Sensitivity of female secondary characters in the crustacean isopod, Armadillidium vulgare, to the androgenic gland hormone : a hypothesis on the existence of an ovary-differentiating factor

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The period during postembryonic development in which the androgenic gland hormone can masculinize female secondary characters was studied, with emphasis on the sexually undifferentiated period, in Armadillidium vulgare. Genetic females were implanted with androgenic glands at various developmental stages to induce masculinization. Instead of injection of androgenic gland extracts, androgenic glands were implanted after treatment with ethanol. Each genetic female received a total of three gland implants at stages 2-8. Masculinization of female endopodites of the first pair of abdominal legs was used to show sensitivity to the androgenic gland hormone. All the female recipients showed at least some masculinization of their endopodites at the first and second molts after receiving the implants regardless of the developmental stages. However, masculinization of their endopodites did not continue at subsequent molts. Only the genetic females, which received implants during the sex differentiation period, had endopodites that had fully developed into male copulatory organs. These results show that the secondary sexual characters of genetic females are sensitive to the androgenic gland hormone not only during the sex differentiation period but also during the sexually undifferentiated period. The effects of the androgenic gland implants on female secondary characters and gonadal development are discussed and an ovary-differentiating factor is hypothesized.