Behavioural responses of female round gobies (Neogobius melanostomus) to putative steroidal pheromones

Abstract

Although reproductive (RF) and non-reproductive (NRF) female round goby are attracted to washings of conspecific reproductive males and RF, respectively, behavioural responses of females to synthesized steroids has not been studied. We tested attraction and avoidance of RF and NRF to different blends of steroids previously shown to be either produced by reproductive males and/or detectable at a concentration of at least 10 −8 M by the olfactory epithelium of RF. Three blends of steroids were used, including: etiocholanolone (3α-hydroxy-5βandrostan-17-one), 11-oxo-etiocholanolone (3α-hydroxy-5β-androstane-11,17-dione), androstenedione, 11β-hydroxy-androstenedione, and 11-ketotestosterone ('free' steroid blend); etiocholanolone glucuronide, etiocholanolone sulfate, 11-oxo-etiocholanolone glucuronide and 11-oxo-etiocholanolone sulfate ('conjugated' steroid blend); and all nine steroids together ('total' steroid blend). NRF were attracted to the free steroid blend and avoided the conjugated blend. RF did not reveal any significant bias to the steroid blends, but there was a tendency for RF to prefer conjugated steroids and avoid free steroids. Because there was no significant attraction by RF to particular blends of synthesized steroids tested, other compounds (sex attractants) not yet identified from the male round goby are likely responsible for initiating courtship and/or spawning behaviours in reproductive females.

Release of Free and Conjugated Forms of the Putative Pheromonal Steroid 11-Oxo-etiocholanolone by Reproductively Mature Male Round Goby (Neogobius melanostomus Pallas, 1814)

“…1A) attracted NRF but repelled RF. These results are very much in line with those of the earlier study [18] that used blends of synthetic steroids (including those shown in Fig. 1A, B, and C, but not E or F).…”

“…However, no specific measurements were made of levels of this compound in the sGnRHa injection studies in the present study. Even though previous behavioral studies suggest that this compound is not likely to be the only attractant pheromone [18], nevertheless, it might contribute to the efficacy of a putative pheromonal mixture. Thus, it will be important in future studies to establish how production of 11-O-ETIO-3-g (Fig.…”

“…Extracts of water that had been conditioned by RM evoked stronger field potential responses from the olfactory epithelium of RF than extracts of water from nonreproductive males [16]; RF were attracted to water that has previously held RM [17]. Nonreproductive females (NRF) were attracted to a blend of synthetic, free steroids (which included 11-O-ETIO) but avoided a blend of synthetic conjugated steroids (which included 3-sulfated and glucosiduronated 11-O-ETIO), whereas RF showed a tendency (not statistically significant) to prefer conjugated steroids and avoid free steroids [18]. In relation to the last of these studies, unconjugated steroids may be suitable for attraction as the round goby olfactory system responds to many of these steroids [8,19], and unconjugated steroids are excreted continuously from the gills [20], thus creating an uninterrupted plume.…”

Invasive male round gobies (Neogobius melanostomus) release pheromones in their urine to attract females

“…The key advantage of EOG (which tests for odour potency) is that it can be used as a rapid procedure to test numerous fractions at intervals of 3-5 min on a single fish. Although a behavioural bioassay was previously developed and applied to N. melanostomus (Gammon et al 2005;Corkum et al 2006Corkum et al , 2008Corkum et al , 2009Yavno and Corkum 2010), it was a time-consuming procedure optimized to test one, possibly two fractions, per day. To fit the screening of several fractions into the brief window RFs are available (a few summer months), and to move towards purifying the attractant pheromone of N. melanostomus, a more streamlined bioassay was needed.…”

Olfactory sensitivity to steroid glucuronates in Mozambique tilapia suggests two distinct and specific receptors for pheromone detection

“…Within the Perciformes, the largest teleost order (Order Summary for Perciformes, www.fishbase.org), studies on olfactory sensitivity to, and pheromonal function of, hormonal steroids are scarce and derive from a few representatives of the Gobiidae (Colombo et al, 1980;Corkum et al, 2008;Murphy et al, 2001;Tierney et al, 2013) and Cichlidae (Cole and Stacey, 2006;Hubbard et al, 2014;KellerCosta et al, 2014). Cichlids are an extremely diverse taxon with currently 1670 described species ('List of Nominal Species of Cichlidae', www.fishbase.org), mostly native to Africa, and adaptation of the sensory and signalling systems to different environmental conditions has been suggested as an important driver in African cichlid radiation (Seehausen et al, 2008).…”