Localization and density of phoretic deutonymphs of the mite Uropoda orbicularis (Parasitiformes : Mesostigmata) on Aphodius beetles (Aphodiidae) affect pedicel length

The phoretic stage of Uropodina mites is a deutonymph with developed morphological adaptations for dispersal by insects. Phoretic deutonymphs are able to produce a pedicel, a stalk-like temporary attachment structure that connects the mite with the carrier. The aim of our study was to determine whether localization and density of phoretic deutonymphs on the carrier affect pedicel length. The study was conducted on a common phoretic mite-Uropoda orbicularis (Uropodina) and two aphodiid beetles-Aphodius prodromus and Aphodius distinctus. Our results show that pedicel length is influenced by the localization of deutonymphs on the body of the carrier. The longest pedicels are produced by deutonymphs attached to the upper part of elytra, whereas deutonymphs attached to femora and trochanters of the third pair of legs and the apex of elytra construct the shortest pedicels. In general, deutonymphs attached to more exposed parts of the carrier produce longer pedicels, whereas shorter pedicels are produced when deutonymphs are fixed to non-exposed parts of the carrier. A second factor influencing pedicel length is the density of attached deutonymphs. Mean pedicel length and deutonymph densities were highly correlated: higher deutonymph density leads to the formation of longer pedicels. The cause for this correlation is discussed, and we conclude that pedicel length variability can increase successful dispersal

ÉTUDE QUANTITATIVE DES UROPODIDES (ACARIENS : ANACTINOTRICHES) D'UN ARBRE MORT DE LA HÊTRAIE DE LA MASSANE 1. _ CARACTÈRES GÉNÉRAUX DU PEUPLEMENT

International audienc

Dispersal in varying enviornments: the case of phoretic uropodid mites

Phoresy is a dispersal strategy in which one animal actively seeks out and attaches to another animal for transport. Phoretic dispersal is vital in many groups of mites that live in specialized microhabitats or unpredictable environments. This study deals with phenotypic plasticity and its relationship to initiation of the migration behaviour in a uropodid mite, Allodinychus flagelliger (Berlese), which inhabits dead wood. The deutonymphs are bimorphic, one morph being sedentary and the other, phoretic morph ensuring migration. Immigration and emigration were estimated for a 5-year period. Migration took place every year, as a result of obligate seasonal phoresy. The phoronts emigrated in spring attached to xylophagous insects. They immigrated in autumn, when their hosts built their galleries. The average annual emigration rate significantly increased as a function of the progressive decomposition of the dead wood, while immigration tended to diminish in the late stages of wood ageing. As a consequence, the deme finally declined and became extinct. Thus, the rate of emigration was manipulated by the deme in response to local conditions. It appeared not to be genetically fixed. The involvement of pleiotropic genes is possibly implied in the activation of migratory behaviour or the production of phoronts. The immigration rate is not fixed, because the arrival flow depends on heterospecific carriers. On the other hand, the rate of production of sedentary morphs did not vary and seemed to be genetically fixed

ÉTUDE QUANTITATIVE DES UROPODIDES(ACARIENS : ANACTINOTRICHES)D'UN ARBRE MORT DE LA HÊTRAIEDE LA MASSANE2. — ÉLÉMENTS DÉMOGRAPHIQUES D'UNE POPULATIOND'ALLODINYCHUS FLAGELLIGER (BERLÈSE, 1910)

International audienc

ÉTUDE QUANTITATIVE DES UROPODIDES(ACARIENS : ANACTINOTRICHES)D'UN ARBRE MORT DE LA HÊTRAIEDE LA MASSANE2. — ÉLÉMENTS DÉMOGRAPHIQUES D'UNE POPULATIOND'ALLODINYCHUS FLAGELLIGER (BERLÈSE, 1910)

International audienc

ÉTUDE QUANTITATIVE DES UROPODIDES (ACARIENS : ANACTINOTRICHES) D'UN ARBRE MORT DE LA HÊTRAIE DE LA MASSANE 1. _ CARACTÈRES GÉNÉRAUX DU PEUPLEMENT

International audienc

Study of ecological influence of fire on fauna in mediterranean ecosystems (soil and above-ground layer). Patterns of post-fire recovery

The effects of wild fire on the fauna (soil arthropods and small mammals) were studied in the Albères chain (Pyrénées Orientales, France). After fire, the vegetation structure tends to go back to the pre-fire situation. Retrogressive ecosystems (i.e. grasslands3 maquis) rapidly return to the pre-fire situation, while forest restoration is very slow. Fire destroys the litter layer and induces strong changes in the humus biological activities. It induces an immediate loss of animals, and also a delayed mortality. But almost all species may recolonize their habitat. In open habitat, characterized by a high primary production where the herbivores /predators system dominates, the recovery is rapid. On the other hand, in woodlands where the necrômass dominates (decomposers system), the disturbances are very strong and the recolonization takes a very long time with many transitional stages.Athias-Binche Françoise, Briard Justine, Fons Roger, Sommer Francisca. Study of ecological influence of fire on fauna in mediterranean ecosystems (soil and above-ground layer). Patterns of post-fire recovery. In: Ecologia mediterranea, tome 13 n°4, 1987. Influence of fire on the stability of mediterranean forest ecosystems. Giens (France) 23-26/03/1987. pp. 135-154