Seasonal changes of progesterone and testosterone concentrations throughout gonad maturation stages of the Mexican octopus, Octopus maya (Octopodidae: Octopus)

Variations in progesterone (P-4) and testosterone (T) levels in the gonad of Octopus maya from Sisal in Yucatan State, Mexico, were investigated by radioimmunoassays and in relation to four gonad maturation stages (GMS) and to the reproductive cycle, as represented by two maturity indices (microscopic MiMI' and macroscopic MaMI'). According to the GMS and the maturity indices, the reproductive season of O. maya from Yucatan occurred from February to June. In females, P-4 and T displayed the same pattern, with a tendency to increase at the same time, although on average, P-4 had seven-fold higher concentrations than T. In contrast, P-4 and T in male gonads displayed a different pattern, where T concentrations were relatively stable throughout all of the study months. In the female gonad P-4 was lowest (close to 0pgg(-1)) during both developing (GMS-I) and maturing (GMS-II) stages, and increased (189 +/- 53pgg(-1)) approaching the mature stage (GMS-III) to a maximum value of 611pgg(-1). Concentrations of T in the male gonad were lowest (106 +/- 9pgg(-1)) during the maturing stage (GMS-II) and increased up to the mature stage (GMS-III), reaching a maximum of 440pgg(-1). Pearson's correlation (r) between hormones and maturity indices showed strong relationships for females (around 0.4 and -0.7; p<0.05), but there were negligible or weak relationships for males (0.2 and -0.1; p>0.05). Hormone correlations in females were inverse with MaMI and direct with MiMI. Our major findings showed that gonadal P-4 levels were elevated during GMS-III and GMS-IV (i.e. periods of vitellogenic oocytes), where the characteristic aspect is an ovary with very high oocyte diameters, with the primary follicle cells deeply infolded in the ooplasm for yolk synthesis. These results suggested a synchrony between P-4 and the process of folliculogenesis, and in turn, vitellogenesis.