How are sponges classified? What are the three classes of Porifera, and what are their characteristics in detail + genera?
- Classified based on types of spicules, shape of sponge, and DNA. NOT BY CANAL TYPES!
- Calcarea: have calcareous spicules (calcium carbonate) which have 3-4 rays. Have tubular or vase shape. Can have asconoid, syconoid, or leuconoid canal system. (Leucosolenia, Scypha)
- Hexactinellida: “glass sponges” have six-rayed siliceous spicules (silicon) (Euplectella aspergillum)
- Demospongiae: “bath sponges” or “horny sponges.” Skeleton of siliceous spicules (silicon), except bath sponges which have spongin (collagen – a protein) instead. Large sponges that have only leuconoid canal system due to size and complexity. Gemmules are released through osculum, and will become a new sponge. (Spongilla, Chalina, Euspongia)