Difference between Radial and Spiral Cleavage

Holoblastic cleavage is most prevalent in eggs with a moderate to sparse quantity of yolk. Amphibians, annelids, echinoderms, mammals, flatworms and nematodes are animals showing holoblastic cleavage. During the process of cytokinesis (cytoplasmic division), these holoblastic cleavage planes go all the way through isolecithal zygotes. The four prominent types of holoblastic cleavage are:

1. Radial holoblastic
2. Spiral holoblastic
3. Rotational holoblastic
4. Bilateral holoblastic

Here, let’s look at the differences between radial and spiral cleavage.

Table of Contents

• Radial Cleavage
• Spiral Cleavage
• Difference between Radial and Spiral Cleavage
• Frequently Asked Questions

Radial Cleavage

Radial cleavage is a characteristic feature in the early embryonic development of deuterostomes. It is one of the simplest cleavage patterns in which the successful division planes are at 90° relative to each other. Thus this cleavage results in daughter cells that are located exactly on top of one another. In other words, the arrangement of the spindle axes are parallel or at 90° to the oocyte’s polar axis. This type of cleavage is seen in deuterostomes like echinoderms and some vertebrates.

Spiral Cleavage

Spiral cleavage is a characteristic feature of protostomes, especially in a clade called Spiralia. Here, the resulting daughter cells are not located exactly on top of each other. Instead, the blastomeres are organised spirally around the embryo’s pole-to-pole axis. It typically results in determinant cells that are programmed to become a specific type of cell, early on during the process. This type of cleavage can be either equal or unequal. Most spiralians undergo equal cleavage that results in blastomeres of equal size. While some spiralians undergo unequal cleavage that results in blastomeres of unequal size.

Indeterminate and Determinate Cleavage

In determinate cleavage, the developmental fate of the cells is predetermined during the early stages of embryogenesis. Molluscs, ascidians and annelids produce the mosaic type of eggs that exhibit determinate cleavage. In indeterminate cleavage, the early embryonic cells retain the capacity to develop into a complete embryo. Thus the blastomeres are qualitatively totipotent. For Example, echinoderms and vertebrates exhibit indeterminate cleavage.

See more: MCQs on Cleavage Biology

Difference between Radial and Spiral Cleavage

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