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1.
Sci Rep ; 11(1): 4427, 2021 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-33627747

RESUMO

Complete functional descriptions of the induction sequences of phenotypically plastic traits (perception to physiological regulation to response to outcome) should help us to clarify how plastic responses develop and operate. Ranid tadpoles express several plastic antipredator traits mediated by the stress hormone corticosterone, but how they influence outcomes remains uncertain. We investigated how predator-induced changes in the tail morphology of wood frog (Rana sylvatica) tadpoles influenced their escape performance over a sequence of time points when attacked by larval dragonflies (Anax junius). Tadpoles were raised with no predator exposure, chemical cues of dragonflies added once per day, or constant exposure to caged dragonflies crossed with no exogenous hormone added (vehicle control only), exogenous corticosterone, or metyrapone (a corticosteroid synthesis inhibitor). During predation trials, we detected no differences after four days, but after eight days, tadpoles exposed to larval dragonflies and exogenous corticosterone had developed deeper tail muscles and exhibited improved escape performance compared to controls. Treatment with metyrapone blocked the development of a deeper tail muscle and resulted in no difference in escape success. Our findings further link the predator-induced physiological stress response of ranid tadpoles to the development of an antipredator tail morphology that confers performance benefits.

2.
Sci Total Environ ; 747: 141112, 2020 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-32791405

RESUMO

How anticipated climate change might affect long-term outcomes of present-day agricultural conservation practices remains a key uncertainty that could benefit water quality and biodiversity conservation planning. To explore this issue, we forecasted how the stream fish communities in the Western Lake Erie Basin (WLEB) would respond to increasing amounts of agricultural conservation practice (ACP) implementation under two IPCC future greenhouse gas emission scenarios (RCP4.5: moderate reductions; RCP8.5: business-as-usual conditions) during 2020-2065. We used output from 19 General Circulation Models to drive linked agricultural land use (APEX), watershed hydrology (SWAT), and stream fish distribution (boosted regression tree) models, subsequently analyzing how projected changes in habitat would influence fish community composition and functional trait diversity. Our models predicted both positive and negative effects of climate change and ACP implementation on WLEB stream fishes. For most species, climate and ACPs influenced species in the same direction, with climate effects outweighing those of ACP implementation. Functional trait analysis helped clarify the varied responses among species, indicating that more extreme climate change would reduce available habitat for large-bodied, cool-water species with equilibrium life-histories, many of which also are of importance to recreational fishing (e.g., northern pike, smallmouth bass). By contrast, available habitat for warm-water, benthic species with more periodic or opportunistic life-histories (e.g., northern hogsucker, greater redhorse, greenside darter) was predicted to increase. Further, ACP implementation was projected to hasten these shifts, suggesting that efforts to improve water quality could come with costs to other ecosystem services (e.g., recreational fishing opportunities). Collectively, our findings demonstrate the need to consider biological outcomes when developing strategies to mitigate water quality impairment and highlight the value of physical-biological modeling approaches to agricultural and biological conservation planning in a changing climate.


Assuntos
Ecossistema , Rios , Agricultura , Animais , Mudança Climática , Conservação dos Recursos Naturais , Hidrologia
3.
PLoS One ; 10(3): e0120752, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25799555

RESUMO

We provide a novel method to improve the use of natural tagging approaches for subpopulation discrimination and source-origin identification in aquatic and terrestrial animals with a passive dispersive phase. Our method integrates observed site-referenced biological information on individuals in mixed populations with a particle-tracking model to retrace likely dispersal histories prior to capture (i.e., particle backtracking). To illustrate and test our approach, we focus on western Lake Erie's yellow perch (Perca flavescens) population during 2006-2007, using microsatellite DNA and otolith microchemistry from larvae and juveniles as natural tags. Particle backtracking showed that not all larvae collected near a presumed hatching location may have originated there, owing to passive drift during the larval stage that was influenced by strong river- and wind-driven water circulation. Re-assigning larvae to their most probable hatching site (based on probabilistic dispersal trajectories from the particle backtracking model) improved the use of genetics and otolith microchemistry to discriminate among local breeding subpopulations. This enhancement, in turn, altered (and likely improved) the estimated contributions of each breeding subpopulation to the mixed population of juvenile recruits. Our findings indicate that particle backtracking can complement existing tools used to identify the origin of individuals in mixed populations, especially in flow-dominated systems.


Assuntos
Cruzamento , Percas/fisiologia , Distribuição Animal , Animais , Técnicas de Genotipagem , Hidrodinâmica , Larva/genética , Repetições de Microssatélites/genética , Percas/genética
4.
Horm Behav ; 55(4): 520-9, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19470366

RESUMO

Many species assess predation risk through chemical cues, but the tissue source, chemical nature, and mechanisms of production or action of these cues are often unknown. Amphibian tadpoles show rapid and sustained behavioral inhibition when exposed to chemical cues of predation. Here we show that an alarm pheromone is produced by ranid tadpole skin cells, is released into the medium via an active secretory process upon predator attack, and signals predator presence to conspecifics. The pheromone is composed of two components with distinct biophysical properties that must be combined to elicit the behavioral response. In addition to the behavioral response, exposure to the alarm pheromone caused rapid and strong suppression of the hypothalamo-pituitary-adrenal (HPA) axis, as evidenced by a time and dose-dependent decrease in whole body corticosterone content. Reversing the decline in endogenous corticosterone caused by exposure to the alarm pheromone through addition of corticosterone to the aquarium water (50 nM) partially blocked the anti-predator behavior, suggesting that the suppression of the HPA axis promotes the expression and maintenance of a behaviorally quiescent state. To our knowledge this is the first evidence for aquatic vertebrate prey actively secreting an alarm pheromone in response to predator attack. We also provide a neuroendocrine mechanism by which the behavioral inhibition caused by exposure to the alarm pheromone is maintained until the threat subsides.


