The type of cleave found in insects

The correct option is Superficial.

To understand why this is the correct answer, let's break down the concepts of embryonic cleavage:

1. What is Cleavage?
Cleavage refers to the rapid series of mitotic cell divisions that occur after fertilization, transforming the single-celled zygote into a multicellular embryo. The pattern of cleavage is largely determined by the amount and distribution of yolk in the egg.

2. Classification of Eggs by Yolk Content
Insect eggs are typically centrolecithal, meaning they have a large concentration of yolk located centrally in the egg, surrounded by a thin layer of active cytoplasm at the periphery.

3. Meroblastic vs. Holoblastic Cleavage
Because yolk inhibits the division of cytoplasm, eggs with large amounts of yolk do not undergo complete division of the entire cell (which is called holoblastic cleavage). Instead, they undergo incomplete or meroblastic cleavage, where cell division is restricted to the yolk-free regions of cytoplasm.

4. Why Superficial Cleavage Occurs in Insects
Superficial cleavage is a highly specialized type of meroblastic cleavage:
- After fertilization, the zygote nucleus undergoes multiple rounds of mitotic divisions in the center of the egg without the division of the cytoplasm (cytokinesis), creating a multinucleated cell (syncytium).
- These nuclei then migrate outward toward the periphery of the egg into the outer, yolk-free layer of cytoplasm (the periplasm).
- Once positioned at the periphery, cell membranes form around each nucleus, creating a single layer of cells (the blastoderm) enclosing the central yolk core.

Since this cleavage pattern is restricted to the outer surface (superficial layer) of the egg, it is called superficial cleavage, which is a characteristic feature of insect development.