THE HISTOLOGY AND ANATOMY OF THE REPRODUCTIVE SYSTEM OF THE LITTORAL GASTROPOD BEMBIGIVM NANUM (LAMARCK) (FAM. LITTORINIDAE) Lynne Bedford University of Sydney [Read 28th April, 1965.] Synopsis In Bembiciam nanum the sexes are separate and easily distinguishable ; the female by the yellow ovipositor, the male by the conspicuous penis. The histology and anatomy of the male reproductive system of B. nanum, apart from the shape of the penis, the absence of penial glands, the compact nature of the testis and the germinal epithelium of the testis, are similar in general to other littorinids. However, in the female reproductive system, greater differences are found ; the renal oviduct is lined by a phagocytic syncytium, the receptaculum seminis is modified for storage, nourishment and phagocytosis of sperm, and the bursa copulatrix functions only as an organ for reception of spermatozoa. Time of spawning appears to be independent of the time of year and different for each individual. Egg masses are slightly more numerous in the spring and summer months. Large seasonal differences in the size of the reproductive system and extensive resorption of gametes do not occur. In B. nanum resorption of spermatozoa is restricted to the vesicula seminalis of the male system and to the receptaculum seminis of the female system. Slight resorption of ova appears to occur in the renal oviduct of the female reproductive system of B. nanum. This limitation of phagocytosis of gametes in B. nanum, in comparison with North Sea littorinids, may be related to the milder climatic variations in the Sydney coastal areas. Introduction Little is known of reproduction and development in Australian littorinids (Anderson, 1960). Apart from a brief and rather inaccurate description by Kesteven (1902) and a brief reference by Anderson (1958) in a taxonomic survey of tbe genus Bembicium, no details of the reproductive system of B. nanum have yet been described. In the following work, the anatomy and histology of the reproductive system of B. nanum are described. Differences from North Sea littorinids are noted and related to continuous breeding throughout the year in B. nanum. Methods Males and females of B. nanum were collected at intervals during 1961 and 1962 on the rock platforms of the ocean coast near Sydney. Animals, removed from their shells and relaxed in fresh water, were dissected under a binocular microscope. For histological studies, Smith's formol-bichromate, 5% formol saline and Baker's formaldehyde calcium were found to be the most suitable fixatives. To prevent hardening, material was taken to 95% alcohol, trans-ferred to 1% celloidin in methyl benzoate, followed by benzene, then embedded in paraffin (M.P. 56°C). Sections were cut at 8[x and stained in Ehrlich's haematoxylin and eosin or Heidenhain's azan stain. Results Male Reproductive System As in all male prosobranchs, the testis (Fig. 1) in B. nanum lies in the visceral spire over the digestive gland, its tubules being grouped around the visceral arterial system (Anderson, 1958). The wall of each tubule is a flattened germinal epithelium. Within this lies a dense layer of spermatocytes, then a layer of spermatids, while mature spermatozoa (Fig. 2) and nurse cells (Fig. 3) with finely vacuolated cytoplasm and attached spermatids and spermatozoa occupy the lumen. Proceedings of the Linnean Society of New South Wales, Vol. 90, Part 1
BioStor
