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Carinaria cristata forma japonica Okutani, 1955b

Overview

This is a very large shelled pelagic snail, up to 15 cm long, with an almost completely transparent body. 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 N-Pacific Ocean. (Carinaria c. japonica 1).

Taxonomic Description

The forma differs from Carinaria c. cristata in shell shape and the shape of the tail crest. The shell is perfect triangular with a top angle of 66° and nearly straight sides. The keel is low. The embryonic shell, with 4 whorls, has fine transverse striation, a narrow umbilicus and an elevated spire (Carinaria c. japonica). The juveniles have a rounded operculum with a central nucleus. The transverse striae on the protoconch are regular. The body has a rather thick cutis with several tubercles, especially on the ventro-lateral sides. The tail crest resembles Carinaria lamarcki by being slightly triangular. The posterior tail part is pigmented as in the forma cristata. The eyes are broad based and triangular. The fin is round and has a sucker in both sexes; the wing muscles are well separated. The tentacles are small and equal in shape and size.
Maximum body length is 80 to 158 mm; the shell is 15 mm high and 19.5 mm in diameter.

Juveniles

The juveniles have a small dextrally coiled shell. A special description is not available.

Reproduction

In this form the sexes are separate.

Ecology

This form is carnivorous and epipelagic. For this forma described predators are turtles and tuna (Okutani, 1961). It feeds on Euphausia larvae, Paracalanus parvus, Calanus spec. Oithona pulmifera, Amphipoda juveniles, Evadne spec., Sagitta bedoti and Thalassiothrix longissima. Thaliacea, chaetognaths and copepods form the predominate food sources.

Distribution

This form is found in the N-Pacific Ocean, for more information see the forma cristata, see the Carinaria c. japonica map.

Types

Carinaria japonica Okutani, 1955: 251, figs. 1-3.
Holotype: female preserved in Tkai Regional Fisheries Research Laboratory.
Type locality: 36°21'N 141°00'E.

Carinaria cristata japonica