Description of a new species of Rhombognathus (Halacaridae, Acari), its spermiogenesis and spermatozoa

This is the first record of the subfamily Rhombognathinae on the Brazilian coast. A new species is described, Rhombognathus levigatoides sp. nov., which shares most diagnostic features with R. levigatus Bartsch, 2000, but differs from it by measurements of ds‐1, dorsal plates, and spermatophorotype. A detailed account is provided of its spermiogenesis and sperm cell morphology. Rhombognathus sperm cells show features that should be regarded as probable plesiomorphies if contrasted with those found in the other two halacarid spermatozoa studied until now, Halacarellus thomasi and Thalassarachna basteri, such as the almost unmodified mitochondria, type of nuclear condensation similar to that observed in most Actinedida mites, complete acrosomal complex, and presence of a single kind of globular secretion.