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Amphibians

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The Golden poison frog (Phyllobates terribilis) is among the species of poison frogs that have potential significance to medical research.

Frogs acquire the toxins needed for chemical defense by either producing them through glands on their skin or through their diet[1]. The source of toxins in their diet are primarily arthropods, ranging from beetles to millipedes[2]. When the required dietary components are absent, such as in captivity, the frog is no longer able to produce the toxins, making them nonpoisonous[3]. The profile of toxins may even change with the season, as is the case for the Climbing Mantella, whose diet and feeding behavior differ between wet and dry seasons[4].

The evolutionary advantage of producing such toxins is the deterrence of predators. There is evidence to suggest that the ability to produce toxins evolved along with aposematic coloration, acting as a visual cue to predators to remember which species are not palatable[1].

While the toxins produced by frogs are frequently referred to as poisonous, the doses of toxins are low enough that they are more noxious than poisonous[2]. However, components of the toxins, namely the alkaloids, are very active in ion channels[2]. Therefore, they disrupt the victim's nervous system, making them much more effective. Within the frogs themselves, the toxins are accumulated and delivered through small, specialized transport proteins[5].

Besides providing defense from predators, the toxins that poison frogs secrete interest medical researchers. Golden frogs, of the Bufonidae family, secrete batrachotoxin[3]. This toxin has the potential to act as a muscle relaxant, heart stimulant, or anesthetic[3]. Multiple species of frogs secrete epibatidine, whose study has yielded several important results[6]. It was discovered that the frogs resist poisoning themselves through a single amino acid replacement that desensitizes the targeted receptors to the toxin, but still maintains the function of the receptor[6]. This finding gives insight to the roles of proteins, the nervous system, and the mechanics of chemical defense, all of which promote future biomedical research and innovation.

References

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  1. ^ a b Summers, K.; Clough, M. E. (2001-05-22). "The evolution of coloration and toxicity in the poison frog family (Dendrobatidae)". Proceedings of the National Academy of Sciences. 98 (11): 6227–6232. doi:10.1073/pnas.101134898. ISSN 0027-8424. PMC 33450. PMID 11353830.{{cite journal}}: CS1 maint: PMC format (link)
  2. ^ a b c Daly, John (1995). "The Chemistry of Poisons in Amphibian Skin". Chemical Ecology: The Chemistry of Biotic Interaction. Washington, D.C.: The National Academies Press. pp. 17–26. ISBN 9780309052818.
  3. ^ a b c "Poison frogs". Smithsonian's National Zoo. 2016-06-06. Retrieved 2020-12-01.
  4. ^ Moskowitz, Nora A.; Roland, Alexandre B.; Fischer, Eva K.; Ranaivorazo, Ndimbintsoa; Vidoudez, Charles; Aguilar, Marianne T.; Caldera, Sophia M.; Chea, Jacqueline; Cristus, Miruna G.; Crowdis, Jett P.; DeMessie, Bluyé (2018-12-26). Chaves, Alex V. (ed.). "Seasonal changes in diet and chemical defense in the Climbing Mantella frog (Mantella laevigata)". PLOS ONE. 13 (12): e0207940. doi:10.1371/journal.pone.0207940. ISSN 1932-6203. PMC 6306172. PMID 30586404.{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
  5. ^ Caty, Stephanie N.; Alvarez-Buylla, Aurora; Byrd, Gary D.; Vidoudez, Charles; Roland, Alexandre B.; Tapia, Elicio E.; Budnik, Bogdan; Trauger, Sunia A.; Coloma, Luis A.; O'Connell, Lauren A. (2019-06-15). "Molecular physiology of chemical defenses in a poison frog". The Journal of Experimental Biology. 222 (12): jeb204149. doi:10.1242/jeb.204149. ISSN 0022-0949.
  6. ^ a b Tarvin, Rebecca D.; Borghese, Cecilia M.; Sachs, Wiebke; Santos, Juan C.; Lu, Ying; O’Connell, Lauren A.; Cannatella, David C.; Harris, R. Adron; Zakon, Harold H. (2017-09-22). "Interacting amino acid replacements allow poison frogs to evolve epibatidine resistance". Science. 357 (6357): 1261–1266. doi:10.1126/science.aan5061. ISSN 0036-8075. PMC 5834227. PMID 28935799.{{cite journal}}: CS1 maint: PMC format (link)