Structure of the male reproductive accessory glands of Pterostichus nigrita (Coleoptera: Carabidae), their role in spermatophore formation

Abstract

Accessory gland secretions of male insects have many important functions including the formation of spermatophores. We used light and electron microscopy to investigate the structure of the accessory glands and posterior vasa deferentia of the carabid beetle Pterostichus nigrita to try to determine where spermatophore material is produced. Each accessory gland and posterior vas deferens had an outer layer of longitudinal muscle, beneath which was a layer of connective tissue and a thin band of circular muscle, all of which surrounded a layer of epithelial cells lining the lumen of the ducts. Based on the ultrastructure of the epithelial cells, and their secretory products, we identified two epithelial cell types in each region (distal and proximal) of the accessory glands and four types in the posterior vas deferens. Most secretory products, which stained positively for proteins and some mucins, were released into the lumen of the ducts by apocrine secretion. The accessory glands produced one type of secretory product whereas in posterior vasa deferentia, four types of secretory products were found layered in the lumen. Our results suggest that most of the structural material used to construct a spermatophore is produced by the cells of the posterior vasa deferentia.

Keywords:

• vas deferens
• secretory cells
• spermatophore formation
• ultrastructure
• histochemistry
• Insecta

Acknowledgments

This study was funded by grants to from Rhodes University, the National Research Foundation and Institute of Biology, University of Halle-Wittenberg to ANH, and the DAAD- German Academic Exchange Service to SK. We would like to thank Prof. Dr. G. Moritz for use of the Jeol 1100 TEM in the Institute of Biology, University of Halle-Wittenberg, and to Mr C. van der Merwe and Mr A. Hall of the Laboratory for Microscopy and Microanalysis, University of Pretoria, for use of the Jeol JEM 2100F TEM. We thank Eva Schladitz for assistance with the protein gel electrophoresis. ANH would also like to thank Prof. M.G. Bentley for handling the editorial work on this paper.