Question

briefly describe characteristics of these representatives that allow you to dintisguish the diferent orders.

Calcarea

Demospongia

Hexactinellidae

Answer 1

Ans:

Characteristics of Calcarea:

- Exclusively marine, shallow coastal water species, restricted to depth less than 100 meters and require hard substratum for attachment.

- Cylindrical or vase like in shape.

- Skeleton represented by free calcareous spicules.

- Canal system is asconoid, syconoid and leuconoid type.

- Osculum provided with oscular fringe.

Characteristics of Desmospongia:

- Mostly marine but a few are fresh water, brackish water forms.

- Skeleton either absent or silicious, fibrous.

- Canal system leuconoid type only.

- Flagellated chambers small and rounded.

- Brilliant colouration in most species, for the presence of pigment granules within amoebocytes.

Characteristics of Hexactinellidae:

- All marine, mostly deep wtaer.

- Usually cup, vase or urn like shape.

- Skeleton of six rayed siliceous spicules.

- Canal system may be either syconoid or leuconoid type.

- There is no cellular dermal epithellium.

- Commonly called glass sponge.