Cane toads (Rhinella marina) rely on water access, not drought tolerance, to invade xeric Australian environments

Brusch, George A.; Christian, Keith A.; Brown, Gregory P.; Shine, Richard; DeNardo, Dale F.

doi:10.1007/s00442-018-4321-1

Cited by 11 publications

(11 citation statements)

References 77 publications

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“…To date, the link between dehydration and enhanced humoral immunocompetence has been documented in studies focused on individual species of reptiles that live in areas that experience an extended seasonal drought (Brusch & DeNardo, 2017; Brusch et al, 2017, 2019; Moeller et al, 2013). Ours is the first study to explore how a community of mesic‐adapted snakes responds to dehydration, and our results are consistent with previous work: dehydration enhances multiple aspects of humoral immunity (Figure 2a).…”

Section: Discussionmentioning

confidence: 99%

“…Regardless of seasonal differences, we found that plasma osmolality across a community was positively correlated with multiple metrics of humoral immunocompetence (Figure 2b) as expected for our second aim (positive association between dehydration and immunity). There is now a growing body of evidence documenting a link between dehydration (i.e., hyperosmolality) and enhanced humoral immunocompetence that is (a) not the result of increased immune factor concentrations due to lower plasma volume, (b) rapidly reversible upon rehydration, and (c) found in a variety of taxa and life history stages (Brusch & DeNardo, 2017, 2019; Brusch et al, 2017, 2019; Moeller et al, 2013; this study). Additionally, our study provides the first link between dehydration and cellular immunocompetence (Figure 2b), which is an important step to further understanding the link between dehydration and the immune system.…”

Section: Discussionmentioning

confidence: 99%

“…Second, we determined the relationship between hydration state and immune function in this community. Here, we predicted that dehydration (i.e., elevated plasma osmolality) would be positively correlated with humoral and cellular immunocompetence ( sensu Brusch & DeNardo, 2017; Brusch et al, 2017, 2019; Moeller et al, 2013). Third, we explored the relationship between parasite burden and immune function in this community given the strong interdependence of parasites and the immune systems of their hosts (reviewed in Graham, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The ability of an organism to mount a normal response to an antigen (i.e., immunocompetence) has been shown to fluctuate with environmental conditions and throughout ontogeny (Bakar et al, 2016; Love, Salvante, Dale, & Williams, 2008; Nelson & Demas, 1996; Sandland & Minchella, 2003). For example, empirical evidence suggests that season, sex, and hydration can all lead to inter‐ and intra‐individual variation in immunocompetence (Brusch, Christian, Brown, Shine, & DeNardo, 2019; Kelly, Stoehr, Nunn, Smyth, & Prokop, 2018; Walton, Weil, & Nelson, 2011; Zhang, Jin, Qu, & Caviedes‐Vidal, 2017). Despite previous research detailing the internal and external conditions which influence the immune system, there remain substantial gaps in our understanding of the biotic and abiotic factors that influence different components of the immune system in ecologically relevant contexts, including in free‐ranging animals (Viney, Riley, & Buchanan, 2005).…”

Section: Introductionmentioning

confidence: 99%

“…Recent work has demonstrated a link between dehydration and immune function in selected squamate reptiles. Notably, aspects of plasma‐based, innate immunity (i.e., humoral immunity) are enhanced in response to dehydration, at least for the squamates studied to date that are adapted to seasonal droughts (Gila monsters: Moeller, Butler, & DeNardo, 2013; rattlesnakes: Brusch & DeNardo, 2017; Children's pythons: Brusch, Billy, Blattman, & DeNardo, 2017; water pythons: Brusch et al, 2019). However, it is unknown (a) how leukocytes (i.e., cellular immunity) or parasite burden respond to an animal's hydric state, and (b) whether dehydration‐based immunoenhancement can be captured across a community, rather than solely on a species‐specific level as has been previously documented.…”

Section: Introductionmentioning

confidence: 99%

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Dehydration enhances cellular and humoral immunity in a mesic snake community

et al. 2020

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The immunocompetence of a community of free-living animals can be affected by seasonality, sex, and parasite burden. However, each of these factors is often examined independently. Recent studies have also found that dehydration can enhance aspects of immunocompetence in drought-adapted species. To explore how all of these factors interact, and their effect on the immune system in mesic-adapted species, we collected blood samples from a community of free-ranging snakes in coastal South Carolina, United States, across 2 years. We specifically examined (a) how sex and seasonality influence humoral and cellular immunocompetence and parasite burden, (b) the dynamics among hydration state, parasite burden, and immunocompetence, and (c) whether mesic-adapted species also show enhanced innate immunity with dehydration. Consistent with previous work on drought-adapted species, we found that dehydration enhances multiple aspects of humoral immunity in mesic species, and we are the first to report that dehydration also enhances aspects of cellular immunocompetence. Contrary to previous results in other squamates, sex and season did not impact immunocompetence or parasite prevalence.Our results also reveal complex interactions among parasite prevalence, immunocompetence, and hydration state demonstrating that hydration state and parasitism are two ubiquitous factors that should continue to be considered in future studies examining ecoimmunological variation. K E Y W O R D S ecoimmunology, hydration, immunocompetence, osmotic stress, parasitemia

