Can bile acids function as a migratory pheromone in banded kokopu, Galaxias fasciatus (Gray)?

Migratory banded kokopu juveniles exhibit a species-specific attraction to adult conspecifics. The potential for bile acids to function as a component of a migratory pheromone in banded kokopu was investigated by examining which bile acids are present in the gallbladder of adult fish, are released into the water and are detected by adult fish. High-performance liquid chromatography (HPLC) and mass spectrometry (MS) of gallbladder extracts showed that banded kokopu contained high quantities of taurocholic acid (TCA) and taurochenodeoxycholic acid (TCD), and a very small quantity of cyprinol sulphate (5 alpha-CS). The holding water of adult banded kokopu was found to contain only TCA and TCD. In addition, three unknown peaks were evident. Electro-olfactogram recordings revealed that banded kokopu showed strong responses to four bile acids [5 alpha-CS, petromyzonol (P), petromyzonol sulphate (PS), and allocholic acid (ACA)] and low responses to TCA and TCD (< 30% of the L-serine standard). The bile acids TCA and TCD, produced and released by adult banded kokopu, are common among teleosts and are not species specific. Therefore, it is unlikely that these bile acids will function as a migratory pheromone in banded kokopu.