Helmets

from Wikipedia, the free encyclopedia
Cassidae
A snail digs in the sand

A snail digs in the sand

Systematics
Superordinate : Caenogastropoda
Order : Sorbeoconcha
Subordination : Hypsogastropoda
Partial order : Littorinimorpha
Superfamily : Cassoidea
Family : Cassidae
Scientific name
Cassidae
Latreille , 1825
Housing of Semicassis pyrum

The helmet snails (Cassidae) are a family of marine snails that live on soft floors in shallow subtropical and tropical seas. They are predatory and eat almost exclusively echinoderms (Echinodermata).

features

The cases are right-handed and ovoid. They can be rolled up trochospirally to convolute, i.e. H. the last turns completely encompass the previous turns. The mouth can be oval, but also slot-like and extend over the entire length of the housing. The adult size ranges from about 1.7 cm to 40 cm. The foot is large and very muscular with a large propodium . In contrast to the related barrel snails (Tonnidae), the helmet snails have horny opercula . Reproductive strategies vary widely within the family. In many species a sexual dimorphism is pronounced: the females become larger than the males. The egg clutches comprise between a few hundred to several tens of thousands of egg capsules, which are deposited on a hard ground. Often the eggs are guarded by the mother. In these cases the relatively few eggs (a few hundred) are rich in yolks, and small finished animals hatch. In other cases, up to 100,000 Veliger larvae can hatch from the clutches with low- yolk eggs , which then feed on plankton.

distribution

The representatives of the Cassidae family are sometimes widespread in the tropical and subtropical seas. The species common in the Indo-Pacific include B. Cassis cornuta (Linnaeus, 1758), Cypraecassis rufa (Linnaeus, 1758), Semicassis bisulcata (Schubert & Wagner, 1829), Phalium glaucum (Linnaeus, 1758), Phalium areola (Linnaeus, 1758), Casmaria erinacea (Linnaeus, 1758 ) and Casmaria ponderosa (Gmelin, 1791). On the other hand, Cassis tuberosa (Linnaeus, 1758) and Cassis flammea (Linnaeus, 1758) play a very important role as predators of sea urchins in the western Atlantic and the Caribbean .

Way of life

Cassidae live mainly in the tidal and shallow coastal areas, but can also penetrate to a depth of around 1,100 m. They usually settle on soft substrates, but also seek out hard grounds to lay eggs. They live predatory on echinoderms such as sea ​​cucumbers , brittle stars , starfish and sea ​​urchins . Smaller prey, such as B. small sea cucumbers and brittle stars are devoured whole. Sea urchins and starfish are drilled and eaten or eaten in pieces.

Systematics

The family is set by Bouchet and Rocroi as a subfamily to the younger (= later established) family Tonnidae. According to the IRZN, this is not correct. Millard (1997) and Riedel (2000) therefore place them in the superfamily Cassoidea . Bouchet and Rocroi list four subfamilies within the Cassidae:

The majority of authors regard the Tonnidae ( barrel snails ) as an independent family within the superfamily Cassoidea; therefore Bouchet and Rocroi are not followed on this point.

According to Kreipl (1997) the following breakdown results:

Gofas (2011) largely follows this systematic breakdown.

Economical meaning

The meat of the great helmet snail species is eaten in many countries. The family is also very popular among snail collectors.

literature

  • Philippe Bouchet & Jean-Pierre Rocroi: Part 2. Working classification of the Gastropoda . Malacologia, 47: 239-283, Ann Arbor 2005, ISSN  0076-2997 .
  • Serge Gofas: Cassidae. World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=22999 . Retrieved March 7, 2011.
  • Kurt Kreipl: Recent Cassidae . 151 pp., Verlag Christa Hemmen, Wiesbaden 1997, ISBN 3-925919-24-4 .
  • Victor Millard: Classification of the Mollusca. A Classification of World Wide Mollusca . Rhine Road, South Africa 1997, ISBN 0-620-21261-6 .
  • Winston Ponder & David Lindberg: Towards a phylogeny of gastropod molluscs; an analysis using morphological characters . Zoological Journal of the Linnean Society, 119: 83-265, London 1997, ISSN  0024-4082 .
  • Frank Riedel: Origin and evolution of the "higher" Caenogastropoda . Berliner Geoscientific Abhandlungen, Series E, Volume 32, Berlin 2000, 240 pages, ISBN 3-89582-077-6 .

Web links

Commons : Helmet snails (Cassidae)  - Collection of images, videos and audio files