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Dive Dry with Dr. Bill

#486: Mother's Day Magic

I couldn't be with Mom on Mother's Day, so I wanted to indulge in something peaceful, calming, adventurous and exciting. Of course that meant suiting up and heading down to the dive park for the day. But first I wanted to finish the last 150 pages in my latest book, so that resulted in a late start. Good thing as I was also aware the tide would be pretty low in the morning, making entries and exits even on our wonderful stairs a less desirable task. By the time I arrived, the water was rising and my dives would be much easier. After all, I'm a senior citizen!

Although many divers were spending the day with their moms, there were several I knew and could socialize with... further prolonging the beginning of my descent as the tide continued to rise. I spoke with one diver from PCH Scuba who said she had seen some strange behavior while observing two octopi. One seemed to have one arm (although many refer to them as tentacles) stuck inside the other and it was being stretched as the second octopus retreated from the diver's view. Being the highly trained dive bum (er, marine biologist) that I am, I knew this was probably an act of the other "M" word besides munching. You guessed it... the two appeared to be in the process of mating!

I've only filmed octopi mating a few times. Once, out on Ship Rock, I actually filmed an interesting example of mate selection by a female. She was being pursued by the make across the rocks. He exhibited all the vigor seen on Saturday night at the Chi Chi or Marlin Clubs. For whatever reason, she did not seem to be "in the mood." I don't know if these cephalopds get "headaches," but something just wasn't right for her that day. As he closed in for "the kill," she released a cloud of ink that seemed to stop him in his tracks... and slide into a small crevice to escape his amorous advances. Whew... I'm glad the ladies I approach (always like a gentleman) do not ink me... or spray me with pepper spray!

Finally I entered the water and proceeded toward the Suejac (harbor) end of the park. My last two dives had been relatively deep so I decided to be a fairly "shallow fellow" this time and extend my bottom time so I could film more footage. It was a good decision. Along my route I encountered several octopi and filmed brief segments. Shortly after I turned around, I spotted a fairly rare nudibranch (shell-less snail), Peltodoris mullineri, and filmed it. I remained above 30 ft on my return and ran into one of the octos I had seen on my way out. Something looked unusual, but it wasn't until it moved that I realized what I was seeing.

As this octopus retreated back into its little cave, I noticed that it appeared to have 16 rather than the usual eight arms. Was this some genetic mutation, I wondered. No, it was another octopus resting beneath the first one. Hmmm... pretty suspicious if you ask this trained professional. The first octopus inched back into the cave. I slowly squeezed my way into the narrow opening so I could get a better camera angle. The second octopus seemed to accept my presence and stood its ground, although it did pull a wavy top shell in front of its body for protection. I've seen them use these large and strong snail shells this way many times... they will even plug up their holes with the pointed shell.

Then suddenly an arm full of sucker disks lashed out and grabbed the poor lady. The male had climbed up on top of a rock above her and now pounced on the poor girl. What ensued was a wrestling match not unlike those in my high school gym classes (which, unfortunately, were not co-ed back in the Dark Ages). Our dashing, debonair dude appeared to insert his third arm on the right side. Given my decades of training, I knew this to be a modified arm known as the hectocotylus which is used to insert a sperm capsule into the target of his passion. A male octopus can also use this structure to scrape out her cavity and remove the amorous intentions of males who previously courted the lady.

I won't go into all the gory details of this mating encounter. I still want to retain a PG-13 rating for this column. However, it is interesting to note that a structure at the end of the male's hectocotylus known as the ligula shares a characteristic far more common with vertebrates than invertebrates. It gets... er... um.. hmmm... "excited" if you know what I mean. In fact, it is the only invertebrate known to have such a structure. Normally the ligula is much smaller, which is a good thing. Since it is white in color, a permanently "large" ligula might attract the attention of a predator. Ouch! Let's move on to less "sensitive" areas.

Once she has mated, the female retreats into a sheltered area to lay her eggs. Several thousand is the norm, but there may be as many as 150,000. WOW... some Mother's Day that makes. She will then brood and defend the eggs for one to four months, the duration of which is probably dependent on water temperature. It is said mom does not eat during this time and is so weakened by lack of nourishment that they often die after the eggs hatch. An octopus may live up to three years, suggesting more than one season of mating may occur. I'm sure glad female humans no longer experience high death rates during childbirth... what kind of Mother's Day would that make?

© 2012 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Sequence of images showing the initial stages of octopus mating (male on top).

This document maintained by Dr. Bill Bushing.
Material and images © 2011 Star Thrower Educational Multimedia