Differential female preference for individual components of a reproductive male round goby (Neogobius melanostomus) pheromone

Female round gobies were placed in the middle of a four-way maze that received either of these steroids released by reproductive males: 1) 3α-hydroxy-5β-androstane-11,17-dione-3-sulfate (11-O-ETIO-3-S), previously shown to be synthesized by the testes, to be present in the urine of males and to be detected at very low concentrations by the olfactory epithelium of this species; or 2) 3α-hydroxy-5β-androstane-11,17-dione (11-O-ETIO), the non-sulfated version of the same steroid, which has also previously been shown to be made and released into the water by males (in this case via the gills rather than the urinary bladder) and to be detected by the olfactory epithelium; or 3) 3α,17β-hydroxy-5β-androstan-11-one-3-sulfate (17-S), a steroid also previously shown to be present in male urine, but not to be detected by the olfactory epithelium or 4) solvent only. After each experiment, the females were sacrificed to determine their reproductive status. Those with relatively large ovaries (classified as 'reproductive' females) showed a significant attraction to 11-O-ETIO-S. Those with relatively small ovaries (classified as 'non-reproductive' females) showed a significant attraction to 11-O-ETIO. No females (of either stage) showed an attraction to 17-S. Fractionation of reproductive male conditioned water and urine, analysis by ELISA and mass spectrometry showed that reproductive males released levels of 11-O-ETIO-3-S that were likely to be detected by the round goby olfactory system. We suggest that individual compounds released by reproductive males have unique roles with regards to attraction and courtship during reproductive behaviour. Individual compounds could therefore be targeted for specific and purposeful management strategies.