Sollas, 1888
Definition: Order Spirophorida. Sponges with a perfect radial skeleton and consequent near spherical form, often referred to as golf ball sponges (Cinachyrella apion). Megascleres (C. apion spicules) are triaenes and oxeas arranged in a radiate pattern. protriaenes are apomorphic for the family, often protruding from the suface of the sponge. The microscleres are contorted sigmaspires with minute spines. Sometimes other modified triaene spicules are also present (amphiclads, calthrops-like). Inhalant pores are grouped in special pore areas in some genera: poriferous pit or porocalyx (C. apion porocalyx), unique to the family. Reproductive patterns range from the extrusion of fertilized eggs, which fix to the substrate and develop directly, to oviparous, incubation of complete young sponges which are then expelled by localised breakdown of the pinacoderm (C. apion with buds, C. apion buds-close up). No free larvae have yet been described.
Remarks: These sponges are mainly found on soft bottoms and coral rubble deposits, from intertidal habitats to 2000 m depths. Some species possess a root of spicules to attach them to the substrate.
17 nominal genera are presently included in the family, although not all these are valid, with a major revision of the order required. 9 genera are currently recognised. Review: Rützler (1987).
The Lithistid family Scleritodermidae Sollas, 1888, shares the sigmaspires with the Tetillidae, and is probably closely related.
Source: Hooper's Internet Sponge Guide.
Genus represented in the area;
Tetilla Schmidt, 1868 (type species Tetilla euplocamos Schmidt, 1868) (syn. Chrotella Sollas, 1886): without porocalices, without cortex, without unusual accessory megascleres.
Species included:
Tetilla cranium
Tetilla polyura
Tetilla zetlandica