Differential responses of male and female red swordtails to chemical alarmcues

Male and female red swordtails Xiphophorus helleri exposed in the laborator y to sword,tail skin, extract, fathead minnow Pimephales promelas skin extr act and distilled water, significantly decreased activity in response to co nspecific skin extract compared to minnow skin extract or distilled water. Moreover, males and females responded differentially to conspecific skin ex tract. Males tended to occupy the top compartment of the tank, whereas fema les tended to occupy the bottom compartment and seek shelter more. In a sec ond experiment swordtails reduced activity, significantly more in response to swordtail skin extract compared to closely related guppy Poecilia reticu lata skin extract, minnow skin extract or distilled water. Swordtails also reduced activity significantly more to guppy skin extract compared to minno w skin and distilled water. However, males and females did not respond diff erentially to guppy skin extract. This suggests that chemical alarm cues ar e partially conserved within the Poeciliidae, but the level of response is of lower intensity to heterospecific skin extracts. (C) 2001 The Fisheries Society of the British Isles.