Gray, 1867
Definition: Obligatory excavating sponges or burrowing sponges in calcium or siliceous substrata. Ectosomal pores (ostia) are localized on papillae that protrude through the surface, and other papillae, opening at the surface by way of terminal oscules, expel exhalant water. Megascleres are tylostyles. Microscleres are spirasters and microspined oxeas, both sometimes absent. The settled larvae following metamorphosis burrow into a calcareous substratum and dwell in galleries for part or all of their lives, whereas faster-growing species may overgrow the substratum completely, and subsequently become massive, free-living sponges (Cliona celata gamma stage).
Remarks: It can be argued that Clionids should be classified in the family Spirastrellidae, being merely Spirastrellids with an ecologically specialised life strategy, but the obligatory nature of the excavating habit during at least the early stages of the life cycle and the presence of oxeote spicules in some species may constitute valid phylogenetic differences from the Spirastrellids.
Excavation of calcium carbonate is brought about by chemical etching agents secreted at the tips of pseudopodial processes of special etching cells. The processes undermine irregularly shaped chips, 40 to 60 µm in diameter, that find their way out of the sponge by way of the exhalant canal system. Only 2 to 3 percent of the substratum is dissolved during the etching process. Sponge-eroded calcareous chips may compose up to 30 or 40 percent of sediments in low-energy reef environments.
The family occurs in all seas, mostly in tidal and shallow-waters. The deepest record is 2165 m (Hartman, 1982). Fifteen nominal genera of Clionids have been created, but only four of these may be valid.
Source: Hooper's Internet Sponge Guide.
Genera represented in the area:
Alectona Carter, 1879 (type species: A . millari Carter, 1879): Tiny papillae; spined oxea-like megascleres and amphiaster microscleres (Alectona millari).
Cliona Grant, 1826 (type species C . celata Grant, 1826) (syn. Papillina Schmidt, 1862; Raphyrus Bowerbank, 1863; Pione Gray, 1867; Myle Gray, 1867; Sapline Gray, 1867; Idomon Gray, 1867; Pronax , in part, Gray, 1867; Osculina Schmidt, 1868; Papillella Vosmaer, 1885; Papillissa Lendenfeld, 1888; Gapoda de Laubenfels, 1936): Papillae easily visible to the naked eye (Cliona celata); spicules tylostyles and spirasters (which may be lost), occasionally with spined oxeas as accessory microcleres.
Species included:
Alectona millari
Cliona celata
Cliona lobata
Cliona vastifica
Cliona viridis