Differentiation of external morphology of Oribatella Banks, 1895 (Acari: Oribatida: Oribatellidae), in light of the ontogeny of three species

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Abstract
Differentiation of external morphology of Oribatella Banks, 1895 was investigated, in light of the ontogeny of O. quadricornuta (Michael, 1880 Michael, AD. 1880. A further contribution to the knowledge of British Oribatidae. J Roy Micr Soc London, 3: 225–251. [Crossref] [Google Scholar] ), O. superbula (Berlese, 1904 Berlese, A. 1904. Acari nuovi. Manipulus III. Redia, 2: 10–32. [Google Scholar] ) and O. calcarata (CL Koch, 1835 Koch, CL. 1835. “Deutschlands Crustaceen, Myriapoden und Arachniden”. In Regensburg, Germany: Verlag Friedrich Pustet 1–3. [Google Scholar] ) studied here for the first time, and that of the other species from the literature. The pattern of gastronotal setae in larvae is similar, except for lack of seta h 3 in O. nortoni Behan-Pelletier, 2011 Behan-Pelletier, VM. 2011. Oribatella (Acari, Oribatida, Oribatellidae) of eastern North America. Zootaxa, 2973: 1–56. [Google Scholar] , while that of nymphs and adults is differentiated. The nymphs of most species have 15 pairs of gastronotal setae, but those of O. metzi Behan-Pelletier, 2011 Behan-Pelletier, VM. 2011. Oribatella (Acari, Oribatida, Oribatellidae) of eastern North America. Zootaxa, 2973: 1–56. [Google Scholar] and most nymphs of O. calcarata have 13 pairs. The nymphs of most species carry the exuvial scalps of previous instars on apical parts of gastronotal setae da, while setae dm and dp, located under these scalps, are subjected to translocation, reduction in size or loss. In O. berlesei (Michael, 1898 Michael, AD. 1898. “Oribatidae”. In Das Tierreich, Lief. 3. Vol. 8 (Acarina). Berlin: Verlag von R. Friedländer und Sohn Edited by: Schulze, FE . 1–93. [Google Scholar] ), O. nortoni, O. quadricornuta and O. sexdentata Berlese, 1916 pair dp takes a more lateral position, compared with the larvae, in O. superbula and O. canadensis Behan-Pelletier and Eamer, 2010 Behan-Pelletier, VM and Eamer, B. 2010. The first sexually dimorphic species of Oribatella (Acari, Oribatida, Oribatellidae) and a review of sexual dimorphism in the Brachypylina. Zootaxa, 2332: 1–20. [Google Scholar] it is reduced in size (in the latter species pair dm is also reduced), while O. metzi loses setae dm and dp. In contrast, the nymphs of O. calcarata do not carry the scalps, and usually lose setae c 1 and dm. The adults of all species lose setae c 1, c 3 and d-series, compared with the tritonymph, and only 10 pairs of notogastral setae remain (c 2, l-, h- and p-series), but O. quadricornuta and O. calcarata rarely retain seta c 3 unilaterally, which indicates the order of setal loss in Oribatella according to Shaldybina ( 1972 Shaldybina, ES. 1972. Some morphological characters of ceratozetid moss mites (Oribatei). Ucenyje zapiski Gor Gosud Pedagog Institut, Gorki, 130: 35–66. In Russian [Google Scholar] ).