Tuzovskij P.V. 2006. [Description of the water mite larva Sperchon tridentatus Sokolow (Acariformes, Sperchontidae)] // Invertebrate Zoology. Vol.3. No.1: 33–40 [in Russian, with English summary].

Institute for Biology of Inland Waters of the Russian Academy of Sciences, Borok, Yaroslavl Province, 152742, Russia. E-mail: tuz@ibiw.yaroslavl.ru

KEY WORDS: Sperchontidae, Sperchon tridentatus, water mites, larva.

ABSTRACT: The first illustrated description of the larva of Sperchon tridentatus Sokolow and emended larval diagnosis of the genus Sperchon Kramer are given. Larvae are reared from the eggs laid by females in the laboratory settings (glass cylinders, diameter of 15 mm, and height of 10 mm). The embryonic development was completed in 11–14 days at room temperature. Idiosoma carries 18 pairs of setae (2-2-2-4-4-4-4-4-2-4-4) and 5 pairs of lyriform organs. The dorsal plate is elongate (length/width ratio 2.0), covering less than half of the dorsal surfaces of the unengorged larvae. The anterior margin of the plate is straight and wide, the posterior end is narrow. Setae Fch are longer and thicker than trichobothria Fp and Oi; setae Pi, and Pe are subequal. The anal plate may be split into several fragments, sometimes it is reduced completely. Coxae of legs I and II are rather small and triangular; coxae III are large and quadrangular. The pedipalpal tarsus carries three large plumose setae of different length, a single solenidion and four thin short and smooth setae. The larva of S. tridentatus is similar to the larva of  S. clupeifer, but differs by the structure of the pedipalpal tarsus (S. clupeifer has two long and thick and five short setae; two of the short setae are straight and serrate and one is bent and pectinate).

Genus Sperchon Kramer, larval diagnosis: with larval characters of the family Sperchontidae (Prasad, Cook, 1972); the idiosoma is elongate, oval, with 18 pairs of setae; setae Fch usually are longer and thicker than trichobothria Fp and Oi; setae Pe and Pi are approximately equal in length; coxae of legs II are usually with one seta (C3) or with none (S. setiger); the cheliceral stylet has hair-like processes and one subapical denticle; the pedipalpal tarsus has one solenidion and 5–7 simple setae.

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