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Innate immunity of Florida cane toads: how dispersal has affected physiological responses to LPS

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Journal of Comparative Physiology B Aims and scope Submit manuscript

Abstract

Physiological tradeoffs occur in organisms coping with their environments, which are likely to increase as populations reach peripheries of established ranges. Invasive species offer opportunities to study tradeoffs that occur, with many hypotheses focusing on how immune responses vary during dispersal. The cane toad (Rhinella marina) is a well-known invasive species. Populations near the expanding edge of the Australian invasion have altered immune responses compared to toads from longer-established core populations, although this has not been well-documented for Florida populations. In this study, cane toads from a northern edge [New Port Richey (NPR)] and southern core (Miami) population in Florida were collected and injected with lipopolysaccharide (LPS) to compare immune responses. Core population individuals injected with LPS showed greater metabolic increases compared to their baseline rates that were higher compared to those from the edge population. In addition, LPS-injected core individuals had different circulating leukocyte profiles compared to saline-injected cane toads while edge individuals did not. There was a significant interaction between plasma bacteria-killing capability (BKA) and treatment, such that BKA decreased with time in saline compared to LPS-injected individuals, and saline-injected toads from the edge population had lower BKA compared to LPS-injected edge toads at 20 h post-injection. There was also a significant interaction between location and time on circulating corticosterone (CORT) levels following injections with saline or LPS, with CORT decreasing more with time in core population toads. The differential CORT response indicates that differential stress responses contribute to the tradeoffs observed with immunity and dispersal.

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Data accessibility

The data supporting the results will be archived in Mendeley Data: https://doi.org/10.17632/hk24s8jrhk.1

Abbreviations

NPR:

New Port Richey

LPS:

Lipopolysaccharide

BKA:

Bacteria killing assay

GC:

Glucocorticoid

CORT:

Corticosterone

N:L:

Neutrophil:Lymphocyte

V̇O2 :

Volume (ml) of oxygen consumed h1

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Acknowledgements

We thank Tonia Schwartz, Elizabeth Schwartz, and Jeff Goessling for their feedback. We would like to acknowledge the CMB Peaks of Excellence fellowship offered by Auburn University for financial support, as well as the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) through the BEPE scholarship (2017/04802-5) for VRA (https://www.fapesp.br).

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Authors and Affiliations

Authors

Contributions

Ideas and methodology were conceived by SG, VA, AA, and MTM; data was collected by SG, VA, and KS Data analysis was performed by SG, and SG led the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.

Corresponding author

Correspondence to Steven T. Gardner.

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Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

Cane toads were collected under FFWC permit EXOT-17-34. All procedures performed in studies involving animals were in accordance with the ethical standards of Auburn University IACUC (PRN 2017-3106).

Additional information

Communicated by H.V. Carey.

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Supplemental Fig.1

Standard metabolic rate (SMR) increase (%) of Florida cane toads (Rhinella marina) injected into the dorsal lymph sac with either LPS (20 µg g-1 body mass (strain 0111:B4)) (triangles) or saline (squares) from (A) a northern edge (New Port Richey) (n = 9,6 (LPS and saline)) and (B) a southern core (Miami) population (n = 11,5 (LPS and saline)) compared to baseline metabolic rates over a 20h period. All metabolic data were collected from toads responding to the treatments at 32oC. Dashed lines indicate no change in SMR compared to baseline trials. The graphs show mean values for each time point and error bars represent +1 SE (DOCX 93 kb)

Supplementary file2 (DOCX 17 kb)

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Gardner, S.T., Assis, V.R., Smith, K.M. et al. Innate immunity of Florida cane toads: how dispersal has affected physiological responses to LPS. J Comp Physiol B 190, 317–327 (2020). https://doi.org/10.1007/s00360-020-01272-7

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  • DOI: https://doi.org/10.1007/s00360-020-01272-7

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