Histological study of secretory structures of nemerteans subjected to stress: III. Cephalic glands

Abstract

The cephalic glands of three intertidal species of nemerteans, Procephalothrix spiralis (Coe, 1930) (Palaeonemertini), Lineus socialis (Leidy, 1855) (Heteronemertini), and Amphiporus lactifloreus (Johnston, 1828) (Hoplonemertini), were examined for response to various experimental conditions including caudal amputation. Significant differences in the cytology of the cephalic gland cells were only observed during osmotic stress. The cells comprising the cephalic gland of P. spiralis, a species which lacks cerebral organs, appear to release acid mucosubstances into the vascular system under hypoosmotic conditions, whereas the same cells accumulate secretions in a hyperosmotic medium. The secretory activity of the cephalic glands of L. socialis and A. lactifloreus, species which bear cerebral organs, parallels that of P. spiralis under hypo- and hypersaline conditions; however, the cells comprising these glands discharge their secretions to the exterior of the animal rather than into the vascular system. Control mechanisms via the neurosecretory system and the possible action of acid mucosubstances in osmotic stress are discussed.