Neural circuit and genetic bases of behaviour in Platynereis larvae
EcoEvoDevo PhD course | February 24th-26th, 2025, SZN
Centre for Organismal Studies, Heidelberg University
@jekely@biologists.social
What is a larva?
larva
noun ˈlär-və
plural larvae ˈlär-(ˌ)vē, also larvas
1: the immature, wingless, and often wormlike feeding form that hatches from the egg of many insects, alters chiefly in size while passing through several molts, and is finally transformed into a pupa or chrysalis (see chrysalis sense 1a) from which the adult emerges
2: the early form of an animal (such as a frog or sea urchin) that at birth or hatching is fundamentally unlike its parent and must metamorphose before assuming the adult characters
What is a larva?
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 😎
What is a larva?
Platynereis dumerilii
- a gonochorostic species
- lecitotrophic non-feeding larvae
- free-swimming planktonic stage
Platynereis massiliensis
- a protandric hermaphrodite
- lecitotrophic direct development in brood tubes
- absence of a free-swimming stage
A real larva vs. a blob
Platynereis dumerilii
Platynereis massiliensis
“A larva [in a marine invertebrate] is a post-embryonic life-cycle stage that is freely swimming and can be lost during evolution”
Whole-body volume EM of an entire three-day-old larva
Whole-body volume EM of an entire three-day-old larva
Synaptic connectome
Whole-body coordination of cilia
Whole-body coordination of cilia
No arrest in polycystin receptor mutant
UV response in Platynereis larvae
UV-responding brain ciliary photoreceptors (cPRCs)
No UV avoidance in c-opsin1 knockouts
No cPRC response in c-opsin1 knockouts
Circuitry of ciliary photoreceptors
Circuitry of ciliary photoreceptors
Strong cPRC activation after UV exposure
Nitric-oxyde synthase in postsynaptic interneurons
NO is produced in the neuropil after UV stimulation
NOS mutants have altered cPRC response
NOS mutants have altered INRGW response
NOS mutants show defective UV avoidance
An unusual guanylyl cyclase in the cPRCs
An unusual guanylyl cyclase in the cPRCs
NIT-GC morphants have altered circuit activity
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
Photoreceptor responses to pressure are graded
Defects of pressure response in c-opsin1 mutants
Reduced ciliary compartment in c-opsin1 mutants
Defects of ciliary ultrastructure in c-opsin1 mutants
Acknowledgements
Lab members
- Sanja Jasek
- Alexandra Kerbl
- Emily Savage
- Simone Wolters
- Lara Keweloh
- Kevin Urbansky
- Karel Mocaer
- David Hug
- Benedikt Dürr
- Ira Maegele
- Emelie Brodrick (Exeter)
Facilities
- EM Core Facility
- Réza Shahidi
- Charlotta Funaya
- Nikon Imaging Centre
- Ulrike Engel
