SOME MORPHOLOGICAL AND HISTOCHEMICAL ASPECTS OF NEMERTEAN CONNECTIVE TISSUE

The organization of the connective tissue system in three nemertine species, Amphiporus pulcher, Lineus bilineatus and Lineus ruber has been studied. Most attention has been paid to A. pulcher. Light microscopical, histochemical and electron microscopical methods have been employed. Three elements have been found and described: several types of free cells, filaments and ground substance. The filaments belong to the collagen family and form a supportive collagen skeleton in the animals. The ground substance is abundant in A. pulcher and is composed of protein and acid and neutral polysaccharides. The connective tissue cells have been classified in three groups, but intergrading between the cells, especially groups 1 and 3 is found. The connective tissue cells are highly polymorphic and often combine several functions in the same cell, e.g. synthesis of extracellular products, phagocytosis, pigment synthesis or uptake and a function as cellular material for regenerative processes. It is stressed that the connective tissue system probably forms a unity in the animals and no attempt has been made to make a rigid and presumably rather unnatural classification into various types. Comparative aspects of nemertine connective tissue have been discussed in relation to the patterns found in acoel, triclad and polyclad turbellarians. It is concluded that the nemertean connective tissue system still has features in common with turbellarian patterns, especially the one found in polyclads. However, the nemertine connective tissue system exhibits greater complexity than those found in turbellarians. The nemertine connective tissue system both shows continuity to the turbellarian organizations but also has features added so that it conforms with the patterns found in most groups of animals including vertebrates. © 1968 Springer-Verlag.