Cellular geometry controls the efficiency of motile sperm aggregates

TL;DR

This study uses computational models to explore how sperm head shape and adhesive regions influence the stability and mobility of sperm aggregates, revealing that geometry plays a crucial role in their efficiency during fertilization.

Contribution

It introduces a detailed computational approach to analyze the impact of cellular geometry on sperm aggregate performance, highlighting the significance of head shape and adhesive region structure.

Findings

Head geometry significantly affects aggregate stability and mobility.

The apical hook may enhance alignment and efficiency of sperm aggregates.

Shape and adhesive region design are crucial for optimizing sperm cooperation.

Abstract

Teams of cooperating sperm have been found across several vertebrate and invertebrate species, ranging from sperm pairs to massive aggregates containing hundreds of cells. Although the biochemical mechanisms involved in the aggregation process are still unclear, it was found that aggregation can enhance the mobility of the cells, thus offering an advantage during fertilization. Here, we report a thorough computational investigation on the role of cellular geometry in the performance of sperm aggregates. The sperm head is modelled as a persistent random walker characterized by a non-trivial three-dimensional shape and equipped with an adhesive region, where cell-cell binding occurs. By considering both a simple parametric head shape and a computer reconstruction of a real head shape based on morphometric data, we demonstrate that the geometry of the head and the structure of the adhesive region crucially affects both the stability and mobility of the aggregates. Our analysis further suggests that the apical hook commonly found in the sperm of muroid rodents, might serve to shield portions of the adhesive region and promote efficient alignment of the velocities of the interacting cells.