Abstract
Dietary carotenoids are expected to improve vertebrate growth and development, though evidence for beneficial effects remains limited. One reason for this might be that few studies have directly compared the effects of carotenoids from different classes (carotenes versus xanthophylls) at more than one dose. Here, we tested the effect of two doses of dietary β-carotene and lutein (representing two different carotenoid classes) on the growth and development of larval southern corroboree frogs (Pseudophryne corroboree). Individuals were supplemented with either β-carotene or lutein at one of two doses (0.1 mg g-1, 1 mg g-1), or given a diet without carotenoids (control). Each dietary treatment included 36 replicate individuals, and individuals remained on the same diet until metamorphosis (25-39 weeks). We measured larval survival, larval growth (body length), time to metamorphosis, metamorphic body size (mass and SVL), and body condition. Lutein had no detectable effect on larval growth and development. However, larvae receiving a high dose (1 mg g-1) of β-carotene metamorphosed significantly faster than all other dietary treatments, despite no significant differences in growth rate. This result indicates that β-carotene supplementation in P. corroboree has positive effects on development independent of growth effects. Our study provides new evidence for differential effects of carotenoid class and dose on vertebrate development. From a conservation perspective, our findings are expected to assist with the recovery of P. corroboree by expediting the generation of frogs required for the maintenance of captive insurance colonies, or the provision of frogs for release. More broadly, our study highlights the potential for dietary manipulation to assist with the ex situ management of threatened amphibian species worldwide.
Highlights
The establishment of conservation breeding programs is a primary conservation action for threatened animal species worldwide (Gascon, 2007; Conde et al, 2013; Tapley et al, 2015)
Dietary carotenoids are expected to improve vertebrate growth and development, though evidence for beneficial effects remains limited. One reason for this might be that few studies have directly compared the effects of carotenoids from different classes at more than one dose
For the first 50% of individuals to metamorphose from each treatment, there was no significant effect of dietary treatment on snout-vent length (SVL) (LME: F4,58.28 = 0.937, P = 0.449) (Fig. 3A), body mass (LME: F4,59.27 = 0.958, P = 0.437) (Fig. 3B), or body condition (LME: F4,60.58 = 0.405, P = 0.805) (Fig. 3C)
Summary
The establishment of conservation breeding programs is a primary conservation action for threatened animal species worldwide (Gascon, 2007; Conde et al, 2013; Tapley et al, 2015). Conservation breeding programs aim to safeguard threatened species ex situ, while providing individuals for release in situ (Conde et al, 2013). These programs are widely considered to be critical for insuring species survival, but many programs experience low success due to difficulties associated with efficiently producing large numbers of viable individuals (Dolman et al, 2015). There has been an emerging focus on manipulating the diets of captive animals, with a view toward improving the growth and development
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