Male octopuses use a specialised arm called the hectocotylus to deliver sperm to females, and scientists have now discovered this arm can detect the female hormone progesterone. This sensory ability allows the male to locate the female's reproductive tract and mate without seeing her, as observed in California two-spot octopuses. In experiments at Harvard University, males successfully mated through a barrier by extending the arm into the female's mantle and locating egg transport tubes, even in complete darkness. The behaviour did not occur between males, suggesting the arm responds specifically to female chemical cues. Professor Nicholas Bellono, senior author of the study, said the arm acts as both sensor and mating organ, which is crucial for solitary animals that rarely interact. The findings were published in the journal Science by Bellono and first author Pablo Villar.
The discovery that male octopuses rely on hormonal detection through a specialised arm offers insight into reproductive biology that could inform how students understand animal behaviour and sensory adaptation. This research highlights how species evolve precise mechanisms for survival, enriching biology curricula with concrete examples of neurosensory function in invertebrates.
