Muscle system of Diplodiscus subclavatus (Trematoda: Paramphistomida) cercariae, pre-ovigerous, and ovigerous adults

Abstract

The musculature of cercariae, pre-ovigerous, and ovigerous adults of Diplodiscus subclavatus was studied by means of TRITC-conjugated phalloidin staining of filamentous actin and confocal scanning laser microscopy. The body wall appears to include four muscle layers as follows: circular, outer longitudinal, diagonal, and inner longitudinal. Two layers of longitudinal muscle fibers are arranged in different modes due to the secondary transformed paramphistomid body construction. The organization of the acetabulum turned out to be more complex than ever described, with a radial layer, two layers of circular, two layers of meridional, an additional starry layer of muscle fibers, as well as a few separate muscle layers of the accessory sucker. Within the pharynx, I found a group of alar muscle fibers, never described before for any paramphistomids, and some morphological features which were not considered to be characteristic for D. subclavatus (namely—the middle semicircular layer and the transverse muscle fibers in the pre-sphincteric space). No significant reorganizations of the somatic musculature occur throughout the development from the cercaria to the ovigerous adult worm, so the metamorphosis goes in the manner of completion. The cercarial tail includes a layer of circular muscle fibers and a longitudinal muscle layer beneath. The latter consists of two medial longitudinal bundles of smooth muscle fibers and two lateral longitudinal bands of obliquely striated muscle fibers which are partially divided in halves.