Sea urchin sperm exploit extremum seeking control to find the egg

TL;DR

This paper reveals that sea urchin sperm use an extremum seeking control strategy to efficiently locate eggs, providing a new perspective on microorganism navigation and potential bio-inspired robotic applications.

Contribution

The study demonstrates that sea urchin sperm navigation is an implementation of extremum seeking control, bridging control theory and biological taxis mechanisms.

Findings

Sperm navigation follows extremum seeking principles.

A coarse-grained model of signaling explains switching behavior.

Insights may inform bio-inspired robotic design.

Abstract

Sperm cells perform extremely demanding tasks with minimal capabilities. The cells must quickly navigate in a noisy environment to find an egg within a short time window for successful fertilization without any global positioning information. Many research efforts have been dedicated to deriving mathematical principles that explain their superb navigation strategy. Here we show that the navigation strategy of sea urchin sperm, also known as helical klinotaxis, is a natural implementation of a well-established adaptive control paradigm known as extremum seeking. This bridge between control theory and the biology of taxis in microorganisms is expected to deepen our understanding of the process. For example, the formulation leads to a coarse-grained model of the signaling pathway that offers new insights on the peculiar switching-like behavior between high and low gain steering modes observed in sea urchin sperm. Moreover, it may guide engineers in developing bio-inspired miniaturized robots with minimal sensors.