Light-regulated collective contractility in a multicellular choanoflagellate

Area of Science:

• * Developmental Biology
• * Evolutionary Biology
• * Cellular Biology

Background:

• * Collective cell contractions are crucial for animal development and movement.
• * The evolutionary origins of these coordinated cellular behaviors remain largely unknown.
• * Choanoflagellates are the closest living relatives to animals, providing a model for studying early animal evolution.

Purpose of the Study:

• * To investigate the cellular and molecular mechanisms underlying collective cell contractility in choanoflagellates.
• * To explore the sensory and behavioral responses of multicellular choanoflagellate colonies.
• * To gain insights into the pre-bilaterian ancestors of animals.

Main Methods:

• * Isolation and characterization of a new choanoflagellate species, *Choanoeca flexa*, from Curaçao.
• * Observation of colony morphology and behavior in response to environmental stimuli (light levels).
• * Investigation of the cellular machinery involved in colony inversion, including actomyosin and sensory pathways (rhodopsin-cyclic guanosine monophosphate).

Main Results:

• * *Choanoeca flexa* forms multicellular, cup-shaped colonies capable of rapid inversion.
• * Colony inversion is triggered by changes in light levels, detected via a rhodopsin-cyclic guanosine monophosphate pathway.
• * The inversion process is mediated by actomyosin-dependent apical contractility, enabling behavioral switching between feeding and swimming.

Conclusions:

• * *Choanoeca flexa* demonstrates a direct link between sensory input and multicellular contractile responses.
• * This organism provides a model for understanding how early animal ancestors may have integrated environmental sensing with coordinated cellular actions.
• * The findings shed light on the evolution of specialized sensory and contractile cells in animals.