Salazar Valenzuela, David
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Salazar Valenzuela, David
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Quito
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davidsalazar@uti.edu.ec
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26644312900

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Feeding ecology of the Terciopelo pit viper snake (Bothrops asper) in Ecuador

2023 , Loaiza-Lange A. , Székely D , Torres-Carvajal O. , Tinoco N. , Salazar Valenzuela, David , Székely P.

Thoroughly documenting prey items and diet composition is crucial for understanding a predator’s role in the ecosystem. In gape restricted predators, such as snakes, documenting and analyzing the type and size of the prey is important to interpret their ecological role. We describe the diet patterns of a species of venomous snake, the Terciopelo pit viper (Bothrops asper), from its Ecuadorian populations. Examining the gastrointestinal contents of museum specimens collected over an extensive area of the Pacific lowlands of Ecuador, we encountered 69 identifiable prey items from four major taxonomic groups (amphibians, centipedes, mammals, and reptiles). We evaluated the observed composition of prey to check for differences between sexes and size-classes. To complement our observations of the Terciopelo species complex throughout their distribution, we carried out a systematic literature review. Our data show an ontogenetic shift in diet, with a transition from more diverse diet in juveniles towards a mammal-specialized diet in adults, and distinct proportion of prey taxa between the sexes in the juvenile size class. Copyright 2023 Loaiza-Lange et al.

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Harlequin frog rediscoveries provide insights into species persistence in the face of drastic amphibian declines

2022 , Jaynes, K.E. , Páez-Vacas, M.I. , Salazar Valenzuela, David , Guayasamin, J.M. , Terán-Valdez, A. , Siavichay, F.R. , Fitzpatrick, S.W.

Amphibians face global declines, and it remains unclear the extent to which species have responded, and through what mechanisms, to persist in the face of emerging diseases and climate change. In recent years, the rediscovery of species considered possibly extinct has sparked public and scientific attention. These are hopeful cases in an otherwise bleak story. Yet, we know little about the population status of these rediscovered species, or the biology underlying their persistence. Here, we highlight the iconic Harlequin frogs (Bufonidae: Atelopus) as a system that was devastated by declines but now encompasses between 18 and 32 rediscoveries (25–37 % of possible extinctions) in the last two decades. Geographic distributions of rediscoveries closely match regional described species abundance, and rediscoveries are documented at elevations from 100 m to >3500 m, with no significant differences between mean historical and contemporary elevations. We also provide genomic data on six decimated species, with historical sample comparisons for two of the species and find a pattern of decreasing genetic variation the longer a species had been missing. Further, we document marked decrease in heterozygosity in one species, but not the other, indicating potential idiosyncratic consequences of declines. Finally, we discuss research priorities to guide the potential transition from amphibian declines to recoveries and to maximize conservation efforts. © 2022 The Authors

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A new species of pitviper of the genus Bothrops (Serpentes: Viperidae: Crotalinae) from the Central Andes of South America

2019 , Timms J. , Chaparro J.C. , Venegas P.J. , Salazar Valenzuela, David , Scrocchi G. , Cuevas J. , Leynaud G. , Carrasco P.A.

We describe a new species of montane pitviper of the genus Bothrops from the Cordillera Oriental of the Central Andes, distributed from southern Peru to central Bolivia. The new species can be distinguished from its congeners by the characteristic combination of a dorsal body color pattern consisting of triangular or subtriangular dark brown dorsal blotches, paired dark brown parallel occipital stripes, a conspicuous dark brown postocular stripe, the presence of canthorostrals in some specimens, prelacunal fused or partially fused with second supralabial, one scale usually separating internasals, rostral trapezoidal, two canthals oval to rounded, similar size or slightly larger than internasals, three or four medial intercanthals, eight to twelve intersupraoculars, intercanthals and intersupraoculars keeled and frequently slightly keeled, supraoculars oval, one to three suboculars, two to three postoculars, loreal subtriangular, two to six prefoveals, subfoveals absent, two or none postfoveals, one or two scales between suboculars and fourth supralabial, seven or eight supralabials, nine or eleven infralabials, 23-25 middorsal scales, 189-195 ventrals in females and 182-190 in males, 48-58 subcaudals in females and 54-63 in males, exceptionally undivided. The new species is apparently restricted to areas within Andean montane forests that are less humid and devoid of large trees. Copyright © 2019 Magnolia Press.

