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ESCAPE FROM UV THREATS IN ZOOPLANKTON: A COCKTAIL OF BEHAVIOR AND PROTECTIVE PIGMENTATION
Author(s) -
Hansson Lars-Anders,
Hylander Samuel,
Sommaruga Ruben
Publication year - 2007
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/06-2038.1
Subject(s) - zooplankton , daphnia , biology , temperate climate , ecology , water column , ultraviolet radiation , phenotypic plasticity , cladocera , crustacean , latitude , zoology , chemistry , radiochemistry , geography , geodesy
In order to avoid environmental threats, organisms may respond by altering behavior or phenotype. Using experiments performed in high‐latitude Siberia and in temperate Sweden, we show for the first time that, among freshwater crustacean zooplankton, the defense against threats from ultraviolet radiation (UV) is a system where phenotypic plasticity and behavioral escape mechanisms function as complementary traits. Freshwater copepods relied mainly on accumulating protective pigments when exposed to UV radiation, but Daphnia showed strong behavioral responses. Pigment levels for both Daphnia and copepods were generally higher at higher latitudes, mirroring different UV threat levels. When released from the UV threat, Daphnia rapidly reduced (within 10 days) their UV protecting pigmentation—by as much as 40%—suggesting a cost in maintaining UV protective pigmentation. The evolutionary advantage of protective pigments is, likely, the ability to utilize the whole water column during daytime; conversely, since the amount of algal food is generally higher in surface waters, unpigmented individuals are restricted to a less preferred feeding habitat in deeper waters. Our main conclusion is that different zooplankton taxa, and similar taxa at different latitudes, use different mixes of behavior and pigments to respond to UV radiation.