title: Amphibians with infectious disease increase their reproductive effort: evidence for the terminal investment hypothesis.
abstract: Mounting an immune response to fight disease is costly for an organism and can reduce investment in another life-history trait, such as reproduction. The terminal investment hypothesis predicts that an organism will increase reproductive effort when threatened by disease. The reproductive fitness of amphibians infected with the deadly fungal pathogen Batrachochytrium dendrobatidis (Bd) is largely unknown. In this study, we explored gametogenesis in two endangered and susceptible frog species, Pseudophryne corroboree and Litoria verreauxii alpina. Gametogenesis, both oogenesis and spermatogenesis, increased when animals were experimentally infected with Bd In P. corroboree, infected males have thicker germinal epithelium, and a larger proportion of spermatocytes. In L. v. alpina, infected males had more spermatic cell bundles in total, and a larger proportion of spermatozoa bundles. In female L. v. alpina, ovaries and oviducts were larger in infected animals, and there were more cells present within the ovaries. Terminal investment has consequences for the evolution of disease resistance in declining species. If infected animals are increasing reproductive efforts and producing more offspring before succumbing to disease, it is possible that population-level selection for disease resistance will be minimized.
authors.affiliation: One Health Research Group, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia laura.brannelly@my.jcu.edu.au.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Brannelly
authors.affiliation: One Health Research Group, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Webb
authors.affiliation: One Health Research Group, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Lee F
authors.initials: LF
authors.lastname: Skerratt
authors.affiliation: One Health Research Group, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Lee
authors.initials: L
authors.lastname: Berger
mesh_terms: D000818:Animals; D001001:Anura / Q000382:microbiology / Q000502:physiology*; D008411:Chytridiomycota / Q000472:pathogenicity*; D021821:Communicable Diseases, Emerging; D056727:Endangered Species; D005260:Female; D005718:Gametogenesis; D008297:Male; D009181:Mycoses / Q000662:veterinary*; D009929:Organ Size; D011157:Population Dynamics
keywords: chytrid fungus; oogenesis; reproduction; spermatogenesis; terminal investment; wildlife disease