In zebrafish, Danio rerio, a polygenic pattern of sex determination or a female heterogamety with possible influences of environmental factors is assumed. The present study focuses on the effects of an elevated water temperature (35°C) during the embryonic development on sex determination in zebrafish. Eggs derived from 3 golden females were fertilized by the same mitotic gynogenetic male and exposed to a water temperature of 35°C, applied from 5 to 10 h post fertilization (hpf), from 5 to 24 hpf, and from 5 to 48 hpf, which correspond to the following developmental stages: gastrula, gastrula to segmentation, and gastrula to pharyngula stage, respectively. Hatching and survival rates decreased with increasing exposure to high water temperatures. Reductions in the hatching and survival rates were not responsible for differences in sex ratios. Accordingly, exposition of the fertilized eggs to a high temperature (35°C) leads to an increase of the male proportion from 22.0% in the controls to a balanced sex ratio (48.3, 47.5, and 52.6%) in the gastrula, segmentation, and pharyngula groups, respectively. These results prove the possibility to change the pathway of sexual determination during early embryonic stages in zebrafish by exposure to a high water temperature.
Temperature effects on sex determination or differentiation exist in many fish species, with high temperatures predominantly producing more males. The present study aimed at elucidating the genetic background of temperature effects on sex differentiation in zebrafish. Experimental fish were generated by matings between 4 or 6 golden females and a normal or a mitotic gynogenetic male, respectively. All the larvae were reared at 28.5°C until they were divided into 3 groups per full-sib family, a control group raised at 28.5°C and 2 treatment groups reared at 35°C from 20 to 30 dpf or 25 to 35 dpf, respectively. Backcross progenies, reared at 28.5°C, were derived from F1 temperature-treated sons (35°C, 25–35 dpf) that were sired by a mitotic gynogenetic male and their corresponding mothers. No significant differences were observed regarding the survival rate between the control and treatment groups. Significant differences in the phenotypic male proportions from the controls were observed in groups treated at 35°C. The sex ratio in zebrafish was influenced by the male spawner, the female spawner, and a significant interaction of genotype by temperature. Backcross experiments point to a continuum of major genetic, minor genetic, and environmental factors in the expression of the phenotypic sex in zebrafish.
I N chickens, the breast and thigh weights are the most essential meat traits that are needed for production efficiency and economic benefits by affecting the appearance of the carcass. It is necessary to identify the specific genetic markers associated with such carcass traits. The use of gene expression is a desirable and reliable process for this purpose. The present study aimed to evaluate the effects of expression levels of five genes, FABP7, TPD52L1, NCOA7, GJA1, and ASF1A on breast and thigh weights in native Dokki-4 breed, hybrid Mamourah and Inshas breeds and imported Leghorn breed. Compared to the native breed Dokki-4, the results indicated that the high expression of GJA1 and ASF1A, genes in Mamourah breed as well as the up-regulation of ASF1A gene expression in Inshas and Leghorn breeds were pronounced to be associated with high breast weight. Moreover, the overexpression of FABP7 and GJA1 genes in Mamourah breed and high expression of GJA1 in Inshas and Leghorn breeds were found to be correlated with increasing thigh weight. Whereas, in the native Dokki-4 breed, the high expression of TPD52L1 and NCOA7 genes in breast muscle and ASF1A gene in thigh muscle were accompanied by reducing the weights of such muscles as compared to hybrid and imported chicken breeds. In conclusion, the present findings confirmed that the expressions of these genes can be useful genetic markers in chicken breed selection for improving carcass traits through increasing the breast and thigh weights.
In zebrafish (Danio rerio) a polygenic pattern of sex determination or a female heterogamety with possible influences of environmental factors is assumed. The present study focuses on the effects of elevated water temperature (35°C) during the embryonic development on sex determination in zebrafish. Eggs derived from three golden (gol) females were fertilized by the same mitotic gynogenetic male and exposed to a water temperature of 35°C applied from 5-10 hpf, 5-24 hpf and 5-48 hpf, which corresponds to the following developmental stages: gastrula, gastrula to segmentation, and gastrula to pharyngula stage, respectively. Hatching and survival rates decreased with increasing exposure to high water temperatures. Reductions in the hatching and survival rates were not responsible for differences in sex ratios. Accordingly, exposition of the fertilized eggs to high temperature (35°C) lead to an increase of the male proportion from 22.0 % in the controls to a balanced sex ratio (48.3 %, 47.5 %, 52.6 %) in the gastrula, segmentation and pharyngula groups, respectively. These results prove the possibility to change the pathway of sexual determination during early embryonic stages in zebrafish by exposure to high water temperature.
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