Metamerism (biology)

Metamerism is a biological phenomenon that refers to the segmentation of the body plan of an organism. This segmentation can be seen in various forms across different species and is a key aspect of the anatomy and developmental biology of these organisms.

Definition

Metamerism is defined as the condition of being composed of a linear series of repeating parts, each of which is called a metamere or somite. This segmentation is a crucial aspect of the body plan of many organisms, particularly in the animal kingdom.

Types of Metamerism

There are three main types of metamerism:

• Homonomous Metamerism: This type of metamerism is characterized by the repetition of similar segments along the body axis. It is commonly seen in annelids and arthropods.

• Heteronomous Metamerism: In this type, the segments are differentiated into different types of segments, such as thoracic and abdominal segments in insects.

• Pseudometamerism: This is a type of metamerism where the segmentation is not true metamerism but appears to be due to the repetition of certain structures. It is seen in echinoderms and chordates.

Evolutionary Significance

Metamerism has significant evolutionary implications. It allows for the specialization of different body segments for different functions, leading to increased complexity and diversity in body forms. This has been a key factor in the evolutionary success of segmented animals.

See Also

• Segmentation (biology)
• Anatomy
• Developmental biology