Sipuncula

Antillesoma antillarum

The spray worms ( Sipuncula ) are a comprehensive group 320 species of soil-inhabiting marine worms. You are not segmented. The slender trunk-like front body can be retracted into the abdomen. At the end of the forebody a wreath sits with sensors, which catch their food, detritus and small organisms.

The animals reach lengths of between one and 50 centimeters.

Outer systematics

The phylogenetic assignment of the animals was completely unclear until recently. Until late 1960s, in the years they have been associated, for example, with echinoderms ( Echinodermata ), you can also take molluscs ( Mollusca ). Another interpretation put forth relationship with annelids ( Annelida ), in which case both a kind of precursor status of the spray worms, as well as a derived state (ie, secondary loss of body segmentation, starting from the marigold wormlike output stage) has been postulated.

The latter interpretation has recently been strongly supported by molecular genetic studies. Thus, the spray worms are an inner group of polychaetes ( Polychaeta ) in which numerous cases of secondary segmentation losses are known anyway. This classification implies that the Nuchalorgane (special chemosensory organs of sense ) of the spray worms are homologous to the Nuchalorganen the polychaetes, which had previously been largely rejected by the traditional morphology due to fine structural differences.

With this classification in the annelids and the current status of the spray worms as a separate phylum would have to be abandoned. However, the annelids are currently in disarray, so you first have to wait for the reorganization of annelids in this regard. More generally, one could spray the worms as arthropods ( Articulata ) indicate in the broadest sense, but even these once very large group has recently been recognized due to the establishment of molting animals ( Ecdysozoa ) questioned as a community of descent.

Inside systematics

• Class Sipunculidea order Sipunculiformes Family Sipunculidae

• Family Golfingiidae
• Family Phascolionidae
• Family Themistidae

• Order Phascolosomatiformes Family Phascolosomatidae

• Family Aspidosiphonidae