Differences in carotenoid accumulation among three feeder‐cricket species: implications for carotenoid delivery to captive insectivores

Abstract

There are a limited number of feeder-invertebrates available to feed captive insectivores, and many are deficient in certain nutrients. Gut-loading is used to increase the diversity of nutrients present in the captive insectivore diet; however, little is known about delivery of carotenoids via gut-loading. Carotenoids may influence health and reproduction due to their roles in immune and antioxidant systems. We assessed interspecific variation in carotenoid accumulation and retention in three feeder-cricket species (Gryllus bimaculatus, Gryllodes sigillatus and Acheta domesticus) fed one of three diets (wheat-bran, fish-food based formulated diet, and fresh fruit and vegetables). Out of the three species of feeder-cricket in the fish-food-based dietary treatment group, G. bimaculatus had the greatest total carotenoid concentration. All cricket species fed the wheat-bran diet had very low carotenoid concentrations. Species on the fish-food-based diet had intermediate carotenoid concentrations, and those on the fruit and vegetable diet had the highest concentrations. Carotenoid retention was poor across all species. Overall, this study shows that, by providing captive insectivores with G. bimaculatus crickets recently fed a carotenoid-rich diet, the quantity of carotenoids in the diet can be increased.

Ex situ Diet Influences the Bacterial Community Associated with the Skin of Red-Eyed Tree Frogs (Agalychnis callidryas)

“…Carotenoids are a precursor to vitamin A, and so the availability of carotenoids in the diet of A. callidryas may influence mucus production and/or the microenvironment of the skin. Indeed, short tongue syndrome in amphibians and reptiles is associated with a lack of vitamin A, leading to keratinisation of the glandular epithelium in the tongue and a subsequent reduction in mucus production [18], [33], [39]. It is possible that a similar phenomenon is occurring in the epithelial cells of the skin of A. callidryas receiving a carotenoid-free diet, leading to a reduction in mucus availability for subsequent bacterial proliferation.…”

“…One nutritional aspect of interest to amphibian health is dietary carotenoids [33], [34]. In vertebrates, carotenoids are obtained solely from the diet and act as anti-oxidants in the body as well as precursors for vitamin A [35].…”

Insects as Food for Insectivores

“…The amount of carotenoids that accumulates through gut loading differs per insect species. The field cricket, for instance, accumulates more carotenoids on a high-carotenoid diet than the house cricket or the banded cricket (Gryllodes sigillatus Walker) (Ogilvy et al, 2012).…”

Challenges with effective nutrient supplementation for amphibians: A review of cricket studies

“…Brenes and Dierenfeld (this volume) reported that false tomato frogs ( Dyscophus guineti ) fed crickets injected with mixed carotenoids (zeaxanthin, ß‐carotene, canthaxanthin and lutein) had brighter, more saturated and oranger skin coloration, higher growth rates and were found to have higher plasma vitamin A levels compared to frogs fed crickets injected with only ß‐carotene or no carotenoids. Further investigations are required to determine if amphibians have the enzymes required to convert ß‐carotene and other potential precursors to vitamin A [Brenes and Dierenfeld, this volume; Finke, ; Hunt Coslik et al, ; McComb, ; Ogilvy et al, ]. While the addition of carotenoids to gut‐loading diets may be beneficial, the appropriate carotenoids and levels for supplementation have yet to be determined and may not be appropriate (or adequate) to replace vitamin A supplementation in the diet [Finke, ; Hunt Coslik et al, ], although may prove to have synergistic effects that may benefit the fitness of managed amphibian collections [Ogilvy et al, ].…”