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Pneumodermopsis (Crucibranchaea) michaelsarsi Bonnevie, 1913

Overview

This is a naked pelagic snail, up to 1 cm long, it is mainly transparent body, the visceral mass is seen through the body wall. The skin has purple and black chromatophores. There is no median sucker arm. There are two lateral arms each with 8 suckers. A posterior gill is present. The posterior footlobe is short. It is a rather quick swimmer that hunts shelled pteropods as food. It lives in the N-Atlantic Ocean in deeper water layers. The only illustration available is the one of the Pneumodermopsis michaelsarsi holotype.

Taxonomic Description

The skin is faintly pigmented, young specimens are colourless. The visceral mass fills the whole body, except the narrow tapering part which carries the posterior gill. The posterior gill is present and composed of four crests radiating from the body pole. The lateral gill is a triangular fold at the right side of the body, not hanging free from the body wall. The median footlobe is short, pointed. A median foot tubercle is present. The lateral lobes are small, triangular. The sucker arms were never described though they are present in typical specimens, bearing eight short stalked suckers. The radula formula is 6-1-6. The median plate bears, at its lateral sides, cusp like corners which are slightly dentated. In the middle of the plate a large cusp is present which is sometimes divided at its tip into three or two smaller denticles. Massy (1917), however, found no median cusp. Between the central cusp and the cusp-like corners a large, somewhat laterally projecting, cusp is seen which is composed of two parts, a posterior and an anterior part. The lateral plates are twice as large as the median plate and they are slender shaped. The first lateral plates are provided with a cusp projecting from the base towards the median line of the radula. The hook sacs are shallow and bear 30 to 50 short hooks. In young, small specimens of 1.3 mm, only about 20 hooks are found in each sac. The typical differences compared to the most related species Pneumoderma (C.) macrochira is in the development of the lateral gill and the shape and numbers of the lateral suckers.
The maximum length of the body is 11.0 mm.

Juveniles

A special description is not available.

Reproduction

This species is a protandric hermaphrodite.

Ecology

This species is a carnivore.

Distribution

It is restricted to the N-Atlantic Ocean and lives in the upper 1000 meters, see the Pneumodermopsis michaelsarsi map.

Types

Pneumodermopsis michaelsarsi Bonnevie, 1913 (1933): 55, fig. 42,pl. 6, figs. 45-48.
Holotype: ZMVB 30416, sectioned, without head parts (alcohol collection) + 3 slides with buccal organs and appendages, u.s.
Type locality: 28°2'N 14°17'W, 250 m. Coll.: CMSE, stat. 42.

Pneumodermopsis michaelsarsi