Biology subjects

Tarvin, R. D.

Publications and source records attributed to Tarvin, R. D..

13 recordsLinked to original sources

bioRxiv2026

Ingestion of the potent neurotoxin epibatidine does not compromise locomotion or behavior in the poison frog Epipedobates tricolor

Most organisms have evolved mechanisms to reduce the negative effects of toxins in their diet. Some animals that are toxin specialists, such as dendrobatid poison frogs, have amino acid substitutions in proteins targeted by the toxins that prevent or limit the toxins ability to bind and exert its bioactive effects. The Phantasmal poison frog, Epipedobates tricolor, has amino acid substitutions in its neuronal nicotinic acetylcholine receptors that were previously shown to provide resistance to the highly potent neurotoxin epibatidine in vitro. However, it is unclear whether E. tricolor resists the physiological effects of epibatidine in vivo. To investigate this, we examined the effects of epibatidine exposure on the locomotion and behavior of E. tricolor. We performed whole-animal performance assays and behavioral evaluations at multiple time points following the administration of high yet biologically relevant levels of epibatidine. These assays were followed by alkaloid quantification to track chemical concentrations in the skin. Epipedobates tricolor exhibited similar locomotor performance and behavior at both epibatidine doses compared to controls and regardless of the quantity of alkaloid accumulated into the skin. However, we observed an impact of low-percentage ethanol solutions on behavior when compared to water controls, as well as general impacts of handling stress (regardless of the administered solution type), which should be considered in future experimental designs. Overall, we demonstrate that E. tricolor likely avoids a physiological fitness trade-off between toxin ingestion and the defensive benefits of epibatidine sequestration. Our study suggests that the ability to ingest toxins involves multi-faceted resistance mechanisms. Highlights- Whole-animal performance assay shows no impact of epibatidine on frog behavior - Epipedobates tricolor is 20-5000 times more resistant to epibatidine than mice - Assays demonstrate that frogs are sensitive to 6% ethanol and handling stress

physiology↗

bioRxiv2026

Dorsal skin biopsies: A non-lethal sampling method for studying amphibians, including the highly endangered Harlequin frogs (Bufonidae: Atelopus)

Non-lethal sampling methods are increasingly essential for amphibian research as global declines intensify and many species persist in small, vulnerable populations. Skin biopsies offer a promising alternative to whole-animal collection and other minimally invasive approaches; however, systematic evaluations of recovery and impacts on body condition remain limited. Here, we assess the effects of small (2-mm) dorsal skin biopsies in four frog species, including three highly endangered Harlequin frogs (Atelopus bomolochos, A. balios, A. longirostris) and the Gualataco marsupial frog (Gastrotheca riobambae). Under controlled laboratory conditions and in semi-natural enclosures, we monitored wound healing, survival, and body mass trajectories in biopsied and control individuals over a one-month period. Across all species, biopsy sites fully healed within approximately three weeks, following consistent stages of re-epithelialization and subsequent repigmentation. No biopsy-related mortality was observed, and body mass did not differ between biopsied and control individuals, indicating no detectable effects of skin biopsies on body condition during the wound-healing period. Occasional minor post-biopsy reactions resolved without intervention within the observation period. We additionally report anecdotal field recovery observations for three other species (A. coynei, A. laetissimus, and A. sp. aff. longirostris), indicating survival and visible wound closure following release. Together, these results indicate that small dorsal skin biopsies represent a safe, non-lethal sampling method for amphibians, including highly endangered taxa. By providing sufficient tissue for diverse downstream applications--such as chemical analyses, genomics, transcriptomics, microbiome characterization, and disease detection--this approach expands the range of questions that can be addressed while minimizing harm to threatened species.

zoology↗

bioRxiv2025

Whole-genome analyses point to new candidate genes underlying aestivation in amphibians

