Size-structured risk assessments govern Daphnia migration.
One of the more fascinating phenomena in nature is animal mass migrations and in oceans and freshwaters, diel variations in depth distribution of zooplankton are a phenomenon that has intrigued scientists for more than a century. In our study, we show that zooplankton are able to assess the threat level of ultraviolet radiation and adjust their depth distribution to this level at a very fine tuned scale. Moreover, predation risk induces a size-structured depth separation, such that small individuals, which we show are less vulnerable to predation than larger, make a risk assessment and continue feeding in surface waters during day, offering a competitive release from down-migrating larger animals. Hence, we mechanistically show that such simple organisms as invertebrate zooplankton are able to make individual, size-specific decisions regarding how to compromise between threats from both predators and UV radiation, and adjust their diel migratory patterns accordingly.
Hansson
Lars-Anders
LA
Institute of Ecology/Limnology, Ecology Building, Lund University, 223 62 Lund, Sweden. lars-anders.hansson@limnol.lu.se
Hylander
Samuel
S
D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D049628:Body Size; D003621:Daphnia / Q000033:anatomy & histology / Q000502:physiology* / Q000528:radiation effects; D003657:Decision Making; D012309:Risk-Taking; D014466:Ultraviolet Rays