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 'relea sing 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, 17alph a,20beta-P-glucuronide and PGF2alpha and compared the responses with t he closely related goldfish. The olfactory receptor cells of crucian c arp were as sensitive to 17alpha,20beta-P and PGF2alpha as those of th e goldfish, indicating that these hormones may function as reproductiv e signals also in crucian carp. Crucian carp and goldfish detected 17a lpha,20beta-P down to 10(-11) and 10(-10) M, respectively. The respons e was significantly greater at 10(-8) M 17alpha,20beta-P in both sperm iating and immature crucian carp compared with spermiating goldfish. T he crucian carp showed a much higher sensitivity to free 17alpha,20bet a-P compared with its glucuronated form. Immature crucian carp showed a considerably smaller EOG response to 10(-7) and 10(-8) M PGF2alpha c ompared with spermiated and regressed fish. The PGF2alpha response was significantly smaller in immature crucian carp compared with regresse d goldfish.