Effect of daily thermo- and photo-cycles of different light spectrum on the development of Senegal sole ( Solea senegalensis) larvae

Abstract

This paper investigates the impact of different thermo- and photo-cycles of distinct wavelengths on Solea senegalensis larvae from day 1 to 30 post-hatching. In experiment 1, larvae were exposed to 12 h light:12 h dark (12 L:12D) cycle and (A) constant temperature (20.7 °C), (B) thermocycle of 12 h thermophase: 12 h cryophase, 22.1 °C day: 19.0 °C night (referred to as TC) or (C) 12 h cryophase: 12 h thermophase, 19.2 °C day: 22.0 °C night (referred to as CT). In experiment 2, larvae were kept under constant temperature (20.8 °C) and exposed to (A) continuous light (LL), (B) continuous darkness (DD), and LD 12 L:12D cycles of (C) white light (LD W), (D) blue light (LD B) or (E) red light (LD R). The sole larvae achieved the best performance, and showed fastest development and lowest degree of deformity under natural thermocycle conditions (TC) with a deformity percentage of 31.1% and LD B cycles with 27.7% of malformation, conditions which were nearest their natural aquatic environment. Larvae reared under TC started eye migration at 9 day post-hatching (DPH), while larvae exposed to CT started eye migration at 11 DPH. In larvae under the LD B treatment the migration of the eye started earlier than in the other treatments (9 DPH), while larvae reared under LL and DD photoperiods died before metamorphosis. These findings highlight the importance of light and temperature cycles during the early development of S. senegalensis larvae, which should be taken into consideration in experimental or rearing protocols.