Metamer

The word "metamer" comes from a combination of two Greek words "μετά" ("meta") and "μέρος" ("mere") - and means a whole fragment or part. In biology, metameres are successive body parts that arise through a series of divisions and grow continuously as the organism develops.

Metamers are widespread in nature and are found in many classes of animals such as corals, fish, reptiles and mammals. For example, in fish, the body consists of many segments called metameres, between which there is connective tissue.

What are metamers?

Metameres are relatively narrow morphological categories within a phylum. There are 4 categories in total and they are accordingly found in biology where there is a gradation of parts in width.

An analogy can be drawn with a unitary system - a unit consisting of two categories, which are divided into subclasses and so on. For example, the category dolphin can be divided into types: gray, bottlenose dolphin and handicapped bottlenose dolphin. This is the same category, but reformatted for the purposes of a scientific approach. And even if it is not as it really is, then since the goals of the research are set and achieved, the results will be understandable.

Segments and other relatives of metameres in metazoans

Embryonic monochordates have structures called segments. They serve as something between the segmentation of coelenterates and the metameres of vertebrates. It seems that for the monochord (as, probably, for aulopods) the segments are simple appendages with the potential for metameric organization. So, according to this model, metameric division proceeds from simple univeme systems to more complex analogous models in animals of different types. It is possible that the metameric principle itself appeared first, and only then segments and other specialized models of internal organization arose. Thus, true metameric disorganization may not exist. But we will try to figure it out.

Researchers believe that such structures begin to build around common primary bilayer wasps. This two-layer structure is always present in lower chordates. There is a typical neural plate (nerve cord) that separates the intestines from the rest of the body. The leading hypothesis is that during the first hours of life, the process of division along the neural plate begins. Specialized pockets containing nerve tissue are formed. First these pockets represent