On the occurrence of coenospermia in mesothelid spiders (Araneae: Heptathelidae).

Two species of the early derivative spider family Heptathelidae (Heptathela kimurai yanbaruensis and Ryuthela nishihirai nishihirai) have been investigated with respect to spermiogenesis, focussing on late events during which peculiar transfer forms are developed. It is shown, for the first time in detail, that these spiders produce coenospermia. The coenospermia of these species are large aggregates containing more than 20 individual encapsulated spermatozoa. The coenospermia possess a likely flexible envelope formed by a thick multilayered secretion, which protects the spermatozoa during transfer to the female genital system and storage in the receptacula. In addition, a short description of the main cell components of the individual spermatozoa is given as a complement to previous studies. With the observation presented here, the suggestion that coenospermia are an ancestral character in the Araneae is further confirmed, and plesiomorphic features of spider sperms are consolidated.