Biology subjects

Holly, D.

Publications and source records attributed to Holly, D..

3 recordsLinked to original sources

bioRxiv2024

Juvenile agile frogs spatially avoid ranavirus-infected conspecifics, but do not show generalized social distancing or self-isolation

Exposure to contagious pathogens can result in behavioural changes, which can alter the spread of infectious diseases. Healthy individuals can express generalized social distancing or actively avoid the sources of infection, while infected individuals can show passive or active self-isolation. Amphibians are globally threatened by serious contagious diseases, yet their behavioural responses to infections are very scarcely known. We studied behavioural changes in agile frog (Rana dalmatina) juveniles upon exposure to a Ranavirus (Rv). We performed classic choice tests in chambers containing a conspecific infected with Rv in one end compartment and a non-infected conspecific in the other end, with an Rv-infected or non-infected focal individual in the central compartment. We found that both non-infected and Rv- infected focal individuals spatially avoided infected conspecifics, while there were no signs of generalized social distancing, nor self-isolation. Spatial avoidance of infected conspecifics may effectively hinder disease transmission. On the other hand, the absence of self-isolation by infected individuals may facilitate it. Our finding that infected individuals spent more time near the non-infected than infected conspecifics suggests that the strong behavioural drive to avoid infected conspecifics may not be silenced by infection, possibly to prevent secondary infections. The observation that infected focal individuals did not spend more time near conspecifics than non-infected focals renders it unlikely that the pathogen manipulated host behaviour to aid disease spread. More research is urgently needed to understand under what circumstances behavioural responses can help amphibians cope with infections, and how that affects disease dynamics in natural populations. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=68 SRC="FIGDIR/small/588850v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@59b5a9org.highwire.dtl.DTLVardef@1a59896org.highwire.dtl.DTLVardef@c4bc64org.highwire.dtl.DTLVardef@2c76c3_HPS_FORMAT_FIGEXP M_FIG C_FIG

animal behavior and cognition↗

bioRxiv2023

Effects of mild winter conditions and two pyrethroid insecticides on the development and survival of juvenile common toads (Bufo bufo)

Combined effects of pollutants and climate change can have long-term negative effects on Earths biodiversity. We tested how amphibians are affected by exposure to pesticides around metamorphosis in combination with current winter conditions or those projected to become the norm by 2100. We applied two pyrethroid insecticides, cypermethrin or deltamethrin, to newly metamorphosed common toads (Bufo bufo) via spraying, thereafter reared animals in outdoor enclosures, and finally exposed them either to a long&cold winter (1.5 {degrees}C for 91 days) or to a short&mild one (4.5 {degrees}C for 61 days). After hibernation, we examined changes in body mass, size and gross morphology of parotoid glands and visceral organs, and determined the phenotypic sex of the surviving toadlets. In the long&cold winter scenario, we observed high mortality rate, regardless of the chemical treatment (control: 82%, cypermethrin: 78%, deltamethrin: 70%). At the same time, mortality was significantly lower in the short&mild winter scenario (control: 33%, cypermethrin: 41%, deltamethrin: 26%). The decrease in body mass during overwintering did not differ among treatment groups. Our results contradict the hypothesis of sex-biased mortality caused by chemical pollutants, harsh or mild winter conditions or by their combination. No significant deformations of the internal organs were found in either group. Our results suggest that winter conditions becoming ever milder in the temperate zone may prove beneficial for amphibian overwinter survival, and that exposure to the tested pyrethroids at ecologically relevant concentrations after metamorphosis does not interfere with the fitness of juvenile common toads.

zoology↗

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↗