Cliona

Cliona are commonly called boring sponges. These sponges mostly live on reefs and lagoons. They make a hole in calcareous rocks, shells of molluscs and limestones. They are found at the base of the hole as a lump and sometimes grow over it. They are commonly found in oysters and cause great damage to the pearl industry.

Cliona Classification and Examples

Cliona is classified under the phylum Porifera. They belong to the class Demospongiae, characterized by the skeleton of spongin fibres, siliceous spicules or both.

Kingdom

Animalia

Phylum

Porifera

Class

Demospongiae

Order

Clionaida

Family

Clionaidae

Genus

Cliona

The common species of Cliona are:

Cliona celata – red boring sponge

Cliona viridis – green boring sponge

Cliona Structure and Characteristics

  • Cliona are found in lagoons and reefs. They form big colonies and excavate calcareous substratum to which they are attached
  • They are commonly found in mussel beds and oyster
  • They are yellow, orange or green in colour. The colour is due to dinoflagellates (zooxanthellae) present in them
  • The outer surface is smooth, tough and mosaic-like. Beneath the surface, there are galleries excavated by them
  • The skeleton is made up of siliceous spicules and spongin fibres
  • Spicules are megascleres or microscleres. Megascleres are found as irregular and densely arranged tylostyles. If microscleres are present they are raphides
  • The canal system is leuconoid type
  • It aggressively excavates deep in shells of molluscs, coral reefs and destroys them
  • Bore channels are formed due to dissolution of shells and rocks by an acid secreted by them
  • Water gets in through ostioles. Bacteria, protozoa and other small micro-organisms get filtered out
  • Gaseous exchange is through diffusion and water is expelled out through the osculum
  • Reproduction is sexual and asexual
  • They are oviparous but in some of the species such as Cliona celata, eggs are fertilized internally with the sperm that comes with the water flow
  • They are very harmful to shellfish farming and pearl industry

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