From Myo... and the Greek méros, part.
A myomer is a separate muscle segment of the trunk musculature that looks like a transverse band curved in a W shape at an acute angle. The number of myomeres usually corresponds to the number of vertebrae.
Myoseptum is a connective tissue layer separating one myomer from another.
In fish, the number of myomeres usually coincides with the number of vertebrae. Myomeres are innervated initially by the motor branch of a single spinal nerve. The orientation of muscle fibers in the myomeres of fish is not unidirectional, but varies depending on the depth in the myomeres.
Myomeres - segments of trunk musculature of lanceolate, sequentially located along the longitudinal axis of the body. The lanceolate musculature has a metameric (segmental) structure. Each muscle segment (myomer or myotome) is bent at an angle and its apex is directed forward. Neighboring myomeres are separated from each other by gelatinous connective tissue septa - myosepts. Due to the curvature of myomeres, several myomeres and myosepts are visible on transverse sections. Myomeres of one side are displaced by half a segment in relation to myomeres of the other side (asymmetry of musculature). A distinct layer of transverse muscles runs along the ventral side of the body anterior to the atriopore.