Hexactinellida

Hexactinellida [hek‚sak·tə′nel·ə·də]

(invertebrate zoology)

A class of the phylum Porifera which includes sponges with a skeleton made up basically of hexactinal siliceous spicules.

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Hexactinellida 

(or Hyalospongia), a class of sponges. Hexactinellida are predominantly solitary, typically oceanic organisms, usually occurring at depths of more than 100 m, down to the hadal (or ultra-abyssal) zone. The body is saclike, tubular, goblet-shaped, or barrel-shaped, up to 2 meters in height. The skeleton consists of six-rayed siliceous spicules. The rays lie in three mutually perpendicular planes; in some of the needles, one or more rays are reduced. The canals that thread through the body wall (the canal system) are of the simple leuconoid type.

The class comprises about 500 species, 34 of which are found in the USSR—six in northern seas and 28 in Far Eastern seas. The most common are representatives of the genera Hyalonema, Aphrocallistes, Schaudinnia, Aulosaccus, Acanthascus, and Caulophacus.

The skeletons of some Hexactinellida are used for decorative purposes.

REFERENCES

Koltun, V. M. Stekliannye, ili shestiluchevye, gubki severnykh i dal’nevostochnykh morei SSSR. Leningrad, 1967. (Opredeliteli pofaune SSSR, vol. 94.)
Traité de zoologie, vol. 3, part 1. Edited by P.-P. Grassé. Paris, 1974. Page 687.

V. M. KOLTUN