Radiolarian in Phase Contrast Illumination

The radiolarian skeleton (test) presented above was captured utilizing an Olympus BX60 optical microscope operating in phase contrast mode with a 20x plan achromat objective. A single optical section of the specimen was recorded on a Nikon DXM 1200 camera system attached to the microscope.

The specimen, most likely a member of the Carpocanistrum genus (family Carpocaniidae : order Nassellaria), is characterized by a head region (referred to as the cephalis) that is similar in structure to the ovate body (thorax) with longitudinally aligned pores. As with other radiolarians, the pores provide openings for extension of the pseudopods employed in prey capture and limited locomotion. Note in the photomicrograph that the head region is positioned at the top of the thorax, and there is an internal collar ring containing four pores that serves to separate the two regions. Depending on the position of the mouth, the thorax of these radiolarians is highly variable in shape, ranging from nearly cylindrical (when the mouth is open) to almost spherical (when the mouth is closed). Members of this marine planktonic group are found in the southern two-thirds of the Gulf of California, but can often be located further north where they are sometimes carried by ocean currents.

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