Ultraviolet-absorbing compounds in the mucus of shallow-dwelling tropical reef fishes correlate with environmental water clarity

Abstract

Ultraviolet radiation is damaging to fishes, and fishes living in shallow water cope with this radiation by sequestering UV-absorbing compounds in their epithelial mucus. In the shallow waters of coastal Panama, fish may encounter vastly different irradiance environments that vary as a function of their proximity to major riverine inputs. Two common shallow water Caribbean fishes, Scarus iseri and Halichoeres bivittatus, were collected from 1 to 3 m depths at 3 locations within Bahia Almirante, Panama. Irradiance measurements were taken both at the subsurface and at 1 m depth for each of these sites, and 310 nm attenuation coefficients, kd(310), ranged from 0.94 m-1 at the clearest site to 1.83 m-1 at the most turbid site. Fishes from waters where UV was attenuated the most quickly had mucous sunscreen that differed significantly from that of fishes from clearer waters. The 2 species showed different manners of acclimatizing to UV radiation: H. bivittatus from clearer waters shifted the spectral quality of its mucus toward absorbance of shorter, more damaging wavelengths, whereas S. iseri from clearer waters increased the overall UV absorbance of its mucus, with minimal spectral shifting.