When amphibians invaded the terrestrial realm, a strategy such as aestivation may have helped them to survive water and oxygen stress in the novel environment. In fact, aestivation appears to be an ancestral state in amphibians. We conducted a literature review about the genes previously linked to aestivation and then we searched for additional candidate genes related to the aestivation phenotype by comparing evolutionary rates of 13,578 genes in 31 amphibian species, including 10 aestivating species and 21 non-aestivating species. Based on the assumption that aestivation has two main requirements - a) metabolic regulation needed to control transitions to/from dormancy, and b) cell preservation strategies needed to sustain biological processes over long-term dormancy - we expected to find distinct relative evolutionary rates (RER) in genes related to those traits. We identified 323 genes with accelerated or decelerated RERs; these genes were enriched for some processes overlapping with our predictions and with literature findings, such as different modes of ATP production. Other genes related to protein and membrane trafficking (TRAPP, SNARE, and Arp2/3 protein complexes) are newly associated with aestivation. RER patterns suggest that aestivation in amphibians relies on a set of highly conserved core processes and other auxiliary processes that have diversified across the phylogeny. Given the vast number and diversity of aestivating amphibian lineages, we predict that more in-depth molecular studies of amphibian aestivation will offer novel insight into hypometabolic processes that could inspire medical innovations to prevent organ atrophy, address problems with angiogenesis, and combat processes underlying cancer.

evolutionary biology↗

bioRxiv2025

Slowing down: A macroevolutionary approach to the hypometabolic strategies of amphibians

The ability to survive harsh environmental conditions has probably been a key factor in the evolutionary success of organisms that cannot migrate long distances, such as amphibians. We expect that having a hypometabolic strategy (HS) --aestivation or hibernation-- to deal with severe climates, would be a plesiomorphic trait. We 1) inferred the ancestral state of a HS, using two phylogenies for amphibians, 2) tested if species with a HS have larger distributional ranges, and 3) explored how a HS may affect amphibian assemblage resilience using multiple models of climate change. Ancestral state reconstruction for the most recent common ancestor (MRCA) of Class Amphibia showed [~]50% probability of a HS. The probability was higher for the MRCA of each Order (>70%), suggesting a widespread HS in the ancestors of modern amphibians. Phylogenetic regressions showed no relation between the probability of having a HS and the distribution range size. Climate analyses predict that tropical zones will have the greatest change in climate, involving novel harsh seasonality. Since tropical amphibian assemblages have the lowest proportion of species with HS, they may be more vulnerable to climate change. It is probable that HS have been key for the evolutionary success in amphibians, and they will likely impact their future survival in the face of climate change. Despite the potential importance of the HS for amphibians, information was available for a diverse but only a small subset of species; we urge researchers to report data on aestivation or hibernation in amphibians to facilitate future studies.

evolutionary biology↗

bioRxiv2025

A subset of conserved phagocytic genes are likely used for the intracellular theft of cnidarian stinging organelles in nudibranch gastropods

BackgroundPhagocytosis is a universal physiological process in eukaryotes with many important biological functions. In nudibranch gastropods, a novel form of phagocytosis called nematocyst sequestration is specialized for the uptake of venomous stinging organelles stolen from their cnidarian prey. This process is highly selective. Here we use the emerging model nudibranch species Berghia stephanieae and Hermissenda opalescens to identify genes enriched within the body regions where nematocyst sequestration occurs, and investigate how the expression profile of phagocytosis, immune, and digestive genes differs between nematocyst sequestering regions relative to those where other phagocytic functions occur. ResultsWe identified 166 genes with significantly higher expression in sequestering regions in B. stephanieae, including genes associated with development, membrane transport, and metabolism. Of these, 41 overlap with transcripts upregulated in H. opalescens sequestering tissues. Using Hybridization Chain Reaction in situs, we show that at least two of these genes were localized to sequestering cells in B. stephanieae, including a putative C-type lectin receptor and a collagen. Genes annotated with phagocytosis, digestion, or immunity GO terms were often expressed in both sequestering and non-sequestering tissues, suggesting that they may also play a role in sequestration processes. ConclusionOur results suggest that phagocytosis genes likely play a role in the sequestration phenotype, and that a small subset of genes (e.g., collagen) may play unique functions yet to be uncovered. However, we also show that genes categorized in GO terms related to endocytosis, immunity, and digestion show a clear decrease in overall expression in sequestering tissues. This study lays the foundation for further inquiry into mechanisms of organelle sequestration in nudibranchs and other organisms.

