Olfactory sensitivity to bile acids in salmonid fishes

Abstract

Monopolar DC-recordings were made simultaneously from two positions on the olfactory bulb of chars (Salmo alpinus L.) and graylings (Thymallus thymallu L.) using bile acids and amino acids as olfactory stimulants. The bile acids induced responses with characteristic spatial differences from those of the amino acids. The distribution of responses to bile acids indicated a neuronal activity in the medial part of the bulb. In contrast, amino acids elicit responses in the lateral part of the bulb. Taurine conjugated bile acids were up to 1 000 times more potent as olfactory stimuli than methionine. The results suggest that olfactory receptors are of two types, one responding to bile acids, the other to amino acids. 3 -alpha-hydroxysteroids are released from the fish into the water in quantities that suffice for detection by their olfactory system. The odorant potency of the bile acids, their evolutionary history and variability, together with their renowned adherent properties made them interesting candidates for specific signals in the acquatic environment.

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

“…Many species of fish have been shown to have an acute olfactory sensitivity to bile salts (Døving et al, 1980;Siefkes and Li, 2004;Zhang et al, 2001). Although the biological function of this phenomenon is unclear, with the notable exception of the sea lamprey Petromyzon marinus (Li et al, 2002;Polkinghorne et al, 2001;Sorensen et al, 2005), the stability and water solubility of the bile salt molecule makes it an ideal candidate for a role in chemical communication (Rosenthal and Lobel, 2006).…”

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

“…Firstly, the bile fluid is a concentrated source of bile acids (normally 25-50 mM) where the concentration may reach 300-400 mM after starvation (Karlaganis et al, 1989;Grosell et al, 2000). Secondly, many species of fishes have been shown to have a high olfactory sensitivity to bile acids (Doving et al, 1980), thus, it is reasonable to suppose such acids act as chemical signal for fish communication.…”

“…Additionally, extreme olfactory sensitivities to bile acids, coupled with their wide distribution and chemical variations, have been implicated for their role in fish behavior (Doving et al, 1980;Hara et al, 1984;Zhang et 238 al., 2001). For instance, behavioral evidence suggests that one of their functions as olfactory stimulants is their role as pheromones for migratory anadromous fishes, some of which appear to recognize and select the odor of conspecifics when choosing spawning streams (Doving et al, 1980;Stabell, 1992).…”

“…Studies using electro-olfactogram showed that bile acids are potent olfactory stimulants for the Arctic grayling (Thymallus arcticus) and Arctic charr (Salvelinus alpinus) (Doving et al, 1980), and taurocholic acid (TCA) is a potent olfactory stimulus to several salmonids (Hara et al, 1984;Quinn & Hara, 1986;Zhang & Hara, 1991;Hara & Zhang, 1996), and goldfish (Carassius auratus) (Sorensen et al, 1987). Additionally, extreme olfactory sensitivities to bile acids, coupled with their wide distribution and chemical variations, have been implicated for their role in fish behavior (Doving et al, 1980;Hara et al, 1984;Zhang et 238 al., 2001).…”

Identification, release and olfactory detection of bile salts in the intestinal fluid of the Senegalese sole (Solea senegalensis)

“…Fish, however, have also evolved a high olfactory sensitivity to this class of compound. This phenomenon is generally believed to be involved in chemical communication, conspeciWc recognition and/or identiWcation of potential predators and prey (Døving et al 1980;Hara 1994a, b;Sorensen and Caprio 1998;Zhang et al 2001;Giaquinto and Hara 2008;Zhang and Hara 2009). Nevertheless, only in the sea lamprey Petromyzon marinus have clearly deWned roles for bile acids as pheromones been established (Li et al 2002;Sorensen et al 2005).…”