INVERTEBRATE ZOOLOGY IN THREE BOOKS - BOOK 2 - G.I. Shcherbak - 1996

PHYLUM SIPUNCULIDA

Sipunculids are marine benthic animals, with the exception of Phascolosoma lurco, which has adapted to life in damp coastal soils. They occur at various depths—ranging from the intertidal zone down to 5,000 m—with the highest species diversity found on the continental shelf (the coastal zone of the World Ocean up to 200 m deep) of tropical seas. Typically sedentary, they conceal themselves inside mollusk shells, the tubes of sedentary polychaetes, crevices in coral skeletons, or burrow through the substrate.

Over 300 species of sipunculids have been described. Only two species have been recorded in the Black Sea, specifically in the Bosporus region.

Their body consists of a thickened trunk and an elongated introvert (proboscis). A well-developed cutaneous-muscular sac is present. The coelom is unsegmented. The Mouth is located at the tip of the proboscis. The intestine is looped, with the anus opening on the dorsal side near the Base of the proboscis. Excretory Organs are represented by nephromixia; the Circulatory system is absent, and Respiration occurs through the body surface.

Sipunculids are dioecious with external Fertilization, and their development is indirect, proceeding through a trochophore larva.

The phylum Sipunculida comprises a single Class of the same name.