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Gleba cordata (ms Forskal) Niebuhr, 1776

Overview

This is a shell-less pteropod with a large gelatinous slipper-like pseudoconch, 4.5 cm long. The pseudoconch is rounded. The wings are disc-shaped and the visceral mass forms a dark nucleus embedded in the perfectly transparent pseudoconch. The pseudoconch is rounded at both sides and covered with a few warts. The proboscis is prominent and longer than half the wing disc diameter. It is an elegant swimmer that feeds with a mucous web on microplankton. It lives in the warm waters of Atlantic and Indian Oceans (Gleba cordata 2).

Taxonomic Description

Pseudoconch rather flat and broad, posterior end rounded, anterior side nearly straight and ending abruptly. The pseudoconch does not have the typical slipper-like shape. Cavity large but shallow and only clearly seen in the thicker posterior part. The tubercles are small and few in number. The swimming disc is characterised by its straight posterior border and its semi-circular shape (Gleba cordata outline). The muscle bands are like those in Cymbulia and much closer together than in Corolla and they are difficult to be seen separately. Numerous well developed mucous glands are found along the wing border (Gleba cordata). The proboscis is very long and freely movable over most of its entire length and reaches over 2/3 of the swimming disc. At the base of the proboscis there are two small, symmetrical tentacles. The visceral mass is relatively small. The mantle gland shows two complete and one incomplete oblique transparent bands. The gland is asymmetrical as the right side is better developed than the other. The gland is twisted to the left as in all species of this genus and Corolla.
Diameter of the swimming plate up to 60 mm, length of the pseudoconch up to 45 mm.

Juveniles

A special description is not available.

Reproduction

Zarnik (1911) found a diploid chromosome number of 28. It is a protandric hermaphrodite.

Ecology

Gilmer (1972) has described the use of a free and unsupported mucous web for the collecting of food particles by Gleba cordata and Corolla spectabilis. The mucous glands along the swimming plate border are responsible for the secretion of the mucus web, which is many times larger than the animal itself and may reach a maximum diameter of about 2 meters. The web is perforated and the pores are mostly > 15 µm. This explains the possible selection of particles of certain size classes. The connection of web and animal is formed by the proboscis, which collects food from the web. During feeding the animal hangs motionless below the web by its a strongly elongated proboscis. It is phytophagous and epipelagic.

Distribution

The distribution of this species is similar to that of Cymbulia peroni, being only found in warmer waters of the Atlantic Ocean and in the Mozambique Current. Though this species is also found in the Mediterranean, it does only occur in the western part without (like Cymbulia peroni) occurring in the eastern basin, see the Gleba cordata map. The present species shows a more similar distributional pattern to Corolla ovata if the validity of Gleba chrysostricta is questioned and the records are taken together.

Types

Gleba cordata Niebuhr, 1776: 14, pl. 43, fig. D.
Types are not preserved, though the nearly complete collection Forskal is present in ZMUC the types for the pelagic molluscs are absent in the ZMUC.

Gleba cordata