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Robinson KE, Moniz HA, Stokes AN, Feldman CR. Where Does All the Poison Go? Investigating Toxicokinetics of Newt (Taricha) Tetrodotoxin (TTX) in Garter Snakes (Thamnophis). J Chem Ecol 2024:10.1007/s10886-024-01517-7. [PMID: 38842636 DOI: 10.1007/s10886-024-01517-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 05/14/2024] [Accepted: 05/22/2024] [Indexed: 06/07/2024]
Abstract
Animals that consume toxic diets provide models for understanding the molecular and physiological adaptations to ecological challenges. Garter snakes (Thamnophis) in western North America prey on Pacific newts (Taricha), which employ tetrodotoxin (TTX) as an antipredator defense. These snakes possess mutations in voltage-gated sodium channels (Nav), the molecular targets of TTX, that decrease the binding ability of TTX to sodium channels (target-site resistance). However, genetic variation at these loci that cannot explain all the phenotypic variation in TTX resistance in Thamnophis. We explored a separate means of resistance, toxin metabolism, to determine if TTX-resistant snakes either rapidly remove TTX or sequester TTX. We examined the metabolism and distribution of TTX in the body (toxicokinetics), to determine differences between TTX-resistant and TTX-sensitive snakes in the rates at which TTX is eliminated from organs and the whole body (using TTX half-life as our metric). We assayed TTX half-life in snakes from TTX-resistant and TTX-sensitive populations of three garter snake species with a coevolutionary history with newts (T. atratus, T. couchii, T. sirtalis), as well as two non-resistant "outgroup" species (T. elegans, Pituophis catenifer) that seldom (if ever) engage newts. We found TTX half-life varied across species, populations, and tissues. Interestingly, TTX half-life was shortest in T. elegans and P. catenifer compared to all other snakes. Furthermore, TTX-resistant populations of T. couchii and T. sirtalis eliminated TTX faster (shorter TTX half-life) than their TTX-sensitive counterparts, while populations of TTX-resistant and TTX-sensitive T. atratus showed no difference rates of TTX removal (same TTX half-life). The ability to rapidly eliminate TTX may have permitted increased prey consumption, which may have promoted the evolution of additional resistance mechanisms. Finally, snakes still retain substantial amounts of TTX, and we projected that snakes could be dangerous to their own predators days to weeks following the ingestion of a single newt. Thus, aspects of toxin metabolism may have been key in driving predator-prey relationships, and important in determining other ecological interactions.
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Affiliation(s)
- Kelly E Robinson
- Department of Biology and Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, Reno, NV, USA.
- Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, NV, USA.
| | - Haley A Moniz
- Department of Biology and Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, Reno, NV, USA
- Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, NV, USA
- Department of Biological Sciences, California Polytechnic State University, San Luis Obispo, CA, USA
| | - Amber N Stokes
- Department of Biology, California State University Bakersfield, Bakersfield, CA, USA
| | - Chris R Feldman
- Department of Biology and Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, Reno, NV, USA
- Program in Ecology, Evolution and Conservation Biology, University of Nevada, Reno, NV, USA
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Rubiano-Buitrago P, Pradhan S, Aceves AA, Mohammadi S, Paetz C, Rowland HM. Cardenolides in the defensive fluid of adult large milkweed bugs have differential potency on vertebrate and invertebrate predator Na +/K +-ATPases. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231735. [PMID: 39100152 PMCID: PMC11296140 DOI: 10.1098/rsos.231735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 03/19/2024] [Accepted: 04/23/2024] [Indexed: 08/06/2024]
Abstract
Aposematic animals rely on diverse secondary metabolites for defence. Various hypotheses, such as competition, life history and multifunctionality, have been posited to explain defence variability and diversity. We investigate the compound selectivity hypothesis using large milkweed bugs, Oncopeltus fasciatus, to determine if distinct cardenolides vary in toxicity to different predators. We quantify cardenolides in the bug's defensive secretions and body tissues and test the individual compounds against predator target sites, the Na+/K+-ATPases, that are predicted to differ in sensitivity. Frugoside, gofruside, glucopyranosyl frugoside and glucopyranosyl gofruside were the dominant cardenolides in the body tissues of the insects, whereas the two monoglycosidic cardenolides-frugoside and gofruside-were the most abundant in the defensive fluid. These monoglycosidic cardenolides were highly toxic (IC50 < 1 μM) to an invertebrate and a sensitive vertebrate enzyme, in comparison to the glucosylated compounds. Gofruside was the weakest inhibitor for a putatively resistant vertebrate predator. Glucopyranosyl calotropin, found in only 60% of bugs, was also an effective inhibitor of sensitive vertebrate enzymes. Our results suggest that the compounds sequestered by O. fasciatus probably provide consistency in protection against a range of predators and underscore the need to consider predator communities in prey defence evolution.
