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You are here: Home / Associated publications / Belgian Journal of Zoology / Bibliographic References / Evolutionary trends in feminization and intersexuality in woodlice (Crustacea, Isopoda) infected with Wolbachia pipientis (alpha-Proteobacteria)

TTM Vandekerckhove, S Watteyne, W Bonne, D Vanacker, S Devaere, B Rumes, JP Maelfait, M Gillis, JG Swings, HR Braig, and J Mertens (2003)

Evolutionary trends in feminization and intersexuality in woodlice (Crustacea, Isopoda) infected with Wolbachia pipientis (alpha-Proteobacteria)


Sex ratio distortion (SRD) and intersexuality are common phenomena among Isopoda (Arthropoda, Crustacea), caused by the feminizing action of the alpha-Proteobacterium Wolbachia (F) and/or an F DNA segment (f) integrated into the host genome, probably as a transposon. A dominant autosomal masculinizing allele (M) overrides the primary sex determinants (WZ: females; ZZ: males) and f but not F. The latter can be counterbalanced by the transmission suppressor polygenic system (R). The present study pursued a double object. (i) SRD was found in naturally isolated populations of three out of seven Belgian woodlouse species: Oniscus asellus, Armadillidium vulgare and A. pulchellum. They were (inter)sexed based on external and internal morphology, and specimens of the former two underwent PCR and/or microscopic detection of F. (ii) A deterministic but flexible model was set up to describe SRD changes in an initially F-infested A. vulgare population sampled during the last 25 years. Observed and predicted sex ratios fit best if natural transmission rates (i.e., in the absence of M and R) approach 100\%, a condition fulfilled if f is carried on a multicopy transposon. Most often, such a population will then gradually lose its invader to the benefit of f. The stable end situation is a host population consisting of ZZ+f individuals of which 44\% are neo-females (having mm), and 56\% are reversed males (owing to Mm or MM). The model also explains the accelerated SRD evolution under variable degrees of F/f transmission.

isopoda; feminization; intersexuality; sex ratio evolution; Wolbachia
  • ISSN: 0777-6276

ISSN 2295-0451 (online version)
ISSN 0777-6279 (printed version)
impact factor 2015: 0,87.

Prof. Dr. Isa Schön
Royal Belgian Institute of Natural Sciences
Vautierstraat 29
1000 Brussels, Belgium


Annales de la Société malacologique de Belgique
​Annales de la Société royale malacologique et zoologique de Belgique
Annales de la Société Royale Zoologique de Belgique
Belgian Journal of Zoology