THE INFLUENCE OF TEMPERATURE ON THE SEX DIFFERENTIATION PROCESS IN PELED COREGONUS PELED (GMEL.)
Jarosław Król, Krystyna Demska-Zakęś, Piotr Hliwa, Grażyna Korzeniowska
University of Warmia and Mazury in Olsztyn, Poland
Abstract. The objective of this study was to examine the influence of water temperature (10, 17 and 21°C) on the sex differentiation process in peled. A high temperature, even a sub-lethal one, was not observed to have an influence on the sex ratio in this species; from day 81 after hatching until the end of the experiment the sex ratio in all three experimental groups was 1:1. It was noted, however, that thermal conditions determine the rate of sex differentiation and, in particular, of cytological differentiation. The first female-line cells, oogonia, were observed on day 102 after hatching in the peled kept in water at a temperature of 10°C. Cytological differentiation was observed in the fish that were reared in higher temperatures as soon as day 81 after hatching. The first symptoms of anatomical differentiation were noted at this time in fish from all experimental groups. Two types of gonads were observed in histological cross-sections; one had a thicker anterior part with the generative and somatic parts located separately (ovaries), and the other had small, spindle-like gonads (future testes). No cytological differentiation of the male sex cells was observed during the experiment.
Key words: PELED, (COREGONUS PELED), SEX DIFFERENTIATION, ENVIRONMENTAL CONDITIONS, TEMPERATURE
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