Olfactory discrimination of female reproductive status by male tilapia(Oreochromis mossambicus)

Abstract

SUMMARY The current study investigated whether discrimination of sexual status of female tilapia by males is mediated by olfaction. Size-matched groups of female tilapia were assigned as pre- or post-ovulatory according to the time since their last ovulation (15-19 days pre-ovulatory, N=7; 1-3 days post-ovulatory, N=8). Female-conditioned water and body fluids(urine, bile, faeces and plasma) were assessed for olfactory potency in males by recording the electro-olfactogram (EOG). Water extracts, urine and faeces from pre-ovulatory females all evoked significantly larger amplitude EOGs in male fish (N=6), with correspondingly lower thresholds of detection,than those from post-ovulatory females. Plasma and bile evoked very large amplitude EOGs in males but with no differences between the two groups of females. Anosmic males (N=6) did not behave differently towards pre-or post-ovulatory females, while sham-operated males (N=6) showed a marked increase in urination rate towards pre-ovulatory females. We conclude that the ability of male tilapia to discriminate between females of differing reproductive status is mediated by odorants released into the water, probably via the urine and faeces, by pre-ovulatory females.

Olfactory sensitivity to bile fluid and bile salts in the European eel (Anguilla anguilla), goldfish (Carassius auratus) and Mozambique tilapia (Oreochromis mossambicus) suggests a `broad range' sensitivity not confined to those produced by conspecifics alone

“…Olfactory sensitivity to conspecific bile fluid is consistent with previous findings in the case of the eel (Huertas et al, 2007) and tilapia (Frade et al, 2002;Miranda et al, 2005). The fact that fish could detect bile fluid from different species suggests a potential role for bile salts in interactions between species, including prey detection and/or escape from predators (Rosenthal and Lobel, 2006).…”

“…Differences in the composition of the bile fluid between the sexes are also apparent in both the goldfish and tilapia, although they are much less marked than in the eel. Pheromonal communication is known to be important for the goldfish (Kobayashi et al, 2002;Sorensen and Stacey, 2004;Stacey and Sorensen, 2002) and recent work has suggested that it is important in the tilapia (Barata et al, 2007;Miranda et al, 2005). Could bile salts act as pheromones in these species too?…”

Tilapia male urinary pheromone stimulates female reproductive axis

“…Furthermore, signalling of male dominance via controlled urination has been demonstrated. Unlike subordinate males and females, dominant tilapia males store urine which is a vehicle for potent odorants actively released during aggressive disputes and mating behaviour Barata et al, 2007Barata et al, , 2008Miranda et al, 2005). Moreover, the urinary bladders of dominant males are larger and more muscular than those of subordinate males or females, suggesting an adaptation facilitating storage of larger urine volumes for longer and more frequent urination in the appropriate social context, which may modulate aggression between opponent males (Keller-Costa et al, 2012).…”

Visual communication stimulates reproduction in Nile tilapia, Oreochromis niloticus (L.)

“…However, chemical communication has also been reported for cichlids as an important way for reproductive communication (e.g., 13,14). In the cichlid Nile tilapia, Oreochromis niloticus, the dominant male increases chasing and courtship of females injected with 17,20βP, but in anosmic males these behaviors are not demonstrable (15).…”