(embryology) The complete division of an isolecithal or microlecithal egg into blastomeres.
Depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic or meroblastic. The holoblastic type of cleavage is commonly seen in eggs containing moderate to sparse amount of yolk. Examples of animals with eggs that divide holoblastically include the amphibians, mammals, echinoderms, annelids, flatworms, nematodes, etc.
Holobalstic cleavage can be:
- equal cleavage
- unequal cleavage
Compare: meroblastic cleavage