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On this page more about the males of these water mites. After I had found only females
the first time in May, I went to the same pond again in July with the landing net. With
success: there was one male in the catch among the ten Brachypoda mites.
The male is slightly larger and can be recognized by the elliptical body shape and the more
transparent rear end.
The rear end is transparent, because there is a cavity under the dorsal shield - as indicated on the first page. This cavity is there because, compared to the female specimens, the body of the male is 'shifted forward', as it were, under the slightly longer carapace, see the photo below left. The pointed ends of the coxae are also slightly more forward and protrude under the leading edge of the carapace in the male. This is not visible in these pictures.
When looking at the swimming mites, it is not immediately noticeable that the legs of the fourth pair of legs of the male have a special shape: see the photo above right. The 4th and 5th segments have been transformed into a grasping organ, that is used in mating, which is peculiar, as in many arthropods. I have not seen that mating yet. But a number of authors have, such as Motas (1928) who left us a description and sketch. Furthermore Halik (1955) and Olomski (2012), the latter published an article with photos and sketches of mating and the spermatophore.
On the left is the sketch by Motas (1928). For clarity, I have made the female green and the male red. But also rotated the sketch 180 degrees, because that fits better with the description by Olomski (2012), from which the following has been extracted. The male only produces spermatophores when there are females nearby. When he touches a female ready to mate, she assumes a 'ready for action' position and sometimes walks towards the male. The male stands 'in a handstand' on his first and second pair of legs and grabs a sperm packet, the spermatophore, in his genital opening with the tarsi of the third. He then grabs the female with his fourth pair of legs and works her with her front into the cavity at his abdomen, where she is clamped. As the sketch indicates, with the ventral sides towards each other. Then he transfers the spermatophore into the genital opening of the female with his third pair of legs. Mating can last up to an hour and is ended by violent movements of the male.
See also the article by Olomski (2012) for details, photos and sketches. The article points out the similarity of the mating ritual with that of the Piona species and suggests that this may indicate a phylogenetic relationship. Mitchell (1957) is quoted: because Aturus species all have a mating posture similar to that of Arrenurus, the placement of Brachypoda within the Aturidae would no longer be tenable.
This suggestion is mentioned in the chapter "Family Aturidae Thor, 1900" of Gerecke (2016) page 7. But the conclusion there is that no satisfactory alternative has been established in the last decades and the Aturidae is probably a polyphyletic taxon with many different species.
