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Odd Male Octopus Flaunts 2 Unexpected Arm Phalluses

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octopus arm phallus hectocotyli

Image of a more anatomically average giant Pacific octopus; courtesy of Flickr/California Academy of Sciences

Is that a case of bilateral hectocotylization, or are you just extra happy to see me?

Or so might a female octopus say if she met the young subject of a new report about a certain biological oddity—or oddities.

A rare juvenile octopus was captured off the coast of Alaska flaunting not one but two hectocotyli, the arm male octopuses use to fertilize females.

Male octopuses lack what we think of as the standard male sex organ. But they’re certainly not lacking in the appendage department.

They can’t use just any arm to pass along their goods to a female, however. Their third right arm (it’s true) is specially adapted, complete with a channel for the sperm packets and erectile tissue on the tip. It is this arm that they either insert into a female’s mantle during mating or hand over in its entirety, for use at her discretion.

But it’s not every day that researchers find an octopus with two of these arms of love.

In fact, “in over one hundred years of research, double hectocotylization has been reported in only six individual cases,” write Reid Brewer and Andrew Seitz, of the University of Alaska Fairbanks, in a new paper published in Malacologia. In each of these cases the male had the standard third right arm hectocotylus as well as an additional one somewhere else.

Now, Brewer and Seitz report the most unusual case of all: a teen male octopus with two hectocotyli, neither of which was located on the third right arm. Instead, this 14-kilogram giant Pacific octopus (Entreoctopus dofieini) skipped the traditional limb and possessed a hectocotylus on his fourth left and fourth right arms instead.

Still a growing boy, this male’s hectocotyli were each more than 120 centimeters long and similar in length and number of suckers. This symmetry surprised the scientists further. Other anomalous double-barreled male octopuses have had a much more diminutive extra organ. He was also the first of his species to be documented with two hectocotyli. These findings support the going hypothesis that these rare mutations don’t follow the same pattern each time they occur.

The octopus seemed to be on track to develop normally otherwise, the researchers reported. It seems his extra specialized arm hadn’t hurt his (food) hunting abilities. But his luck with the ladies remains unknown.

To learn more about the odd mating rituals of the octopus, take a peek at Octopus! The Most Mysterious Creature In the Sea. I won’t tell.

Illustration courtesy of Ivan Phillipsen

Katherine Harmon Courage About the Author: Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

The views expressed are those of the author and are not necessarily those of Scientific American.

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