Movement and Co-Ordination

Abstract

The somatic muscle cells are grouped in rows between the hypo-dermal cords, with their long axes parallel to that of the body (Figure 1.2). The musculature is classified according to the number of rows and the shape of the muscle cells (Bird, 1971); these can vary in different parts of the same nematode. The contractile region of the muscle cell may be wide and shallow, lying adjacent to the hypodermis (platymyarian), the non-contractile region may bulge into the pseudocoel (coelomyarian) or be partially or completely enclosed by the contractile region (circomyarian). The number of rows of muscle cells between the hypodermal cords also varies. There may be none or only two (holomyarian), two to five rows (meromyarian) or a large number of rows in each sector (polymyarian). The platymyarian, meromyarian pattern is the most common arrangement and may be the basic type from which more complex arrangements have evolved (Bird, 1971). The muscle cells are divided into dorsal and ventral fields by the lateral hypodermal cords, and further into four by the dorsal and ventral hypodermal cords. This division into functional fields is important in determining the pattern of nematode locomotion (see below).