Does Lighting Manipulation During Incubation Affect Hatching Rhythms and Early Development of Sole?

Abstract

Light plays a key role in the development of biological rhythms in fish. Previous research on Senegal sole has revealed that both spawning rhythms and larval development are strongly influenced by lighting conditions. However, hatching rhythms and the effect of light during incubation are as yet unexplored. Therefore, the aim of this study was to investigate the impact of the light spectrum and photoperiod on Solea senegalensis eggs and larvae until day 7 post hatching (dph). To this end, eggs were collected immediately after spawning during the night and exposed to continuous light (LL), continuous darkness (DD), or light-dark (LD) 12L:12D cycles of white light (LD_W), blue light (LD_B; λ_peak = 463 nm), or red light (LD_R; λ_peak = 685 nm). Eggs exposed to LD_B had the highest hatching rate (94.5% ± 1.9%), whereas LD_R and DD showed the lowest hatching rate (54.4% ± 3.9% and 48.4% ± 4.2%, respectively). Under LD conditions, the hatching rhythm peaked by the end of the dark phase, but was advanced in LD_B (zeitgeber time 8 [ZT8]; ZT0 representing the onset of darkness) in relation to LD_W and LD_R (ZT11). Under DD conditions, the same rhythm persisted, although with lower amplitude, whereas under LL the hatching rhythm split into two peaks (ZT8 and ZT13). From dph 4 onwards, larvae under LD_B showed the best growth and quickest development (advanced eye pigmentation, mouth opening, and pectoral fins), whereas larvae under LD_R and DD had the poorest performance. These results reveal that developmental rhythms at the egg stage are tightly controlled by light characteristics, underlining the importance of reproducing their natural underwater photoenvironment (LD cycles of blue wavelengths) during incubation and early larvae development of fish. (Author correspondence: [email protected])

Keywords:

• Circadian
• Development
• Hatching
• Light spectrum
• Photoperiod
• Senegal sole

ACKNOWLEDGMENTS

This research was funded by the Spanish Ministry of Science and Innovation (MICINN) by projects “Circasole” AGL2007-66507-C02 to F.J.S.-V. and J.A.M.-C., AQUAGENOMICS (28502, Consolider-Ingenio Program) and SENECA (05690/PI/07) to F.J.S.-V., and P06-AGR-1939 (Excellence Projects, Junta de Andalucía) to J.A.M.-C. Thanks are also due to COST ACTION 867 (Fish Welfare) and FA0801 (Larvanet), where part of these results were presented and discussed. B.B.-V. was supported by an FPI scholarship from MICINN. The authors would like to thank Patricia Herrera, Águeda Jimena Martín-Robles, and Abdeslam El M'Rabet for their help during sampling.

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.