THE EFFECTS OF TEMPERATURE ON SEXUAL DIFFERENTIATION IN THE TEMPERATURE SENSITIVE THELYGENIC—INTERSEXUAL OFFSPRING OFORCHESTIA GAMMARELLUS(PALLAS) (AMPHIPODA; CRUSTACEA)

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Abstract
Some females of Orchestia gammarellus generate offspring which include too many females as well as intersexual males. This thelygeny related to intersexuality is temperature sensitive; it disappears above 22°C. It is induced by a feminising parasite described in another work. We have studied how the temperature acts on pubescent thelygenic females having either a known or unknown genotype (♀ 2AYY). The increase of female breeding temperature up to 25 or 30°C has two kinds of consequences for their offspring: (i) an increase in the male ratio, that is to say the expression of the normal genetic sex in potential neo females, and (ii) a correlative decrease in the proportion of intersexual males. The strength of these effects varies according to several parameters: temperature, exposure duration and genotype of tested females.