INVERTEBRATE ZOOLOGY IN THREE VOLUMES - VOLUME 1 - H.Y. Shcherbak - 1995

SUBKINGDOM MULTICELLULAR ANIMALS (METAZOA)

SECTION EUMETAZOA

PHYLUM CTENOPHORA

CLASS CTENOPHORA

Subclass Typhlocoela

This subclass unites ctenophores that lack anastomoses (connections) between the canals of the gastovascular system near the oral end of the body.

Order Cydippida

Cydippids are considered to be the most ancient order of ctenophores. In their level of Organization, cydippids resemble the ancestral developmental stage of all other ctenophores. A typical representative of the order, Pleurobrachia pileus, occurs in all oceans of the world, often in massive numbers (Fig. 126, a).

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Fig. 126. Ctenophores: a — Pleurobrachia rhodopis (Cydippida); b — Coeloplana; c — Tialfiella (Platyctenida); d — Beroe cucumis (Beroida); e — Cestus veneris (Cestida)

Some species have retained The ability to swim, such as ctenophores of the genus Ctenoplana, whereas most have lost their comb rows in the adult stage and shifted to a creeping (genus Coeloplana) or even sessile (genus Tialfiella) lifestyle. Creeping Representatives of the order develop a flattened body shape compressed along the oral-aboral axis. They are capable of everting their Pharynx significantly, which then serves as a creeping surface for the body. Creeping ctenophores are frequently found on corals, where they feed on their soft Tissues (Fig. 126, b, c).