evolutionary biology↗

bioRxiv2025

Caecilians maintain a functional long-wavelength-sensitive cone opsin gene despite signatures of relaxed selection and more than 200 million years of fossoriality

Vision is tuned to animals ecologies, evolving in response to specific light environments and visual needs. Transitions to fossorial lifestyles impose strong selective pressures favoring adaptations for underground life, such as increased skull ossification and reduced eye protrusion. Fossoriality may simultaneously relax constraints on vision leading to diminished visual capabilities. Caecilians (Gymnophiona)--specialized, fossorial amphibians--possess reduced eyes covered by skin or bone. For years, these traits, along with the presence of a single photoreceptor expressing one functional opsin gene, have been interpreted as evidence of limited vision, including an inability to focus or perceive color. Our results challenge these assumptions: we identified the long-wavelength-sensitive (LWS) opsin gene in 13 species of caecilians spanning 8 of 10 recognized families. Molecular evidence indicates that LWS is intact and transcribed in the eye of at least one species (Caecilia orientalis). However, the specific photoreceptor type expressing LWS remains uncertain, as our survey of cone phototransduction genes revealed a mosaic of losses, and anatomical observations from five families did not conclusively identify cone-like cells, though they revealed highly organized retinae even in families with vestigial eyes. Altogether, our results suggest that vision in caecilians may be underestimated and the role of light perception in their ecology is possible. TEASER TEXTThe colonization of low-light environments exerts selective pressure to enhance non-visual senses while relaxing selection on vision, often leading to opsin gene loss. We present compelling evidence for the retention of a cone opsin gene (LWS) in caecilians--a fossorial amphibian lineage with a 200-million-year history of burrowing and reduced eyes. Despite signs of relaxed selection, LWS appears functional, echoing patterns in other low-light-adapted vertebrates. Additionally, the loss of key cone phototransduction genes and absence of clear cone cells raises the possibility of LWS expression in rods or a functional change in its use. Our study provides an evolutionary framework for investigating LWS retention in fossorial vertebrates.

evolutionary biology↗

bioRxiv2024

Passive accumulation of alkaloids in putatively non-toxic frogs challenges paradigms of the origins of acquired chemical defenses

