1. Porpita is marine and colonial, found in warm seas.
2. It is found along the South Atlantic coast and occasionally near the U.K. coast.
3. It superficially resembles a medusa. It is most modified siphonophore. The stem is shortened to a flat coenosarc which along with float forms a rounded disk having several concentric air chambers.
4. Body is discoidal, enclosing a chambered, chitinous and porous shell, having air corresponding with pneumatophore of Physalia.
5. A large gastrozooid, having central mouth is encircled by several blastostyles.
6. Margin of the disk contains numerous dactylozooids or tentacles armed with nematocysts.
7. Nectocalyces or swimming bells are absent
8. Each air chamber opens outside by a pair of pores.
9. Space between the gastric cavity of the gastrozooid and the pneumatophore is occupied by a large cellular mass traversed by canals, the so-called liver, supposed to have an excretory function.
10. The reproductive zooids are liberated as free medusae.
Source:
1. Practical Zoology Invertebrates by S.S.Lal. 2. A Manual of Practical Zoology Chordates by Dr. P.S. Verma.
