Tuesday, March 24, 2009

A myth busted... and a new believer is born (10 Mar 09)

How often do you hold onto a belief for years and see it busted to shreds within minutes? Not often, I hope unless you have been living in a cave.

It started as another lesson for a secondary school. These students were brought out of the classroom to yet another field trip to a nearby pond. They were given big, robust nets and told to dig into the bottom mud and be aggressive about it. No big deal for kids 50 years ago but for them, it was a novelty... a thrilling experience no classroom lesson could have prepared them for. Yes, you have be there to get your hands dirty to find out.

You are probably wondering what they were supposed to do with the mud. In short, check out the bugs in the mud. Anything without backbone, isolate and identify them. These include insects, worms, snails and....

Bingo! The students scooped up half a dozen or so leeches! These are not your 1-inch wriggling critters commonly found in Malaysian forests. Imagine these half-foot whoppers* clinging everywhere on your body including those parts of your body not exposed to the sun, furiously competing against one another to feed on your blood.... blood chilling. And I have always believed that there are no carnivorous leeches in Singapore. There goes that belief. Never will I nonchalantly wade into an unknown pool/pond/reservoir here.

Is anyone screaming yet? Oh yes, the students were indeed screaming, not in terror but in excitement. I guess there is a big difference between seeing leeches in a sample bowl and having them stuck on your own body.

On the technical side, the presence of this significant number of leeches indicate a bad water quality with a low oxygen content. This was confirmed by our oxygen tests.

In case you conclude that I hate leeches, on the contrary, they are one of my favourite animals. Not the kind that you keep at home but the kind that you admire. Their tenacity and survivalability rank tops among animals. This is in addition to their arsenal of biochemicals that allow them to do what they do best - all these packed into a compact but ferocious package.

* These half-foot critters are fish fry compared to the half-METRE Amazonian leech.

Figures (L-R, T-B): Classroom lesson of looking at dead (and boring) specimens under the microscope; trying to score some live specimens in the field; mud and bugs are part of the job; searching intently for the tiniest bugs; cute aquatic leeches - are they carnivorous buffalo leeches?; check out my article on the chemical secrets of the leech in Singapore Scientist no. 111 (2008)

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