Assuntos
Comunicação Animal , Corticosterona/metabolismo , Inibição Psicológica , Larva/metabolismo , Feromônios/metabolismo , Ranidae/metabolismo , Animais , Sinais (Psicologia) , Sistema Hipotálamo-Hipofisário/metabolismo , Peptídeos/metabolismo , Sistema Hipófise-Suprarrenal/metabolismo , Pele/metabolismo , Fatores de Tempo
5.
Oecologia ; 158(4): 765-74, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18941784

RESUMO

The prior experience of prey may influence how they assess the level of predation risk associated with an information source. Here, I present the results from a set of experiments that demonstrate how the prior experience of green frog (Rana clamitans) tadpoles can influence their risk assessment during exposure to the chemical cue of predatory larval dragonflies (Anax spp.) consuming conspecific tadpoles. At the short-term scale, green frog tadpoles perceived a higher level of risk when consecutive cue exposures overlapped, but only when the total chemical cue concentration was weak. Weaker chemical cue concentrations may be less reliable than stronger cue concentrations, and overlapping cue exposures may increase the degree of certainty that tadpoles have in their perceived risk. When consecutive cue exposures did not overlap, tadpoles assessed the risk associated with each cue exposure independently. Predator-conditioned tadpoles responded longer during exposure to the Anax chemical cue than nonconditioned tadpoles, which suggests that a tadpole's long-term experience eventually does influence its risk assessment. In general, the results suggest that a prey's prior experience may influence its current perceived risk by influencing either the degree of certainty in or the level of its perceived risk. Understanding how the prior experience of prey influences their current risk assessment requires that the rate of decay of the value of prior experience should be identified at two timescales as an indicator of the current level of predation risk.


Assuntos
Comportamento Animal/fisiologia , Condicionamento Psicológico , Insetos/fisiologia , Ranidae/fisiologia , Risco , Animais , Sinais (Psicologia) , Larva/fisiologia , Comportamento Predatório
6.
J Anim Ecol ; 77(4): 638-45, 2008 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-18397251

RESUMO

1. While the antipredator behaviour of prey has been well studied, little is known about the rules governing the predation risk assessment of prey. In this study, I measured the activity levels of predator-naive green frog (Rana clamitans) tadpoles during and after exposures to the chemical cue of predatory larval dragonflies (Anax spp.). I then used the lengths of the time lags from the end of the cue exposures until the tadpoles returned to a control level of activity as an index of the perceived risk of the tadpoles. 2. While tadpoles always responded upon exposure to the Anax chemical cue by strongly reducing their activity level, their perceived risk increased asymptotically over time during the initial period of the cue exposure. Tadpoles of all size classes perceived increasing risk in proportion to chemical cue concentration, but the length of time that tadpoles responded during cue exposure and the length of their post-exposure time lags decreased with increasing body mass. 3. The results suggest that the perceived risk of green frog tadpoles varies over time and does not correspond directly to their behavioural response (i.e. activity level). However, their perceived risk does appear to vary in accordance with the predation risk associated with the Anax chemical cue and the reliability of the information from the cue, and therefore may be predictable.


Assuntos
Anuros/fisiologia , Sinais (Psicologia) , Insetos/fisiologia , Odorantes , Comportamento Predatório/fisiologia , Medição de Risco , Animais , Anuros/crescimento & desenvolvimento , Feminino , Larva/crescimento & desenvolvimento , Masculino , Densidade Demográfica , Dinâmica Populacional
7.
Am Nat ; 171(4): 545-52, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18241009

RESUMO

Prey trade off predation risk and foraging gain in their activity level. Their response to this trade-off mediates direct and indirect interactions between predators and the community (i.e., nonlethal effects). A prey's activity level may also vary independently because of circadian rhythms. I tested how the antipredator behavior of green frog (Rana clamitans) tadpoles can be influenced by their circadian rhythm (primarily nocturnal feeding) and how the strengths of nonlethal effects vary in turn. Tadpoles exhibited stronger activity reductions when under predation risk during the day (which may result in stronger resource depression). However, when predation risk was high and persistent, tadpoles remained inactive during both day and night. Consequently, the nonlethal effect on tadpoles (growth rate reduction) was more negative at night. Predicting prey behavior and its effects requires identifying how their perceived risk interacts with and is limited by all factors that can influence their response.


Assuntos
Ritmo Circadiano , Insetos , Comportamento Predatório , Ranidae , Animais , Comportamento Alimentar , Larva , Ranidae/crescimento & desenvolvimento , Natação
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