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dehydration enhances cellular and humoral immunity in a mesic snake community

et al. 2020

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Invading nonnative frogs use different microhabitats and change physiology along an elevation gradient

Marchetti,

French,

Virgin

et al. 2023

J Exp Zool Pt A

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The coqui frog (Eleutherodactylus coqui) was introduced to the island of Hawai'i in the 1980s, and has spread across much of the island. There is concern they will invade higher elevation areas where negative impacts on native species are expected. It is not known if coqui change behavior and baseline physiology in ways that allow them to invade higher elevations. We investigated where coqui are found across the island and whether that includes recent invasion into higher elevations. We also investigated whether elevation is related to coqui's microhabitat use, including substrate use and height off the forest floor, and physiological metrics, including plasma osmolality, oxidative status, glucose, free glycerol, and triglycerides, that might be associated with invading higher elevations. We found coqui have increased the area they occupy along roads from 31% to 50% and have moved into more high‐elevation locations (16% vs. 1%) compared to where they were found 14 years ago. We also found frogs at high elevation on different substrates and closer to the forest floor than frogs at lower elevations—perhaps in response to air temperatures which tended to be warmer close to the forest floor. We observed that blood glucose and triglycerides increase in frogs with elevation. An increase in glucose is likely an acclimation response to cold temperatures while triglycerides may also help frogs cope with the energetic demands of suboptimal temperatures. Finally, we found that female coqui have higher plasma osmolality, reactive oxygen metabolites (dROMs), free glycerol, and triglycerides than males. Our study suggests coqui behavior and physiology in Hawai'i may be influenced by elevation in ways that allow them to cope with lower temperatures and invade higher elevations.

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Challenges of dehydration result in a behavioral shift in invasive toads

Madelaire

Barsotti

Wagener

et al. 2020

Behav Ecol Sociobiol

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The adaptive nature of invasive species facilitates their survival in conditions that differ markedly from their native range. Behavioral changes in invasive populations are poorly explored but offer a wide potential when combined with physiological traits. For amphibians invading xeric habitats, finding water is important to function optimally and avoid dehydration. The waterfinding hypothesis postulates that survival can be enhanced through the increased behavioral ability to find water. We tested the water-finding hypothesis in guttural toads (Sclerophrys gutturalis) from their native range and an invasive population. Additionally, we tested if artificially elevated corticosterone levels, which increase during dehydration, affect behavioral traits linked to water balance. In a labyrinth experiment, we observed the toads' ability to find water in different hydration states (100%, 90%, and 80%). We found that individuals from the invasive population took longer to engage in water-searching behavior and spent more time close to the water source after finding it. Toads from the invasive population were also more active, and at 90% hydration, their attempts to find water increased. Moreover, artificially increasing corticosterone in fully hydrated invasive toads increased water-finding success. Our experiments demonstrated that invasive toads show water-conservation behaviors that can optimize water balance and might facilitate survival in an invaded xeric environment. Additionally, we suggest a link between elevated corticosterone levels and water-finding success. Our results lend support to the importance of behavior in successful invasions and the modulation of water-finding behavior by corticosterone. Significant statementInvasion success is associated with behavioral and physiological adaptations of invasive species. For anuran species invading xeric habitats, the ability to find water is an important behavioral trait. Using a labyrinth experiment and toads (Sclerophrys gutturalis) dehydrated at different levels, we observed that individuals invading a hydric challenging habitat showed advantageous water-conservation behaviors (e.g., taking longer to engage in water-searching behavior and spent more time close to the water source after finding it) compared to toads from the native range. Transdermal treatment with corticosterone, a hormone that increases its plasma concentrations under dehydration, increased success of finding water in 100% hydrated animals. Our results indicate that, compared to the native population, invasive toads display water-conservation behaviors that might improve survival rates in a novel xeric environment and that experimental corticosterone elevation modulates this water-finding behavior.

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Cane toads (Rhinella marina) rely on water access, not drought tolerance, to invade xeric Australian environments

Cited by 11 publications

References 77 publications

Dehydration enhances cellular and humoral immunity in a mesic snake community

Dehydration enhances cellular and humoral immunity in a mesic snake community

Invading nonnative frogs use different microhabitats and change physiology along an elevation gradient

Challenges of dehydration result in a behavioral shift in invasive toads

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