Early onset of urea synthesis and ammonia detoxification pathways in three terrestrially developing frogs

Méndez-Narváez, Javier; Warkentin, Karen M.

doi:10.1007/s00360-023-01506-4

Cited by 1 publication

(1 citation statement)

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“…Méndez-Narváez and Warkentin (2022) found that ammonia was 3.6-fold higher in the perivitelline fluid of dry versus wet eggs at age 5.5 days although, to enable fluid extraction, their dry eggs were sampled before reaching a level of dehydration that induces hatching (Salica et al, 2017). Moreover, A. callidryas embryos have some capacity to detoxify ammonia using glutamine synthetase (Méndez-Narváez & Warkentin, 2023). Thus, it is unclear if or when ammonia may reach life-threatening levels within A. callidryas eggs.…”

Section: Discussionmentioning

confidence: 99%

Elevated ammonia cues hatching in red‐eyed treefrogs: A mechanism for escape from drying eggs

Lisondro‐Arosemena,

Salazar‐Nicholls,

Warkentin

2024

J Exp Zool Pt B

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Egg dehydration can kill terrestrial frog embryos, and this threat is increasing with climate change and deforestation. In several lineages that independently evolved terrestrial eggs, and retained aquatic tadpoles, embryos accelerate hatching to escape from drying eggs, entering the water earlier and less developed. However, the cues that stimulate drying‐induced early hatching are unknown. Ammonia is a toxic, water‐soluble metabolic waste that accumulates within eggs as embryos develop and concentrates as eggs dehydrate. Thus, increasing ammonia concentration may be a direct threat to embryos in drying eggs. We hypothesized that it could serve as a cue, stimulating embryos to hatch and escape. The embryos of red‐eyed treefrogs, Agalychnis callidryas, hatch early to escape from many threats, including dehydration, and are known to use mechanosensory, hypoxia, and light cues. To test if they also use high ammonia as a cue to hatch, we exposed stage‐matched pairs of hatching‐competent, well‐hydrated sibling embryos to ammonia and control solutions in shallow water baths and recorded their behavior. Control embryos remained unhatched while ammonia‐exposed embryos showed a rapid, strong hatching response; 95% hatched, on average in under 15 min. This demonstrates that elevated ammonia can serve as a hatching cue for A. callidryas embryos. This finding is a key step in understanding the mechanisms that enable terrestrial frog embryos to escape from egg drying, opening new possibilities for integrative and comparative studies on this growing threat.

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Section: Discussionmentioning

confidence: 99%