Dive Dry with Dr. Bill

#224: Brachiopods: Lampshells That "Light" the Deep

Those of you who follow my column are aware that I have been doing a lot of deep diving the past year or so. I consider "deep diving" anything beyond the normal recreational limit of 130 but above my basement depth on air of 200 feet. During my first 40 years of diving, I always considered a dive to 100 feet as deep and had no desire to venture much beyond that. As a kelp forest ecologist, most kelp is within that range anyway. Depth itself is not a goal for me... I'm no macho man, just a research biologist who dives to film his "subjects" (hmmm, does that make me a "King?"). In fact, I've advised many divers to avoid the temptation to dive deep since they had little experience with how they'd react to a serious challenge such as equipment failure, or to the mind altering effects of nitrogen narcosis.

One day I wandered into Scuba Luv and saw something unusual on the counter. Mayor Bob asked me if I knew what it was, and I told him it was a brachiopod or lampshell... a deep water invertebrate with two hinged shells similar to clams, but totally unrelated to them. I asked where he had found it and he said he saw large fields of them at 250 feet while diving on a rebreather. My interest in deep diving had its birth that day... I wanted to film these critters since I never see them at recreational depths here. Very few divers have ever seen them in our waters. Interestingly enough, I recently identified a brachiopod that Angela Clark brought to me following a day of fishing... it came up on their line

My interest in deep diving increased when one of Scuba Luv's dive instructors returned from an attempt to retrieve the boat's anchor, which had become entangled in some old machinery at the Empire Landing Quarry dive site. His computer displayed a maximum depth of 192 feet, and he said he had been seriously narc'ed and had aborted the dive. I realized I had little knowledge of my tolerance for nitrogen narcosis since I'd never been to depths where the effect was really obvious to me. I had tested my response a few years at 100 feet off the Great Barrier Reef, and knew that my ability to solve numerical puzzles was affected at that depth.

I started to experiment with deep diving not long after that. I assumed I would probably have to learn mixed gas or rebreather diving to reach my goal, the brachiopod fields. However I also wanted to test my reaction to nitrogen narcosis at increasing depth so I knew my personal limits. Each individual has different reactions due to their own physiology... and those tolerances can change with each dive based upon the diver's physiological state and task loading. I began diving deeper than 130 feet, increasing my depth slowly as I assessed my physiological reactions. I found I could easily reach depths of 180 feet, and my ultimate limit on air (200 feet, without being seriously impaired by narcosis. I judged my level of impairment by whether I could locate a subject to film, frame it properly in my viewfinder, and follow it as it moved. Focusing on a task like finding and filming critters helps alleviate the effects of narcosis because the brain is occupied by the task. It was in this depth range that I finally saw my first brachiopods in our waters.

"Okay, Doc... what's so special about a brachiopod?" Good question. Of course I get "turned on" by some pretty weird stuff (no, not kinky stuff... critter stuff... at least that's my story and I'm sticking to it). Certainly the fact that they are rare to non-existent in recreational diving depths here is a factor. Rarity is often attractive (for example, women divers). However, I usually look for the common species, the ones that often have the greatest impact on an ecosystem. Brachiopods are an ancient group, known from the earliest emergence of complex living things in the Cambrian (slightly before I started diving). Fossil species number 30,000 but there are only about 300 species alive today. The one I found is believed to have remained a separate species for the last 20 million years. During that time, we've evolved from primitive primates to the primitive human beings we are today. Evolutionary biologists are very interested in lampshells because they seem to be intermediate between two major evolutionary lines: the worms and molluscs on one side; and the echinoderms (starfish, sea urchins, etc.) and chordates (us) on the other.

Lampshells or brachiopods have a unique feeding structure known as a lophophore. Other groups using such a structure include the bryozoa and phoronid worms, both in different phyla. It is a feathery coiled or spiral structure used to filter food from the surrounding water. In this respect, they are quite different from clams, mussels and other bivalves which also have two shells and filter food. The rest of their body, known as the trunk, contains the digestive tract, reproductive organs, the structures that secrete their thin shells, and the pedicel which attaches them to rocks and other hard structures.

Lampshell blood is either colorless, or contains the red pigment hemerhythrin. They have very simple nervous systems, so few probably suffer from stress due to the workplace or family. In the latter endeavor, they simply release their young into the water as larvae which drift with the plankton before colonizing a new location. During this larval stage they do not feed. The species I found was present in clusters at 180-200 feet, but can be found as deep as 5,500 feet (and I'm NOT "going there"). In the colder waters of its northern range (Alaska) , they can occasionally be found in the lower intertidal but submerges to much greater depths in the warmer waters of our region and further south into Baja.

My brachiopod encounters have also led me to an interest in filming the residents of these deeper Catalina habitats between 100 and 200 feet. Because my bottom time is quite limited, usually less than 10-12 minutes total in that range, I have to make a number of dives to locate and film the species I find there. Eventually I plan to create a "Dive Dry with Dr. Bill" cable TV episode and DVD on "Deep Ecology." Until I get further tech training, I will limit my depth to this range. Recently while diving on the King Neptune, I met a "fellow" Harvard grad who had lived in Hurghada on Egypt's Red Sea and dived to a depth of 240 feet there! I found her very intelligent and interesting (oh, and attractive), but I'm worried she may be too "deep" for me!

REMEMBER, do not try deep diving "at home" unless you are properly trained and know through your dive experience how you will react to equipment emergencies and nitrogen narcosis. I do not advocate such diving to anyone, even my worst enemies (if I had any). It is my job to bring the wonders of the briny deep back to you, my readers, so you can learn about them by "diving dry" with Dr. Bill... no wetsuit or cold water required! Let me do the hard work for you.

© 2007 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles" or "Gentle Giants: Giant Sea Bass" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

A brachiopod in the hand is worth a group of them at 200 feet; broken shell showing
lophophore (feeding structure) and shell showing pedicel (at lower right).

This document maintained by Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia