Does chronic exposure to ammonium during the pre-metamorphic stages promote hindlimb abnormality in anuran metamorphs? A comparison between natural-habitat and agrosystem frogs

Hind limb morphology is directly responsible for locomotion of metamorph (Zamora-Camacho and Aragón, 2019a) and adult anurans (Zamora-Camacho, 2018), either from terrestrial (Gomes et al., 2009) or aquatic environments (Herrel et al., 2012), regardless of their locomotion mode (Enriquez-Urzelai et al., 2015). [...]hindlimb abnormality in this group is likely eradicated by natural selection due to its severe negative effects on locomotion (Zamora-Camacho and Aragón, 2019b). Limb abnormalities are particularly common in metamorphs (Kiesecker, 2002; Piha et al., 2006), seemingly because reduced locomotor performance (Zamora-Camacho and Aragón, 2019b) might cause their death shortly after metamorphosis. Besides a genetic origin (Droin and Fischberg, 1980), hindlimb abnormalities in anurans have been related to biotic interactions such as predatory pressure (Johnson and Bowerman, 2010) or parasite infections (Roberts and Dickinson, 2012), as well as abiotic factors such as ultra- violet-B radiation (Pahkala et al., 2001). The other aquaria contained untreated spring water, as a control. [...]we had 15 aquaria with eggs from frogs from each habitat and treatment, totalling 60 aquaria, in a 2 x 2 factorial experimental design. A window let natural daylight in, permitting adjustment of circadian rhythms. Because tadpole diet can affect limb abnormality rates in this species (Martínez et al., 1992), all specimens were standardly fed boiled spinach ad libitum.