One of Rachel's dissertation chapters was published today in the journal Comparative Biochemistry and Physiology. Carotenoids, which are vibrant pigments acquired through diet, provide health benefits and are crucial for reproductive success in some animals. The fungal pathogen Batrachochytrium dendrobatidis (Bd) causes a disease called chytridiomycosis that infects the skin of amphibians, disrupts their regulatory processes, and can lead to death. Rachel hypothesized that the energy needed to fight a Bd infection would lead to a depletion of skin carotenoids in strawberry poison frogs (Oophaga pumilio). She predicted that an energetic or immunological trade-off would force the frogs to prioritize fighting the infection over sequestering these colorful pigments. However, the study's findings challenged this prediction, showing that the frogs were able to maintain their skin carotenoids even while infected.
To investigate this, Rachel infected a group of adult male and female strawberry poison frogs with Bd and compared their skin carotenoid concentrations to a mock-infected control group. All frogs were given a consistent, carotenoid-rich diet for six months before the experiment to ensure they had high levels of these pigments. Using high-performance liquid chromatography (HPLC), they measured the types and concentrations of 17 different skin carotenoids. The infected frogs developed a range of infection loads, from around 1.0×101 to over 1.0×107 zoospore equivalents. However, statistical analysis showed no difference in skin carotenoid concentrations between the infected and control frogs, regardless of the sex of the animal. The results suggest that in captive O. pumilio with abundant dietary carotenoids, Bd infection is not a sufficient stressor to alter their ability to sequester skin carotenoids. This might be due to the availability of sufficient energy to combat the infection while also maintaining skin carotenoids. The importance of skin carotenoids for ecological processes, such as mate choice, may outweigh the pressure from the Bd infection, leading the frogs to prioritize maintaining these pigments.
Citation: Prokopius, R., K. McGraw, and A. Catenazzi. 2025. Fungal disease does not affect skin carotenoid concentration in dietary-supplemented strawberry poison frogs. Comparative Biochemistry and Physiology, Part B 279: 111113
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