Understanding the origins of novel, complex phenotypes is a major goal in evolutionary biology. Poison frogs of the family Dendrobatidae have evolved the novel ability to acquire alkaloids from their diet for chemical defense at least three times. However, taxon sampling for alkaloids has been biased towards colorful species, without similar attention paid to inconspicuous ones that are often assumed to be undefended. As a result, our understanding of how chemical defense evolved in this group is incomplete. Here we provide new data showing that, in contrast to previous studies, species from each undefended poison frog clade have measurable yet low amounts of alkaloids. We confirm that undefended dendrobatids regularly consume mites and ants, which are known sources of alkaloids. Thus, our data suggest that diet is insufficient to explain the defended phenotype. Our data support the existence of a phenotypic intermediate between toxin consumption and sequestration -- passive accumulation -- that differs from sequestration in that it involves no derived forms of transport and storage mechanisms yet results in low levels of toxin accumulation. We discuss the concept of passive accumulation and its potential role in the origin of chemical defenses in poison frogs and other toxin-sequestering organisms. In light of ideas from pharmacokinetics we incorporate new and old data from poison frogs into an evolutionary model that could help explain the origins of acquired chemical defenses in animals and provide insight into the molecular processes that govern the fate of ingested toxins. ResumenComprender los origenes de fenotipos novedosos y complejos es un objetivo central en biologia evolutiva. Las ranas venenosas de la familia Dendrobatidae han desarrollado una novedosa habilidad para adquirir alcaloides de su dieta como defensas quimicas, al menos tres veces. Sin embargo, el muestreo de taxones en busca de alcaloides ha estado sesgado hacia las especies coloridas, sin prestar atencion similar a las poco conspicuas que a menudo se presume, no tienen defensas. Como resultado, nuestra comprension de como evolucionan las defensas quimicas en este grupo es incompleta. Aqui, proporcionamos nuevos datos que muestran que, en contraste con estudios anteriores, las especies de cada clado de ranas venenosas no defendidas tienen cantidades bajas pero cuantificables de alcaloides. Confirmamos que los dendrobatidos no defendidos consumen regularmente acaros y hormigas, que son fuentes conocidas de alcaloides. Por lo tanto, nuestros datos sugieren que la dieta es insuficiente para explicar el fenotipo defendido. Nuestros datos respaldan la existencia de un fenotipo intermedio entre consumo y secuestro de toxinas (acumulacion pasiva), que difiere del secuestro en que no implica formas derivadas de mecanismos de transporte y almacenamiento, pero da lugar a bajos niveles de acumulacion de toxinas. Discutimos el concepto de acumulacion pasiva y su potencial rol en el origen de defensas quimicas en ranas venenosas y otros organismos que secuestran toxinas. Considerando ideas de farmacocinetica, incorporamos datos nuevos y antiguos de ranas venenosas dentro de un modelo evolutivo que podria ayudar a explicar los origenes de defensas quimicas adquiridas en animales, y proporcionar una vision de los procesos moleculares que regulan el destino de las toxinas ingeridas.

evolutionary biology↗

bioRxiv2024

Honoring the Afro-Colombian musical culture with the naming of Epipedobates sp. nov. (Anura: Dendrobatidae), a frog from the Pacific rainforests

