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Pneumoderma atlanticum (Oken, 1815) subsp. atlanticum (Oken, 1815) forma pygmaeum (Tesch, 1903)

Overview

This is a small naked pelagic snail, about 0.3 cm long. It is oval, with a slightly transparent, usually pigmented skin. The wings are small, the posterior footlobe are long. The buccal mass has two lateral arms, each with up to 8 suckers. It lives in warm waters of all oceans, in the upper water layers, but is never very abundant (Pneumoderma a.a. pygmaeum).

Taxonomic Description

The body is extremely small and rounded. The rays of the posterior gill have two small fringes at their median side. The lateral gill is small, with fringed, lateral somatic crests. The sucker arms are short, with about eight large suckers. In the original description, Tesch stated that the distal suckers are smaller than the others, while, in 1904, he stated that they are all of subequal size. This is correct. The hook sacs are well developed, each with 40 to 100 hooks. The median footlobe is blunt. The radula formula is 4-0-4, the lateral teeth are subequal with square basal plates, except for the outermost ones which have larger basal plates. Jaw with 6 spines.
Body length up to 3 mm.

Juveniles

A special description is not available.

Reproduction

This species is a protandric hermaphrodite.

Ecology

This species is a carnivores.

Distribution

It is restricted in distribution to the N-Atlantic, Indo-Malayan, and N-Pacific Oceans, see the Pneumoderma a.a. pygmaeum map.

Types

Pneumonoderma pygmaeum Tesch, 1903: 115 (1904), pl. 10, figs. 120-122.
Lectotype: ZMAN (alcohol collection). Paralectotypes: ZMAN, 2 spec. (alcohol collection).
Type locality: 1°S 128°30'E. Coll.: Siboga, stat. 144.

Pneumoderma atlanticum atlanticum pygmaeum