New Species of Oribatid Mites (Acari, Oribatida) from Sakhalin Island

Abstract

Two new oribatid mite species collected in the park zone of Yuzhno-Sakhalinsk (Sakhalin Island, Russia) are described. Xenillus similis sp. n. is a large pale brown mite with lamellae covering the major part of the proterosoma. Its cusps are separate, large, and blade-shaped with sharpened diverging medial teeth. The translamella is narrow with a tiny tooth between the cusps. Sensilli are fusiform. The new species differs from the closely related X. sculptrus Kulijev, 1963 in the finer rostral and lamellar setae, long interlamellar setae, and different shape of sensilli (fusiform vs. clavate), lamellae (in X. sculptrus they are broadened towards the anterior end), and cusps. The new species differs from X. tegeocranus (Hermann, 1904) in the presence of fine and poorly pubescent dorsal and ventral setae, shorter lamellar setae, longer and sparsely pubescent interlamellar setae, the fusiform sensilli (vs. clavate), and the shape of cusps with more elongated internal teeth. Lasiobelba (Lasiobelba) sakhalinensis sp. n. is a middle-sized mite with slightly projecting and rounded rostrum. Costulae are absent, prodorsal setae are smooth. Sensilli are fusiform without apical spine. Ten pairs of notogastral setae are long and smooth (except for setae c which are represented by alveoli); p1–p3 are shorter than other setae. The anogenital setae are fine and smooth. The discidium is pointed. Leg claws are fine. The new species differs from morphologically similar L. (L.) remota Aoki, 1959 and L. (L.) insulata Ohkubo, 2001 in the smaller size, fusiform sensilli without apical spine (both L. (L.) remota and L. (L.) insulata possess long sensilli widened in the middle part and with the apical spine), shorter interlamellar setae (in compared species, they nearly reach bases of lamellar setae), and in the smooth prodorsal and notogastral setae.