Quantitative analysis of steroids and steroid glucuronides in the seminal vesicle fluid of feral spawning and feral and cultivated nonspawning African catfish, Clarias gariepinus

Abstract

The seminal vesicles of African catfish, Clarias gariepinus, can produce at least seven different steroid glucuronides, especially during the breeding season. In the present experiments quantification of the seven compounds and their free steroids was carried out by means of gas chromatography-mass spectrometry in particular by selected ion monitoring, using seminal vesicle fluid of Afrian catfish collected in the Hula nature reserve (Israel) and from a nearby fish farm. Some of the feral fish were in spawning condition; the others and the pond fish were in nonspawning condition. Compared to the nonspawning groups, in the feral spawning animals a significantly higher level was found especially of 5β-pregnane-3α,17α-diol-20-one-glucuronide, but also of 5β-androstane-3α,17β-diol-glucuronide, 5β-androstane-3α,17β-diol-11-one-glucuronide, and 5β-pregnane-3α,17β-diol-20-one. The feral and pond nonspawning groups mainly differed in a significantly higher concentration of 5β-pregnane-3α,17α-diol-20-one-glucuronide in the feral nonspawning fish. For the levels of etiocholanolone, testosterone, 5β-androstane-3β,17β-diol, and their glucuronides no significant differences were observed between the three groups, and 5β-dihydrotestosterone and its glucuronide could not be detected in the seminal vesicle fluid of any of the animals. The increase in the concentration of three 5β-reduced steroid glucuronides may point to a pheromonal function of one or more of these compounds, as demonstrated for the entire steroid glucuronide fraction of the seminal vesicle fluid. Experiments are being carried out to verify this hypothesis.