Energetics of metamorphic climax in the southern toad ( Bufo terrestris )

Beck, Christopher W.; Congdon, Justin D.

doi:10.1007/s00442-003-1374-5

Cited by 27 publications

(33 citation statements)

References 16 publications

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“…Additionally, we considered a hypothetical case where maternal and dietary Hg exposure resulted in minor additional adult mortality (5% reduction in survival; dotted line). We examined the effects of Hg exposure on quasi-extinction probability and mean annual adult population size for each case across varying strengths of density dependence (c; 95% CI for B. americanus period of increased vulnerability for immunological (Todd 2007), energetic (Beck and Congdon 2003), and ecological (Arnold and Wassersug 1978) reasons, and is a time when adverse effects of contaminants frequently manifest (e.g., Marian et al 1983, Snodgrass et al 2004, Unrine et al 2004. Such effects likely have important population-level consequences in most species.…”

Section: Discussionmentioning

confidence: 99%

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

Willson

Hopkins

Bergeron

et al. 2012

Ecological Applications

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Abstract. Concern that environmental contaminants contribute to global amphibian population declines has prompted extensive experimental investigation, but individual-level experimental results have seldom been translated to population-level processes. We used our research on the effects of mercury (Hg) on American toads (Bufo americanus) as a model for bridging the gap between individual-level contaminant effects and amphibian population viability. We synthesized the results of previous field and laboratory studies examining effects of Hg throughout the life cycle of B. americanus and constructed a comprehensive demographic population model to evaluate the consequences of Hg exposure on population dynamics. Our model explicitly considered density-dependent larval survival, which is known to be an important driver of amphibian population dynamics, and incorporated two important factors that have seldom been considered in previous amphibian modeling studies: environmental stochasticity and sublethal effects. We demonstrated that decreases in embryonic survival and sublethal effects (e.g., reduced body size) that delay maturation have minor effects on population dynamics, whereas contaminant effects that reduce late-larval or post-metamorphic survival have important population-level consequences. We found that excessive Hg exposure through maternal transfer or larval diet, alone, had minor effects on B. americanus populations. Simultaneous maternal and dietary exposure resulted in reduced population size and a dramatic increase in extinction probability, but explicit prediction of population-level effects was dependent on the strength of larval density dependence. Our results suggest that environmental contaminants can influence amphibian population viability, but that highly integrative approaches are needed to translate individual-level effects to populations.

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Section: Discussionmentioning

confidence: 99%

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

Willson

Hopkins

Bergeron

et al. 2012

Ecological Applications

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“…Spinal malformations in amphibian larvae have been previously linked to dietary Hg and exposure to coal ash pollutants [12,31], and developmental abnormalities and altered swimming in amphibian larvae have also been linked to maternal exposure to trace elements derived from coal fly ash [6]. Finally, maternal Hg exposure increased the duration of metamorphic climax, a period of increased vulnerability for immunological [32], energetic [33], and ecological reasons, a consequence that may increase mortality risk in natural settings.…”

Section: Effects Of Maternal and Dietary Mercury In Amphibiansmentioning

confidence: 95%

Aquatic and terrestrial stressors in amphibians: A test of the double jeopardy hypothesis based on maternally and trophically derived contaminants

Todd

Bergeron

Hepner

et al. 2011

Enviro Toxic and Chemistry

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Amphibians with biphasic life histories occupy aquatic and terrestrial habitats at different times in their lives, leading to a double jeopardy of contaminant risk in both habitats. The present study examines individual and interactive effects of mercury exposure to terrestrial adults and aquatic larvae on fitness-related traits of American toads, Bufo americanus. Eggs from reference mothers or contaminated mothers were allowed to hatch and larvae were fed diets of either no added Hg or 2.5 or 10 µg/g total Hg (dry wt). Both dietary and maternal Hg had adverse effects on developing larvae, but there was no interaction between these factors. Dietary Hg had a marginal effect of decreased survival with increasing Hg in the diet. Animals from Hg-exposed mothers weighed 14% less than those from reference mothers, and size at metamorphosis was directly correlated with hopping performance. Animals from Hg-exposed mothers also took longer to complete metamorphosis and had 2.5 times the prevalence of spinal malformations compared with those from reference mothers. Results of the present study demonstrate that amphibians do indeed face a double jeopardy of contaminant exposure stemming from terrestrial and aquatic environments, because both exposure pathways adversely affected developing offspring. The present study also demonstrates that all possible routes of exposure over an organism's life history must be examined to provide a comprehensive picture of the ecological consequences of habitat contamination.

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“…The larval period is certainly a period of development and growth (Wilbur and Collins 1973), but it is also a period during which lipids can be stored for later use. Amphibian larvae need lipid reserves during metamorphosis itself, a period when larvae do not feed due to changes in oral and digestive morphology (Beck and Congdon 2003). But amphibians do not exhaust energy stores during metamorphic climax, and emerge with size-dependent energy reserves (Beck and Congdon 2003, this study).…”

Section: Trade-offs and Amphibian Modelsmentioning

confidence: 99%

Amphibian lipid levels at metamorphosis correlate to post-metamorphic terrestrial survival

et al. 2007

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In organisms that have complex life cycles, factors in the larval environment may affect both larval and adult traits. For amphibians, the postmetamorphic transition from the aquatic environment to terrestrial habitat may be a period of high juvenile mortality. We hypothesized that lipid stores at metamorphosis may affect an animal's success during this critical transition period. We examined variation in total lipid levels among years and sites in recently metamorphosed individuals of two pond-breeding salamander species, the marbled salamander (Ambystoma opacum) and the mole salamander (A. talpoideum), with limited data for one anuran species (southern leopard frog, Rana sphenocephala). Lipid levels were allometrically related to body size and ranged from 1.9 to 23.8% of body dry mass. The two salamander species differed in lipid allocation patterns, with A. opacum apportioning a higher percentage of total lipid reserves into fat bodies than A. talpoideum. Species differences in lipid allocation patterns may primarily reflect that large metamorphs will mature as one-year olds, and, regardless of species, will alter lipid compartmentalization accordingly. We used mark-recapture data obtained at drift fences encircling breeding ponds for 13 A. opacum cohorts to estimate the proportion of postmetamorphic individuals that survived to breed (age 1-4) and the mean age at first reproduction. Regression models indicated that size-corrected lipid level at metamorphosis (i.e., lipid residuals), and to a lesser extent rainfall following metamorphosis, was positively related to adult survival. Snout-vent length at metamorphosis was negatively related to age at first reproduction. We suggest that lipid stores at metamorphosis are vital to juvenile survival in the months following the transition from aquatic to terrestrial habitat, and that a trade-off shaped by postmetamorphic selection in the terrestrial habitat exists between allocation to energy stores versus structural growth in the larval environment.

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Energetics of metamorphic climax in the southern toad ( Bufo terrestris )

Cited by 27 publications

References 16 publications

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

Aquatic and terrestrial stressors in amphibians: A test of the double jeopardy hypothesis based on maternally and trophically derived contaminants

Amphibian lipid levels at metamorphosis correlate to post-metamorphic terrestrial survival

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