Unexpected lower testosterone in faster growing farmed saltwater crocodile (Crocodylus porosus) hatchlings

John W Finger Jr; Peter C Thomson; Sally R Isberg

doi:10.1016/j.ygcen.2015.11.016

Unexpected lower testosterone in faster growing farmed saltwater crocodile (Crocodylus porosus) hatchlings

Gen Comp Endocrinol. 2016 Jan 15:226:1-4. doi: 10.1016/j.ygcen.2015.11.016. Epub 2015 Nov 26.

Authors

John W Finger Jr¹, Peter C Thomson², Sally R Isberg³

Affiliations

¹ Department of Environmental Health Science, University of Georgia, Athens, GA 30602, USA; Interdisciplinary Toxicology Program, University of Georgia, Athens, GA 30602, USA; Faculty of Veterinary Science, University of Sydney, NSW 2006, Australia; Centre for Crocodile Research, PO Box 329, Noonamah, NT 0837, Australia.
² Faculty of Veterinary Science, University of Sydney, NSW 2006, Australia.
³ Faculty of Veterinary Science, University of Sydney, NSW 2006, Australia; Centre for Crocodile Research, PO Box 329, Noonamah, NT 0837, Australia. Electronic address: sally@crocresearch.com.au.

PMID: 26631457
DOI: 10.1016/j.ygcen.2015.11.016

Abstract

Agricultural production of the saltwater crocodile (Crocodylus porosus) is an emergent industry in northern Australia with many of the factors affecting production remaining unknown. In this study, we sought to expand upon our previous findings of reference corticosterone and immune function by reporting baseline sex hormone levels [testosterone (TEST) and estradiol (ESTR)] and their association with growth. This was achieved by sampling 253 hatchling crocodiles repeatedly at 3, 6, and 9months of age. Sampling age had a significant effect on both TEST (p<0.001) and ESTR (p<0.001) suggesting climatic/abiotic factors have an influence even in prepubescent crocodiles. Stress, as measured by plasma corticosterone, had no detectable effect on plasma ESTR or TEST levels. Unexpectedly however, TEST was higher in slower-growing crocodiles, which is contrary to what has been reported for the American alligator. ESTR was not associated with growth.

Keywords: Estradiol; Growth; Saltwater crocodile; Stress; Testosterone.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Alligators and Crocodiles / blood*
Alligators and Crocodiles / growth & development
Animals
Australia
Estradiol / blood
Female
Male
Testosterone / blood*

Substances

Testosterone
Estradiol