Publications by authors named "Ioana Chiver"

3 Publications

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Repeated assessment of changes in testes size in canaries by X-ray computer tomography.

Gen Comp Endocrinol 2021 May 6;310:113808. Epub 2021 May 6.

GIGA Neurosciences, University of Liège, Belgium. Electronic address:

Numerous studies have evaluated changes in time of testicular development in birds by exploratory laparotomy or post-mortem autopsy. The invasive nature of these approaches has obviously limited the frequency at which these measures can be collected. We demonstrate here that accurate assessment of gonadal size can be reliably and repeatedly obtained by computer-assisted X-ray tomography (CT scans). This approach provides images of the testes in the three orthogonal planes that allow measuring either the largest diameter or even the volume of the testes, providing results that match those obtained by surgical approaches.
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http://dx.doi.org/10.1016/j.ygcen.2021.113808DOI Listing
May 2021

Behavioral Sex Differences and Hormonal Control in a Bird with an Elaborate Courtship Display.

Integr Comp Biol 2021 Apr 22. Epub 2021 Apr 22.

Panama Avenida Williamson # 156, Gamboa, Panama.

Gonadal hormones can activate performance of reproductive behavior in adult animals, but also organize sex-specific neural circuits developmentally. Few studies have examined the hormonal basis of sex differences in the performance of elaborate, physically complex and energetic male courtship displays. Here we describe our studies over more than 20 years examining sex difference and hormonal control of courtship in Golden-collared manakins (Manacus vitellinus) of Panamaian rainforests. Our recent studies of birds studied in an artificial "lek" in a rainforest aviary provide many new insights. Wild and captive males and females differ markedly in their performance of male-typical behaviors. Testosterone (T) treatment augments performance of virtually all of these behaviors in juvenile males with low levels of circulating T. By contrast, T-treatment of females (with low circulating T) either failed to activate some behaviors or activated male behaviors weakly or strongly. These results are discussed within a framework of our appreciation for hormonal vs genetic basis for sex differences in behavior with speculation about the neural mechanisms producing these patterns of hormonal activation.
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http://dx.doi.org/10.1093/icb/icab033DOI Listing
April 2021

Neuromuscular mechanisms of an elaborate wing display in the golden-collared manakin ().

J Exp Biol 2017 Dec 23;220(Pt 24):4681-4688. Epub 2017 Oct 23.

Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA.

Many species perform elaborate physical displays to court mates and compete with rivals, but the biomechanical mechanisms underlying such behavior are poorly understood. We address this issue by studying the neuromuscular origins of display behavior in a small tropical passerine bird, the golden-collared manakin (). Males of this species court females by dancing around the forest floor and rapidly snapping their wings together above their back. Using radio-telemetry, we collected electromyographic (EMG) recordings from the three main muscles that control avian forelimb movement, and found how these different muscles are activated to generate various aspects of display behavior. The muscle that raises the wing (supracoracoideus, SC) and the primary muscle that retracts the wing (scapulohumeralis caudalis, SH) were activated during the wing-snap, whereas the pectoralis (PEC), the main wing depressor, was not. SC activation began before wing elevation commenced, with further activation occurring gradually. By contrast, SH activation was swift, starting soon after wing elevation and peaking shortly after the snap. The intensity of this SH activation was comparable to that which occurs during flapping, whereas the SC activation was much lower. Thus, light activation of the SC likely helps position the wings above the back, so that quick, robust SH activation can drive these appendages together to generate the firecracker-like snap sonation. This is one of the first looks at the neuromuscular mechanisms that underlie the actuation of a dynamic courtship display, and it demonstrates that even complex, whole-body display movements can be studied with transmitter-aided EMG techniques.
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http://dx.doi.org/10.1242/jeb.167270DOI Listing
December 2017