Structure and function of the seminal vesicles and the spermatheca in Bracon hebetor say (hymenoptera: braconidae)

Abstract

DURING a study of some ecological and biological characteristics of the braconid wasp, Bracoll hebelOr Say, we found the information about the seminal vesicle and spermatheca of this insect to be incomplete. Therefore we made observations on the structure and function of these organs. B. hebetor females were reared as parasites of Allagasta kuehlliella (Zeller) at 25 ± IDC and 50-60 % RH. They were dissected in a drop of the following saline: 7·5 gm NaCl, 0·35 gm KCI, and 0·21 gm CaCl 1000 ml H20, and brought to a pH of 7·2 with the aid of a few drops of phosphate buffer (0'01 M). Observations were made through a dissecting microscope (Olympus X or Wild M5), and a compound microscope with phase contrast (Wild M20). Sperm movement and the influence of CO2 and O2 upon it were examined in small perfusion cells made by placing 2 semicircular pieces of Parafilm M* on a glass slide; and covering them with a round cover slip. The parts and the so-formed cell were then warmed up and pressed firmly together. Spermatogenesis occurs in the pupa, and the sperm start to leave the round and swollen testes during the last pre-emergence day. However, in contrast to the situation in Spalallgia call1erolli Perkins (Gerling and Lenger, 1968), the testes of the adult male are not deplete, and the sperm continue to move from them into the seminal vesicles for as long as the male lives. In the young male pupa the vesicles are oblong. They become round at the time of sperm entrance, 1-2 days before emergence. No sperm motion was observed in genital systems that were dissected from male pupae, but in emerged males, the sperm within the vesicles are in motion, and the walls of the vesicles undulate rhythmically in an anteroposterior direction. This motion can be artificially induced by applying cover-slip pressure on a dissected genital system of a male pupa, shortly before emergence.