Back to the past, looking for sea urchins and other deep sea life Sea urchin (Araeosoma belli) with poison sacs on the end of its spines. (Lower, left) Zoologist Dave Pawson ready to descend in a submersible for a deep sea dive. (Smithsonian/Dave Pawson)
Back to the past, looking for sea urchins and other deep sea life
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While this animal looks like a pincushion, you would not find it in a sewing kit. This venomous sea urchin is also called A. belli. It lives on the ocean bottom as deep as several thousand meters. Scientists study it and other deep ocean dwellers using submersibles and remotely operated vehicles (ROVs). These vehicles explore the ocean depths equipped with cameras and collecting gear. 

But, original observations of these deep-water urchins were made before research submersibles or ROVs were in use. How did scientists back then learn about animals that lurked way beyond the reach of scuba gear?

Ole Theodor Jensen Mortensen, a Danish zoologist, was one such scientist. In 1938, he described the stomach contents of relatives of A. belli. It had been brought to the surface by a trawling ship

He was not able to observe the animals alive in their deep habitat. But the remarkable observation of plant material inside their bodies led him to propose that some sea urchins were vegetarians. These individuals had apparently fed on plants that had broken off from shallow sea grass beds. Or they floated down rivers, then drifted down to the deep sea. 

Decades later, Mortensen’s discovery was confirmed by other scientists. One such scientist was Dave Pawson, a Smithsonian Zoologist. Pawson found sea grass in specimens of A. belli. The specimens are from the historic US Fish Commission Steamer Albatross, the first dedicated U.S. ocean research ship. It made expeditions from 1883-1921. Trawling with long nets for months, the Albatross collected millions of specimens, often from great depths. Aboard the Albatross in 1906 was a young Austin Clark, the ship's lead naturalist. Among the animals Austin catalogued were hundreds of species of sea urchins and relatives that greatly expanded the echinoderm collection at the Smithsonian’s “U.S. National Museum.”  

Echinoderms also include sea stars, sea cucumbers, brittle stars, and crinoids. Their diverse body shapes reflect the range of marine habitats they occupy, from shallow reefs to deep ocean bottom. While sea urchins do justice to the name (echino = “spiny”; derm = “skin”), other echinoderms may be soft, smooth, feathery, or bumpy. What they all have in common is a body with five-part symmetry. This is obvious in a five-armed sea star but hidden under the skin of a sea cucumber. Austin Clark, in his later work at the U.S. National Museum, described nearly 500 new species of echinoderms. 

Today, scientists continue to study echinoderms, probing mysteries about their life histories. Zoologist Dave Pawson, at what is now called the National Museum of Natural History, combines data from museum specimens, research at sea, and observations of live animals. He looks to see what echinoderms reveal about life in the deep sea and its connection to shallow-water habitats. Learn more about his discoveries in a "Smithsonian Science How" webcast video. During “A Century of Discovery of Sea Urchins and Relatives,” Dave will take you on a historical research journey. You can also get teaching resources to use with the webcast.

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CRITICAL THINKING QUESTION
Why was it more difficult to study the deep sea when these sea urchins were first discovered?
Write your answers in the comments section below


COMMENTS (47)
  • JaredI-del
    10/30/2017 - 06:23 p.m.

    the sea urchins would go really deep and you cant go that deep

  • TiffanyW-del
    10/30/2017 - 06:38 p.m.

    It was more difficult to study the deep sea when these sea urchins were first discovered because they were blocking the way to the deep part of the ocean, as they have been discovered.

  • PoojaT-del
    10/30/2017 - 06:39 p.m.

    But, original observations of these deep-water urchins were made before research submersibles or ROVs were in use. How did scientists back then learn about animals that lurked way beyond the reach of scuba gear?He was not able to observe the animals alive in their deep habitat. But the remarkable observation of plant material inside their bodies led him to propose that some sea urchins were vegetarians. These individuals had apparently fed on plants that had broken off from shallow sea grass beds. Or they floated down rivers, then drifted down to the deep sea.

  • ChloeR-del
    10/30/2017 - 07:00 p.m.

    They didn't have any submersibles at the time. Back then people didn't have enough technology to go that far down where the urchins live.

  • EvanC-del
    10/30/2017 - 07:01 p.m.

    I love other sea animal and love to find them. Mortonsens discovery was amazing and i would love to see it

  • David M-del
    10/30/2017 - 07:03 p.m.

    .

  • AngelinaB-del
    10/30/2017 - 07:18 p.m.

    This article is about sea urchins and other deep sea animals. These sea urchins, aka A. belli, live on the deep ocean bottom. Scientists use remotely operated vehicles (ROVs), to study A. belli. However, before ROVs were made, scientist Ole Theodor Jensen Mortensen studied the A. belli by studying its stomach contents of relatives of A. belli.

  • JustinM-del
    10/30/2017 - 07:24 p.m.

    The main idea of this article is about looking for sea urchins and other deep sea life under water. It was also about new sea creatures that we haven't seen and to study them from now om

  • AkshayB-del
    10/30/2017 - 07:27 p.m.

    The story is about how long sea urchins and other deep sea life were discovered by scientists. One of the sea urchins was a belli. Ole Theodor Jensen Mortensen, a Danish zoologist, was one such scientist that described the stomach contents of relatives of A. belli.Today, scientists continue to study echinoderms, probing mysteries about their life histories.

  • RushB-del
    10/30/2017 - 07:45 p.m.

    It was difficult to study the deep sea creature because the technology at the time was just not advanced enough, for example when they first discovered the urchins they did not have the advanced remotely operated vehicles to travel deep sea.

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