Sperm morphology of mud dauber Sceliphron fistularium dahlbom (Hymenoptera: Apoidea: Sphecidae), as an indication of bees relation.

The morphology of spermatozoon of Sceliphron fistularium is very similar to that described for bees. In particular, the response to E-PTA stains is similar to that observed in corbiculated Apidae, especially Meliponini bees. Spermatozoa measure 285 microm and are composed of 1) a bilayered acrosome (acrosomal vesicle and perforatorium); 2) a homogeneous and compact nucleus; 3) a 9+9+2 axoneme; 4) a rod-shaped centriolar adjunct; 5) two asymmetrical mitochondrial derivatives with paracrystalline material exclusively in the larger one, and 6) two accessory bodies. Only the accessory microtubules of axoneme and the paracrystalline material are E-PTA positive. Comparison of S. fistularium sperm to data on Hymenoptera corroborates their proximity with bees.