Sperm morphology of predatory pirate bugs Amphiareus constrictus and Blaptostethus pallescens (Heteroptera: Anthocoridae) with phylogenetic inferences

Abstract

The sperm morphology of two predatory bugs Amphiareus constrictus and Blaptostethus pallescens, representing the tribes Dufouriellini and Blasptostethini, respectively, was described using light and transmission electron microscopy. The spermatozoa of Amphiareus constrictus and Blaptostethus pallescens are fine and long, each measuring 216.6 μm and 181.0 μm in length, of which 37.0 μm and 11.6 μm, respectively, comprise the nuclei. When stained with DAPI (for DNA), the posterior half of the nucleus in B. pallescens exhibited low fluorescence, while in A. constrictus this feature was observed only in the last 6 μm. In both species, as in Heteroptera in general, the spermatozoa have, in the head region, an acrosome and nucleus, and in the flagellar region, an axoneme with 9 accessory tubules, 9 peripheral doublets and 2 central microtubules (9 + 9 + 2 microtubules), 2 mitochondrial derivatives (MDs), and a centriolar adjunct in the nucleus-flagellum transition. However, unlike most Heteroptera, in these species, the MDs are asymmetric, and the centriolar adjunct is quite long and encompasses completely the posterior nuclear end and the anterior tips of the MDs. These features are considered as derived, thus supporting the condition derived of Anthocoridae within Cimicomorpha. In addition, several traits of the spermatozoa of these two species easily distinguish one species (and probably a tribe) from the other; for example, the difference of formats in the MDs, and the long anterior projection of the centriolar adjunct parallel to the nucleus in B. pallescens.