Structure and ultrastructure of the spermatozoa of Bephratelloides pomorum(Fabricius) (Hymenoptera : Eurytomidae)

The spermatozoa of Bephratelloides pomorum are very long and fine. Each spe rmatozoon measures about 620 mu m in length by 0.38 mu m in diameter and, w hen seen under the light microscope, appears to be wavy along its entire le ngth. The head, which is approximately 105 mu m, comprises a small acrosome and a nucleus. The acrosome is made up of a cone-shaped acrosomal vesicle surrounding the perforatorium and the anterior end of the nucleus. Innumera ble filaments radiate from it. The perforatorium has a diameter equal to th at of the nucleus at their junction, where it fits with a concave base onto the rounded nuclear tip. The nucleus is helicoidal and completely filled w ith homogeneous compact chromatin. It is attached to the tail by a very lon g and quite electron-dense centriolar adjunct that extends anteriorly from the centriole in a spiral around the nucleus for approximately 8.5 mu m. Th e tail consists of an axoneme with the 9+9+2 microtubule arrangement pitche d in a long helix, as well as a pair of spiraling mitochondrial derivatives (with regularly arranged cristae) that coil around the axoneme, and two sm all accessory bodies. As well as the spiraling of the nucleus, mitochondria l derivatives and axonemal microtubules, the sperm of B. pomorum present ot her very different morphological features. These features include the acros ome and centriolar adjunct, both of which differentiate the spermatozoa fro m the majority of sperm found in other Hymenoptera. In addition these struc tural variations demonstrate that the sperm of chalcidoids provide characte ristics that can certainly prove useful for future phylogenetic analysis at the subfamily level and, possibly, the genus too. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.