Tonna galea

Tonna galea, from 5 m depth on sand, Vouliagmeni ( Βουλιαγμένη ), Greece

The Great Snail tons or Large tun ( Tonna galea ) is a snail from the family of tons of snails ( Tonnidae ), which is common in the Atlantic, Mediterranean and Indo-Pacific total. It feeds on echinoderms.

Features

The pale yellow-brown shell of Tonna galea has a very bulbous, almost spherical body dealing from which the thread is little projecting. The whorls are bent at the seams and furrowed. As with all tons screw the housing is thin-walled and provided with convex ribs which follow the convolutions, so that the edge of the casing is curled. Switch toward the front with smaller ribs. The house achieved in adult worm 15 to 25, sometimes 35 cm in length. The very large feet and the head are just like the proboscis ( snout ) and Sipho white with black speckles. The siphon is usually folded back over the house. The proboscis is extendable over the length of the building addition.

Dissemination

The Great tonnes snail is common in warm seas worldwide and occurs in the Mediterranean, Caribbean Sea, Gulf of Mexico, the Atlantic, Indian Ocean and Western Central Pacific on. It is the largest snail species of the Mediterranean.

Habitat

Large tons of snails live in mud, sand or lime, also coral reefs, from 5 to 80 meters depth.

Life cycle

Like other prosobranch Tonna galea is dioecious. The female lays the eggs in about 30 cm long, 5-8 cm wide, and 1.6 and 1.9 mm thick gelatinous bands, which consist of about 2 to 3 mm large egg capsules. An egg capsule contains according to measurements on tons of snails in India about 95 and 110 eggs with a diameter of about 217-234 microns, almost all develop into embryos. About 15 to 17 days after oviposition slip out of the capsule, the veliger larvae, which have a about 418 microns large brown shell. Until the metamorphosis to the finished worm larvae go through several months of pelagic period, which contributes to the considerable spread of the worm.

Food

Tonna galea feed on echinoderms. Preferred prey are sea cucumbers, including Holothuria tubulosa and Holothuria sanctori. The prey is stunned with the acidic saliva of the screw, which contains two to four per cent free sulfuric acid and aspartic acid, and dissolved the limestone skeleton. The feeding process can take several minutes.

Relevance to humans and hazard

The Great Snail tons is collected for their meat and because of the housing. In addition, it is vulnerable to trawls, where they often forms bycatch. Thus man can be considered as a major enemy. Because of their predatory nature, the tons of worm is sensitive to changes in the ecological balance. Therefore Tonna galea is endangered in the Mediterranean. It is protected under the federal Species Protection Regulation and the Berne Convention. Worldwide it is, however, not previously listed in the Red List.