Dive Dry with Dr. Bill

#497: They Take Their Chances... and Roll the Dice

Some people feel I am obsessed with sex. I have to wonder about them since there are two fundamental activities almost every species engages in, hence my cable TV show about Munching and Mating in the Macrocystis (Giant Kelp)." The individual must munch to ensure its survival and the species must reproduce to ensure it persists. Anyone who does NOT think about these things is open to question in my professional opinion! These are fundamental necessities of life. Yes, I know... breathing is also pretty fundamental, but I doubt I'd get many readers for this column or viewers of my TV show if I focused strictly on respiration! Agreed?

Summer is the time for night dives. The water and air are warmer, so I can enjoy a long, toasty submersion with plenty of bottom time to film "the night shift." Perhaps of equal importance is that I can drive home in my wet wetsuit without developing hypothermia! The only drawback to summer night diving is that the sun sets later in the evening, requiring me to skip any other nocturnal entertainment like karaoke at El Galleon or a movie in the Casino theater... the social sacrifices we scientists have to make to further our careers.

A few weeks back I drove down to the dive park dressed in my wetsuit and waited for the sun to sink below the horizon. I set up my video and SCUBA gear as darkness fell. No sooner had I dropped down to a mere 15 ft than I came across a pair of garibaldi mating! I had never seen them mate at night. Usually the males won't even tend their nests, and hide in the rocks nearby to avoid being eaten by nocturnal predators such as sea lions or sharks. I'm guessing this garibaldi male was the shy, modest type who preferred the cover of darkness and was willing to risk death for love! How gallant. How stupid!

On this dive I cruised way beyond my normal range in search of subjects to film. The "night shift" was out in force... lobster, black sea urchins, crabs and various species of snails cruised the kelp forest in search of munchies. The "day shift" including sheephead, blacksmith and garibaldi were tucked away in their cozy rock beds to avoid the horror of being munched. Those who only dive during the day are missing much of the picture of the ecological relationships in giant kelp habitats. Those who don't dive, can enjoy some of this by comparing what they see on the glassbottom boats day and night... or just watch my TV show episodes on "the Night Shift" on YouTube! It's well worth the price of admission.

I was nearing an hour underwater and making my way back near the dive park stairs when I looked up and saw one of my sought after subjects. There was a lonely segmented worm wriggling up through the water column towards the light... only the shine wasn't from the moon, it was from my video lights. I started recording and suddenly the worm let loose a cloud. It was spawning... releasing either sperm or eggs in hopes that they would encounter their opposite somewhere in the water column.

I turned toward the open ocean and noted that dozens of these worms were now ascending, and that was just counting the ones I could detect with my video lights. There were countless others beyond the range of my LEDs. I had encountered one of the most incredible nocturnal orgies I've ever filmed with these worms. They wriggled their way up towards the surface, often with detours to head in the direction of my lights. Several released their gametes as they rose, creating clouds of white between them.

Now by casting their gametes into the water together and relying on chance, these worms don't indulge in any niceties like mate selection and courtship. Mating is almost entirely random in their case. As a scientist trained in evolutionary biology, I have to wonder how all this sorts out via natural selection. Many critters select their mates carefully based on criteria that enhance their chances for survival of the young: brawny muscles to do well in the hunt or an ample bosom to nourish the kids. Some, like myself, wisely add intelligence to the list (and leave off the brawny muscles)! These worms just roll the dice and take their chances.

One thing that amazed me is that although the worms were highly visible in my beams, I never saw a single one gulped down by any of the fish predators out for an evening snack or a late dinner. I wondered if perhaps these worms were toxic and the fish had learned through trial and error not to gobble them up. The only predators I saw while filming this amazing encounter were the sea lions that cavorted below me as I filmed suspended in mid-water. Of course I had to check to make sure those shapes did not sport dorsal fins and sharp teeth!

I have not been able to get an ID on these worms over the past few years. Dr. Leslie Harris from the Los Angeles County Museum of Natural History has offered to do so if I could capture a specimen and send it to her. In the past I've been reluctant to do so because I treated the dive park as a de facto marine protected area (MPA). Now that it has officially become a State sanctioned MPA, I would be violating the law by sampling even one. Heck, I'm one who stops cleanly at every stop sign, yields right-of-way to uphill traffic and doesn't walk around town with open containers (unless it's a soft drink or coffee). Such a goody two shoes! Oh, and I don't take "chances."

© 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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Individual polychaete worm and cluster of spawning worms; worm releasing gametes and cloud of gametes from several worms.

This document maintained by Dr. Bill Bushing.
Material and images © 2012 Star Thrower Educational Multimedia