Efeitos de variáveis ambientais sobre a simetria bilateral de larvas de peixes de cultivo marinho: uma abordagem experimental

Abstract

In Brazil, marine fisheries have little participation in the economic sector. However, some species have a great potential, as a carapeba, Eugerres brasilianus. The larviculture is still a bottleneck due to a rarity of protocols that aid in the survival and performance of larvae, requiring identifying the stressing agents on the fish phenotype in larviculture. Fluctuating Asymmetry (FA) emerges as a performance indicator builder, and can be used for these studies. This study aimed to assess the occurrence of FA in larvae of E. brasilianus at different temperatures and salinities. The diameter of the eyes was used to calculate the AF levels in three individual indexes: FA1 = | D-E | FA2 = | D- E | ÷ [(D + E) ÷ 2]; and FA5 = (D-E) 2, as proposed by PALMER (1994), where: D = right side; and E = left side. A total of 95 larvae were analyzed. The t-student test validated the presence of FA in carapeba larvae (p=0.53). The larvae survival did not differ significantly under different temperatures (PERMANOVA, F=0.57, p = 0.58) and salinities (PERMANOVA; F=0.42, p =0.68). Significant differences were found in FA indexes for experiments with different temperatures (PERMANOVA; F =20.85; p = 0.0001), but were not in the different salinities (PERMANOVA; F=0.25; p=0.77). The absence of a significant relationship between FA and survival possibly occurred because larvae did not absorb their yolk sac, which justifies the low mortality rate. Carapeba is an eurihaline species, and as the treatments did not reach critical levels, the salinity tested was not considered stressful for the species, but the lowest temperatures (20oC). In this context, the AF in the diameter of the eyes at lower temperatures can reduce the aptitude of the individuals affecting the visual capacity of the species and its zootechnical performance, being an economic problem in fish farms.