vEM and Neuronal Connectomics in Marine Zooplankton Larvae
Volume Electron Microscopy
Gordon Research Conference
May 4 - 9, 2025, Castelldefels
Centre for Organismal Studies, Heidelberg University
@jekely@biologists.social
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Ciliated zooplankton larvae
Platynereis dumerilii
- breeding culture
- genome sequence
- microinjection, transgenesis
- neuron-specific promoters
- knock-out lines
- neuronal connectome
- neuronal activity imaging
Volume EM with Array Tomograpy
Array tomography workflow
Array tomography workflow
Multiciliated cells form ciliary bands
- basal-body spacing: 0.35-0.55 μm
Precise orientation of multiciliary arrays
expansion microscopy
Whole-body annotation of all ciliary basal bodies
Whole-body annotation of all ciliary basal bodies
- ~10,000 motile cilia
- high degree of left-right symmetry
- 3D additive manufacturing from anterior to posterior of the cell
Whole-body annotation of all ciliary basal bodies
Metachronal waves
- metachronal waves
- large-scale coordination of cilia
- steric interactions dominate
Towards vEM-informed simulations of ciliary fields
Annotation of all cell types
Annotation of desmosomes and their connections
Desmosomal connectome
Cell-type-level synaptic connectome
Neural circuit of the visual eyes
Startle recruits body-wide circuits and effectors
Whole-body coordination of cilia
Pressure response in Platynereis larvae
Precise control of pressure in the pressure chamber
Pressure response is graded
Swimming speed increases, trajectories straighten
ctr
pressure
Ciliary beating increases under pressure
Which cells respond to pressure?
Microscopy pressure chamber 
Calcium imaging 
Pressure is sensed by photoreceptors with ramified cilia
Defects of pressure response in c-opsin1 mutants
Reduced ciliary compartment in c-opsin1 mutants
Defects of ciliary ultrastructure in c-opsin1 mutants
Circuit of ciliary photoreceptors
Pressure increases ciliary beating through serotonergic cells
Mechanism of barotaxis
The ctenophore gravisensory organ
Ctenophore balancer organ
Ctenophore balancer organ
Ctenophore balancer organ
The ctenophore gravisensory organ
Balancer – a bundle of cilia supporting a statolyth
The beating of balancer cilia is coordinated by a nerve net
Synchronisation of balancer cilia
Conntectome of the ctenophore balancer
- global neuronal coordination
- synchronisation of arrests
- synchronisation of re-beat
- synchronisation of beat frequency
What’s next?
Comparative vEM & connectomics of marine larvae
- 12 labs (EU, UK)
- vEM of marine invertebrates
- evolution of cell types
- integrate with molecular atlases
Acknowledgements
- Alexandra Kerbl
- Karel Mocaer
- Sanja Jasek
- David Hug
- Jules Duruz
- Mateusz Kostecki
- Benedikt Dürr
- Kata Szabó
- Iva Verbanac
- Lara Keweloh
- Emily Savage
- Simone Wolters
- Selin Heinzelmann
- Kevin Urbansky
Alumni
- Kei Jokura (NIBB, Okazaki)
- Luis Bezares (LBDV, Villefranche-sur-mer)
- Emelie Brodrick (Sussex)
- Csaba Verasztó (EPFL)
Facilities
- Réza Shahidi
- Charlotta Funaya
- Ulrike Engel
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