Porifera

Porifera

  • Porifera, commonly known as sponges.
  • Porifera are a phylum of simple multicellular organisms within the animal kingdom.
  • They may appear as stationary and immobile creatures.
  • They are generally marine.
  • Digestion is intracellular.

 

Characteristics-

 

Body Organization:

    • Porifera lack true tissues and organs. Their bodies are composed of specialised cells embedded in a gelatinous matrix called mesohyl.
    • Body of Porifera is supported by a skeleton made up of spicules or spongin fibres.
    • They are mostly asymmetrical animals.
    • They have a porous body with numerous channels and cavities, allowing water to flow through their structures.
    • Sponges come in various shapes, ranging from encrusting forms to branching or vase-like structures.

Locomotion:

  • Adult sponges are generally sessile (meaning they are permanently attached to a substrate and do not exhibit active locomotion).
  • However, some sponge larvae are capable of limited movement through the use of cilia or flagella.
  • They can swim or drift in the water column until they find a suitable substrate to settle on.

Reproduction:

  • In budding, new sponge individuals develop as outgrowths from the parent sponge.
  • Fragmentation involves the breaking of a piece of the sponge, which can grow into a new individual.
  • Sponges can be hermaphroditic, meaning they possess both male and female reproductive structures.
  • Sperm are released into the water, where they are captured by other sponges and used to fertilise their eggs. Larvae are formed from the fertilised eggs and are released into the water.
    • Sponges have both asexual and sexual modes of reproduction.
    • Asexual reproduction occurs through budding or fragmentation.
    • Sexual reproduction involves the production of eggs and sperm.

Feeding Strategies:

  • Sponges are filter feeders, primarily obtaining nutrients from organic particles suspended in the water.
  • They have specialised cells called choanocytes that line their internal canals. These cells possess flagella that create water currents and trap food particles. Choanocytes then engulf and digest the captured food particles.
  • The water is drawn into the sponge through numerous small pores called ostia and expelled through larger openings called oscula.
  • Examples:

Sycon (Scypha), Spongilla (Freshwater sponge) and Euspongia (Bath sponge).

 

        Sycon (Scypha)