Pontarachna hinumaensis Imamura, 1958

Smit, Harry, 2002, Two new species of the water mite family Pontarachnidae (Acari: Hydrachnidia), with a discussion of the taxonomic status of Pontarachna hinumaensis Imamura, Zootaxa 22, pp. 1-8 : 6

On the identity of Pontarachna hinumaensis Imamura

Imamura (1958) described P. hinumaensis from a brackish water marsh in Japan. In his description he pointed on the similarity of this species with P. anellata Sokolov , known from the Sea of Ochotsk (Russian Pacific coast). According to Imamura (1958) differences between the two species can be found in the shape of the posterior apodemes of the fourth coxal plates and in the relatively longer PIV of P. hinumaensis . When comparing the illustrations of both species, they show a striking similarity in the shape and configurations of the wheel­like acetabula: the wheel­like acetabula are very large, a characteristic not found in other Pontarachna species. The length of PIV of the two species is almost the same. Pontarachna anellata is only known from the female sex, and P. hinumaensis only known from the male sex. Within the genus Pontarachna sexual dimorphism can be found in the shape of the posterior apodemes of the fourth coxal plates, as can be seen in the illustrations of P. pacifica by Uchida (1935). The female of P. pacifica has longer apodemes compared to the male, and this is also found in anellata and hinumaensis . The only difference between the two species is the complete suture line of the second and third coxal plates in hinumaensis , but as this is only found on one side, it must be considered more as an anomaly than as a character of this species. Therefore, I consider P. h i n u m a e n s i s a junior synonym of P. anellata .