# What is the difference between Spiral Cleavage and Radial Cleavage?

## Radial vs. spiral cleavage

The Difference between Spiral Cleavage and Radial Cleavage is that cleavage in which the planes of cell division are diagonal to the vertical axis of the embryo is called Spiral Cleavage while cleavage during which the cleavage planes parallel or perpendicular to the vertical axis of the embryo is called Radial Cleavage.

the term cleavage belongs to the embryology. it is a kind of division of cells in the early embryo stage. this whole process is done by fertilization.

however, the cleavage is further divided into two major cleavages such as determinate (Spiral) and indeterminate (Radial). the difference between these two is expressed in tabular form.

## Radial & Indeterminate cleavage

1. In this cleavage, the line or planes of cleavage are not symmetrical (not one above the other) between poles. 1. In this cleavage, the planes of cleavage are symmetrical to the polar axis.
2. These planes are diagonal (cross) to the polar axis. So they produce unequal cells around the axis of polarity. 2. This cleavage produces tiers of the cells on the top of each other.
3. The role of all the blastomeres is determined in the formation of an embryo. The fate of each blastomere is foretold. 3. The fate of each blastomere is not pre-determined.
4. Each blastomere cannot produce a new complete embryo. 4. Anyone blastomere can produce a complete embryo.
5. E.g. Annelida. 6. E.g. Echinodermata

## What is Radial Cleavage?

Radial Cleavage is a holoblastic cleavage. in radial cleavage, the successive cleavage furrow cut straight through the egg at right angles to one another so that the resultant blastomeres appeared to be arranged radially. it has symmetry around the pole to the pole axis of the embryo as compared to spiral cleavage.

all those eggs which have holoblastic cleavage, exhibit radial cleavage.

• Synepta Eggs

## What is Spiral Cleavage?

Spiral cleavage is a modification of radial cleavage. the mitotic spindles of the third clv in the four blastomeres are laid down obliquely and are arranged in a sort of spiral so that the 4 blastomeres of upper-tier do not lie over the corresponding blastomeres of lower-tier but between them. this type of cleavage is known as spiral cleavage. the turn of the spiral may be in a clockwise or counterclockwise direction.