Biradial Symmetry

Biradial symmetry is observed in species that exhibit both bilateral and radial symmetry with morphological (internal or external) characteristics. It’s distinct from radial symmetry since the organism is separated by two planes but not more than two. It may represent an intermediate stage in the evolution from a radially symmetric ancestor with bilateral symmetry. Comb jellies are an example of a biradial-symmetric organism.

Including the anteroposterior axis, there are also two other axes or planes of symmetry at right angles to it and to each other: the axes sagittal, or median vertical-longitudinal, and the axes transverse, or cross. The most noticeable biradial symmetry for the species community is the ctenophores. Many scientists assume that those with radial symmetry have evolved from animals with bilateral symmetry. Consequently, such an object not only has two ends but also two pairs of symmetrical hands. In ctenophores, the two planes of symmetry are (1) tentacle plane and (2) pharynx plane. Roughly 99 percent of animals today have bilateral symmetry, so it is assumed that it offers advantages that radial symmetry does not provide.

In addition to the present group, evidence for biradial symmetry has even been found within the ‘perfectly radial’ freshwater polyp Hydra (a cnidarian). There are but two planes of symmetry during a biradial animal, one passing through the anteroposterior and sagittal axes and also the other through the anteroposterior and transverse axes. Several scientists assume that biradial animals are an intermediate retained from the transition from radial symmetry to bilateral. The phylum ctenophore, or comb jellies, exhibits this sort of symmetry.

Biradial symmetry is more widespread than originally accounted for, especially when considering both internal and external features. This phylum includes several animals, with different body shapes and sizes. This group of animals lives in marine environments and propels themselves with cilia combs, which are tiny hair-like structures usually associated with bacteria and not with animals. Like all the traits of organisms, symmetry (or indeed asymmetry) evolves thanks to a bonus to the organism that could be a process of a natural process. This involves changes within the frequency of symmetry-related genes throughout time.

The existence of these asymmetric features involves a process of breaking symmetry during growth, in plants and animals alike. Symmetry breakage happens at different rates to produce the anatomical asymmetry that we observe. Such levels include expression of the asymmetric genes, protein production, and cell function.


Information Sources:

  3. wikipedia