Ontogeny of morphological traits in Phenopelopidae (Acari: Oribatida)

Abstract

In this study, the complete ontogenetic development of morphological traits in Phenopelopidae was investigated on the base of juvenile and adult specimens of Eupelops hirtus (Berlese, 1916) and Peloptulus phaenotus (CL Koch, 1844) and literature. The juveniles of Eupelops Ewing, 1917, Peloptulus Berlese, 1908 and Propelops Jacot, 1937 show plicate integument and a dorsoventrally flattened hysterosoma, with short setae c1, c3 and of d-series on the gastronotum, which seem to be typical of Phenopelopidae. However, the juveniles of Eupelops and Peloptulus have some or all marginal setae on the gastronotum longer and thicker than other setae, at least one setal pair on the posterior part of gastronotum (h1 in larva and h3 in nymphs), whereas those of Propelops have these setae long or short. The juveniles and adults of Eupelops and Peloptulus differ distinctly from those of Propelops in the type of subcapitulum and chelicerae; the two former genera have the subcapitulum secondarily anarthric and the chelicerae pelopsiform, whereas the latter genus has the subcapitulum diarthric and the chelicerae normal. The adults of Eupelops and Propelops have 10 pairs of notogastral setae, including c2 and 2–3 or three pairs of p-series, respectively, whereas that of Peloptulus has eight pairs, including c2 and p1 (p2 and p3 are lost). The two former genera have also setae of ad-series, whereas the latter genus lacks them. In Eupelops seta in is long and phylliform, whereas in other genera it is setiform; long in Propelops and short or long in Peloptulus. In all genera the anterior part of notogaster protrudes over the prodorsum as a tectum, but in Eupelops this tectum is considerably larger than in other genera.