The number of amphibian species described yearly shows no signs of slowing down, especially in tropical regions, implying that the biodiversity of amphibians remains woefully underestimated. We describe a new species of poison frog from the Pacific lowlands of southwestern Colombia: Epipedobates currulao sp. nov., named for the Pacific music and dance genre known as bambuco viejo or currulao. This species inhabits lowland forests from 0-260 m a.s.l. This taxon differs from congeners by having a combination of bright yellow blotches in the dorsal anterior region of the thigh and upper arm, homogenous dark-brown dorsal coloration, and advertisement calls of long duration and many pulses. We also describe the courtship call of E. currulao, which is lower in frequency and shorter in duration than its advertisement call. Molecular phylogenetic analyses confirm the monophyly of the populations sampled and its position as the sister species of Epipedobates narinensis, which occurs in southwestern Colombia. Among species of Epipedobates, the new species has been previously confused with E. boulengeri, but we find that the two species are allopatric and represent two divergent clades (1.77% divergent for 12S-16S and 5.39% for CYTB). These species can be distinguished by the presence of a bright yellow blotch on the dorsal anterior region of the thigh and on the upper arm of E. currulao, blotches that are either more white than yellow or absent in E. boulengeri. In addition, the advertisement calls are distinct, with E. currulao having a single but long call in each call series while E. boulengeri has 2-6 calls in a series with each call being much shorter in length. Epipedobates currulao is the most northern species of Epipedobates, which extends southwards along the western edge of the Andes. Known as the Choco, this biogeographic region has been largely converted to agriculture in Ecuador and is experiencing widespread transformation in Colombia, which may endanger E. currulao and biodiversity in the region. A Spanish translation of the main text is available in the Supplementary Materials. ResumenEl numero de especies de anfibios descritas cada ano continua aumentando, especialmente en las regiones tropicales, lo que implica que la biodiversidad de anfibios sigue siendo subestimada. Describimos una nueva especie de rana venenosa de las tierras bajas del Pacifico del suroccidente de Colombia: Epipedobates currulao sp. nov., nombrada asi por el genero de musica y danza del Pacifico conocido como bambuco viejo o currulao. Las ranas de esta especie habitan en bosques de tierras bajas desde el nivel del mar hasta los 260 m. Este taxon se diferencia de sus congeneres por tener una combinacion de manchas amarillas brillantes en la region dorsal anterior del muslo y los brazos, una coloracion dorsal homogenea marron oscuro y cantos de advertencia mas largos y en consecuencia con mayor numero de pulsos. Tambien describimos la llamada de cortejo de E. currulao, con menor frecuencia pico y duracion que la llamada de advertencia. Los analisis filogeneticos confirman la monofilia de la especie y su posicion como hermana de Epipedobates narinensis, la cual se distribuye en el suroccidente de Colombia. Entre las especies de Epipedobates, la nueva especie ha sido previamente asignada a E. boulengeri, pero las dos especies son alopatricas y representan dos clados filogeneticamente divergentes (1.77% divergentes para 12S-16S y 5.39% para CYTB). Estas especies se pueden distinguir fenotipicamente por la presencia de una mancha amarilla brillante en la region dorsal anterior del muslo y en la parte superior del brazo en E. currulao, que son mas blancas que amarillas o estan ausentes en E. boulengeri. Ademas, los cantos de advertencia son distintos, E. currulao tiene una unica y larga llamada en una serie de llamadas, mientras que E. boulengeri tiene de 2 a 6 llamadas por serie, siendo cada llamada mucho mas corta. Epipedobates currulao es la especie distribuida mas al norte del genero Epipedobates, el cual se extiende hacia el sur a lo largo del flanco occidental de la cordillera de los Andes. Esta region conocida como el Choco biogeografico, ha sido fuertemente transformada por agricultura en Ecuador y esta experimentando una transformacion generalizada de sus bosques en Colombia, lo cual pone en peligro a E. currulao y toda su biodiversidad en un futuro cercano. Una traduccion al espanol del texto principal esta disponible en el material suplementario.

zoology↗

bioRxiv2023

Genome size evolution and phenotypic correlates in the poison frog family Dendrobatidae

Adaptive and neutral processes have produced a spectrum of genome sizes across organisms. Amphibians in particular possess a wide range in C-values, from <1 to over 125 pg. However, the genome size of most amphibians is unknown, and no single family has been comprehensively assessed. We provide new estimates for 32 poison frog species representing the major lineages within Dendrobatidae using Feulgen staining of museum specimens and flow cytometry of fresh tissue. We show that genome size in Dendrobatidae has likely evolved gradually, with potential evolutionary rate shifts in the genera Phyllobates and Hyloxalus, which respectively possess species with the largest (13.0 pg) and second smallest (2.6 pg) genomes in the family. Phylogenetically controlled regression analyses indicate that genome size is positively correlated with snout-vent-length, oocyte number, and clutch size, but negatively correlated with active metabolic rate and metabolic scope. While body size and metabolic rate are also correlates of toxicity, we found no relationship between genome size and evolution of chemical defense within Dendrobatidae. Genome size evolution in Dendrobatidae provides insight into the processes shaping genome size evolution over short timescales and establishes a novel system in which to study the mechanistic links between genome size and organismal physiology.