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A First Look at the Inhibitory Potential of Urospatha sagittifolia (Araceae) Ethanolic Extract for Bothrops atrox Snakebite Envenomation

2022 , Vera-Palacios, A.L. , Sacoto-Torres, J.D. , Hernández-Altamirano, J.A. , Moreno, A. , Peñuela-Mora, M.C. , Salazar Valenzuela, David , Mogollón, N.G.S. , Almeida, J.R.

Bothrops atrox snakebites are a relevant problem in the Amazon basin. In this biodiverse region, the ethnomedicinal approach plays an important role as an alternative to antivenom therapy. Urospatha sagittifolia (Araceae) is a plant used for this purpose; however, its neutralizing properties have not been scientifically accessed. To fill this gap, we investigated the ability of U. sagittifolia to modulate the catalytic activity of Bothrops atrox venom, and their toxic consequences, such as local damage and lethality. The venom profile of B. atrox was assessed by chromatography and electrophoresis. Inhibition of the three main enzymatic and medically important toxins from the venom was evaluated using synthetic substrates and quantified by chromogenic activity assays. Additionally, the neutralization of lethality, hemorrhage and edema were investigated by in vivo assays. The possible interactions between venom proteins and plant molecules were visualized by polyacrylamide gel electrophoresis. Finally, the phytochemical constituents present in the ethanolic extract were determined by qualitative and quantitative analyses. The ethanolic extract reduced the activity of the three main enzymes of venom target, achieving ranges from 19% to 81% of inhibition. Our in vivo venom neuralizations assays showed a significant inhibition of edema (38.72%) and hemorrhage (42.90%). Additionally, lethality was remarkably counteracted. The highest extract ratio evaluated had a 75% survival rate. Our data support the biomedical value of U. sagittifolia as a source of natural enzyme inhibitors able to neutralize catalytically active B. atrox venom toxins and their toxic effects. © 2022 by the authors.

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Bothrops atrox from Ecuadorian Amazon: Initial analyses of venoms from individuals

2021 , Patiño R.S.P. , Salazar Valenzuela, David , Medina-Villamizar E. , Mendes B. , Proaño-Bolaños C. , da Silva S.L. , Almeida J.R.

Bothrops atrox is the most clinically relevant snake species within the Amazon region, which includes Ecuadorian territories. It comprises a large distribution, which could contribute to the genetic and venomic variation identified in the species. The high variability and protein isoform diversity of its venom are of medical interest, since it can influence the clinical manifestations caused by envenomation and its treatment. However, in Ecuador there is insufficient information on the diversity of venomic phenotypes, even of relevant species such as B. atrox. Here, we characterized the biochemical and toxicological profiles of the venom of six B. atrox individuals from the Ecuadorian Amazon. Differences in catalytic activities of toxins, elution profiles in liquid chromatography, electrophoretic patterns, and toxic effects among the analyzed samples were identified. Nonetheless, in the preclinical testing of antivenom, two samples from Mera (Pastaza) required a higher dose to achieve total neutralization of lethality and hemorrhage. Taken together, these data highlight the importance of analyzing individual venoms in studies focused on the outcomes of envenoming. © 2021 Elsevier Ltd

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Resistance Is Not Futile: Widespread Convergent Evolution of Resistance to Alpha-Neurotoxic Snake Venoms in Caecilians (Amphibia: Gymnophiona)

2023 , Mancuso M. , Zaman S. , Maddock S.T. , Kamei R.G. , Salazar Valenzuela, David , Wilkinson M. , Roelants K. , Fry B.G.

