Comparative study of the reproductive strategy in the roach (Rutilus rutilus L.) and in the gudgeon (Gobio gobio L.) under controlled temperature conditions

Abstract

The effect of controlled cooling on the oogenesis dynamic in a group-synchronous (roach) and an asynchronous (gudgeon) fish was studied. The levels of plasma steroid hormones [testosterone (T), estradiol-17 β (E₂) and 17âˆÂ, 20 β-dihydroxyprogesterone (17âˆÂ,20 β-P)] were estimated and associated with the stage of oocyte maturity of each fish. In the roach, the mean levels of plasma steroid hormones were very low, the extremes were respectively: 0.29-0.58 ng/mL; 0.16-0.32 ng/mL and 1.28-11.27 ng/mL. The assessment of gonad development of the examined fish revealed that these ones were strongly affected by pre-ovulatory atresia. In the gudgeon the E₂ levels (0.05 to 1.23 ng/mL) were present during the whole experiment, showing a prolonged vitellogenic activity. The T concentrations (0.99 to 2.10 ng/mL) follows rather well the E₂ profile. The 17âˆÂ,20 β-P presented a progressive and opposite evolution to E₂ profile. Peaks of 17âˆÂ,20 β-P related to temperature changes were monitored, but they were quite low, between 0.66 and 4.41 ng/mL. The histology of the gonads showed a great individual variation, some females had a lot of vitellogenic oocytes, some had already spawned, others were preparing another spawning and others were in a recuperation phase.