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Affiliation(s)
- P. Rubiano-Buitrago
- Research Group Predators and Toxic Prey, Max Planck Institute for Chemical Ecology, Jena, Germany
- Research Group Biosynthesis/NMR, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - S. Pradhan
- Research Group Predators and Toxic Prey, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - A. A. Aceves
- Research Group Predators and Toxic Prey, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - S. Mohammadi
- Research Group Predators and Toxic Prey, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - C. Paetz
- Research Group Biosynthesis/NMR, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - H. M. Rowland
- Research Group Predators and Toxic Prey, Max Planck Institute for Chemical Ecology, Jena, Germany
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Medina-Ortiz K, Navia F, Mosquera-Gil C, Sánchez A, Sterling G, Fierro L, Castaño S. Identification of the NA +/K +-ATPase α-Isoforms in Six Species of Poison Dart Frogs and their Sensitivity to Cardiotonic Steroids. J Chem Ecol 2023; 49:116-132. [PMID: 36877397 PMCID: PMC10102066 DOI: 10.1007/s10886-023-01404-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 03/07/2023]
Abstract
Cardiotonic steroids (CTS) are a group of compounds known to be toxic due to their ability to inhibit the Na+/K+-ATPase (NKA), which is essential to maintain the balance of ions in animal cells. An evolutionary strategy of molecular adaptation to avoid self-intoxication acquired by CTS defended organisms and their predators is the structural modification of their NKA where specific amino acid substitutions confer resistant phenotypes. Several lineages of poison dart frogs (Dendrobatidae) are well known to sequester a wide variety of lipophilic alkaloids from their arthropod diet, however there is no evidence of CTS-sequestration or dietary exposure. Interestingly this study identified the presence of α-NKA isoforms (α1 and α2) with amino acid substitutions indicative of CTS-resistant phenotypes in skeletal muscle transcriptomes obtained from six species of dendrobatids: Phyllobates aurotaenia, Oophaga anchicayensis, Epipedobates boulengeri, Andinobates bombetes, Andinobates minutus, and Leucostethus brachistriatus, collected in the Valle del Cauca (Colombia). P. aurotaenia, A. minutus, and E. boulengeri presented two variants for α1-NKA, with one of them having these substitutions. In contrast, O. anchicayensis and A. bombetes have only one α1-NKA isoform with an amino acid sequence indicative of CTS susceptibility and an α2-NKA with one substitution that could confer a reduced affinity for CTS. The α1 and α2 isoforms of L. brachistriatus do not contain substitutions imparting CTS resistance. Our findings indicate that poison dart frogs express α-NKA isoforms with different affinities for CTS and the pattern of this expression might be influenced by factors related to evolutionary, physiological, ecological, and geographical burdens.
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Affiliation(s)
- Katherine Medina-Ortiz
- Laboratorio de Herpetología Y Toxinología, Department of Physiological Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia.
| | - Felipe Navia
- Laboratorio de Herpetología Y Toxinología, Department of Physiological Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia
| | - Claudia Mosquera-Gil
- Laboratorio de Herpetología Y Toxinología, Department of Physiological Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia
| | - Adalberto Sánchez
- Laboratorio de Herpetología Y Toxinología, Department of Physiological Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia
| | - Gonzalo Sterling
- Laboratorio de Herpetología Y Toxinología, Department of Physiological Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia
| | - Leonardo Fierro
- Laboratorio de Herpetología Y Toxinología, Department of Physiological Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia
| | - Santiago Castaño
- Laboratorio de Herpetología Y Toxinología, Department of Physiological Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia.
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Massoud D, Bin-Meferij MM, El-Kott AF, Abd El-Maksoud MM, Negm S. Histology and histochemistry of the major salivary glands in the southern white-breasted hedgehog (Erinaceus concolor). Anat Histol Embryol 2023; 52:254-261. [PMID: 36271751 DOI: 10.1111/ahe.12878] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 09/21/2022] [Accepted: 10/11/2022] [Indexed: 11/30/2022]
Abstract
This study aimed to investigate the major salivary glands in the southern white-breasted hedgehog (Erinaceus concolor) histologically and histochemically. Five adult males were included in this study. The results showed that anatomically the shape of the parotid, submandibular and sublingual glands of the Erinaceus concolor was respectively almost pear, elliptical to pyramidal and oval. Histologically, the parotid gland had serous acini and secretory cells showed negative reaction to alcian blue (AB) (pH = 2.5) and negative response to aldehyde fuchsin (AF), methylene blue (MB) and PAS stains. The submandibular gland was a mixed gland of mucous and serous acini. The mucous acini were strongly positive for PAS, AB, MB and AF. However, serous acini were week for PAS and negative against AB, MB and AF stains. The sublingual gland was purely composed of mucous acini. The mucous acini of the sublingual gland were strongly positives for PAS, AB and MB methods. While their reaction to the AF staining was negative. In conclusion, the histological and histochemical observations of the major salivary glands of the southern white-breasted hedgehog (E. concolor) indicated that these glands shown similarities and some special different histochemical features as compared to other mammalian species.
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Affiliation(s)
- Diaa Massoud
- Department of Biology, College of Science, Jouf University, Sakaka, Al-Jouf, Saudi Arabia.,Department of Zoology, Faculty of Science, Fayoum University, Fayoum, Egypt
| | - Mashael M Bin-Meferij
- Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.,Histopathology Unit, Research Department, Health Sciences Research Center (HSRC), College of Science, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia
| | - Attala F El-Kott
- Department of Biology, College of Science, King Khalid University, Abha, Saudi Arabia.,Department of Zoology, Faculty of Science, Damanhour University, Damanhour, Egypt
| | - Mona M Abd El-Maksoud
- Department of Community Health Nursing, Nursing College, King Khalid University, Abha, Saudi Arabia.,Department of Community Health Nursing, Faculty of Nursing, Helwan University, Helwan, Egypt
| | - Sally Negm
- Department of Life Sciences, Faculty of Science and Art Mahail, King Khalid University, Abha, Saudi Arabia.,Unit of Food Bacteriology, Central Laboratory of Food Hygiene, Ministry of Health, Sharkia, Egypt
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