Intra-specific variation in nitrate tolerance in tadpoles of the Natterjack toad

Abstract

Anthropogenic sources of nitrogen that pollute bodies of water can have toxic and sub-lethal effects on amphibians. It has been hypothesized that such exposure may promote local adaptation, that is, selection for higher tolerance in individuals in populations exposed to pollutants. We tested this hypothesis with respect to the Natterjack toad (Bufo calamita Laurenti, 1768), by comparing the nitrate dose response of tadpoles from eight populations (doses: 0, 50, 100, 500 and 1000 mg/l nitrate) from relatively unpolluted and intensively farmed environments. We evaluated the effect of nitrate exposure by observing the behavior (movements) of tadpoles exposed to different concentrations of nitrates. Exposure to high nitrate levels did not cause tadpole mortality in the populations used in our experiments; however, we did observe changes in activity for all populations, with these changes being either dose-related responses (decreased activity after exposure to 500 or 1000 mg/l), or more complex responses (increased activity when exposed to 50 or 100 mg/l nitrate, followed by decreased activity at higher concentrations). Natterjack toad tadpoles exhibited variable behavioural responses among the tested populations. Although these populations were selected on the basis of their potential agrochemical contamination, the observed variation in population tolerance was not related to the parameters used to estimate this contamination in these breeding sites. Possible explanations for this apparent lack of local adaptation in B. calamita tadpoles include inadequate estimates of the toads' actual nitrate exposure in the field, and the biological characteristics of B. calamita, which may limit the effects of exposure or favor phenotypic plasticity.

Histopathological and biochemical changes in the liver, kidney, and bloodof amphibians intoxicated with cadmium

“…In Bufo regularis (Hilmy et al, 1986) and Bufo raddei (Zhang et al, 2007), alterations caused by Cd have been reported in several hematological parameters. However, the effect and dimensions of the alterations observed are not common to all amphibian species, since there can be interspecific (Birge et al, 2000) and intraspecific variations (Miaud et al, 2011).…”

Combining ex situ and in situ methods to improve water quality testing for the conservation of aquatic species

“…Unsuitable water quality conditions that are not harmful enough to cause death can still have damaging effects on the health of aquatic species, and prevent them from functioning normally (Hallare et al, 2005;Miaud et al, 2011). Unsuitable water quality conditions that are not harmful enough to cause death can still have damaging effects on the health of aquatic species, and prevent them from functioning normally (Hallare et al, 2005;Miaud et al, 2011).…”

“…The similarity between mean body condition and time to metamorphosis in breeding and nonbreeding ponds strengthens the hypothesis that water quality at non-breeding ponds is suitable for bell frog tadpoles. Unsuitable water quality conditions that are not harmful enough to cause death can still have damaging effects on the health of aquatic species, and prevent them from functioning normally (Hallare et al, 2005;Miaud et al, 2011). Delayed time to metamorphosis is a recognized response of amphibian larvae to poor water quality (Griffis-Kyle, 2007), as is reduced feeding activity (Marco et al, 1999), which should cause affected individuals to have a lower body condition than those raised in suitable conditions.…”

“…One approach has been to expose individuals to artificially made solutions that increase in extremity along a gradient of a single parameter of water chemistry, and examining the effects on behaviour, development and survival (Freda and Dunson, 1985;Marco et al, 1999;Miaud et al, 2011). One approach has been to expose individuals to artificially made solutions that increase in extremity along a gradient of a single parameter of water chemistry, and examining the effects on behaviour, development and survival (Freda and Dunson, 1985;Marco et al, 1999;Miaud et al, 2011).…”

“…However, the process of determining conclusively whether water quality is suitable at a given site for a particular species is challenging. One approach has been to expose individuals to artificially made solutions that increase in extremity along a gradient of a single parameter of water chemistry, and examining the effects on behaviour, development and survival (Freda and Dunson, 1985;Marco et al, 1999;Miaud et al, 2011). These types of studies provide information on the tolerance range of individual species for a particular aspect of water chemistry, which can be used to compare with values in the field to determine if poor water quality is likely to be limiting the distribution of that species (Rouse et al, 1999).…”