Biology subjects

Mishkind, D.

Publications and source records attributed to Mishkind, D..

3 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↗

bioRxiv2023

A dynamic Hedgehog gradient orients tracheal cartilage rings

The patterning of periodic stripes during embryonic development generates similar structures that repeat at regular spatial intervals within a tissue. These patterns are often attributed to a Turing-like mechanism, which self-organizes characteristically spaced stripes, but these patterns are predicted to be disorganized. Conversely, well-oriented, parallel stripes are often observed in nature. We investigate this phenomenon during the formation of the cartilage rings that support the amniote airway. We find evidence that a Turing-like mechanism underpins the formation of the repeating cartilage elements. Additionally, SHH is transiently expressed in a thin dorsal domain along the length of the developing trachea, resulting in a dorsoventral gradient of Hedgehog activity that recedes over time. Using mathematical modelling, we predict that the spatiotemporal dynamics of the gradient are required to organize the stripes into parallel rings. Comparing in silico predictions with experimental SHH manipulations shows that the Hedgehog gradient is essential for proper tracheal cartilage patterning.

developmental biology↗