Comparative analyses of the internal anatomy and functional morphology of the Eleutherengona

Abstract

The study summarizes data on the internal anatomy of the mites belonging to the parvorder Eleutherengona (Acariformes: Trombidiformes) mainly based on the families Tetranychidae, Cheyletidae, Syringophilidae, Myobiidae, and Demodicidae. The arrangement and functioning of the digestive tract, propodosomal glands, connective tissue, and reproductive system of both sexes are taken into account to reveal common features of the Eleutherengona as well as possible phylogenetically informative characters in particular families. The study shows that all the examined eleutherengone families demonstrate a mixture of relatively primitive and advanced features. The following most striking internal characters are common to all studied eleutherengone species. The postventricular midgut is represented by a simple tube-like excretory organ, which is usually in open connection with the ventriculus. The anal and genital\n openings of the females are close to each other and located at the terminal end of the body. The glandular component of the testicular epithelium is absent or highly reduced, as well as the male accessory glands. The number of salivary glands is reduced or these glands are lost in some parasitic forms. The coxal glands are either devoid of the proximal filter sacculus or provided by a sacculus with a considerably reduced lumen. The coxal gland epithelium does not possess a regular brush border, showing high pinocytotic activity.