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Pique ’n your interest

A fish tale


There are many things in this world which - as talk-show host Arsenio Hall annoyingly mused, finger-to-lips and, perhaps, once too often before his equal-opportunity gong show was mercifully laid to rest-make you go "hmmm..."

For me, these usually fall into the category of callous human actions, like: how it's possible for anyone in 2010 to leave empty bottles and cans in a shared public space like a disc golf course (you might know who you are, but since you clearly can't read, this subtle message is moot); the profound depth of absurdity in being handed stewardship of an unsustainable practice like old-growth logging, commensurate not with an ability to make a choice over the matter, but a proviso to continue in ignorance (you definitely know who you are); and the notion that blurbs on the cover of Oprah Magazine like "Don't change your body-change your jeans!" are somehow empowering (sadly, you have no idea who you are).

Now, you may be going "hmmm..." in realization that I managed to get all that off my chest before tipping my hat to the real point of this column, but here it is. Being well-familiar with the natural world as a biologist and occasional science journalist, seldom do I find myself pondering the more arcane wonders that gurgle up from nature's depths. For example, I know that certain frogs turn off their digestive juices, swallow their tadpoles, and raise the kids in their stomachs; I know that flamingos are pink because they eat shrimp, and; I know that although the sub-telomeric chromosomal DNA in booze-producing Saccharomyces yeasts is gene poor, repetitive, and transiently silenced, it evolves rapidly due to transposon activity, increased recombination and a surprising level of nucleotide divergence. What I have never known or understood, however, is the what, where, why and how of those miserable metallic commas you regularly encounter, in even the most fastidiously clean of abodes, bending surreptitiously around faucet handles and scuttling along countertops. So I put it to you here, the way Discovery channel would never dare: silverfish-WTF?

Indeed. These denizens of darkness, exclusively revealed when you flick on a light in the kitchen or bathroom, are always a surprise. Perhaps not the horrifying revelation of a rat, or the gross-out of cockroaches, but a surprise that nonetheless begs its fair share of questions: What is it doing here? Where did it come from? Does it bite? Is it the vanguard of an infestation? Should I call my strata? Not to mention the query perpetually on my mind: What's up with an animal that, as demonstrated by late-Carboniferous fossils, has been around in identical form for some 300,000,000 years but whose natural habitat seems to be my sink? The animal hasn't changed, but something is fishy. Hmmm...

Predictably, the explanation is a good news-bad news scenario.

Good: Although sink-and-bathtub-sightings are a worldwide phenomenon, most involve a single ubiquitous species: Lepisma saccharina , a small, wingless insect of the order Thysanura. Called silverfish, fishmoth, carpet shark, or paramite depending where you live, Lepisma have primitive mouthparts, don't bite and don't spread disease. Best of all, in the light they're defenseless and easy to squish.

Bad: "Silverfish" (in use since about 1855) comes from the animal's silvery blue colour combined with the piscine movements of its well-jointed body, while the scientific moniker (traceable to 1758 and the father of modern taxonomy, Carl Linnaeus, no less) refers to its diet of simple polysaccharide carbohydrates-sugars and starches found not just in the food stores it happily infests, but in glue and adhesives, book bindings and paper; in carpet, clothing and linens of cotton, silk, leather and even synthetics; even in body exuvia like hair and dandruff. In short, 21 st century humanity offers silverfish an unparalleled smorgasbord: They'll eat your pancake mix, leave holes in your clothes, destroy your books.

Good: It's not just you. Like fleas, silverfish have accompanied human habitation since it began-wild Lepisma favour caves and other dank areas with a humidity between 75 and 95 per cent. You find them in sinks and bathtubs not because they live there, but because their Carboniferous-crafted appendages don't do well on the modern world's smooth surfaces; they've simply become trapped in these vessels, attracted by the moisture and food prospects rising from your drains (de facto encouragement to keep these clean).

Bad: Unsquished, silverfish will live out of sight in your home-quite unlike the ephemerality of other insect pests-for two to eight years. They can go a year without food.

Good: Their reproductive rate is low; a single female will lay less than 100 eggs over her lifetime. They take weeks or months to hatch and if they dry out they're done.

Bad: Known predators of the silverfish are also cave-happy things that you usually aren't psyched about seeing around the house: spiders, earwigs and those über-creepy, long-legged house centipedes known as scutigers.

The latter are also frequently found stuck in sinks and bathtubs. And now I know why: they're hunting silverfish. Which might make me think twice before I squish them . Sometimes a little knowledge is a terrible thing.