Occurrence of Paramyosin among the Nematomorpha

Abstract

PREVIOUSLY, the longitudinal body wall muscles of freshwater nematomorphs were considered to be histologically similar to the coelomyarian type muscle fibres common among nematodes^{1, 2} and, although double oblique striations were found by Rauther³ in nematomorph muscle preparations, their underlying structure remained unknown. But on the basis of ultra-structural information, mechanical responses and biochemical analyses⁴, the longitudinal body wall muscles of Paragordius varius (Leidy) and Gordius robustus Leidy are now considered to be of the paramyosin smooth type. The phenomenon of “tight coiling” in these species (Fig. 1A) requires the slow, tonic type muscle structure.