The Spermatozoa of the Thysanuran Insects Petrobius brevistylis Carp. and Lepisma saccharina L.

Abstract

The spermatozoa of Petrobius and Lepisma share a few general insect features (filamentous shape, two mitochondria, compact acrosome vesicle, bilateral symmetry) but differ fundamentally with regard to specializations. In Petrobius, a long coiled acrosome, a coiled nucleus, and a “body” with axonema, two mitochondria, and a pair of lateral bodies follow each other in normal sequence. In Lepisma the acrosome is a small vestige in the spoon‐shaped anterior end, the centriole is dislocated anteriorly, and nucleus, two mitochondria and axonema run like parallel filaments through most of the spermatozoon. The centriole adjunct develops into a postnuclear body in Lepisma but forms a pair of complicated “lateral bodies” in Petrobius. It is concluded that ancestral forms must have had fairly primitive spermatozoa and that specialization has proceeded independently within each evolutionary line.

Sperm structure and spermiogenesis in Atelura formicaria Heyden (Zygentoma, Insecta)

“…Such a reduction of the sperm length is similar to that observed in the related species Tricholepidion (Dallai et al . 2001b); on the contrary, the lepismatids Lepisma and Thermobia have very long sperm cells (Bawa 1964; Werner 1964; Wingstrand 1973).…”

“…1999): a 9 + 9 + 2 pattern and accessory tubules with 16 protofilaments in their tubular wall and an electron‐dense material in their lumen. Intertubular material is present and associated with microtubular doublets, as in the lepismatids Lepisma and Thermobia (Wingstrand 1973; Dallai et al . 1992) and in Tricholepidion (Dallai et al .…”

“…Spermatozoa in the two orders have a different organization. Members of Microcoryphia have a flagellar axoneme with accessory microtubules that shift towards two opposite sides of the 9 + 2 axoneme at the end of spermiogenesis (Dallai 1972; Wingstrand 1973). In contrast, species of the Zygentoma possess a conventional 9 + 9 + 2 axoneme with accessory tubules arranged in order outside the microtubular doublets, as in most pterygotan insects (Bawa 1964; Werner 1964; Wingstrand 1973; Dallai and Afzelius 1990; Dallai et al .…”

“…Zygentoma consists of five families: Lepidotrichidae, Maindroniidae, Nicoletiidae, Ateluridae and Lepismatidae (Bach 1994). So far, sperm ultrastructure has been studied only in Lepidotrichidae and some Lepismatidae (Bawa 1964; Werner 1964; Wingstrand 1973; Dallai et al . 2001a).…”

“…2001b). In the lepismatids studied so far, a sperm conjugation has been described at the end of spermiogenesis or during sperm storage into the seminal vesicles (Bawa 1964; Werner 1964; Wingstrand 1973; Dallai and Afzelius 1984). This feature has been erroneously considered as a common trait shared by all members of the family, and even as a possible autapomorphy of the whole order (Kristensen 1998).…”