Sperm storage in the uterium of the insect-parasitic nematode Sphaerularia vespae (Nematoda: Sphaerulariidae)

摘要

The spermatheca found in the 'uterium' (highly transformed part of parasitic female) of the sphaerularioidid nematode Sphaerulaha vespae, an endoparasite of a common Japanese hornet, Vespa simillima, was studied with TEM. The uterium consists of a thick trophic epithelium exposed to the insect haemocoel and a protective cavity which contains the female genital tube and storage cells (fat body). The uterium cavity contains the female reproductive system composed of the usual parts: uterus, oviduct andovary. The genital pore of the young uterium is an opening of the short narrow uterine tube which joins to the voluminous spermatheca. The spermatheca is a dilated distal part of the uterus, storing numerous tiny spermatozoa. The spermatheca is blockeddistally by the oviduct. The spermatozoa are uniform amoeboid cells only 1.4-1.6 pm in size with a highly condensed nucleus about 0.8 p.m in size. The transparent sperm cytoplasm contains several mitochondria, small membranous organelles (specific organelles characteristic of nematode spermatozoa), occasional bundles of fibres and centriole-like bodies. The 5. vespae spermatozoa are very similar to the spermatozoa stored in the uterus of infective females of another sphaerularioidid nematode, Deladenussp., and have the main features of sperm found in many other rhabditid nematodes.