Ontogeny of immunity and potential implications for co-infection

Immunity changes through ontogeny and can mediate facilitative and inhibitory interactions among co-infecting parasite species. In amphibians, most immune memory is not carried through metamorphosis, leading to variation in the complexity of immune responses across life stages. To test if the ontogeny of host immunity might drive interactions among co-infecting parasites, we simultaneously exposed Cuban treefrogs (Osteopilus septentrionalis) to a fungus (Bactrachochytrium dendrobaditis) and a nematode (Aplectana hamatospicula) at tadpole, metamorphic, and post-metamorphic life stages. We measured metrics of host immunity, host health, and parasite abundance. We predicted facilitative interactions between co-infecting parasites as the different immune responses hosts mount to combat these infectious are energetically challenging to mount simultaneously. We found ontogenetic differences in IgY levels and cellular immunity but no evidence that metamorphic frogs were more immunosuppressed t..., Animal Husbandry
Cuban treefrog (Osteopilus septentrionalis) tadpoles were collected from 140-L pools filled with rainwater at the University of South Florida botanical gardens (Tampa, FL, USA) in the summer of 2017. Individuals collected early in the season (May), midseason (July), and later in the summer (August) were all reared to post-metamorphic, metamorphic, and tadpole life stages respectively. See supplemental methods for additional details.
Experimental Design
To examine how the life stage of amphibians affect host-parasite dynamics, we exposed O. septenrionalis to one of four treatments at each of the three amphibian life-stages. Treatments included no parasite exposure, and exposures to either Bd alone, A. hamatospicula alone, or Bd and A. hamatospicula together. These four treatments were applied at the tadpole (Gosner development stage 28-35; Gosner 1960), metamorphic (stage 42-45 frogs), and post-metamorphic stages. In total, there were 5,8, and 9 control individuals for t...,