And You Think You Are Stressed Out?

Stress is a part of everyone’s life.

The ability to minimize and/or manage it is most important to our overall health. Descending into the underwater realm is a method that we divers can use to relieve stress and relax. But what of the creatures that live there already? 

While visiting Cedar Beach/49th Parallel Dive Charters on Thetis Island, John and Mary Munch of Monterey, California dove at Escape Reef, in Stuart Channel on July 19, 2012. Keen nudibranch seekers, they encountered many of these creatures during the dive. Particularly abundant and obvious was the opalescent nudibranch Hermissenda crassicornis – a favorite of many divers.

Upon returning to the lodge and reviewing the day’s ‘take’ of images, photograph A elicited a puzzled look from John and Mary. From its shape and striping – particularly the orange one outlined with white at the head end – this ‘damaged’ individual is no doubt an opalescent. Compare it with the normal looking specimen in Mary’s other image (B). But what happened?

Many years ago, while collecting specimens for the Vancouver Aquarium, I observed a similar event. I gathered a number of opalescent nudibranchs, put them in a plastic bag and after sealing it off, stowed in my goodies bag. Upon sorting the entire collection later, I noticed several specimens in the same state as Mary’s.

Nudibranch guru Dave Behrens informed us that under stress from either a predator or in a dense concentration of its own kind, the ‘stressie’ casts off its cerata (frilly structures on its back) and crawls away. This process is called autotomy. Dave likens it to a lizard dropping its tail as a wriggling diversion. Fortunately for the anxious individual, an opalescent nudibranch can re-grow its cerata. This story and other nudibranch knowledge is readily available via Dave’s various books including "Nudibranch Behavior" and the west coast ‘bible’ "Eastern Pacific Nudibranchs" both published by Sea Challengers.