Biology

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.

difference between Spiral Cleavage and Radial Cleavage

the term cleavage belongs to the embriology. it is a kind of division of cells in the erly embriyo stage. this whole process is done by fertilization.

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

Spiral & Determinate cleavage

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 embryo. The fate of each blastomere is foretold.3. The fate of each blastomere is not pre-determined.
4. Each blastomere cannot produce new complete embryo.4. Any one 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 succssesive cleavage furrow cut straight through the egg at right angles to one another so that the resultant blastomeres appared to be arranged radially. it has a symetry around pole to pole axis of the embryo as compared to spiral cleavage.

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

Examples of 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 sorf of spiral so that the 4 blastomeres of upper tier do not lie over the corresponding blstomeres of lower tier but between them. this type of cleavage is known as spiral cleavage. the turn of spiral may be in a clockwise or counter clockwise direction.

Examples of Spiral Cleavage

  • Annelids
  • molluscs

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