Differences in morphology and in composition and release of parotoid gland secretion in introduced cane toads (Rhinella marina) from established populations in Florida, USA

Steven T. Gardner, Megen Kepas, Casey R. Simons, Logan M. Horne, Alan H. Savitzky, Mary T. Mendonça

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Cane toads are highly toxic bufonids invasive in several locations throughout the world. Although physiological changes and effects on native predators for Australian populations have been well documented, Florida populations have received little attention. Cane toads were collected from populations spanning the invaded range in Florida to assess relative toxicity, through measuring morphological changes to parotoid glands, likelihood of secretion, and the marinobufagenin (MBG) content of secretion. We found that residual body indices increased in individuals from higher latitude populations, and relative parotoid gland size increased with increasing toad size. There was no effect of latitude on the allometric relationship between gland size and toad size. We observed an increase in likelihood of secretion by cane toads in the field with increasing latitude. Individuals from southern and northern populations did not vary significantly in the quantity of MBG contained in their secretion. Laboratory-acclimated cane toads receiving injections of epinephrine were more likely to secrete poison with increasing dose, although there was no difference in likelihood of secretion between southern and northern populations. This suggests that differences between populations in the quantities of epinephrine released in the field, due to altered hypothalamic sensitivity upon disturbance, may be responsible for the latitudinal effects on poison secretion. Our results suggest that altered pressures from northward establishment in Florida have affected sympathetic sensitivity and defensive mechanisms of cane toads, potentially affecting risk to native predators.

Original languageEnglish
Pages (from-to)1013-1022
Number of pages10
JournalEcology and Evolution
Volume11
Issue number2
DOIs
StatePublished - Jan 2021
Externally publishedYes

Funding

We thank Vania Assis and Jessica Ertel for their assistance with collecting and obtaining images of cane toads in 2018 and 2019, respectively. We also thank undergraduates from the Mendonça laboratory during 2019 with their assistance with toad husbandry. We acknowledge the CMB Peaks of Excellence fellowship offered by Auburn University for financial support for S.G. during 2018.

FundersFunder number
Auburn University

    Keywords

    • Rhinella marina
    • bufadienolide
    • epinephrine
    • invasion
    • phenotypic plasticity
    • sympathetic sensitivity

    Fingerprint

    Dive into the research topics of 'Differences in morphology and in composition and release of parotoid gland secretion in introduced cane toads (Rhinella marina) from established populations in Florida, USA'. Together they form a unique fingerprint.

    Cite this