Solenogastres

Class of molluscs

The Solenogastres (less often referred to as Neomeniomorpha), common name the solenogasters, are one class of small, worm like, shell less molluscs (Aplacophora), the other class being the Caudofoveata (Chaetodermomorpha). Some recent literature, and recent molecular evidence, indicates that the Aplacophora may be polyphyletic, and therefore these taxonomists divide Solenogastres and Caudofoveata into separate classes.

In contrast to all other molluscan classes, the Aplacophora have no shell, and are instead covered by aragonitic sclerites (calcareous spicules), which can be solid or hollow. These spicules can be arranged perpendicular to one another within the cuticle to form a skeleton, or can stick up to form a palisade, or can lie flat against the cuticle. 80% of solenogaster species have a radula, while in others it is secondarily lost. The radula may bear one or more teeth per row; where there is more than one tooth, there is no central radular tooth.

During development many Solenogastres are covered by a spiny scleritome comprising spines or scale like plates; this has been likened to the halwaxiid scleritome. Sclerites of Epimenia start out solid before developing a hollow stem that subsequently solidifies. Solenogastres can be found in a diverse range of habitats across the world, from the coast to the deep ocean.

Solenogastres feed on cnidaria and ctenophores, either sucking their bodily fluids or eating their tissue. They do not use their radulae to rasp prey, as other molluscs do.

There is some uncertainty regarding the phylogenetic position of the solenogastres. Traditionally considered to be the most basal molluscan group and the sister group to the Caudofoveata, alternatives to both of these statements have been proposed on various lines of evidence. However, there are cryptic species which are hard to delineate due to their being a lack of multiple morphological characteristics that are necessary.