The advantages of the pentameral symmetry of the starfish

TL;DR

This study uses mathematical and physical analyses to demonstrate that pentameral symmetry in starfish offers optimal performance in key survival functions, explaining its evolutionary dominance.

Contribution

The paper provides a novel quantitative analysis showing the evolutionary advantage of five-armed starfish over other arm numbers.

Findings

Five-armed starfish perform best overall in detection, turning over, autotomy, and adherence.

Five-armed starfish exhibit superior autotomy capabilities.

The dominance of five-armed starfish is supported by their functional advantages.

Abstract

Starfish typically show pentameral symmetry, and they are typically similar in shape to a pentagram. Although starfish can evolve and live with other numbers of arms, the dominant species always show pentameral symmetry. We used mathematical and physical methods to analyze the superiority of starfish with five arms in comparison with those with a different number of arms with respect to detection, turning over, autotomy and adherence. In this study, we determined that starfish with five arms, although slightly inferior to others in one or two aspects, exhibit the best performance when the four aforementioned factors are considered together. In addition, five-armed starfish perform best on autotomy, which is crucially important for starfish survival. This superiority contributes to the dominance of five-armed starfish in evolution, which is consistent with the practical situation. Nevertheless, we can see some flexibility in the number and conformation of arms. The analyses performed in our research will be of great help in unraveling the mysteries of dominant shapes and structures.