Hélène de Maleprade (IRPHE) - Shape and coordinated motion in the simplest multicellular alga
Microscopic green algae are commonly found in mud, puddles or lakes, and show great diversity in structural complexity. The unicellular Chlamydomonas exhibits two flagella whose beating enables it to swim in a breast stroke towards light, a nowadays widely studied behaviour favouring photosynthesis. One also finds Gonium, an algae made of 16 Chlamydomonas-like cells. It is flat and squared, with all flagella on one side of the plate. This simple algae is a key organism to understand the evolution towards multicellularity. In the absence of central nervous system, how can each cell adapt its individual photoresponse to efficiently reorient the whole algae? How crucial is the distinctive squared structure? In this talk, I will present our experiments investigating the shape and the phototactic swimming of Gonium, using trajectory tracking and micro-pipette techniques. I will explain our model linking the individual flagella response to the 16-cell colony trajectory. This eventually emphasises the importance of biological noise to succeed swimming towards light.
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- 2021-01-19 11:00