Confocal laser scanning microscopy analysis of the phalloidin-labelled musculature in nemerteans

The musculature of 31 species was studied using phalloidin labelling and confocal laser scanning microscopy. New data are presented on the patterns of the body wall, proboscis and gonadal musculature. Two kinds of epidermal muscles are described in the palaeonemerteans and heteronemerteans - radial fibres (common in anoplans) and a muscular meshwork of longitudinal and diagonal fibres found in Carinoma mutabilis. All palaeonemerteans and hoplonemerteans studied here were found to possess diagonal muscles between the outer circular and the inner longitudinal body wall musculature; however, seven studied heteronemerteans had diagonal muscles only in the cutis. The proboscis musculature of all nemerteans studied here includes inner circular muscles. In addition, palaeonemerteans and heteronemerteans have a layer of outer diagonal muscles in the proboscis. The gonadal musculature of the hoplonemerteans consists of muscle meshwork or regularly arranged longitudinal fibres. Confocal studies of nemertean musculature may provide useful new characters for phylogenetic analysis of this phylum.