Story perspectives

Male Octopuses Prioritize Arm Safety Over Reproduction

4/9/2026

Summary

Story summary

Male Japanese pygmy octopuses avoid using their right third arm, the hectocotylus, when exploring potential dangers.
In experiments, females used the hectocotylus freely, showing a sex difference in limb use.
Losing the hectocotylus could greatly reduce a male's reproductive ability, since regeneration takes two to three months.
The study suggests protecting the hectocotylus is a more efficient evolutionary strategy than developing a longer penis; the findings appear in Ethology.

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Story summary

Male Japanese pygmy octopuses avoid using their right third arm, the hectocotylus, when exploring potential dangers.
In experiments, females used the hectocotylus freely, showing a sex difference in limb use.
Losing the hectocotylus could greatly reduce a male's reproductive ability, since regeneration takes two to three months.
The study suggests protecting the hectocotylus is a more efficient evolutionary strategy than developing a longer penis; the findings appear in Ethology.