Boreal fishes and ultraviolet radiation : actions of UVR at molecular and individual levels

Abstract

Eeva-Riikka Vehniäinen on väitöskirjatyössään tutkinut UV-säteilyn vaikutuksia siian, hauen ja muikun poikasissa. Ihmisen aiheuttama otsonikerroksen ohentuminen on lisännyt maan pinnalle saapuvan ultravioletti-B-säteilyn (UVB) määrää viime vuosikymmenten aikana, ja lisääntymisen odotetaan jatkuvan vielä noin 2050-luvulle saakka. UVB-säteily on haitallista eliöille, koska se aiheuttaa vaurioita solun keskeisissä rakenteissa: DNA:ssa, proteiineissa ja lipideissä.Vehniäinen arvioi lisääntyvän UVB-säteilyn aiheuttamaa riskiä taloudellisesti ja ekologisesti tärkeille makeanveden kalalajeillemme, siialle, muikulle ja hauelle, niiden herkimmässä elämänvaiheessa välittömästi kuoriutumisen jälkeen. Lisäksi hän selvitti UVB-säteilyn vaikutuksia näissä lajeissa solu- ja molekyylitasolla ja integroi havaittuja vaikutuksia yksilötason vasteisiin.

Anthropogenically-caused stratospheric ozone depletion has increased the amount of UVB on Earth, and the predictions in Fennoscandia for the future suggest a further 20–60 % increase in the coming decades. This work explores the effects of UVB on larval boreal freshwater fishes at both the cellular and molecular level, and connects them to impacts at the individual level (mortality and growth retardation). Larval coregonids were very tolerant against UVR, but simultaneous exposure to UVB and retene, a polynuclear aromatic hydrocarbon, resulted in high mortality. On the contrary, in larval northern pike no photoinduced toxicity of retene was detected, but irradiation with currently occurring fluence rates and doses of UVB alone resulted in high mortality. Sublethal effects of UVB on pike included severe behavioural disorder followed by delayed mortality, growth attenuation, DNA damage, and changes in mRNA and protein expression. DNA damage occurred in the skin of pike larvae irradiated with current fluence rates of UVB. The higher the fluence rate the deeper in tissues the DNA damage was found. The DNA damage in the brain of pike larvae was followed by changes in protein expression, such as HSP/HSC70 decline. DNA damage and changes in protein expression in brain coincided with the behavioural disorder, suggesting the disorder was of neural origin. UVB caused less DNA damage in whitefish, the more tolerant and more pigmented species, than in pike. Also the UVB-induced transcriptomic changes differed between species and age groups. The results suggest connections between DNA damage and other molecular changes at the cellular level and the abnormal behaviour in pike.