Abstract
Electro‐olfactogram (EOG) recordings of the olfactory epithelium of both male and female roach Rutilus rutilus demonstrated that both sexes were able to detect free and glucuronidated 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) with high sensitivity. Male, but not female, roach were also sensitive to androstenedione. Sexually mature female roach were shown to release free 17,20β‐P, glucuronidated 17,20β‐P and androstenedione into the water; for all three steroids, the rate of release was significantly enhanced by injection of carp pituitary extract (CPE). A series of trials was also carried out which showed that mature males, and to a lesser extent immature males and females, were able also to release free and glucuronidated 17,20β‐P, both before and after CPE treatment. Water extracts from containers that had held CPE‐treated mature male and female roach were examined for the presence of other steroids. This revealed that free and glucuronidated 17,20β‐P plus free and glucuronidated 17,20β,21‐trihydroxy‐4‐pregnen‐3‐one (17,20β, 21‐P) predominated in water extracts from both sexes. The free moieties of 17,20α‐dihydroxy‐4‐pregnen‐3‐one, 17‐hydroxyprogesterone and 11‐deoxycortisol were found at concentrations which were between four and 20 times lower than those of free 17,20β‐P. Androstenedione was found at concentrations which were 25‐fold lower than those of 17,20β‐P. Despite its apparent high rate of release by sexually mature male and female roach, free 17,20β,21‐P was found not to exhibit any EOG activity at the highest dose tested (10 −7 M).