Bile acids as potential pheromones in pintado catfish Pseudoplatystoma corruscans (Spix &amp; Agassiz, 1829): eletrophysiological and behavioral studies

Percília Cardoso Giaquinto,Eliane Gonçalves-De-Freitas,Gilson Luiz Volpato,Marisa Fernandes-De-Castilho,Rodrigo Egydio Barreto

doi:10.1590/1982-0224-20140013

Bile acids as potential pheromones in pintado catfish Pseudoplatystoma corruscans (Spix & Agassiz, 1829): eletrophysiological and behavioral studies

Percília Cardoso Giaquinto, Eliane Gonçalves-De-Freitas + Show 3 more

Open Access

https://doi.org/10.1590/1982-0224-20140013

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Abstract

Bile acids are potent olfactory and gustatory stimulants for fish. Electro-olfactogram recording was used to test whether the olfactory epithelium of pintado catfish Pseudoplatystoma corruscans is specifically sensitive to bile acids, some of which have been hypothesized to function as pheromones. Five out of 30 bile acids that had been pre-screened for olfactory activity in fish were selected. Cross-adaptation experiments demonstrated that sensitivity to bile acids is attributable to at least 3 independent classes of olfactory receptor sites. The taurocholic acid (TCA) and taurochenodeoxycholic acid (TCD) were the most potent compounds. By using avoidance/preference tests, we found that P. corruscans prefers water containing TCA. Bile acids are discriminated by olfactory epithelium of pintado, supporting that these compounds could function as pheromones.

Highlights

Bile acids are known to act as potent odorants for teleosts (Hara, 1994; Zhang et al, 2001; Giaquinto & Hara, 2008), and conspecific bile fluid has been shown to have pheromonal activity for some fish species (Vermeirssen & Scott, 2001; Huertas et al, 2007)
Responses to all concentrations of bile acids ranged from –9% to 640%, and the blank water control elicited a mean response of 7.9±6.5%
The free bile acids deoxycholic acid (DC), chenodeoxycholic (CD) and cholic acid (CA) had similar, nearly parallel C-R curves with detection thresholds 10-9 M 10-11 M and 10-9 M, respectively (Fig. 1). Both the bile acids conjugated with taurine, taurochenodeoxycholic acid (TCD) and taurocholic acid (TCA), had essentially identical C-R curves, with relatively lower detection thresholds of 10-11 M and 10-10 M, respectively (Fig. 1)

Summary

Introduction

Bile acids are known to act as potent odorants for teleosts (Hara, 1994; Zhang et al, 2001; Giaquinto & Hara, 2008), and conspecific bile fluid has been shown to have pheromonal activity for some fish species (Vermeirssen & Scott, 2001; Huertas et al, 2007). As a nocturnal and predatory fish, chemicallymodulated reactions are expected to play a major role in intra and inter-specific relationships Based on these findings, we planned to investigate a possible biological role of bile acids in pintado, Pseudoplatystoma corruscans, by testing which of them would be detected by olfaction. From 30 bile acids tested, five showed evident EOG responses; among them, taurocholic acid (TCA) was investigated in a behavioral study as a possible pheromone because it showed the strongest response and previous reports showing that this bile acid is released in feces in high proportion (Zhang et al, 2001) and authentic bile acids are important inducing behavioral responses in fish (Jones & Hara, 1985)

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Discussion