How to tell if your Abdopus aculeatus is a male.

[Neogonodactylus]

It isn't always easy to sex an octopus, but it is fairly simple to tell if an Abdopus aculeatus is male. When the animal climbs onto the front wall of the aquarium (which they usually will do), look at the suckers near the base of the first and second pair or arms. In mature males, they are enlarged. They are smaller in females and juveniles.

The hectocotylized arm of the male is also easy to spot. It is the third, right arm. In this shot it looks like the fourth, but it's actually the third. When they look to the side they usually stick their eye over the web between arms I and II- so the left arm I is draped over to the right side, throwing off the count. Note the spermatophoral groove on the trailing edge. It extends the entire length of the arm. Not visible is the small ligula on the tip of the arm.

 

[Thales]

Thanks Roy.

 

[Neogonodactylus]

A. aculeatus ligula

Like Mucktopus said, the ligula in this species is small. This is the best photo I have of it. It is the claw-shaped object at the center of the whirl.

Roy

 

[DWhatley]

Roy, I copied the first post to an older thread in the biology section to add content and will add the ligula photo post as well since Tony promoted the original to an article from that section.

 

[Neogonodactylus]

Better shots of A. aculeatus ligula

The last shot that I posted of the ligual was not very clear since males usually keep the tip of the hectocotylus coiled. These shots are slightly better.

Roy