Biology subjects

Goller, F.

Publications and source records attributed to Goller, F..

4 recordsLinked to original sources

bioRxiv2025

Courtship vocalizations in male ducks: spectral composition and resonance of the syringeal bulla

Ducks display a unique and dramatic sexual dimorphism in their vocal organ, the syrinx. Males have a left-sided bulla that is not present in females and that has been long hypothesized to play a role in courtship vocalizations, though this connection has never been tested. The large, hollow morphology of the bulla and its proximity to the sound-producing vocal folds introduce the possibility that it may work as a Helmholtz resonator, which makes it possible to predict the resonance frequencies enhanced by this structure. We find that during early ontogeny, the distribution of energy across the harmonic spectrum of contact calls is not different between males and females. We then used micro-CT scans of duck syrinxes to estimate resonance frequencies of the bullae and compared these to spectral features of their vocalizations. This comparison overall supports the idea that the bulla resonance may specifically enhance aspects of courtship vocalizations, especially in species that have a tonal courtship whistle. We also see potential influence in non-courtship vocalizations, which could be explored further with a greater understanding of the input of other vocal tract features that influence vocalization. We observed that bulla size is positively correlated with bird body mass with the largest exception in the Common Eider, which had a small bulla for its body mass and for which we saw no evidence of bulla-input to its vocalizations. This study found support for the long-held hypothesis that the adult male duck bulla influences resonance frequencies, in particular in courtship vocalizations.

physiology↗

bioRxiv2024

Integration of sexual dimorphism and left-right asymmetry in the development of the duck syrinx

Embryonic morphogenesis is regulated across multiple dimensions. In ducks, the syrinx, the avian vocal organ, undergoes morphogenic processes that result in both left-right asymmetric and sexually dimorphic development. Although these properties are thought to be controlled by the NODAL-PITX2 left-right signaling cascade and the sex steroid pathways, how these mechanisms work together to produce an asymmetric structure in a sexually dimorphic manner remains unclear. Here, we first establish evidence for sexual selection driving the evolution of the duck syrinx. During its development, we observe that PITX2 is expressed on the left side in both male and female ducks, although not in other birds. Asymmetric activation of PITX2 in this domain is triggered by bilateral BMP signaling but is limited to the left side by left-specific stably accessible chromatin established during an earlier asymmetric wave of PITX2 expression. Ultimately, there is an induction of left-specific WNT and BMP signaling in the syrinx primordium, which synergistically elevates cell proliferation on the left, leading to asymmetric growth. Estrogen receptor expression is also shown to be induced on the left side of the forming syrinx. This has no effect in males, but in females where the hormone is present, estrogen signaling reduces left-sided cell proliferation, thus promoting bilaterally symmetric growth. These data demonstrate how sexually dimorphic left-right asymmetry can be integrated to produce an adaptive trait.

developmental biology↗

bioRxiv2019

Skeletal muscles that actuate sexual displays are specialized for de novo androgen synthesis

The gonads (testes) act as the primary organ where androgenic hormones are made to regulate reproductive behavior in male vertebrates. Yet many endocrinologists have also long suspected that other tissues in the body can autonomously synthesize their own androgens to support behavioral output. We examine this idea here by studying whether avian skeletal muscles that actuate elaborate socio-sexual displays are specialized to maintain the molecular machinery otherwise needed for de novo androgen synthesis. Our results show that the vocal organ, or syrinx (SYR), of two songbirds species does in fact express all transporters and enzymes necessary to create androgenic hormones from scratch. This includes genes that encode proteins to mediate rate-limiting steps of steroidogenesis, which are seldom found outside of the gonads. We also show that expression levels of these genes are far greater in the SYR than non-display muscles, matching expression levels found in another extra-gonadal site of steroidogenesis--the brain. Furthermore, we uncover a nearly identical gene expression signature in a woodpecker neck muscle, the longus colli ventralis (LC). This tissue actuates the birds social drum display, which serves the same functions as song. This same study also demonstrates that the elevated expression of steroidogenic genes persists in this neck muscle year-round, suggesting that the LCs capacity to make androgens is a constitutive trait. Altogether, our findings suggest that muscles involved in sexual display is uniquely specialized to locally make steroid hormones, likely supporting their own role in behavioral production.

physiology↗

bioRxiv2018

Synthetic stimuli reveal a predictive and switch-like activation of the songbird’s vocal motor program

Acquisition and maintenance of complex vocal behaviors like human speech and oscine birdsong require continuous auditory feedback. The exact way in which this feedback is integrated into the vocal motor programs is not completely understood. Here we show that in sleeping zebra finches (Taeniopygia guttata), the activity of the song system selectively evoked by playbacks of their own song can be detected in the syrinx. Measuring the electrical activity of syringeal muscles, we found playback-evoked patterns identical to those recorded during song execution. Using this global and continuous readout we studied the activation dynamics of the song system elicited by different auditory stimuli. We found that a synthetic version of the birds song, rendered by a physical model of the avian phonation apparatus, evoked exactly the same response, albeit with lower efficiency. Analysis of these responses reveal a predictive and switch-like activation of the motor program, with preferred activation instants within the song.\n\nSignificanceThe study of the integration between sensory inputs and motor commands has greatly benefited from the finding that in sleeping oscine birds, playback of their own song evokes highly specific firing patterns in neurons also involved in the production of that song. Nevertheless, the sparse spiking patterns that can be recorded from few single neurons gives limited information of the overall activity of the song system. Here we show that this response is not limited to the central nervous system, but reaches vocal muscles. Combining this integrated measure of the activity of the system with surrogate synthetic songs, we found an all-or-nothing and predictive activation of the system, suggesting the existence of a pre-programmed internal dynamics.

neuroscience↗