Life from life

Warning: yuckology ahead.

If you spied sandwich bags hanging from the branches of trees near the science building recently, you might wonder, “What’s going on here?” Maybe your curiosity would lead you close enough to discern mouse-sized lumps of semi-liquid matter in the bags. And then, you would probably detect movement, a squirming in some of the bags. You might wish you hadn’t been so curious.

Or maybe you would be intrigued enough by this overt display of decomposition – a process generally hidden and infrequently discussed – to inquire what in the world was going on here. A seventh grader would tell you that this is a Jemicy-style replication of the first known controlled study done by Francesco Redi in 1668. Redi was trying to disprove the then-popular theory of spontaneous generation, which held – among other wonders – that flies were produced by rotting meat. It’s a simple experimental design: take two pieces of meat (in our case, frozen mice that we use as snake food), put one in a bag that is sealed, and one in a bag with holes, hang them outside, and observe for a week or so. The results are striking, and usually unequivocal. As the mouse in the sealed bag slowly decomposes, it is amazing to see how much liquid it contains. The mouse in the bag with holes also decomposes, but the process is aided by flies, which are attracted to the smell, enter and lay eggs, which hatch into larvae. Any variation on these results forces us to consider what variables we might not have controlled.

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Most years, the smell of rotting mouse is enough to make us bury the results of the experiment immediately. This year, though, several students asked if we could dissect the decomposed mice to see what had happened to the mouse internally, and if, by chance, the control mouse contained maggots. “Please? It’s my birthday!” begged one girl. And so the team of yuckologists held its breath and did just that. When we were finished with confirming the theory of biogenesis, we buried the remains in the compost bin, where other decomposers will complete the job of returning the mouse to its mineral components and enrich the garden soil next spring.

The cycling of matter from life into death, and back into new forms of life, creates gripping narratives and inspires rituals that memorialize the former life and celebrate the new. Impromptu funeral services traditionally celebrate deceased animals at school. A dead squirrel found in a fort received a burial with handfuls of acorns, while a cicada was sent down the stream on a raft, also with an acorn, “so that wherever it lands, it can help make a new tree for another cicada.” The final moments of a goldfish’s life were observed attentively, respectfully; it was eventually buried alongside the squirrel, with its own eulogy.

The youngest students get firsthand experience with decomposition and the life it supports by setting up and maintaining a worm farm throughout the year. They supply it regularly with the composted remains of their lunches: apple cores, orange peels, bread crusts, etc. Every so often, they empty the bin to check the worms’ progress. Last spring’s discovery that the mysterious golden cases in the farm were worm cocoons set off a flurry of activity: sorting and counting them, establishing a nursery, keeping watch until the tiny wormlets finally emerged. “Babies! We have babies!”

The “yuck” factor is balanced and often overcome by this fascination of witnessing complex, dynamic living systems and the new life that emerges from them. One young girl called out to me from the playground one day, “Come see what I found on the climber! I think you’ll like it, because it’s kind of gross!”

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Sure enough, there was a jumping spider (Phidippus audax) with a recently caught stinkbug – and at least two species of flies imbibing bug juices. As a friend put it when he saw the photo, “The small flies have bloated abdomens like they just slurped up some liquid. This looks like a scene in the African plains where the lion has taken down a gazelle and the vultures are starting to gather.”

It’s a big lesson played out vividly in miniature: Life cycles intersect with and depend upon the decomposition of other living things.

 

 

 

 

 

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