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DIVE DRY WITH DR. BILL #843: LAMP SHELLS

Discussion in 'California' started by drbill, Dec 28, 2019.

  1. drbill

    drbill The Lorax for the Kelp Forest Scuba Legend

    # of Dives: 2,500 - 4,999
    Location: Santa Catalina Island, CA
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    DIVE DRY WITH DR. BILL #843: LAMP SHELLS

    Over a decade ago I was doing a lot of deep diving on air. My maximum "safe" depth was 200 ft. I never ventured deeper than that with the exception of one day when my brakes weren't working and I slid down to 201 ft. In my early years of diving back in the 60s and 70s, I considered 100 ft to be a deep dive. That was fine with me since as a kelp forest ecologist, most of my subject matter was above that depth.

    Two factors got me interested in deep diving to see what was down there critter-wise. One day on the King Neptune we were out at Sea Fan Grotto. The anchor got stuck on something and instructor Tim Mitchell went down to free it. When he came back up he walked toward me ghostly white in the face with his computer in his outstretched hand. It read 198 ft. That intrigued me.

    Later I walked into Scuba Luv's dive shop and saw a string of shelled critters resting on the counter. Bob Kennedy asked me what they were and I replied brachiopods. I asked him where he found them. He said he was on a rebreather dive at 250 ft. I definitely wanted to film these invertebrates since I'd never seen them in recreational diving depths here.

    I spent two months gradually increasing my maximum depth until I finally hit 200 ft. Although most would be seriously narced at such depths, my mind was clear enough to locate subjects, frame them properly and follow them as they moved. I never felt like I'd had several martinis and not once did I pull my regulator from my mouth or head down even deeper to certain death. I attributed it to the fact I was doing up to 350 dives a year and my body was probably saturated with nitrogen.

    And down there I found brachiopods all over the bottom. I also found other invertebrates and fish that I had never seen at shallower depths. These included clams, unusual gorgonians (soft corals), long-spined combfish and thornback rays. I kept returning to the deep hoping to see Jacqueline Bisset and to film the members of the deep ecosystems.

    Brachiopods, also referred to as lamp shells, are an ancient group that even pre-date my first dives. They emerged in the Cambrian, well before our species even evolved. At one time there were tens of thousands of different species, but back about 250 million years ago, at the end of the Paleozoic, they were decimated by a major extinction event. Now there are a mere 300. Most live in cold water up near the poles or at significant depths.

    I believe the species I observed way down under is Laqueus californianus although I'm not 100% certain of that. Strangely there doesn't seem to be much information on our local species. One of the few web sites I found that described it said the shell is white to light tan. I'd call mine orange. Apparently the northern individuals may be of the former color and the southern individuals, the latter. It also said that they are attached to rocks by a pedicle, but the ones I saw seemed to be loose in the soft substrate. According to that site the geographic range is British Columbia to southern California and down to 486 meters (nearly 1,600 ft). Other sites had what appeared to be the wrong images for this species.

    Brachiopods have two shells but they are not related to clams, mussels and other bivalves. They are in a unique phylum. They feed using a gill-like structure known as a lophophore. Other groups utilizing a lophophore include the bryozoa and phoronid "worms." They filter food out of the water column. Having no anus, they eject the indigestibles out through the mouth. How gross!

    Brachs have two sexes that are separate. They reproduce by broadcast spawning, casting eggs and sperm out into the surrounding water column. I guess many of them must be winning that lottery as I saw plenty of this species at depth. Apparently the larvae don't feed so I'm assuming that life stage is fairly short lived and they don't disperse far. Sadly, I wonder how much damage the cruise ship anchors are doing to them off Avalon.


    © 2019 Dr. Bill Bushing. For the entire archived set of over 800 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page

    Image caption: Brachiopods in soft sediment at 200 ft, brach in hand for size comparison and cluster of brachs found dredged up in shallows.

    DDDB 843 brachiopods sm.jpg
     

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