evolutionary biology↗

bioRxiv2023

Deep Divergences Among Cryptic Clades of Epipedobates Poison Frogs

Poison frogs (Dendrobatidae) are famous for their aposematic species, having a combination of diverse color patterns and defensive skin toxins, yet most species in this family are inconspicuously colored and considered non-aposematic. Epipedobates is among the youngest genus-level clades of Dendrobatidae that includes both aposematic and inconspicuous species. Using Sanger-sequenced mitochondrial and nuclear markers, we demonstrate deep genetic divergences among inconspicuous species of Epipedobates but relatively shallow genetic divergences among conspicuous species. Our phylogenetic analysis includes broad geographic sampling of the inconspicuous lineages typically identified as E. boulengeri and E. espinosai, which reveals two putative new species, one in west-central Colombia (E. sp. 1) and the other in north-central Ecuador (E. aff. espinosai). We conclude that E. darwinwallacei is a junior subjective synonym of E. espinosai. We also clarify the geographic distributions of inconspicuous Epipedobates species including the widespread E. boulengeri. We provide a qualitative assessment of the phenotypic diversity in each nominal species, with a focus on the color and pattern of inconspicuous species. We conclude that Epipedobates contains eight known valid species, six of which are inconspicuous. A relaxed molecular clock analysis suggests that the most recent common ancestor of Epipedobates is [~]11.1 million years old, which nearly doubles previous estimates. Last, genetic information points to a center of species diversity in the Choco at the southwestern border of Colombia with Ecuador. A Spanish translation this text is available in the supplementary materials on the publishers website (biorxiv does not allow posting in non-English languages).

evolutionary biology↗

bioRxiv2022

Diurnality shapes the visual opsin genes of colorful Neotropical frogs

Amphibians are ideal for studying visual system evolution because their biphasic (aquatic and terrestrial) life history and ecological diversity expose them to a broad range of visual conditions. Here we evaluate signatures of selection on visual opsin genes across Neotropical anurans and focus on three diurnal clades that are well-known for the concurrence of conspicuous colors and chemical defense (i.e., aposematism): poison frogs (Dendrobatidae), Harlequin toads (Bufonidae: Atelopus), and pumpkin toadlets (Brachycephalidae: Brachycephalus). We found evidence of positive selection on 44 amino acid sites in LWS, SWS1, SWS2, and RH1 opsin genes, of which one in LWS and two in RH1 have been previously identified as spectral tuning sites in other vertebrates. Given that anurans have mostly nocturnal habits, the patterns of selection revealed new sites that might be important in spectral tuning for frogs, potentially for adaptation to diurnal habits and for color-based intraspecific communication. Furthermore, we provide evidence that SWS2, normally expressed in rod cells in amphibians, has likely been lost in the ancestor of Dendrobatidae, suggesting that under low-light levels, dendrobatids have inferior wavelength discrimination compared to other frogs. This loss might follow the origin of diurnal activity in dendrobatids and could have implications for their chemical ecology, biodiversity, and behavior. Our analyses show that assessments of opsin diversification in understudied groups could expand our understanding of the role of sensory system evolution in ecological adaptation.

evolutionary biology↗

bioRxiv2022

Characterizing Potential Tetrodotoxin Resistance in Domain IV of the Voltage-Gated Sodium Channel Nav1.4 of Pacific Chorus Frogs, Pseudacris regilla