Predatory innovations impose reciprocal selection pressures upon prey. The evolution of snake venom alpha-neurotoxins has triggered the corresponding evolution of resistance in the post-synaptic nicotinic acetylcholine receptors of prey in a complex chemical arms race. All other things being equal, animals like caecilians (an Order of legless amphibians) are quite vulnerable to predation by fossorial elapid snakes and their powerful alpha-neurotoxic venoms; thus, they are under strong selective pressure. Here, we sequenced the nicotinic acetylcholine receptor alpha-1 subunit of 37 caecilian species, representing all currently known families of caecilians from across the Americas, Africa, and Asia, including species endemic to the Seychelles. Three types of resistance were identified: (1) steric hindrance from N-glycosylated asparagines; (2) secondary structural changes due to the replacement of proline by another amino acid; and (3) electrostatic charge repulsion of the positively charged neurotoxins, through the introduction of a positively charged amino acid into the toxin-binding site. We demonstrated that resistance to alpha-neurotoxins convergently evolved at least fifteen times across the caecilian tree (three times in Africa, seven times in the Americas, and five times in Asia). Additionally, as several species were shown to possess multiple resistance modifications acting synergistically, caecilians must have undergone at least 20 separate events involving the origin of toxin resistance. On the other hand, resistance in non-caecilian amphibians was found to be limited to five origins. Together, the mutations underlying resistance in caecilians constitute a robust signature of positive selection which strongly correlates with elapid presence through both space (sympatry with caecilian-eating elapids) and time (Cenozoic radiation of elapids). Our study demonstrates the extent of convergent evolution that can be expected when a single widespread predatory adaptation triggers parallel evolutionary arms races at a global scale. © 2023 by the authors.

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Divergence of tropical pitvipers promoted by independent colonization events of dry montane Andean habitats

2019 , Salazar Valenzuela, David , Kuch U. , Torres-Carvajal O. , Valencia J.H. , Gibbs H.L.

Aim: A poorly explored feature of the origin and maintenance of Neotropical biodiversity is how the evolutionary dynamics of colonization and differentiation in relation to lowland and highland habitats has impacted lineage formation. Most speciation models for this region have focused on vicariant events, whereas the need to assess the influence of demographic processes has been recognized only recently. We evaluate if the origin of Andean montane lineages of terciopelo pitvipers is explained by either of two historical processes that represent distinct phylogeographic mechanisms: differentiation by isolation within the highlands or different dispersal events from the lowlands. Location: Western Ecuador. Taxon: Terciopelo pitvipers (Bothrops asper species complex). Methods: We use genomic data and genetic clustering analyses, evaluation of historical migration between genetic clusters and demographic model selection to investigate recent diversification events in South America using a vertebrate group rarely explored in phylogeographic studies: tropical Andean snakes. Specifically, the origin of two Ecuadorian montane lineages of terciopelo pitvipers was evaluated given ambiguous phylogenetic relationships with the presumably ancestral Pacific lowland lineage. Results: Discrepancies of evolutionary relationships previously obtained with tree-like methods are resolved through the use of modelling approaches. We found strong support for the independent origin of montane lineages based on topologies inferred by maximum-likelihood trees and modelling approaches that take into account possible gene flow. This suggests dispersal rather than in-situ differentiation as the most likely mechanism by which the montane linages originated. Main conclusions: Recent large-scale studies have found support for identifying dispersal events as important drivers of diversification in the Neotropical region. We contribute to these ideas by identifying a fine-scale case in a rarely studied group of animals -Andean snakes- in which river valleys acted as an entrance for the upward colonization of montane dry habitats and subsequent ecological diversification. © 2019 John Wiley & Sons Ltd

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Evaluating the utility of camera traps in field studies of predation

2019 , Akcali C.K. , Pérez-Mendoza H.A. , Salazar Valenzuela, David , Kikuchi D.W. , Guayasamin, Juan M. , Pfennig D.W.

