Class Hexactinellida Schmidt, 1870

摘要: Hexactinellida Schmidt (Porifera) are deep-water marine sponges defined by their production of siliceous spicules hexactinic, triaxonic (cubic) symmetry, or shapes clearly derived from such forms reduction primary rays terminal branches added to the ends rays. They lack calcareous minerals and sclerified organic spongin as skeletal components. Siliceous may be entirely loose, partially fused form a rigid basal choanosomal framework. Their living tissues mainly syncytial, with distinctive porous plugs joining differentiated regions syncytium each other discrete cellular Flagellated-collar units anucleate. Hexactinellids viviparous and, detailed study single species, produce trichimella larvae. Two subclasses recognized different microsclere — amphidiscs hexasters. include about 500 described 7% all Porifera, distributed in 5 orders, 17 families 118 genera.