INVERTEBRATE ZOOLOGY IN THREE BOOKS - BOOK 1 - H.I. Shcherbak - 1995

SUBKINGDOM MULTICELLULAR ANIMALS (METAZOA)

SECTION TRUE MULTICELLULAR ANIMALS (EUMETAZOA)

PHYLUM CTENOPHORA (COMB JELLIES)

CLASS XENOTURBELLIDA

This Class has been established for a single species, Xenoturbella bocki, found in marine environments at depths of 40–100 m on muddy bottoms (Fig. 141). Xenoturbellids reach a length of 2–3 cm. They differ from turbellarians by the absence of an excretory system and a cerebral ganglion. Its

Fig. 141. Class Xenoturbellia (Xenoturbella bocki) — general view (a), longitudinal section (b):

1 — ciliated ring furrow; 2 — intestinal epithelium; 3 — parenchyma; 4 — Skin-Muscle sac; 5 — eggs; 6 — statocyst

Nervous system has a plexus-like Structure and lies within the basal region of the integumentary epithelium. On the sides of the body, in its anterior part, There is a pair of ciliated furrows; additionally, a circular ciliated furrow is located posterior to the Mouth. These structures presumably serve a sensory function. The Development of xenoturbellids remains unstudied.