Artificial prey techniques-wherein synthetic replicas of real organisms are placed in natural habitats-are widely used to study predation in the field.We investigated the extent to which videography could provide additional information to such studies. As a part of studies on aposematism and mimicry of coral snakes (Micrurus) and their mimics, observational data from 109 artificial snake prey were collected from video-recording camera traps in three locations in the Americas (terra firme forest, Tiputini Biodiversity Station, Ecuador; premontane wet forest, Nahá Reserve, Mexico; longleaf pine forest, Southeastern Coastal Plain, North Carolina, USA). During 1,536 camera days, a total of 268 observations of 20 putative snake predator species were recorded in the vicinity of artificial prey. Predators were observed to detect artificial prey 52 times, but only 21 attacks were recorded. Mammals were the most commonly recorded group of predators near replicas (243) and were responsible for most detections (48) and attacks (20). There was no difference between avian or mammalian predators in their probability of detecting replicas nor in their probability of attacking replicas after detecting them. Bite and beak marks left on clay replicas registered a higher ratio of avian:mammalian attacks than videos registered. Approximately 61.5% of artificial prey monitored with cameras remained undetected by predators throughout the duration of the experiments. Observational data collected from videos could provide more robust inferences on the relative fitness of different prey phenotypes, predator behavior, and the relative contribution of different predator species to selection on prey. However, we estimate that the level of predator activity necessary for the benefit of additional information that videos provide to be worth their financial costs is achieved in fewer than 20% of published artificial prey studies. Although we suggest future predation studies employing artificial prey to consider using videography as a tool to inspire new, more focused inquiry, the investment in camera traps is unlikely to be worth the expense for most artificial prey studies until the cost:benefit ratio decreases. © 2019 PeerJ Inc. All rights reserved.

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Systematics of south american snail-eating snakes (Serpentes, dipsadini), with the description of five new species from ecuador and peru

2018 , Arteaga A. , Salazar Valenzuela, David , Mebert K. , Peñafiel N. , Aguiar G. , Sánchez-Nivicela J.C. , Alexander Pyron R. , Colston T.J. , Cisneros-Heredia D.F. , Yánez-Muñoz M.H. , Venegas P.J. , Guayasamin, Juan M. , Torres-Carvajal O.

A molecular phylogeny of the Neotropical snail-eating snakes (tribe Dipsadini) is presented including 43 (24 for the first time) of the 77 species, sampled for both nuclear and mitochondrial genes. Morphological and phylogenetic support was found for four new species of Dipsas and one of Sibon, which are described here based on their unique combination of molecular, meristic, and color pattern characteristics. Sibynomorphus is designated as a junior subjective synonym of Dipsas. Dipsas latifrontalis and D. palmeri are resurrected from the synonymy of D. peruana. Dipsas latifasciata is transferred from the synonymy of D. peruana to the synonymy of D. palmeri. A new name, D. jamespetersi, is erected for the taxon currently known as Sibynomorphus petersi. Re-descriptions of D. latifrontalis and D. peruana are presented, as well as the first photographic voucher of an adult specimen of D. latifrontalis, along with photographs of all known Ecuadorian Dipsadini species. The first country record of D. variegata in Ecuador is provided and D. oligozonata removed from the list of Peruvian herpetofauna. With these changes, the number of Dipsadini reported in Ecuador increases to 22, 18 species of Dipsas and four of Sibon. © 2018, Pensoft Publishers. All rights reserved.

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A mouth full of blood – autohaemorrhaging in three Ecuadorian snakes (Squamata: Colubridae & Tropidophiidae)

2023 , Rödel M.-O. , Loaiza-Lange A. , Penner J. , Neira-Salamea K.D. , Salazar Valenzuela, David

[No abstract available]

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