Morphological differentiation of Limnozetes Hull, 1916 (Acari: Oribatida: Limnozetidae) in the light of ontogenetic studies

Morphological variability of Limnozetes Hull, 1916 was investigated in light of the ontogeny of L. lustrum Behan-Pelletier, 1989 and L. rugosus (Sellnick, 1923). The adults of this genus are similar, but the nymphs are differentiated, either boatshaped, with thick and stiff posterior gastronotal setae and rather smooth cuticle, as in L. lustrum, or stocky, with thin gastronotal setae and plicate cuticle, as in L. rugosus. The adult of L. lustrum has ten pairs of notogastral setae, while that of L. rugosus has 10 or 11 pairs, which is noted here for the first time in Limnozetes and has phylogenetic importance. The morphology of juvenile stages of presented species has not been investigated so far. Moreover L. lustrum is recorded for the first time from Europe. Morphological groups within Limnozetes are proposed: ‘ciliatus group’, with L. lustrum and ‘rugosus group’, with L. rugosus.