[Changes in the readiness for sexual and aggressive action of the sword tail Xiphophorus helleri (Pisces, Poeciliidae) under the influence of social isolation].

Social deprivation for 3 to 112 days caused an increase in copulation attempts and other motivational changes of sexual activities. Furthermore, it could be demonstrated that the tendencies for nipping, backing, copulation attempts, and gonopodial swinging fluctuated independently as a result of non-release of these activities. A rise in copulation tendency does not necessarily lead to increased aggressiveness. In the social hierarchy inferior individuals exhibited the highest levels of sexual and aggressive responsiveness.