Assessment of interactive effects of elevated salinity and three pesticides on life history and behavior of southern toad (Anaxyrus terrestris) tadpoles

Abstract

Because habitats are increasingly exposed to multiple stressors simultaneously, assessing the interactive effects of stressors is crucial for understanding how populations respond to human-altered habitats. Salinization of freshwater habitats is increasing and has the potential to interact with other stressors. Chemical pollutants also contribute to habitat degradation in freshwater environments, and both salinity and various pesticides can harm amphibians. The present study used a factorial experiment to investigate the effect of elevated salinity alone and in combination with each of 3 pesticides-atrazine, carbaryl, and glyphosate-on life history and behavior of southern toad larvae (Anaxyrus terrestris). Tadpoles were negatively affected by elevated salinity and by exposure to the insecticide carbaryl, with the most deleterious outcomes associated with both stressors combined. Carbaryl exposure led to reduced survival as well as sublethal effects on growth, activity and feeding behavior, escape response swimming, and time to metamorphosis. Tadpoles reared at elevated salinity were also smaller and less active, and ultimately metamorphosed later and at smaller size. Together, carbaryl and elevated salinity had a synergistic effect, resulting in particularly poor growth, depressed activity and feeding, and sluggish escape swimming among tadpoles exposed to both stressors simultaneously. These results suggest that both elevated salinity and carbaryl represent threats for amphibian populations and that pesticide exposure in salinized habitats may pose a particularly high risk.

Adaptive responses to salinity stress across multiple life stages in anuran amphibians

“…Larvae may be more tolerant of osmotic stress than embryos if they can increase the activity or concentration of ion pumps in the gills. However, tadpoles raised in saltwater tend to have stunted developmental rates and metamorphose at smaller sizes compared to freshwater-raised tadpoles [ 46 , 52 , 59 , 64 , 65 , 116 , 117 ], which can affect adult survival and reproductive success [ 118 ]. Adults, on the other hand, are less confined to aquatic environments and thus can reduce contact with stressful habitats via behavioral avoidance or dispersal.…”

Chronic Exposure to High Concentrations of Road Salt Decreases the Immune Response of Dragonfly Larvae

“…The majority of studies examining the biological effects of salinization in freshwater systems have focused on vertebrates. Amphibians have been found to be negatively affected by increased salinity with reduced survival to metamorphosis and longer developmental times (Bernabò et al, 2013;Hopkins et al, 2013;Kearney et al, 2014;Wood and Welch, 2015), reduced activity levels (Wood and Welch, 2015;Jones et al, 2017), decreased sperm motility and velocity (Wilder and Welch, 2014), and physical abnormalities (Sanzo and Hecnar, 2006) including morphological alterations of gill epithelium following salinity exposure (Bernabò et al, 2013). Key fitness metrics, including reduced body length and mass, have also been reported in fish exposed to high salinity (e.g., Hintz and Relyea, 2017).…”

Greater reproductive investment, but shorter lifespan, in agrosystem than in natural-habitat toads

“…Pesticides could diminish prey availability for amphibians, which, along with the aforementioned ecological and physiological stressors in agrosystems, could restrict matter and energy transmission, and ultimately, growth rates ( Madsen & Shine, 2000 ). Agrosystems exert negative effects on both tadpole and adult development and growth ( Wood & Welch, 2015 ). Morphology and functioning of gonads may appear altered in agrosystem amphibians ( McCoy et al, 2008 ).…”