Tuesday, July 26, 2011

Singapore Protozoans Part 1

Heliozoan from Kranji Reservoir. Each unit on the graticule scale is 2.5 microns.

Microscope, murky water, a camera, and free time.

Lately I've been volunteering at Darren Yeo's new freshwater biology lab, but Maxine, the graduate student whose project I'm supposed to help with, has been busy with the Honours fieldtrip to Pulau Tioman and with getting sick (get well soon!) In the meantime, I've found that her plankton net samples from Kranji Reservoir are teeming with interesting and picturesque protozoa!

Today I captured some shots of microscopic aquatic life to share online, and you can browse the full set on Flickr [update 6/9/11 - I've moved all the media to my new protist website and the album is no longer available]. The picture above shows an organism called a heliozoan. The long radiating arms, called axopods, appear to be beaded with dew drops, which are actually organelles involved in prey capture called extrusomes. The spherical cell body itself is covered in a layer of spicules, which seem like a fuzzy layer of hair, but reveal finely ornamented detail under electron microscopy.

These pictures were taken in a fairly primitive way: by balancing a camera in front of the eyepiece of the microscope. The microscope was set up for brightfield illumination, but I closed down the condenser aperture to improve contrast, in the absence of any better option. Still, there's enough detail to recognize lots of protozoans and to tell a good story.

When I've got a decent bunch of these pictures and descriptions, I'd like to eventually put up a photographic guide to common protozoans in Singapore. That might help to address some of the 'macrobe' bias in the natural history scene here, by showing the beauty hidden in the very small.

As a bonus here's a video of ciliates squirming in the carcass of a dead planktonic crustacean. The bright droplets are oil globules, which the ciliates are feeding on (ingested oil globules are also visible within their cytoplasm). Outside the animal carcass you can see another ciliate which has been left out of the feeding frenzy, and is trying to find its way in....

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