Embodied cognition in miniature brains and bodies of marine zooplankton

Pushing the Boundaries: Neuroscience, Cognition, and Life
June 25-27, 2023

Gáspár Jékely

Living Systems Institute, University of Exeter
Centre for Organismal Studies, University of Heidelberg

The ‘brain’

Ciliated zooplankton larvae

Platynereis dumerilii

breeding culture, full life-cycle
embryos daily, year round
genome sequence
microinjection, transgenesis
neuron-specific promoters and antibodies
knock-out lines
neuronal connectome
whole-body neuronal activity imaging
whole-animal pharmacology by bath application 😎

Platynereis dumerilii

Spawning
movie by Albrecht Fischer

Synchronously developing larvae

Whole-body volume EM of an entire three-day-old larva

The nervous system of the larva

~2,000 neurons

Synaptic connectome

Phototaxis

Helical swimming, sensing and turning are tightly linked

Whole-body coordination of cilia

Whole-body coordination during startle

Coordinated arrest of all cilia

No arrest in polycystin receptor mutant

Copepod attack

wild type polycystin mutant

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

Pressure is sensed by photoreceptors with ramified cilia

cPRC - ciliated Photoreceptor Cells

Circuitry of ciliary photoreceptors

Serotonergic neurons to activate cilia

Ser-h1 neurons, EM reconstruction

Mechanisms of barotaxis

UV-responding brain ciliary photoreceptors (cPRCs)

UV response in Platynereis larvae

Mediated by a UV-absorbing c-opsin1 photopigment

No UV avoidance in c-opsin1 knockouts

Strong c-opsin1-dependent cPRC activation by UV light

Nitric-oxyde synthase in postsynaptic interneurons

HCR Transgenic labelling

NO is produced in the neuropil after UV stimulation

NOS mutants show defective UV avoidance

NOS mutants have altered cPRC response

Mathematical modelling of the circuit

Integration and memory of UV exposure

What is the representation?

Principle 9: learning occurs at the lowest level to enable a causal influence on behaviour

Up or down?

‘front-wheel drive’ head cilia fast

‘rear-wheel drive’ head cilia slow

Acknowledgements

Emelie Brodrick
Cyrielle Kaltenrieder
Réza Shahidi
Milena Marinkovic
Daniel Thiel
Sanja Jasek
Cameron Hird
Rebecca Turner
Luis A. Bezares-Calderón
Kei Jokura
Luis Yanez Guerra
Alexandra Kerbl

Former lab members

Albina Asadulina
James Beard
Markus Conzelmann
Nadine Randel
Philipp Bauknecht
Martin Gühmann
Cristina Pineiro-Lopez
Nobuo Ueda
Aurora Panzera
Csaba Verasztó
Elizabeth Williams