Hexactinellida


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Related to Hexactinellida: Demospongiae

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.

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

References in periodicals archive ?
The specimens of Aphrocallistes vastus [Schulze] (Porifera, Hexactinellida, Hexasterophora, Hexactinosida, Aphrocallistidae) were collected from Saanich Inlet and Barkley Sound, British Columbia (Canada) by scuba diving.
Second, the phylogenetic analyses confirm that, based on the autapomorphic character for Metazoa, the RTKs, sponges as a taxon are monophyletic; the Hexactinellida have been calculated to be the oldest class, followed by the Demospongia and finally by the Calcarea.
The Hexactinellida, for example, are mostly syncytial (Reiswig, 1979; Mackie and Singla, 1983), a condition that allows symplastic transport of food (Perez, 1996; Wyeth et al.
Feeding in sponges has been well-documented, and with the exception of the two examples cited in the introduction, the Cladorhizidae and the Hexactinellida, particle uptake in sponges occurs at the choanocytes in the flagellated chambers or at the pinacoderm-lined incurrent canals.