In this article we will discuss about the structure of Porpita with the help of a diagram.
1. It is a marine and polymorphic colony found in abundance around southern Atlantic coasts.
2. It is discoidal in shape and thus resembles a medusa.
3. A distinct and independent float is absent, but the disc is chitinous, multi-chambered and encloses sufficient quantity of air in these chambers, and acts as pneumatophore.
4. Below the chitinous part is present a layer of coenosarc which is traversed by numerous ectodermal and endodermal tracheae (canals). The former communicated with the air chambers and to outside and the later with the coelenteron of the zooids.
5. The zooids are of three types namely:
(a) Dactylozooids which hang from the peripheral margins of the disc and are armed with nematocysts, thus acting as offensive and defensive zooids
(b) Gonozoids, which are found in bunches attached along the lower surface of disc around the gastrozoid and which act as reproductive zooids
(c) Gastrozoid is single, pitche “shaped and is situated in the centre along the lower surface of disc and acts as nutritive zooid.
6. The gonozoids produce medusae.