Alcyonaria

(invertebrate zoology) A subclass of the Anthozoa; members are colonial cnidarians, most of which are sedentary and littoral.

A subclass of the Anthozoa. These coelenterates are colonial; most are sedentary and littoral, and some live at great depths. The ordinary polyp, the autozooid, has eight motile, contractile, hollow, pinnately branched tentacles. Eight complete mesenteries are present, of which the dorsal or asulcal pair is the most developed and bears the largest, heavily ciliated ectodermal filaments. The remaining mesenteries bear endodermal filaments having many glandular cells. Longitudinal retractor muscles are strongly developed on their ventral or sulcal surfaces. The stomodeum or pharynx, with a single siphonoglyph in its sulcal edge, is lined by a ciliated glandular epithelium. The gastrovascular cavity of each polyp is interconnected by complex canal systems or solenia. These permeate the colonial spiculiferous mesoglea or coenenchyme. The skeleton is formed by a deposition of horny material secreted by ectoderm cells, or by ectodermal scleroblasts which secrete calcareous spicules or sclerites of various shapes. The musculatures are not particularly well developed.

The oral end of the polyp is termed the anthocodium. The basal portion, or anthostele, is embedded in coenenchyme containing numerous ameboid cells and scleroblasts.

The Alcyonaria are characterized by a strongly developed siphonoglyph, which serves to circulate water in a colony. Alcyonaria are either dioecious or monoecious. The gonads ripen in the endodermal mesenteric filaments. The daughter polyp buds asexually from the solenial system or from a parent's body wall. Pennatulacea and some other forms are dimorphic. The siphonozooid is smaller than the autozooid. It lacks tentacles or the tentacles are rudimentary and usually sterile. See also Anthozoa; Coelenterata.