Question

Bipinnaria is larval stage of
A. Asteroidea
B. Holothuroidea
C. Echinoidea
D. Crinoidea

Answer 1

In the larval development of most starfish, bipinnaria is the first stage and is typically followed by the brachiolaria stage.

Complete Answer:
Bipinnaria is a part of the zooplankton which is free-living. The whole body is protected by cilia when it is in initial forms, but when it develops, these become restricted to a narrow band containing a series of loops across the surface of the body. A pair of small, stubby arms soon forms on the body, with the ciliated bands reaching through them.

Now, let us find the solution from the options-
A: The larval form is referred to as brachiolaria in most asteroids at the next stage of development, and has three additional arms used to connect the larva to the seafloor. In all Asteroids, the bipinnaria stage is followed by the brachiolaria stage, but conclusive evidence is only presented in two examples, such as Asterias glacialis and A. vulgaris. Therefore, this option is correct.

B: In Holothuroidea, the larva stage is known as an auricularia larva. Therefore this option is incorrect.

C: In Echinoidea, there is a single larval stage called Echinopluteus that is bilaterally symmetrical. Therefore this option is incorrect.

D: The fundamental larval stage of Crinoidea is pentactula, but it moves into the egg. Therefore this option is incorrect.

Thus, the correct answer is option (A) Asteroidea.

Note: It is the larva that is found in the Star fish's life history. The egg that is fertilised is homolecithal. It undergoes holoblastic cleavage and dives into processes of blastula and gastrula. The gastrulae elongates in length and it gives birth to Bipinnaria larva.