Blog 8 – Radiolarians!

Viewing live organisms under the microscope on a research vessel cannot get any better. Just a few drops of sea water can reveal a mesmerizing universe of movement and rich pigments that characterize so many species. While doing this, I realized that when I attended college I had only observed preserved samples. I could not stop looking. I was fascinated.

Some of the very interesting organisms in that drop of water were radiolarians. Radiolarians are beautiful, single-celled protozoans that consist of soft bodies and intricate skeletons made of silicate minerals. Their core may look a bit green due to symbiotic algae living there. The perfect symmetry of their skeletons has inspired scientists, artists, and architects since their popularization in the early 1900s by the detailed drawings made by German biologist and artist Ernst Haeckel. But radiolarians have been around much, much longer. Fossil records indicate their presence in the early Cambrian period close to 600 million years ago!

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Radiolarian skeleton, photographed by Tristan Biard.

Although radiolarians have been around for a long time, and are abundant in our oceans, very little is known about them. Dr. Andrés Gutiérrez from Station Biologique de Roscoff (CNRS-UPMC) of France is interested in figuring out the vertical distribution of radiolarians along the California coast. This means he wants to know the diversity or types of radiolarians at different depths of water. There are different ways to do this. These include underwater photography, and collecting samples and analyzing their appearance (morphology) or their DNA. Radiolarians may be studied as a community, which means that a sample of water is taken from the ocean at a certain depth and all the organisms at those depths are studied as a group using their DNA sequences.

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Dr. Andrés Gutiérrez and Tristan Biard, Ph.D. student, and looking for radiolarians from their sea water samples.

Tristan Biard, Ph.D. student, also from the Station Biologique de Roscoff, is especially intrigued by a photograph of a single radiolarian taken by a UVP, the Underwater Vision Profiler. He is interested in identifying this specific type of deep-water radiolarian. Using images from the UVP allows him to compare photographs with collected samples. Marc Picheral, research engineer from the Laboratoitre Océanographique de Villefranche-sur-Mer (CNRS-UPMC), France, has a lot of experience working with the UVP, which consists of flashing LEDs covered in glass cylinders and sensitive cameras. Every second, one meter of water flows between the LED lights and 10 photographs are taken. This means that at the end of one hour 36,000 photographs have been taken. Marc then uses computer programs to count and size the photographs of radiolarians and other organisms, and to sort them for identification.

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Marc Picheral, research engineer, analyzing images from the UVP.

A method called DNA bar coding will be used by these scientists to create a DNA database once the science team returns to land. If the DNA of radiolarians collected on this expedition does not match a previously studied radiolarian by DNA or morphology, there is a chance they will have identified a new species.

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Tristan Biard, next to the UVP, Underwater Vision Profiler.

This valuable information will allow scientists in the future to ask other research questions concerning changes in radiolarians along the California coast. It will also allow them to compare radiolarians off California with other oceans regions, such as the Mediterranean Sea.

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Dr. Andrés Gutiérrez studies the ecology of radiolarians.