Penetrating the mysteries of sex in deep-sea squid

Undoubtedly you’ve already seen the above video of deep-sea squids mid-coitus at 1400 meters (0.86 miles) deep in the Gulf of Mexico.  The male and female Pholidoteuthis adami are unconcerned with the lights, cameras, and audience. However, you may not know what is actually going on here.  Well you may have some idea.  Well I’m going to give you all of the scintillating details as if I was Miranda on Sex on the City.  And yes I’m embarrassed I both know and made that pop cultural reference.

Stop reading here if you are at work.

First, the male is on top and the female is on bottom, facing opposite directions.  The pair is in sort of twisted missionary or inverse, reverse cowgirl.  The female is actively swimming with her fins.  So it is more a moving-inverse-reverse-cowgirl.  This position is so far unique among squids who typically prefer something closer to missionary.  Although there are several hypotheses for this, one of my favorites is it prevents the female from grabbing and eating the male. It happens.

From the picture below you can see he has a three way grip on her.  Two arms extend above her fins, another two below, and another two straddle her mantel (i.e. body). The arms are labelled AII-AIV in the photo for arm pairs two through four.  Yes the arm pairs in squid are numbered! In museum specimens scarring actually is found on females from being held tightly and passionately.

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Now some basics of squid sex. Male squids have spermatophores, basically an organ that hold millions of sperm.  The spermatophore contains a sperm mass, the spermatangium, that is released during the lovely sounding spermatophoric reaction.  This reaction is triggered either when the spermatophore is brought outside the body and in contact with seawater or by physical stimulation during coitus. The spermatangium than can either attach or implant into the female’s body.  Squid often have a modified arm called the hectocotylus for “aiding” the transfer of the spermatophore.  Basically, the hectocotylus is the throwing arm for a ball of sperm.  Watch for the switchup.  But, deep-sea squids don’t have hectocotyli.  In deep-sea squids the spermatophore storage sac is elongated into a terminal organ, hehe terminal organ, basically a penis.

So in the video and photo above that white think labelled TO, terminal organ, is mister winky.  The male here is not inserting the terminal organ into the female.  Think of this more as a firehose scenario but instead of water its packets of sperm.  In specimens of females, most of the spermatangium were found deeply embedded in the muscle of the mantle near the base of the fins. It may be the moving-inverse-reverse-cowgirl position also allows for greater movement of the firehose.

H. J. T. Hoving and M. Vecchione Mating Behavior of a Deep-Sea Squid Revealed by in situ Videography and the Study of Archived Specimens Biol Bull 2012 223:263-267

Dr. M (1729 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, a National Science Foundation supported initiative. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web. His forthcoming book, Science of the South (, connects cultural icons of South such as pecan pie with the science behind them.

2 comments on “Penetrating the mysteries of sex in deep-sea squid
  1. I thought that said “…in contact with sweater or by physical stimulation during coitus…”

    I was so confused I had to re-read the whole thing.

  2. Pingback: I’ve got your missing links right here (19 January 2013) – Phenomena: Not Exactly Rocket Science

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