The sperm structure and spermatogenesis of trypophloeus klimeschi (Coleoptera: Curculionidae: Scolytinae)

Abstract

The male reproductive system, sperm structure, and spermatogenesis of Trypophloeus klimeschi (Coleoptera: Curculionidae: Scolytinae), which is one of the most destructive pests of Populus alba var. pyramidalis (Bunge), were investigated using light microscopy, scanning electron microscopy, and transmission electron microscopy. The male reproductive system of T. klimeschi is composed of testes, seminal vesicles, tubular accessory glands, multilobulated accessory glands, vasa deferentia, and a common ejaculatory duct. In spermatogenesis, two phenomena are apparent: The nuclear chromatin condenses into two different patterns, and an oval preacrosomal vesicle is present at the flank of the Golgi apparatus. The sperm are short, measuring 76.7 ± 1.8 µm in length, and are 508.1 ± 12.9 nm in width. The sperm are composed of a three-layer acrosomal complex, a cylindrical nucleus, two mitochondrial derivatives, a 9 + 9 + 2 axoneme, and two accessory bodies with a large “puff”-like expansion. Mature sperm are individually stored in seminal vesicles. During spermiogenesis, the similarities in the nuclear chromatin condensation characteristics of Curculioninae and Scolytinae are indicative of their close phylogenetic relationship. It appears that the preacrosomal vesicle being flanked by the Golgi apparatus is a characteristic of spermatogenesis in Curculionidae.