Meeting Abstract
109.1 Tuesday, Jan. 7 08:00 Why Be red? Testing an Alternative Explanation for Color Polymorphism in Diaptomid copepods RHODES, A.C.; Texas A & M University Corpus Christi arhodes2@tamucc.edu
A striking color polymorphism exists in diaptomids inhabiting adjacent alkaline lakes in the Grand Coulee area of Eastern Washington. These highly alkaline lakes were formed following the last Ice Age, when the Columbia River became channelized. Copepods isolated from Soap Lake exhibit higher levels of red pigmentation at all times of the year in comparison to copepods from Lake Lenore. Nutrients, salinity, light and predation pressure have all been proposed to explain the difference in pigmentation between the lakes. Copepods from Lake Lenore cannot be induced to express the bright red coloration of Soap Lake copepods, even though Soap Lake copepods can lose their color in the lab. An alternative hypothesis to explain the difference in coloration between the populations of diaptomid copepods is genetic adaptation to the more stressful environment of Soap Lake. It is possible that copepods from Soap Lake and Lake Lenore represent parapatric groups formed by dispersal from allopatric Pleistocene refugia during the formation of the Grand Coulee. Soap Lake is deeper, saltier and more alkaline than Lake Lenore, and the lakes are not connected. These unique mineral and geological conditions could have led to a genetic divergence in coloration, enhanced by the more extreme alkalinities experienced by Soap Lake diaptomid copepods. Carotenoid biosynthesis might be increased in Soap Lake copepods due to a shared pathway for lipid desaturation utilizing oxidoreductase. The production of carotenoids increases antioxidant activity and allows for lipid storage and utilization in highly alkaline conditions. It is possible that intense red color is a byproduct of basic metabolic functions involving lipid storage and utilization in copepods. The function of carotenoid genes in Soap Lake diaptomids could provide clues as to why so many species of copepods in extreme environments are bright red.
