Rôle des bactéries symbiotiques dans l'intersexualité, la monogénie et la spéciation chez des crustacés oniscoïdes

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Abstract
Role of symbiotic bacteria in the intetsexuality, monogeny and speciation of oniscoid crustaceans In various populations of the Oniscoid Armadillidium vulgare, thelygeny (TF) and the various types of intersexes: IM, IMF, IM to which they are related are induced by a symbiotic bacterium (F) which is present in all tissues and transmitted by the oocytes. This bacterium which acts on the neurosecretory system controling the androgenic gland transforms the infested genetic males into neo‐females and more or less feminized intersexes which are resistant to experimental masculinization. A dominant gene M seems to be responsible with the bacterium for the differentiation of the inter‐sexes. Another type of thelygeny lineage (Tf‘) is supplied by neo‐females deprived of bacteria. Arrhenogenic progenies (Arf) issued from neo‐females provide the functional males; these progenies are often allelogenic and sometimes include intersexes (♂og and ♀+). The neo‐females Tf‘ and Arf are experimentally masculinizable. The f and f’ feminizing factors, which present a matroclin transmission, seem to correspond to 2 different states (according to the genotypes) of a sole epigenetic element released by the bacterial DNA. The females of the sub‐species Porcellio dilatatus petiti display in their oocytes symbiotic bacteria necessary for the development of the eggs. The crossing of a P. d. petiti male with a female of the subspecies Porcellio dilatatus dilatatus (morphologicaly similar but deprived of bacteria) is most of the times infertile: during the segmentation of the eggs, some chromosomes come out of the mitotic spindle. The bacterium is supposed to provide substances ensuring the fixation of chromosomes to the spindle and/or the duplication of some genes necessary for the development of the eggs. This bacterium assured reproductive isolation of P. d. petiti from P. d. dilatatus.

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