Question

Feeding zooids are called as
(a) Medusae
(b) Hydranths
(c) Blasto Styles
(d) None of the above

Answer 1

Hint: A zooid is a single, multicellular animal that is a part of a colonial animal. A feeding zooid is an animal that belongs to a larger colony and is specialized for feeding through specialized parts. A colony has various zooids that carry out different functions.

Complete step by step answer:
- The hydranth is the part of the hydroid (hydrozoan) colony that is responsible for feeding. Hence, it is the feeding zooid.
- These zooids are asexual.
- They are tentacled and are usually white, pink, or violet in color.
- In Obelia, the chitinous coating or perisarc enclosing the hydranths forms a supporting cup called a hydrotheca. Each hydrant terminates in a cone known as a hypostome bearing the mouth and surrounded by a ring of about 24 tentacles.
So, the correct answer is ‘Hydranths’.

Additional Information:
- The feeding zooid is also called a gastrozooid. Their mouths look like flowers and have a circle of stinging tentacles surrounding a mouth.
- A number of hydrozoans have an asexual and sexual phase. They are identified as the polypoid and medusoid stage, respectively.
- Hydrants alternate in the structure of Obelia.
- The medusae are sexually reproducing buds on the surface of the hydroid colony.
- The blasto styles are reproductive polyps from which the medusae grow.
- Hydroid colonies are dioecious i.e. all the zooids in the colony can be either male or female but not both.

Note:
- Examples of hydrozoans are freshwater jellyfish, Obelia, hydra, Portuguese man o’ war, etc.
- The zooids in a hydroid colony are connected to each other by tubelike hydrocauli.
- The majority of the polyps or zooids in a colony are specialized for feeding.