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Pterotrachea scutata Gegenbaur, 1855b

Overview

This is a large naked pelagic snail, up to 20 cm long (Pterotrachea scutata 2), with an almost completely transparent cylindrical body and the proboscis is perpendicular to the body. Only the visceral nucleus is dark, the large eyes with black retina and the mouth organs are clearly visible. The body is long cylindrical, flattened near the head, with one swimming fin. It hunts large prey such as fishes, shelled pteropods and other heteropods (Pterotrachea scutata with eyes). It lives in the upper layers of the warm waters of all oceans.

Taxonomic Description

These animals are immediately recognised by the completely transparent gelatinous disk of cutis around the anterior part of the body. The cutis is completely covered with denticles except for before the eyes. The hyaline disk forms the "fold" in which the proboscis can bend backwards and is present in all Pterotracheidae but never as clearly as in this species (Pterotrachea scutata). The proboscis is relatively short and the buccal mass is small. The mouth is surrounded by peribuccal teeth (cf. Tesch, 1949: 44). The Pterotrachea scutata radula formula is 2-1-1-1-2. The eyes are cylindrical with a narrow base the same type as in Pterotrachea coronata. The visceral nucleus is about the same shape as in P. minuta that is intermediate between Pterotrachea coronata and Pterotrachea hippocampus. The number of gills varies up to 8, though some authors mentioned the presence of more than 20. The fin only has a sucker in males and is placed anterior to the nucleus but at a relatively smaller distance than in the other species in this genus. The tail with four muscle bands and the cardiform expansion normally found in this genus, is beset with tubercles. Around the base of the fin and near the base of the proboscis ventrally warts are present.
Body length up to 200 mm.

Juveniles

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

Reproduction

In this species the sexes are separate.

Ecology

This species is carnivorous and epipelagic.

Distribution

This species has a very wide north-south range in comparison to other Heteropoda. Its distribution is as Pterotrachea hippocampus neritic. Penetration into oceanic environments is evident only in the Tasman Sea and NE-Pacific, see the Pterotrachea scutata map. The distribution, especially for the Indian Ocean, is comparable to Cardiapoda placenta though Pterotrachea scutata seems to occur in colder areas.

Types

Pterotrachea scutata Gegenbaur, 1855: 185, 215, pl. 8, figs. 19, 20.
Types: 4 spec. were concerned.
Type loc. Messina. Col. Gegenbaur.

Pterotrachea scutata