Female Round Goby (Neogobius Melanostomus) Behavioural Responses to Fractionated Male-Conditioned Water and to Steroids Released by Males

The round goby, Neogobius melanostomus, is an invasive fish species to the Great Lakes. There is evidence that male round gobies release steroids that may function as pheromones. We have developed a high-throughput fractionation-attraction behaviour assay in order to progress towards the identification of pheromones. Both reproductive (RF) and non-reproductive (NRF) females were attracted to a blend of synthetic steroids. Both RFs and NRFs were strongly attracted to urine and methanol extracts of urine from GnRH-injected males. An HPLC fraction pool taken from GnRH-injected male-conditioned water including unknown conjugate(s) of 11-oxo-ETIO was highly attractive to RFs and less attractive to NRFs. In contrast, an HPLC fraction pool including free 11-oxo-ETIO was attractive to NRFs - but not to RFs. Our findings suggest that males release unknown conjugate(s) of 11-oxo-ETIO into the urine that may function as reproductive pheromones.