Janthinidae

Violet snail rinsed with raft on the beach in Maui (Hawaii).

The raft snails ( Janthinidae ) are about 9 species of medium-sized a small family, exclusively marine snails that are found in tropical and temperate seas worldwide. The representatives of the family living on the sea surface as pelagic predators of cnidarians.

Features

Characteristic of all representatives of the raft snails which is formed by the body's own mucus, up to 12 cm long chitin raft of transparent, air-filled bubbles on the drive the animals at the water surface and are so widespread across the seas. The mucus of the raft is formed in a gland at the base of the screw. Since the snails with the ventral side and thus also the case mouth hang up, they are counter- chat advantage vice versa.

The dextral, smooth body of the raft worm is thin and fragile, so that saves on weight. During the veliger larvae still have an operculum, this is no longer present in adult rats.

The snails have a large head and a very flexible neck. The very small eyes are located at the base of the sensor. The ribbon-shaped radula has similar to the spiral staircase screw means no teeth on each side and a plurality of hook -shaped lateral teeth. Each hand of the radula there is also a pine with a smooth edge, in the genus Recluzia Stilettos at the outputs of the salivary glands.

The snails are first males and females later. Violet snails do not have a penis, and the sperm is transferred onto the females from the males in seed packets. In Janthina exigua and Janthina pallida the female egg capsules attached with a total of up to two and a half million eggs on the underside of the raft, which hatch free-swimming veliger larvae. Janthina janthina other hand, is ovoviviparous, that is, the eggs develop until hatching in the oviduct of the mother, the leave the veliger larvae through the genital opening. For the genus Recluzia there are not studied. It follows a prolonged period of Veliger as zooplankton.

At the time of metamorphosis the juvenile snail forms a long slimy stalk with a bale of air bubbles at the end, by means of which the animal reaches the surface, where the final raft is formed. The air-containing mucus bubbles are formed with the foot, are being used for a bubble for about 10 seconds. Loses a raft screw their raft, they can only be a new form when it has contact with the water surface and thus to the air, for example, hanging on a sail jellyfish.

Life, the occurrence and distribution

The Janthinidae are widespread in tropical and temperate seas. They are playing their raft on the sea surface and feed on here of pelagic cnidarians, especially sailing jellyfish and Portuguese galleys.

System

After Bouchet and Rocroi ( 2005), the family Janthinidae one of three families in the superfamily Epitonioidea. To the family Janthinidae includes two genera:

• Janthina Röding, 1798 with 5 species
• Recluzia Petit de la Saussaye, 1853 with 4 types

The two genera differ inter alia in the coloring of the housing. So these are brown with violet Janthina and Recluzia.

For the genus Janthina about 60 species have been described, but Laursen has this reduced in 1953 in a revision on the basis of anatomy, Radulastruktur and the reproductive cycle of the worm in 5 ways: Janthina janthina (Linnaeus, 1758), Janthina exigua Lamarck, 1816 janthina globosa Swainson, 1822 janthina pallida W. Thompson, 1840 and janthina umbilicata d' Orbigny, 1841 For the genus Recluzia there are 11 species descriptions, of which perhaps only 2 or 3 of a revision to withstand.

The two genera Iodes Mörch, 1860 and Iodina Mörch, 1860 are synonyms of Janthina Röding, 1798.