Akera

Akera bullata

The ball screw ( Akera ) are a genus of medium-sized and family usually, in all oceans occurring marine housing carrying snails in the order of the Breitfußschnecken ( Anaspidea ). Akera is the only genus of the family Akeridae. It comprises five recognized species.

Features

The ball screw wear on their backs, a thin-walled, oval shell with several whorls, which can not absorb all of the body of the worm. The head shield is provided with inconspicuous, round, wing-like extensions. The snails have on both sides of her foot large parapodia, which meet on the shell and can swim which the worm using. The mantle cavity contains a gill. The snails have a gizzard with numerous plates. The radula is multiple rows with central tooth and lateral teeth on either side more.

The snails are hermaphrodites that mate to several in series. There are ribbon-like nests deposited with numerous eggs, which hatch veliger larvae metamorphose after a pelagic phase to young snails.

The ball screw feed primarily on green algae, red algae as well. But they are at least partially also able seagrass ( Zostera ) to eat.

Dissemination

Ball snails live mainly on sandy grounds and in seagrass beds. They are found in oceans worldwide.

System

After Bouchet and Rocroi (2005 ) the family Akeridae forms in addition to the Aplysiidae one of two families in the suborder Aplysiomorpha. To the family Akeridae include five types:

• Akera Bavarian Ev. Marcus & Er. Marcus, 1967 ( synonym: Akera thompsoni Olsson & McGinty, 1951, nomen nudum )
• Akera bullata O. F. Müller, 1776 ( type species )
• Akera julieae Valdés & Barwick, 2005
• Akera Whistling Ortea & Moro, 2009
• Akera soluta ( Gmelin, 1791)