Morphological ontogeny of Melanozetes azoricus with comments on Melanozetes (Acari: Oribatida: Ceratozetidae)

Abstract

In this study the morphological ontogeny of Melanozetes azoricus Weigmann, 1976 is described and illustrated for the first time and compared with that of other species of Melanozetes Hull, 1916. The juveniles of M. azoricus have a humeral organ and a humeral macrosclerite, with seta c1, that is typical of Melanozetes, and all juvenile stages and adult have broad leg femora, with large ventral carina, which often occur in Melanozetes. The juveniles of M. azoricus differ from those of other species by the shape of most gastronotal setae, whereas the adult differs mainly by the body size, shape of lamellar cusp, presence and shape of the translamella and shape of notogastral setae. The diagnosis of Melanozetes is unclear in literature, but we follow the setal diagnostic character of Melanozetes (14 pairs, including c2 and c3) that is supported by the size of humeral macrosclerite in the juveniles, with seta c1, and the length and location of solenidion ω2 on tarsus I of nymphs and adults; this solenidion is longer than ω1 and is located anterolateral to ω1. In Fuscozetes Sellnick, 1928, which is sometimes mistaken with Melanozetes, solenidion ω2 is shorter than ω1 and is placed posterolateral to ω1. A revised diagnosis of Melanozetes is proposed, systematic status of some species of Melanozetes is discussed and M. azoricus floresianus is proposed as a synonym of M. azoricus.