Effects of temperature on eggs and larvae of Paralichthys orbignyanus sole
The objective of this work was to determine the effects of temperature on eggs and larvae of Paralichthys orbignyanus sole. The eggs were exposed to temperatures of 14, 17, 20, 23, 26 and 29 ° C. After hatching, the standard length of the larvae was measured, the volume of the yolk sac and its consumption were calculated, the percentage of malformed individuals and the larval resistance to fasting at each temperature were determined. The larvae were grown at temperatures 17, 20, 23 and 26 ° C, with 500 larvae distributed in 10 L tanks and fed with rotifers and nauplii from Artemia sp. Every five days the standard length of the larvae was recorded and the number of individuals killed was recorded daily. The results were submitted to Analysis of Variance (ANOVA) and, when significant differences were found (P <0.05),the Tukey test was applied. The hatching time was inversely proportional to the temperature, but the percentage of malformed larvae was higher at extreme temperatures, decreasing at temperatures 20, 23 and 26 ° C. The standard length of the newly hatched larvae was similar (P> 0.05) between 17 and 29 ° C (1.76-1.81mm), but was significantly shorter (P <0.05) at 14 ° C (1 , 58 mm). The volume of the yolk sac was inversely proportional to the temperature, with the exception of larvae hatched at 14 ° C, whose volume was lower than that of 17 ° C. The larvae survived on a fasting period when kept at 23 ° C. There was 100% mortality of larvae kept at 17 ° C on the 12th day after hatching, survival was significantly lower (P <0.05) at 20 ° C (2.1%) than at 23 ° C (11 , 7%) and 26 ° C (11.7%).The length at the end of the metamorphosis was similar to 20 and 26 ° C, 9.29 ± 0.15mm and 9.02 ± 0.11mm respectively, but significantly longer than that of the 23 ° C larvae, 8.23 ± 0, 07mm (P <0.05). The metamorphosis was completed more quickly at 23 and 26 ° C (20 days), than at 20 ° C (35 days). The index of malformed juveniles after metamorphosis was 59% at 26 ° C, higher than the 21 and 17% obtained at 20 and 23 ° C, respectively. The results of this work suggest that eggs and sole larvae are kept at 23 ° C, because although growth is lower at this temperature, there is good survival and the rate of malformed individuals is low.