Histological description of the ink gland of the tropical sea hare Aplysia dactylomela Rang, 1828

Abstract

This work describes for the first time the ink gland of Aplysia dactylomelaRang,1828 using light microscopy and histochemical tests. The results reveal thatthis organ is covered by a layer of simple epithelium and that there are somedifferences between the epithelium facing the mantle shelf and that facing themantle cavity. The former consists of columnar cells, which may have asecretory function, whereas the latter is a cuboidal epithelium. Underneath theepithelium and along the whole gland there are fibres of smooth muscle andcollagen, organized in groups of parallel bundles. There are vesicles of differentdiameters, apparently with similar morphology. Some are filled with ink,whereas others are either granular or clear. The ink is released through a ductformed by invaginations of the cuboidal epithelium. Tests with bromophenolblue and periodic acid Schiff indicated that the ink and granulated vesiclescontain proteins and carbohydrates or maybe glycoproteins. Between the fibrebundles and the vesicles there are dispersed cells. A diagram is presentedemphasizing the covering epithelium, the distribution of muscle and collagenfibres, the dispersed cells, vesicles and ducts. This organization is similar to thatof the other Aplysia species studied to date, A. californica.