Morphological and functional adaptations of the female reproductive system in Veigaiidae (Acari: Gamasida) and implications regarding the systematic position of the family

Veigaiidae are predatory gamasid mites with a controversial systematic position. Some authors see a close relationship with Parasitina, others with Dermanyssina. Since the morphology of the genital system is of high relevance in terms of the systematics of Gamasida, we have carefully studied the ultrastructure of the female reproductive system. It consists of two parts, one which accepts spermatozoa (sperm access system), and the other which produces and delivers eggs. Since we have already published a detailed account of the sperm access system we add only some further information here on that system and focus instead on egg production and delivery. The unpaired gonad is divided into a germinal and a nutritive region, the latter of which is a compact structure as in Parasitina and does not show lateral arms as seen in most studied Dermanyssina. The oviduct (uterus, vaginal duct) is an unpaired structure that terminates in a vagina (genital atrium) covered by the genital plate. Two small vaginal glands open into the vagina, which is provided with a peculiar interlocking system. First observations on spermatozoa found in one female reveal similarities with those of Parasitina. Our results are discussed under morphological aspects and compared with other gamasid mites. In conclusion, the veigaiids show some peculiar features that are shared either with Parasitina or with Dermanyssina. These observations make it difficult to simply assume that the Veigaiidae belong either to the Dermanyssina or to the Parasitina. They appear instead to comprise an intermediate entity.

► Veigaiidae are gamasid mites with a controversial systematic position.
► The morphology of the genital system is of high relevance in terms of the systematics of Gamasida.
► It is difficult to include the Veigaiidae either in the Dermanyssina or in the Parasitina.
► They appear instead to comprise an intermediate entity.