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Toxins 2018, 10(7), 271; https://doi.org/10.3390/toxins10070271

Venom Ontogeny in the Mexican Lance-Headed Rattlesnake (Crotalus polystictus)

1
School of Biological Sciences, University of Northern Colorado, Greeley, CO 80639, USA
2
Departamento de Zoología, Universidad de Granada, 18071 Granada, Spain
3
Department of Biology, University of Washington, Seattle, WA 98195-1800, USA
4
Burke Museum of Natural History and Culture, Seattle, WA 98195, USA
5
Moore Laboratory of Zoology, Occidental College, Los Angeles, CA 90041, USA
6
Department of Molecular Medicine and Neurobiology, The Scripps Research Institute, La Jolla, CA 92037, USA
*
Author to whom correspondence should be addressed.
Received: 8 June 2018 / Revised: 26 June 2018 / Accepted: 27 June 2018 / Published: 3 July 2018
(This article belongs to the Section Animal Venoms)
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Abstract

As trophic adaptations, rattlesnake venoms can vary in composition depending on several intrinsic and extrinsic factors. Ontogenetic changes in venom composition have been documented for numerous species, but little is known of the potential age-related changes in many rattlesnake species found in México. In the current study, venom samples collected from adult and neonate Crotalus polystictus from Estado de México were subjected to enzymatic and electrophoretic analyses, toxicity assays (LD50), and MALDI-TOF mass spectrometry, and a pooled sample of adult venom was analyzed by shotgun proteomics. Electrophoretic profiles of adult males and females were quite similar, and only minor sex-based variation was noted. However, distinct differences were observed between venoms from adult females and their neonate offspring. Several prominent bands, including P-I and P-III snake venom metalloproteinases (SVMPs) and disintegrins (confirmed by MS/MS) were present in adult venoms and absent/greatly reduced in neonate venoms. Age-dependent differences in SVMP, kallikrein-like, phospholipase A2 (PLA2), and L-amino acid oxidase (LAAO) activity levels were confirmed by enzymatic activity assays, and like many other rattlesnake species, venoms from adult snakes have higher SVMP activity than neonate venoms. Conversely, PLA2 activity was approximately 2.5 × greater in venoms from neonates, likely contributing to the increased toxicity (neonate venom LD50 = 4.5 μg/g) towards non-Swiss albino mice when compared to adult venoms (LD50 = 5.5 μg/g). Thrombin-like (TLE) and phosphodiesterase activities did not vary significantly with age. A significant effect of sex (between adult male and adult female venoms) was also observed for SVMP, TLE, and LAAO activities. Analysis of pooled adult venom by LC-MS/MS identified 14 toxin protein families, dominated by bradykinin-inhibitory peptides, SVMPs (P-I, P-II and P-III), disintegrins, PLA2s, C-type-lectins, CRiSPs, serine proteinases, and LAAOs (96% of total venom proteins). Neonate and adult C. polystictus in this population consume almost exclusively mammals, suggesting that age-based differences in composition are related to physical differences in prey (e.g., surface-to-volume ratio differences) rather than taxonomic differences between prey. Venoms from adult C. polystictus fit a Type I pattern (high SVMP activity, lower toxicity), which is characteristic of many larger-bodied rattlesnakes of North America. View Full-Text
Keywords: bradykinin-inhibitory peptide; enzyme; evolution; phenotypic variation; toxins; venomics bradykinin-inhibitory peptide; enzyme; evolution; phenotypic variation; toxins; venomics
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Mackessy, S.P.; Leroy, J.; Mociño-Deloya, E.; Setser, K.; Bryson, R.W.; Saviola, A.J. Venom Ontogeny in the Mexican Lance-Headed Rattlesnake (Crotalus polystictus). Toxins 2018, 10, 271.

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