Question

Larval form found in sponge is
A. Planula
B. Parenchymula
C. Cysticercus
D. Glochidium

Answer 1

Hint:-In the animal kingdom, various phylums are included consisting of primitive to modern animals of their respective phylums. The phylums of animal kingdom are Protozoa, porifera, coelenterata, ctenophora, platyhelminthes, aschelminthes, annelida, arthropoda, mollusca, echinodermata, hemichordata and chordata. The organisms included in these phylums either develop through larva (indirect development) or develop without any larval stage (direct development).

Complete Answer:-
The members of phylum Porifera are commonly called sponges. All these animals are aquatic and sessile (remains attached to the surface), mostly marine but few are found in fresh waters also. They are either solitary or colonial. Their entire body is porous with numerous small pores called ostia for entry and one large opening osculum for the exit of water. Reproduction in sponges takes place by means of both asexual and sexual means. Asexual reproduction takes place by budding or fragmentation or by special cell masses called gemmules (endogenous budding).
Sexually sponges are hermaphrodites which means they are bisexual. In sponges, cross fertilisation and internal fertilisation takes place with indirect development. There are some other phylums in the animal kingdom which have indirect development through larval stages. For example, phylum coelenterata have the larva called as planula, phylum platyhelminthes have the larva called as cysticercus and phylum mollusca have the larva called as glochidium. The common larval stages found in sponges are Amphiblastula (found in scypha) and parenchymula (found in leucosolenia).
Thus, the right option is B.

Note:- The larval stage of a sponge is morphologically distinct from adults. First of all, formation of ova and spermatozoa takes place, then internal fertilisation takes place in another sponge through water current and a zygote is formed. Thus, zygote undergoes cleavage to form larval stage. The larva then escapes from the osculum and develops into an adult sponge.