Question

Insect egg is:
A)Homolecithal
B)Telolecithal
C)Centrolecithal
D)Alecithal

Answer 1

Egg can be differentiated on the basis of concentration of yolk present in the cytoplasm of the egg. In the Homolecithal egg, yolk is present in very small concentrations. The Telolecithal concentration of yolk is unevenly distributed in the whole cytoplasm. In case of centrolecithal, all distribution of yolk is present at the centre of egg and in alecithal, the amount of yolk is very small or it is not present.

Complete answer:
To solve this question we will try to understand available options then will try to conclude the discussion.
Option ‘A’: Homolecithal- In this type of egg, a small concentration of yolk is present and it is evenly distributed all over the cytoplasm of the egg. It is mostly found in case of urchins, tunicates, etc but it is not present in case of insects.
Option ‘B’: Telolecithal- In this type of eggs, yolk is present and unevenly distributed in the cytoplasm of the egg. This type of eggs are found in birds, reptiles, etc but not in insects thus, this option is also not correct.
Option ‘C”: Centrolecithal- In this type of egg, all material of yolk is present at the centre and evenly distributed. This centre is surrounded by the cytoplasm of egg. This type of configuration is shown by many arthropods.
Option ‘D’: Alecithal- In this type of arrangement, eggs have no yolk and or have very less amount and thus it is mostly seen in oviparous organisms.

Hence, the correct answer is option (C)

Note: During cytokinesis of cell cycle of arthropods, zygote having centrolecithal arrangement undergoes meroblastic cleavage. In this cleavage, the cleavage plane extends just to accumulate yolk of the egg. Due to the large density of yolk, it triggers a delayed embryonic development.