Myzostomida

Three camouflaged copies of Myzostoma fuscomaculatum on their host, the crinoid Tropiometra carinata.

The Myzostomidae are a family of marine worms that live as commensals or parasites on echinoderms ( Echinodermata ), the most for feather stars or sea lilies, some species of starfish or brittle stars. They prefer Stachelhäuterarten deeper than 200 m life and encourage them to form in the interest of protecting the Myzostomidae to small, bile -like skeletal elements.

Features

The animals have a disc-shaped, flattened body with strong dorsal and Ventralmuskulatur and are surrounded by hook-like bristles to hold on to their hosts. Through the parapodia and the segmental arranged lateral nerves of the modified to a uniform mass ladder nervous system segmentation can be seen. A ganglion is located at the upper throat. The intestine has ceca.

Propagation

The animals are simultaneous hermaphrodites. Copulation takes place on the mutual attachment of complex spermatophores from 5 different cell types. The spermatophore penetrates root like the body and transports the sperm to the egg cells. There is a Spiralfurchung. The larva is a spherical trochophore larva.

System

The taxonomic classification is uncertain. Traditionally, the Myzostomidae be counted among the Vielborstern ( Polychaeta ). Their organs are arranged segmentally as in annelids. However, molecular studies suggest a relationship with the flatworms ( Platyhelminthes ).

Genera

There are about 140 species in six genera.

• Cystimyzostomum Jagersten, 1940
• Endomyzostoma Perrier, 1897
• Hypomyzostoma
• Myzostoma Leuckart, 1829
• Notopharyngoides
• Protomyszostomum