Big barrel snail

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Big barrel snail
Tonna galea, from a depth of 5 m on sand, Vouliagmeni (Βουλιαγμένη), Greece

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

Systematics
Subordination : Hypsogastropoda
Partial order : Littorinimorpha
Superfamily : Cassoidea
Family : Barrel snails (Tonnidae)
Genre : Tonna
Type : Big barrel snail
Scientific name
Tonna galea
( Linnaeus , 1758)

The large barrel snail or large barrel snail ( Tonna galea ) is a snail from the family of barrel snails (Tonnidae), which is distributed in the Atlantic , Mediterranean and the entire Indo-Pacific . It feeds on echinoderms .

features

Housing by Tonna galea , different views

The pale brownish yellow shell of Tonna galea has a very bulbous, almost spherical body, from which the thread protrudes only a little. The whorls are curved and furrowed at the seams. As with all barrel snails, the shell is thin-walled and provided with convex ribs that follow the passageways, so that the edge of the shell is wavy. They alternate forward with smaller ribs. The house reaches 15 to 25, sometimes 35 cm in length in adult snails. The very large foot and head, like the proboscis (trunk) and the sipho, are white with black speckles. The Sipho is usually folded back over the house. The proboscis can be extended beyond the length of the house.

distribution

The large barrel snail is found in warm seas around the world and occurs in the Mediterranean , Caribbean , Gulf of Mexico , Atlantic , Indian Ocean, and western central Pacific . It is the largest species of snail in the Mediterranean.

habitat

Large barrel snails live on mud, sand or lime, also on coral reefs , from 5 to 80 meters deep.

Life cycle

Like other gill snails , Tonna galea is separate sexes. The female lays the eggs in gelatinous ribbons about 30 cm long, 5 to 8 cm wide and 1.6 to 1.9 mm thick, which consist of about 2 to 3 mm large egg capsules. According to measurements on barrel snails in India, an egg capsule contains around 95 to 110 eggs with a diameter of around 217–234 µm, almost all of which develop into embryos. About 15 to 17 days after egg-laying, the Veliger larvae hatch from the capsule and have a brown shell of around 418 µm. Until the metamorphosis into the finished snail, the larvae go through a pelagic period lasting several months , which contributes to the considerable spread of the snail.

food

Tonna galea feeds on echinoderms . Preferred prey are sea ​​cucumbers , including Holothuria tubulosa and Holothuria sanctori . The prey is stunned with the snail's acidic saliva, which contains two to four percent free sulfuric acid and aspartic acid , and the calcareous skeleton is dissolved. The eating process can take several minutes.

Significance for humans and danger

The large barrel snail is collected for its meat and shell. It is also endangered by trawls , in which it often forms bycatch . So man can be seen as a major enemy. Because of their predatory way of life, the barrel snail is sensitive to changes in the ecological balance. Therefore Tonna galea is endangered in the Mediterranean. It is protected under the Federal Species Protection Ordinance and the Bern Convention . Worldwide, however, it has not yet been included in the Red List.

Individual evidence

  1. ^ C. Brüggemann (1838): The natural history in faithful illustrations and with a detailed description of the same. Eduard Eisenach publisher, Leipzig 1838. Die Weichthiere, p. 66. e) Tonne (Dolium).
  2. ↑ a b Sealifebase: Tonna galea (Linnaeus, 1758), giant tun
  3. ↑ World Register of Marine Species , World Marine Mollusca database: Tonna galea (Linnaeus, 1758)
  4. ^ AV Natarajan (1957): Studies on the egg masses and larval development of some prosobranchs from the Gulf of Mannar and the Palk Bay . Proceedings of the Indian Academy of Sciences, vol. 46 (3) (1957), pp. 170-228. Dolium: pp. 187 (PDF; 242 kB), 188 (PDF; 236 kB), 189 (PDF; 175 kB), 190 (PDF; 267 kB). doi : 10.1007 / BF03052428 .
  5. ↑ Richard Semon (1890): On the purpose of excreting free sulfuric acid in sea snails. Biological Centralblatt 9, page 80.
  6. ↑ Hermann Weber (1927): The intestine of Dolium galea L., a comparative anatomical study with special consideration of the Tritoniumarten. Journal of Animal Morphology and Ecology No. 8, pages 663-804.
  7. ^ F. Bentivegna & A. Toscano (1991): Observation au laboratoire sur le comportement alimentaire de trois espèces de la superfamille Tonnoidea (Mollusca, Gastropoda). Revue Française d'Aquariologie Herpetologie, 18: 33-38.
  8. ↑ Fischhaus Zepkow: Family Tonnidae - barrel snails

Web links

Commons : Large Barrel Slugs  - Collection of images, videos, and audio files