title: Persistence of chironomids in metal polluted andean high altitude streams: does melanin play a role?
abstract: In high altitude Andean streams an intense solar radiation and coinciding metal pollution allow the persistence of only a few specialized taxa, including chironomids. The aim of the present study was therefore to determine the mechanisms underlying the persistence of chironomids under these multiple stress conditions, hypothesizing that melanin counteracts both the adverse effects of solar radiation and of metals. Melanin was determined in chironomids from reference and metal polluted streams at 3000 and 4000 m altitude, being 2-fold higher at 4000 m compared to 3000 m, and 2-fold higher in polluted streams than in reference streams at both altitudes. The field observations were experimentally verified by assessing the combined effects of Cu and UV-B on the survival and melanin concentration in larvae of the model species Chironomus riparius (Chironomidae, Diptera). In laboratory exposures, the highest melanin concentrations were found in larvae surviving toxic Cu concentrations, but not in those exposed to the highest UV-B radiation. Pre-exposure to UV-B decreased the sensitivity of the larvae to UV-B and to Cu+UV-B. It is concluded that in the field, melanin may protect chironomids partially against both elevated metal concentrations and solar radiation, allowing them to persist under the harshest conditions in high altitude streams.
authors.affiliation: Laboratory of Ecotoxicology, Faculty of Sciences and Philosophy, Universidad Peruana Cayetano Heredia, Av Honorio Delgado 430, PO Box 4314, Lima 31, Peru.
authors.forename: Raúl A
authors.initials: RA
authors.lastname: Loayza-Muro
authors.forename: Jenny K
authors.initials: JK
authors.lastname: Marticorena-Ruiz
authors.forename: Edwin J
authors.initials: EJ
authors.lastname: Palomino
authors.forename: Camille
authors.initials: C
authors.lastname: Merritt
authors.forename: Milo L
authors.initials: ML
authors.lastname: De Baat
authors.forename: Maarten
authors.initials: M
authors.lastname: Van Gemert
authors.forename: Rudo A
authors.initials: RA
authors.lastname: Verweij
authors.forename: Michiel H S
authors.initials: MH
authors.lastname: Kraak
authors.forename: Wim
authors.initials: W
authors.lastname: Admiraal
mesh_terms: D000818:Animals; D002683:Chironomidae / Q000187:drug effects* / Q000378:metabolism; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D008543:Melanins / Q000378:metabolism*; D008670:Metals / Q000032:analysis / Q000633:toxicity*; D010568:Peru; D045483:Rivers; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D008543:Melanins; D008670:Metals; D014874:Water Pollutants, Chemical