• José H. Leal

A Challenging, Striking Microgastropod!

Micromollusks* present a challenge to our efforts to visually document collection specimens. Take, for instance, the shell of Orbitestella aequicostata Raines, 2002 in the image below. That adult shell measures 0.66 mm (about 0.03 inch), and is a paratype, one of the individuals examined and referenced by Bret Raines in his original description of the species from Easter Island. (The normally whitish shell appears iridescent, as it had earlier been coated with metal for scanning electron microscopy.)

Orbitestella aequicostata, from Rapa Nui (Easter Island.) Images by James F. Kelly.

Photographing small objects is difficult, even when using powerful microscopes and lenses. The main reason is that the depth-of-field, or the part of the object that is in sharp focus, decreases dramatically as we increase magnification. One of the techniques used by our Digital Imaging Specialists James F. Kelly and Patricia A. Starkey, known as focus stacking, combines multiple images taken at different focal distances (each image with a different area of the shell in focus) to form a final image that is “more in focus” than any of the individual source images.

Using a digital camera coupled to a dissecting microscope, James F. Kelly captures images of micromollusk shells.

*Loosely defined as mollusks measuring less than 5 mm.

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