Thread snails

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Thread snails
Flabellina iodinea

Flabellina iodinea

Systematics
Class : Snails (gastropoda)
Subclass : Orthogastropoda
Superordinate : Heterobranchia
Order : Hind gill snails (Opisthobranchia)
Subordination : Nudibranchia (Nudibranchia)
Partial order : Thread snails
Scientific name
Aeolidida
Cuvier , 1798

The thread snails (Aeolidida) are a suborder of the nudibranch within the order hind gill snails . The small to medium-sized shell -less snails found in all oceans are carnivores . They mostly eat cnidarians , whose nettle capsules they deposit in their cerata and thus use them as kleptocnids themselves.

features

The translucent thread snails are usually no longer than 4 to 5 cm, so that the wide-waxy thread snail ( Aeolidia papillosa ) is one of the large species, up to 10 cm long . Most thread snails have a pair of long, very odor and flow-sensitive antennae, the rhinophores , which can be shortened but never completely drawn in. In addition, there are usually additional feelers on the mouth (mouth tentacles) that can be longer than the rhinophores. In addition to the radula, there are jaws for biting. The anus is well forward on the right side.

Like other nudibranch snails, the thread snails lack a shell and shell. Your back is covered with numerous cerata, appendages that serve both breathing and defense. Runners of the highly branched midgut gland lead into the cerata and end under the skin at the apex in s. G. Hives sacs, also called cnido sacs, which lead to the outside through a normally closed porus. The nettle capsules of eaten cnidarians do not explode when they eat and are not digested, but rather shifted by the midgut gland into the cerata and stored in the nettle sacs. The deposited nettle capsules, the kleptocnids, are ejected via the porus when touched by other animals, and thus ward off the snail's predators.

Most thread snails are benthic and usually eat sessile cnidarians. Some species, such as Glaucus atlanticus and Glaucilla marginata in the Glaucidae family , live as pelagic predators of pelagic cnidarians, mostly colony-forming hydrozoans ( Portuguese galley , sailing jellyfish ). These free-swimming species also deposit kleptocnids in their cerata. The also pelagic Fiona pinnata , however, mostly eats barnacles ( Lepas ) and only occasionally pelagic cnidarians. It does not deposit kleptocnides.

The thread snails are hermaphrodites that mate with each other with their penises . Every animal produces eggs and sperm and has both a female and a male genital opening that are next to each other. The eggs are laid in egg strings made from thousands of egg capsules, from which Veliger larvae hatch. During their pelagic phase, these sometimes carry a tiny shell , which is later lost again, so that the metamorphosis creates a shell -less nudibranch.

Systematics

According to Bouchet and Rocroi (2005), thread snails (Aeolidida) include three superfamilies with eleven families. Some species examples are also given:

In earlier systematics, the thread snails formed a superfamily Aeolidiacea.

literature

  • Luise Schmekel, Adolf Portmann: Opisthobranchia of the Mediterranean: Nudibranchia and Saccoglossa . Springer-Verlag, Berlin Heidelberg New York 1982. Subordo Aeolidacea Odhner, 1934 : pp. 183-272.
  • Adam Sedgwick, Joseph Jackson Lister, Sir Arthur Everett Shipley: A Student's Text-book of Zoology: Protozoa to Chaetognatha . S. Sonnenschein and Company, 1898. Aeolidioidea : pp. 412f.
  • Philippe Bouchet & Jean-Pierre Rocroi: Part 2. Working classification of the Gastropoda . Malacologia, 47: 239-283, Ann Arbor 2005, ISSN  0076-2997 .
  • Victor Millard: Classification of the Mollusca. A Classification of World Wide Mollusca . Rhine Road, South Africa 1997, ISBN 0-620-21261-6 .
  • Rudie H. Kuiter , Helmut Debelius : Nudibranchs of the world's oceans: 1200 species worldwide. Kosmos Verlag, Stuttgart 2007. ISBN 3-440-11133-4 .

Web links

Individual evidence

  1. ^ Friedrich Heinrich Wilhelm Martini, Johann Hieronymus Chemnitz, Heinrich Carl Küster, Wilhelm Kobelt: Aeolidiacea, Systematisches Conchylien-Cabinet von Martini and Chemnitz. Verlag von Bauer & Raspe (Emile Küster), Nuremberg 1855.