Steroids and steroid glucuronides in the ovarian fluid of the African catfish,Clarias gariepinus, between ovulation and oviposition

Abstract

As part of a series of experiments concerning a possible pheromonal function of steroids and steroid glucuronides excreted by the sex organs of the African catfish,Clarias gariepinus, qualitative and quantitative studies, using GCMS, were carried out to examine the presence of the steroids, that can be synthesized by the ovary during oocyte maturation and ovulation, and of the corresponding steroid glucuronides, in the fluid surrounding the eggs in the ovarian cavity shortly after ovulation.Full mass spectra were obtained of 5β-pregnane-3α,17α-diol-20-one, 5β-pregnane-3α,17α,20α-triol, 5β-pregnane-3α,6α,17α-triol-20-one, 5β-pregnane-3α,6α,17α,20β-tetrol, 5β-androstane-3α,17β-diol and 5β-androstane-3α,17β-diol-11-one. After selected ion monitoring the following steroids could be detected by the presence of at least two characteristic ions at the expected retention time: 5β-pregnane-3α, 17α,20β-triol, etiocholanolone, 5β-dihydrotestosterone, 5β-androstane-3α,11β-diol-17-one, testosterone and estradiol. After treatment with β-glucuronidase the following steroids could be determined in a similar way: 5β-pregnane-3α,17α-diol-20-one, 5β-pregnane-3α,17α,20α-triol, 5β-pregnane-3α,17α,20β-triol, 5β-pregnane-3α,6α,17α-triol-20-one, 5β-pregnane,3α,6α,17α,20β-tetrol, 5β-androstane-3α,17β-diol, etiocholanolone, 5β-dihydrotestosterone, testosterone and estradiol.The free steroids 5β-pregnane-3α,6α,17α,20β-tetrol and 5β-pregnane-3α,6α,17α-triol-20-one and the steroid glucuronides of testosterone, 5β-dihydrotestosterone and estradiol appeared to be the most abundant of these compounds. The results indicate that very polar steroids and steroid glucuronides, synthesized in the ovary, can be excreted via the ovarian fluid shortly before and during oviposition, and possibly function as sex attractants, inducing reproductive behaviour in male conspecifics.