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Effect of photoperiod manipulation on rainbow trout (Oncorhynchus mykiss) egg quality: A genomic study
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Conference: 4th Fish and Shellfish Larviculture Symposium, Ghent Univ, Gent, Belgium, Sep. 05-08, 2005. International audience. The purpose of this study was to investigate the effect of photoperiod advanced spawning on egg quality and egg transcriptome. Experimentation was performed using 2 groups of rainbow trout (Oncorhynchus mykiss) from an autumn-spawning strain. In 2003, a first group of females was exposed, after their first natural spawning, to a long-short photoperiod regime beginning in January (photoperiod manipulated group, PM group, n = 17) resulting in a second reproduction in June-July. A second group of females achieved their first reproduction in the fall (2003) and was used as a control (n = 25). For each female, egg quality was assessed by monitoring survival at eyeing (E) and yolk-sac resorption (YSR) as well as the occurrence of malformations at YSR. We observed a significant decrease of egg quality in PM group. Survival at eyeing was 49 +/- 18% (means +/- 95% CI) in PM group while a 93 +/- 3% survival was observed in control group. At YSR, the frequencies of alive alevins exhibiting no noticeable malformation were 37 16% in PM group and 84 +/- 5% in the control group. This increase of mortality was associated with a higher individual variability between females and an increase of malformations observed on alive alevins. These malformations were mostly characterized by defects of yolk-sac resorption (48% of malformations observed in PM group). Transcriptome analysis was performed using nylon microarrays displaying 9152 rainbow trout cDNAs spotted. Differential analysis allowed the identification of 6 genes significantly less abundant in PM eggs than in control eggs. These results suggest that photoperiod manipulation of spawning date can induce significant egg quality defects. Moreover, the transcriptome of unfertilized oocyte appears to be influenced by environmental perturbations, such as photoperiod regime, and seems to be reflective of egg developmental capacities after fertilization.
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