Host defense or parasite cue: Skin secretions mediate interactions between amphibians and their parasites

Abstract

Amphibian skin secretions (substances produced by the amphibian plus microbiota) plausibly act as a first line of defense against parasite/pathogen attack, but may also provide chemical cues for pathogens. To clarify the role of skin secretions in host–parasite interactions, we conducted experiments using cane toads (Rhinella marina) and their lungworms (Rhabdias pseudosphaerocephala) from the range‐core and invasion‐front of the introduced anurans’ range in Australia. Depending on the geographical area, toad skin secretions can reduce the longevity and infection success of parasite larvae, or attract lungworm larvae and enhance their infection success. These striking differences between the two regions were due both to differential responses of the larvae, and differential effects of the skin secretions. Our data suggest that skin secretions play an important role in host–parasite interactions in anurans, and that the arms race between a host and parasite can rapidly generate spatial variation in critical features of that interaction.

When Defenses Fail: Atelopus zeteki Skin Secretions Increase Growth of the Pathogen Batrachochytrium dendrobatidis

“…One potential explanation for our results is that some components of the chemically rich skin secretions enhanced pathogen growth despite the presence of other inhibitory immune components. Besides AMPs, skin secretions also contain proteins, carbohydrates, sugars, and biomolecules with functions other than immune defense, which may serve as nutrients or chemical signals for Bd ( Moss et al 2008 ; Van Rooji et al 2015 ; Varga et al 2019 ; Mayer et al 2021 ; Wang et al 2021 ). Another potential explanation is that the immunogenic protection of the skin secretions stems from interactions with other components of the immune system, and by isolating the skin secretions in vitro , they lose their inhibitory effectiveness ( Conlon 2011 ).…”

Parasite transmission in size‐structured populations

“…Body size is one host trait that can be highly heterogeneous and may impact parasite transmission in many systems. For example, larger individuals may provide a greater target area for vectors (Poulin, 2004; Yan et al, 2021), may provide more resources and thus tolerate a larger burden of macroparasites (Hechinger et al, 2019), may be more apparent to parasites that actively seek out their host using chemical cues (Mayer et al, 2021; Théron et al, 1998), or may encounter a greater abundance and diversity of parasites if they are exploring larger territories (Han et al, 2015). Furthermore, body size has the potential to vary drastically among individuals in a population due to age, genetics, feeding history, and/or environmental stressors (Kooijman, 2010).…”

Parasite transmission in size-structured populations

“…Body size is a one host trait that can be highly heterogenous and may impact parasite transmission in many systems. For example, larger individuals may provide a greater target area for vectors (Poulin 2004, Yan et al 2021, may provide more resources and thus tolerate a larger burden of macroparasites (Hechinger et al 2019), may be more apparent to parasites that actively seek out their host using chemical cues (Théron et al 1998, Mayer et al 2021, or may encounter a greater abundance and diversity of parasites if they are exploring larger territories (Han et al 2015). Furthermore, body size has the potential to vary drastically among individuals in a population due to age, genetics, feeding history, and/or environmental stressors (Kooijman, S.A.L.M.…”