Animals that frequently encounter toxins often select for mechanisms of toxin resistance. Both predators that consume toxic prey and organisms in physical contact with a toxin or pollutant in their environment may experience natural selection for resistance. Based on field observations that Pacific Chorus Frogs (Pseudacris regilla) sometimes eat and mistakenly amplect tetrodotoxin (TTX)-defended Taricha newts, we predicted that P. regilla may possess resistance to TTX. We tested this prediction by comparing the amino acid sequences of the molecular target of TTX, the muscle voltage-gated sodium channel gene SCN4A (NaV1.4), in populations of P. regilla that are sympatric and allopatric with Taricha. We identified a single substitution in NaV1.4 of P. regilla in a conserved site near the pore loop where TTX binds. Although the role of this site in TTX resistance has not been functionally assessed, both allopatric and sympatric P. regilla had this substitution, suggesting that it may be unrelated to TTX exposure from Taricha. Thus, there is no conclusive evidence that P. regilla has selected for TTX resistance encoded by amino acid substitutions in this domain. In addition, California occurrence data from the last 50 years indicate that Taricha activity peaks in January while the activity of P. regilla peaks in April. These relatively distinct activity patterns suggest that P. regilla may not be exposed to levels of TTX from Taricha that are high enough to select for mutations in the sodium channel. Nevertheless, other unidentified mechanisms of TTX resistance could be present in P. regilla and other species that are sympatric with toxic newts. ResumenLos animales que tienen contacto frecuente con toxinas suelen desarrollar mecanismos de resistencia a las mismas. Tanto los depredadores que consumen presas toxicas como los organismos en contacto cercano con una toxina o contaminante en su entorno pueden experimentar una presion de seleccion que los lleva a evolucionar resistencia a toxinas. Basandose en las observaciones de que las ranas coro del Pacifico (Pseudacris regilla) a veces comen por error y/o amplexan salamandras del genero Taricha que poseen tetrodotoxina (TTX), se planteo la hipotesis de que P. regilla podria poseer resistencia a la TTX. Esta prediccion fue probada comparando las secuencias de aminoacidos en el loop del poro del dominio IV en el gen del canal de sodio voltaje dependiente muscular SCN4A (proteina NaV1.4) en poblaciones de P. regilla que son simpatricas y alopatricas con Taricha. Se identifico una unica sustitucion en el NaV1.4 de P. regilla en un sitio conservado cerca del loop del poro donde se une la TTX. Aunque el papel de este sitio en la resistencia a la TTX no ha sido evaluado funcionalmente, tanto el P. regilla alopatrico como el simpatrico tienen esta sustitucion, lo que sugiere que no esta relacionado con la exposicion a la TTX secretada por Taricha. Por lo tanto, no hay evidencias concluyentes de que P. regilla haya evolucionado resistencia a la TTX por medio de sustituciones de aminoacidos en este dominio. Por otro lado, los datos de ocurrencia en California de la actividad de Taricha en los ultimos 50 anos indican alcanza su maximo en enero, mientras que la de P. regilla lo hace en abril. Estos patrones de actividad relativamente distintos sugieren que P. regilla puede no estar expuesta a niveles de TTX provenientes de Taricha que sean lo suficientemente altos como para inducir la evolucion de mutaciones en el canal de sodio. Sin embargo, otros mecanismos no identificados de resistencia a la TTX podrian estar presentes en P. regilla y en otras especies simpaticas a los salamandras toxicas. Palabras clave: Resistencia a las toxinas; California; Toxinas ambientales; Insensibilidad en el sitio de union; Salamandras; Ecologia quimica

evolutionary biology↗

bioRxiv2021

Toxin breakdown does not preclude the potential for defensive toxin use in a fruit fly

Animals that ingest toxins can become unpalatable and even toxic to predators and parasites through toxin sequestration. Because most animals rapidly eliminate toxins to survive their ingestion, it is unclear how populations transition from susceptibility and toxin elimination to tolerance and accumulation as chemical defense emerges. Studies of chemical defense have generally focused on species with active toxin sequestration and target-site insensitivity mutations or toxin-binding proteins that permit survival without necessitating toxin elimination. Here, we investigate whether animals that presumably rely on toxin elimination for survival can utilize ingested toxins for defense. We use the A4 and A3 Drosophila melanogaster fly strains from the Drosophila Synthetic Population Resource (DSPR), which respectively possess elevated and reduced metabolic nicotine resistance amongst DSPR fly lines. We find that ingesting nicotine increased A4 but not A3 fly survival against Leptopilina heterotoma wasp parasitism.Further, we find that despite possessing genetic variants that enhance toxin elimination, A4 flies accrued more nicotine than A3 individuals likely by consuming more media. Our results suggest that enhanced toxin metabolism can allow for greater toxin intake by offsetting the cost of toxin ingestion. Passive toxin accumulation that accompanies increased toxin intake may underlie the early origins of chemical defense.

evolutionary biology↗