A STUDY OF THE OLFACTORY SENSITIVITY OF CRUCIAN CARP (CARASSIUS-CARASSIUS) AND GOLDFISH (CARASSIUS-AURATUS) TO 17-ALPHA,20-BETA-DIHYDROXY-4-PREGNEN-3-ONE AND PROSTAGLANDIN-F2-ALPHA

In the male goldfish (Carassius auratus), the hormones 17alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha,20beta-P) and prostaglandin F2alpha (PGF2alpha) have been suggested to act as sexual 'priming' and 'releasing pheromones', respectively. We have in the present study examined the sensitivity of the olfactory receptor cells (electro-olfactogram, EOG) of crucian carp (Carassius carassius) to 17alpha,20beta-P, 17alpha,20beta-P-glucuronide and PGF2alpha and compared the responses with the closely related goldfish. The olfactory receptor cells of crucian carp were as sensitive to 17alpha,20beta-P and PGF2alpha as those of the goldfish, indicating that these hormones may function as reproductive signals also in crucian carp. Crucian carp and goldfish detected 17alpha,20beta-P down to 10(-11) and 10(-10) M, respectively. The response was significantly greater at 10(-8) M 17alpha,20beta-P in both spermiating and immature crucian carp compared with spermiating goldfish. The crucian carp showed a much higher sensitivity to free 17alpha,20beta-P compared with its glucuronated form. Immature crucian carp showed a considerably smaller EOG response to 10(-7) and 10(-8) M PGF2alpha compared with spermiated and regressed fish. The PGF2alpha response was significantly smaller in immature crucian carp compared with regressed goldfish.