Metamerism: Definition, Types of Segmentation And Its Wide Range of Occurrence In Invertebrates.

Metamerism Definition

The repeating of homologous body segments is known as metamerism. Annelids, which include earthworms, leeches, tube worms, and their cousins, exhibit this form of development. Arthropods, or crustaceans, insects, and their cousins show it in a more evolved form. Metamerism is the result of teloblastic development, which occurs when cells divide asymmetrically to create rings of tiny cells surrounding the embryo.


These cells multiply across the worm’s many segments and may be homonomous (meaning extremely similar) or differentiated into a range of activities. These segments are known as heteronomous segments. Metamerism has resulted in a wide range of annelids, arthropods, and other segmented creatures. Annelids may live in a variety of environments, from the deepest sections of the ocean to the soil of some of the tallest mountains, due to their basic segmented form.

Related Biology Terms

  • Segmentation:is a kind of growth in which a large number of similar portions proliferate quickly and subsequently increase.
  • Homonomous:In worms and related species, simple and highly identical segments are generated.
  • Heteronomous:Insects and crustaceans have highly distinct segments.

Question and Answer

1. Scorpions, king crabs, earthworms, and fleas are all segmented animals. They have varied levels of differentiation between the segments. Which of the following terms describes all of the animals?

  1. Metamerism
  2. Homonomous Segmentation
  3. Heteronomous Segmentation

A is correct. All of these animals show metamerism, or a segmented body plan that arises from teloblastic development. The scorpion, crabs, and fleas all belong to Arthropoda, and show heteronomous segmentation. The earthworm shows mostly homonomous segmentation, though certain areas are specialized for reproduction and other tasks.

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