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

SUBKINGDOM MULTICELLULAR ANIMALS (METAZOA)

SECTION TRUE METAZOA (EUMETAZOA)

PHYLUM COMB JELLIES (CTENOPHORA)

CLASS GYROCOTYLIDEA (GYROCOTYLIDA)

This Class comprises ten species of Flatworms that parasitize the intestine, specifically the spiral valve, of chimaeroid Fishes. They are small worms, measuring 2–5 cm in length. The anterior end bears a conventional sucker, while the posterior end features a specialized attachment organ in the form of a folded rosette. On its anterior part, adjacent to the trunk, There is a small dorsal depression (funnel) at the bottom of which embryonic hooks are retained. The margins of the body are also scalloped. The Internal Structure of gyrocotylids is similar to that of cestodes: a Digestive System is absent, a well-developed protonephridial excretory system is present, The Nervous system is of the orthagonal type, and Sense Organs are poorly developed. Gyrocotylids are hermaphroditic (Fig. 160). The eggs hatch into a free-swimming lycophore larva, which is covered with ciliated epithelium and bears ten hooks at its posterior end. The Development of gyrocotylids proceeds without an intermediate host, although the pathways by which the parasites infect fish remain insufficiently studied.

Fig. 160. Gyrocotyle fimbriata:

1 — cuticular spines; 2 — ganglion; 3 — scalloped body margins; 4 — nerve trunks; 5 — shell glands; 6 — nerve ring; 7 — attachment rosette; 8 — sucker; 9 — Vagina opening; 10 — vagina; 11 — Testes; 12 — Uterus pouch; 13 — uterus; 14 — seminal receptacle; 15 — Ovary; 16 — ganglion of the attachment rosette