Biology subjects

Kasler, A.

Publications and source records attributed to Kasler, A..

3 recordsLinked to original sources

bioRxiv2022

Amphibian larvae benefit from a warm environment under simultaneous threat from chytridiomycosis and ranavirosis

Rising temperatures can facilitate epizootic outbreaks, but disease outbreaks may be suppressed if temperatures increase beyond the optimum of the pathogens while still within the temperature range that allows for effective immune function in hosts. The two most devastating pathogens of wild amphibians, Batrachochytrium dendrobatidis (Bd) and ranaviruses (Rv), co-occur in large areas, yet little is known about the consequences of their co-infection and how these consequences depend on temperature. Here we tested how co-infection and elevated temperatures (28 and 30{degrees}C vs. 22{degrees}C) affected Bd and Rv prevalence, infection intensities, and resulting mortalities in larval agile frogs and common toads. We found multiple pieces of evidence that the presence of one pathogen influenced the prevalence and/or infection intensity of the other pathogen in both species, depending on temperature and initial Rv concentration. Generally, the 30{degrees}C treatment lowered the prevalence and infection intensity of both pathogens, and, in agile frogs, this was mirrored by higher survival. These results suggest that if temperatures naturally increase or are artificially elevated beyond what is ideal for both Bd and Rv, amphibians may be able to control infections and survive even the simultaneous presence of their most dangerous pathogenic enemies.

evolutionary biology↗

bioRxiv2021

"Heat waves" experienced during larval life have species-specific consequences on life-history traits and sexual development in anuran amphibians

Extreme temperatures during heat waves can induce mass-mortality events, but can also exert sublethal negative effects by compromising life-history traits and derailing sexual development. Ectothermic animals may, however, also benefit from increased temperatures via enhanced physiological performance and the suppression of cold-adapted pathogens. Therefore, it is crucial to address how the intensity and timing of naturally occurring or human-induced heat waves affect life-history traits and sexual development in amphibians, to predict future effects of climate change and to minimise risks arising from the application of elevated temperature in disease mitigation. We raised agile frog (Rana dalmatina) and common toad (Bufo bufo) tadpoles at 19 {degrees}C and exposed them to a simulated heat wave of 28 or 30 {degrees}C for six days during one of three ontogenetic periods (early, mid or late larval development). In agile frogs, exposure to 30 {degrees}C during early larval development increased mortality. Regardless of timing, all heat-treatments delayed metamorphosis, and exposure to 30 {degrees}C decreased body mass at metamorphosis. Furthermore, exposure to 30 {degrees}C during any period and to 28 {degrees}C late in development caused female-to-male sex reversal, skewing sex ratios strongly towards males. In common toads, high temperature only slightly decreased survival and did not influence phenotypic sex ratio, while it reduced metamorph mass and length of larval development. Juvenile body mass measured two months after metamorphosis was not adversely affected by temperature treatments in either species. Our results indicate that heat waves may have devastating effects on amphibian populations, and the severity of these negative consequences, and sensitivity can vary greatly between species and with the timing and intensity of heat. Finally, thermal treatments against cold-adapted pathogens have to be executed with caution, taking into account the thermo-sensitivity of the species and the life stage of animals to be treated.

ecology↗

bioRxiv2020

Sex reversal and ontogeny under climate change and chemical pollution: are there interactions between the effects of elevated temperature and a xenoestrogen on early development in agile frogs?

Anthropogenic environmental change poses a special threat to species in which genetic sex determination can be overwritten by the thermal and chemical environment. Endocrine disrupting chemicals as well as extreme temperatures can induce sex reversal in such species, with wide-ranging consequences for fitness, demography, population viability and evolution. Despite accumulating evidence suggesting that chemical and thermal effects may interact in ecological contexts, little is known about their combined effects on sex reversal. Here we assessed the simultaneous effects of high temperature (masculinizing agent) and 17-ethinylestradiol (EE2), a widespread xenoestrogen (feminizing agent), on sexual development and fitness-related traits in agile frogs (Rana dalmatina). We exposed tadpoles to a six-days heat wave (30 {degrees}C) and/or an ecologically relevant concentration of EE2 (30 ng/L) in one of three consecutive larval periods, and diagnosed sex reversals two months after metamorphosis using species-specific markers for genetic sexing. We found that high temperature induced female-to-male sex reversal, decreased survival, delayed metamorphosis, decreased body mass at metamorphosis, and increased the proportion of animals that had no fat bodies, while EE2 had no effect on these traits. Simultaneous exposure to heat and EE2 had non-additive effects on juvenile body mass, which were dependent on treatment timing and further complicated by a negative effect of sex reversal on body mass. These results show that environmentally relevant exposure to EE2 does not diminish the masculinizing effects of high temperature. Instead, our findings on growth suggest that climate change and chemical pollution may have complex consequences for individual fitness and population persistence in species with environment-sensitive sex determination.

pharmacology and toxicology↗