ADVERTISEMENTS:
In this article we will discuss about the structure of Valella with the help of a diagram.
1. It is a small pelagic and marine colony in the tropical seas.
ADVERTISEMENTS:
2. It is discoidal in shape and is of bright blue colour.
3. The disc is generally oval and flat, but may also be some-what rhomboidal in some cases.
4. Just as in porpita, the disc has a chitinous and multi-chambered shell with air trapped inside and acting as pneumatophore.
5. All along the body axis, from the pneumatophore, arises a vertical hollow and transparent crest-like sail.
ADVERTISEMENTS:
6. The zooids are of three types namely:
(a) A large central gastrozoid hanging from the lower surface of disc and working as nutritive zooid,
(b) Numerous gonozoids attached to the lower surface of disc surrounding the gastrozoid and working as reproductive zooids,
(c) Large number of elongated and tubular dactylozoids hanging all along the peripheral margins of the disc and provided with nematocysts for offence and defence.
7. The gonozoids produce medusae.
