The embryos of egg-laying species are exposed to variable thermal regimes, which can influence not only the resultant hatchling’s morphology (e.g., size, sex) and performance (e.g., locomotor speed), but also its cognitive performance (learning ability). To clarify the proximate basis for this latter effect, we incubated eggs of the scincid lizard Bassiana duperreyi under simulated ‘hot’ and ‘cold’ natural nest temperatures to examine the effect of incubation temperature on the structure of the telencephalon region of the forebrain. Hatchlings from low-temperature incubation had larger telencephalons (both in absolute terms and relative to body size) and larger neurons in their medial cortices, whereas the medial cortices of hatchlings from high-temperature incubation had fewer neurons overall, but greater neuronal density, and more neurons in certain areas. These temperature-induced differences in B. duperreyi forebrain development are consistent with (and may explain) the disparities in learning ability between hatchlings from our two incubation treatments. The phenotypic plasticity of lizard telencephalon anatomy in response to incubation temperature presents exciting opportunities for studies on the evolutionary and developmental determinants of intelligence in vertebrates, but also offers a cautionary tale. Global climate changes, wrought by anthropogenic activities, may directly modify brain structure in reptiles.
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For funding, we thank the Australian Research Council and the Natural Sciences and Engineering Research Council of Canada. We thank Sanaz Maleki and Shanna Trollip (University of Sydney) for their guidance with histological preparations, and acknowledge Melanie Elphick, Breanna Chipney and Chris Chipney for technical assistance and Lainy Day (University of Mississippi), Ester Desfilis (Universitat de Lleida), Pau Carazo (University of Oxford) and Roger Pamphlett (University of Sydney) for sharing their expertise in neuroanatomy. Input from reviewers substantially improved the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All research was approved by the University of Sydney Animal Ethics Committee (L04/12-2010/3/5449). Collecting permits were provided by the ACT Government Territory and Municipal Services.
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