skip to content

Department of Zoology

 
Subscribe to Upcoming Seminars and Events feed
This list is intended to include all talks and seminars taking place in the Department of Zoology.
Updated: 36 min 38 sec ago

Wed 29 May 13:00: Extreme morphogenetic canalization of ascidian embryonic development

Mon, 13/05/2019 - 17:20
Extreme morphogenetic canalization of ascidian embryonic development

Canalization of developmental processes ensures the reproducibility and robustness of embryogenesis within each species. In its extreme form, found in ascidians, early embryonic cell lineages are invariant between embryos within and between species, despite rapid genomic divergence. To resolve this paradox, we used live light-sheet imaging and developed automated single-cell segmentation and tracking procedures to quantify individual embryonic cell behaviors. This quantitative approach revealed that individual cell lineages, cell geometries, positions and even contacts are highly reproducible between embryos. This extreme reproducibility may be linked to the control of fate specification by local cell inductions. While in vertebrates the outcome of cell inductions is usually controlled by the concentration of diffusible extracellular ligands, ascidian cell inductions appear to be controlled by the area of contacts between signalling and responding cells, rather than by differential concentrations of ligands. We propose that the duality between genetic and geometric control of inductions contributes to the counterintuitive inverse correlation between geometric and genetic variability during embryogenesis.

Add to your calendar or Include in your list

Wed 08 May 13:00: TBC

Fri, 03/05/2019 - 13:18
TBC

TBC

Add to your calendar or Include in your list

Wed 29 May 13:00: Extreme morphogenetic canalization of ascidian embryonic development

Tue, 30/04/2019 - 13:28
Extreme morphogenetic canalization of ascidian embryonic development

Canalization of developmental processes ensures the reproducibility and robustness of embryogenesis within each species. In its extreme form, found in ascidians, early embryonic cell lineages are invariant between embryos within and between species, despite rapid genomic divergence. To resolve this paradox, we used live light-sheet imaging and developed automated single-cell segmentation and tracking procedures to quantify individual embryonic cell behaviors. This quantitative approach revealed that individual cell lineages, cell geometries, positions and even contacts are highly reproducible between embryos. This extreme reproducibility may be linked to the control of fate specification by local cell inductions. While in vertebrates the outcome of cell inductions is usually controlled by the concentration of diffusible extracellular ligands, ascidian cell inductions appear to be controlled by the area of contacts between signalling and responding cells, rather than by differential concentrations of ligands. We propose that the duality between genetic and geometric control of inductions contributes to the counterintuitive inverse correlation between geometric and genetic variability during embryogenesis.

Add to your calendar or Include in your list

Wed 15 May 13:00: From development to deep time: the macroevolutionary consequences of phenotypic integration in living and extinct tetrapods

Mon, 29/04/2019 - 16:57
From development to deep time: the macroevolutionary consequences of phenotypic integration in living and extinct tetrapods

Interactions among morphological traits, or phenotypic integration, reflect genetic, developmental, and functional relationships among traits and can significantly bias morphological evolution. Simulations using theoretical and empirical trait covariance matrices confirm that integration can result in both more and less disparate organisms, and most often the latter, than would be expected under unconstrained evolution. However, high rates can persist even when morphological disparity is constrained by trait integration. Similar to a “fly in a tube”, trait integration may restrict evolution to particular regions of possible morphospace, but it doesn’t necessarily limit the pace of evolution within those regions. Importantly, high evolutionary rates within restricted regions of morphospace would be expected to result in a high degree of convergence and homoplasy.

Here, I discuss the patterns of cranial phenotypic integration and morphological evolution in a dataset spanning over 1000 species of living and extinct tetrapod species and representing over 300 million years of evolution. While most large-scale studies of phenotypic integration and morphological evolution utilise relatively limited descriptors of morphology, hindering comparisons across clades, surface sliding semi-landmark analysis allows for detailed quantification of complex 3D shapes, even across highly disparate taxa. Our dense 3D morphometric dataset of 700-1500 landmarks and sliding semi-landmarks demonstrates that patterns of cranial modularity are generally conserved across large clades (e.g., within mammals, birds, squamates, caecilians), there are clear shifts in patterns of integration across these clades. Tempo and mode are similarly highly variable across cranial regions and clades, with high variance concentrated in neural crest-derived regions, in particular the jaw joint and facial regions. While some clades show evidence that high integration constrains morphological evolution, there is not a consistent pattern of constraint across tetrapods.

Add to your calendar or Include in your list