Ontogenetic studies of three species of Gymnodamaeidae (Acari: Oribatida) with a focus on regressions of hysterosomal setae

Abstract

Ontogeny of loss of gastronotal setae in Arthrodamaeus reticulatus (Berlese, 1910), Gymnodamaeus bicostatus (C.L. Koch, 1836) and Jacotella neonominata Subías, 2004 was investigated. From the larval setation, the protonymph of these species loses three pairs of d-series and two pairs of l-series; these losses continue through subsequent nymphal stages and adult. Between tritonymph and adult, setae of h-series are subject to loss; A. reticulatus loses none, G. bicostatus loses one pair (h 3) and J. neonominata loses two pairs (h 2 and h 3). The nymphs of these species bear the gastronotic exuviae of previous instars, but they differ in the appearance of the exuviae, the manner of their connection with the gastronotum, and the shape of setae c 3 and lp, which in some species helps secure the exuviae to the body. Other aspects of ontogeny of these species are described and illustrated for the first time, and morphological characters that distinguish Arthrodamaeus, Gymnodamaeus and Jacotella are discussed.