HISTOLOGY AND ULTRASTRUCTURE OF THE ACCESSORY NIDAMENTAL GLAND OF SEPIELLA MAINDRONI
曼氏无针乌贼(Sepiella maindroni)副缠卵腺的组织学及超微结构

Histology and ultrastructure of the accessory nidamental gland (ANG) of Sepiella maindroni were investigated using light and transmission electron microscopy. The ANG was found to consist of an accessory nidamental wall, connective tissue, and many tubules, manifesting certain structural features of a secretory organ that contain many tubules haboring dense populations of coccoid- and rod-shaped bacteria. The tubule wall was found to be lined by epithelial cells containing many cytoplasmic vesicles. Based on the ultrastructural observation, we postulated that these vesicles might be secreted through exocytosis. We hold the ANG may play a secretory role in the reproductive cycle and coat the ovulated eggs with a layer of symbiotic bacteria that can ward off egg pathogens; and moreover the symbiotic bacteria may come from environmental seawater rather than from the proceeding S. maindroni through vertical transmission via the egg case sheath.