Observations on spindly leg syndrome in a captive population of Andinobates geminisae

Amphibian health problems of unknown cause limit the success of the growing number of captive breeding programs. Spindly leg syndrome (SLS) is one such disease, where affected individuals with underdeveloped limbs often require euthanization. We experimentally evaluated husbandry-related factors of SLS in a captive population of the critically endangered frog, Andinobates geminisae. SLS has been linked to tadpole nutrition, vitamin B deficiency, water filtration methods, and water quality, but few of these have been experimentally tested. We tested the effects of water filtration method and vitamin supplementation (2017) and the effects of tadpole husbandry protocol intensity (2018) on time to metamorphosis and the occurrence of SLS. We found that vitamin supplementation and reconstituted reverse osmosis filtration of tadpole rearing water significantly reduced SLS prevalence and that reduced tadpole husbandry delayed time to metamorphosis. A fortuitous accident in 2018 resulted in a decrease in the phosphate content of rearing water, which afforded us an additional opportunity to assess the influence of phosphate on calcium sequestration. We found that tadpoles that had more time to sequester calcium for ossification during development had decreased the prevalence of SLS. Taken together, our results suggest that the qualities of the water used to rear tadpoles plays an important role in the development of SLS. Specifically, filtration method, vitamin supplementation, and calcium availability of tadpole rearing water may play important roles. Focused experiments are still needed, but our findings provide important information for amphibian captive rearing programs affected by high SLS prevalence.