Funktionelle Anatomie und phylogenetische Abwandlung des männlichen Genitalsystems der actinotrichen Milben (Acari)

Abstract

The goal of this paper is to expand the knowledge about the functional anatomy of the male genital system of actinotrichid mites and to contribute to phylogenetic questions. Histological studies were carried out on three taxa: Ameronothrus lineatus (Oribatida, Brachypylina), Linopodes spec. (Prostigmata, Eupodoidea) and Tydeus californicus (Prostigmata, Tydeoidea).The proximal genital system of the taxa shows a rather consistent arrangement, which is in agreement to those of other Actinotrichida. It consists of a testis, which is divided into a germinal and a glandular part, and paired vasa deferentia which fuse before leading into the ductus ejaculatorius.The distal genital system of the three taxa consists of a ductus ejaculatorius and a genital chamber, with some profound differences in the specific arrangements of Oribatida and Prostigmata. There is no evidence for homology of the particular structures in both taxa. The ductus ejaculatorius of Linopodes spec. is divided into three chambers, an arrangement which is known from other Prostigmata as well as from Endeostigmata. Furthermore, an unpaired anterior accessory gland can be found in Linopodes spec. and Tydeus californicus, which is also known from other prostigmatid and endeostigmatid mites. Thus, the formation of spermatophores of Linopodes spec. is probably homologous to that described from other Prostigmata.Ultrastructural results of the accessory organ of Ameronothrus lineatus do not give any evidence for a glandular function of this organ, as hypothesized in previous studies.The spermatozoa of Ameronothrus lineatus exhibit structures typical for higher oribatida, i.e., loss of an acrosome complex, modification of mitochondria and possession of electron dense bodies. In the spermatogenesis of Linopodes spec. and Tydeus californicus, some characteristics can be found, which support a close relationship of Eupodoidea and Tydeoidea.