Epidermal mucus and the reproduction of a crinoid echinoderm

Abstract

THE unstalked crinoid Comanthus japonica spawns during the first part of October each year^1,2. For a study of gametogenesis² specimens of Comanthus were collected periodically over 14 months. During these collections one of us (J. G.) noticed that the animals became unusually slimy to the touch during the six to eight weeks that preceded spawning. This transient slimyness is correlated with an enlargement of an epidermal mucous cell population. The general position of the mucous cells is shown in Fig. 1 in which they are darkly stained. In both male and female genital pinnules these cells occur mostly in the oral and lateral body wall. Each individual mucus cell is oval and contains a single nucleus. The cytoplasm stains with beta- to gamma-metachromasia in azure A. In addition the cytoplasm stains strongly with alcian blue at pH 3 but fails to stain with periodic acid–Schiff. These histochemical criteria indicate an abundance of sulphated acid mucopolysaccharides (possibly mixed with non-sulphated acid mucopolysaccharides). It is not known if similar mucous cells occur in the arms and central mass of the crinoids since these body regions were not preserved for histology.