Morphology of juvenile stages and ontogeny of three species and genera of Eremaeidae (Acari, Oribatida)

Abstract

The morphology of juvenile stages of Eremaeus cordiformis Grandjean, 1934 is redescribed and illustrated, and those of Eueremaeus laticostulatus Bayartogtokh, 2003 and Proteremaeus punctulatus Bayartogtokh, 2000 are described and illustrated for the first time. The juveniles of these species differ from each other mainly by the presence of distinct prodorsal ridges in the central part of the prodorsum, shape and distribution of some setae, and number of adanal and anal setae. The larva of Er. cordiformis has these ridges, whereas other species lack them. Eueremaeus laticostulatus has relatively long and barbed prodorsal seta in in the larva and most gastronotal setae similarly ornamented in all juveniles, whereas other species have these setae short and smooth. The nymphs of Er. cordiformis and Eu. laticostulatus have three pairs of posterior gastronotal setae (p₁, h₁, h₂), which are inserted close to each other in transverse row, whereas those of P. punctulatus have only two pairs (p₁, h₁) there, and seta h₂ is inserted far from seta h₁ and closer to seta p₂. The nymphs of all species lose dorsal gastronotal setae of d-series and carry the exuvial scalps of previous instars directly on the glabrous gastronotum mainly due to lateral folds. The nymphs and adult of P. punctulatus have three pairs of adanal setae and two pairs of anal setae, whereas those of other species have at least five pairs of each series. The adult of Er. cordiformis has 11 pairs of notogastral setae, whereas other species investigated here have 10 pairs. The adults of all species have lamellar costulae on the prodorsum, but in P. punctulatus they are more widely separated than in other species. At present the systematic position of Proteremaeus is controversial in the literature, but the morphology of juveniles and adult of P. punctulatus investigated here confirms the membership of this genus in the Eremaeidae. A number of morphological characters support the separation of Er. hepaticus and Er. cordiformis and we provisionally reject their synonymy, until the type or topotypic material is compared.

Keywords:

• Oribatid mites
• Eremaeus cordiformis
• Eueremaeus laticostulatus
• Proteremaeus punctulatus
• juveniles
• ontogeny
• leg setation

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Corrigendum

Acknowledgements

We are grateful to Prof. Dr. Juan Carlos Iturrondobeitia (Department of Zoology and Cellular Animal Biology, University of the Basque Country, Leioa, Spain) for his invitation to visit the Basque University under the Erasmus programme, which allowed us to collect the samples of oribatid mites, including Er. cordiformis, and to Dr. Radomir Graczyk (Department of Ecology, University of Technology and Life Sciences, Bydgoszcz, Poland) for collecting Er. hepaticus from the Preserve Wronie (Poland) for this study. We also thank an anonymous reviewer for thorough review of this paper, and all professional suggestions that considerably improved the value of is paper, and Dr. David Evans Walter, Editor-in-Chief of International Journal of Acarology, for all helpful scientific and editorial suggestions and a nice cooperation.