Caractéristiques biodémographiques d'un acarien oribate (Carabodes willmanni) des pelouses xérophiles

Abstract

An analysis of biodemographic characteristics was undertaken under experimental conditions in Carabodes willmanni, the first study of its kind in the superfamily Carabodoidea. The species dominates the microarthropod fauna of dry Cladonia cover. Immature stages have a very soft integument and live within the decomposing lichen layer. The population is characterized by the following: (i) low fecundity, strongly density dependent; (ii) relatively long postembryonic development for such a small species, lasting 117 days at 20 °C; (iii) extended premoulting stage (pupation), lasting 28% of postembryonic development; (iv) high but very variable longevity, with values varying from 200 to 600 days between egg laying and death of the adult; (v) strong influence of temperature on fecundity, adult survival, and duration of embryonic and postembryonic developments: development is inhibited at 10 °C. Based on previously acquired information on the phenology of the population, a model for the life cycle under natural conditions is proposed. Periods favorable to development being greatly shortened by environmental factors, the duration of the cycle is lengthened and probably takes as much as 1 year under the harshest conditions. The success of C. willmanni in such an environment can be explained by the capacity of the immature stages to take advantage of the lichen substrate both as a source of food and as a means of protection against desiccation.[Journal translation]