread. The tail crest has a dark pigment over its entire length on the underside. The fin is rounded and bears a sucker in both sexes. The visceral nucleus, with about 10 gills, is higher and more pointed than in the other species of the genus. Eyes are relatively small, broad based, with triangular retinal body (Carinaria c. cristata eyes). Tentacles present, the right one being the smallest. Cutis thick with small tubercles. Shell high, elevated, curved backwards and higher than in Carinaria l. lamarcki. Keel of the shell is small. Embryonic shell with 4 smooth whorls, the spire is slightly elevated. The fin muscles are well separated. The Carinaria c. cristata radula 1 formula is 2-1-1-1-2. The Carinaria c. cristata radula shows a tricuspioid median teeth with long cusps. (Carinaria c. cristata radula).
Body length up to 500 mm.

Juveniles

The juveniles have a small, dextrally coiled shell. The spire is slightly elevated and a keel is absent.

Reproduction

In this form the sexes are separate.

Ecology

This form is carnivorous and epipelagic.

Distribution

This form is endemic in the Indo-Pacific Ocean. Like Carinaria lamarcki the present species shows a continuous distribution. In the S-Pacific only one record is known. The forma japonica seems more eurythermic than the forma cristata and is restricted to the Pacific Ocean. Records in the Indian Ocean are rare, see the Carinaria c. cristata map. Seapy (1974) found the forma japonica in the transitional zones of the Pacific Ocean, off South California in oceanic waters with maximum abundance during August. In oceanic waters near Guadalupe Island, Bay of California, low population levels are found during all seasons. In neritic waters off South California it is present in low numbers between July and December when conditions seem most favourable for their entry into the S-Californian eddy. It is absent between January and March.

Types

Patella cristata Linnaeus, 1766: 1260.
Types are not located.

Carinaria cristata cristata