14 January 2010

A cool fish and a new word

On a less depressing note, I stumbled upon last year’s BBC story about the wonderfully bizarre Dolichopteryx longipes. I blogged about this fish on a now-defunct site when I first read about it a year ago. D. longipes, the brownsnout spookfish, is, you see, famous for its four eyes – or, more precisely, for the two different light-gathering structures which serve each of its two eyes. Most fishes’ eyes – and humans and other mammals, belonging evolutionarily to the clade of fishes, are no different in this – use lenses to focus light. Lenses are not the only optical solution, however: mirrors can do the same job, and with generally better efficiency. (This is one reason serious astronomical telescopes are almost invariably reflectors rather than refractors.) Little D. longipes (probably uniquely) uses both techniques, each eye having both lens and mirror optics. The result is that the fish can see up to the bright, sunlit shallows (with the normal lens) and down to the dimmer, bioluminescence-lit depths (with the reflecting structures) at the same time.

If that’s not cool, I don’t know what is.

I am also indebted to my new favourite opisthoproctid for teaching me a new word – at least indirectly. (No, the new word isn’t opisthoproctid, though that is quite fun to say.) You see, I was perusing FishBase’s entry for D. longipes when I noticed the following in the Reproduction Summary: Mode: dioecism. Quoi? I had to know. And here’s what I found: diœcism refers to a species’s being diœcious (pronounced, according to Merriam-Webster, roughly dye-EE-shuss). That term derives from Linnæus’s (now obsolete) botanical class Diœcia, a subdivision of the Diclinia. The Diclinia (flores maſculi & feminei in eadem ſpecie, according to the tenth edition of the Systema naturæ) had two distinct sexes of flower, as opposed to the Monoclinia (flores omnes hermaphroditi ſunt). The Diœcia bore their male and female flowers on different individual plants – in two different οἶκοι (houses), as it were – while among the other Diclinia, the Monœcia, each individual bore both male and female flowers.

Linnæus’s botanical classes have long been discarded as having no phylogenic validity, but the distinction between monœcious and diœcious species lives on, with the terms now applied to animals as well. So what FishBase was telling me was that D. longipes, with its two-house reproductive mode, has distinct male and female individuals. No kidding! I’ve been living as a diœcious species my whole life and never even knew it.

Incidentally, the expected American spelling of the word would be diecious (œconomics, for example, is rare even in British usage nowadays, and even words like fœtus are nearly always spelled with a simple e in American English). But Merriam-Webster and American Heritage both prefer the spelling dioecious (abstaining, as always, from the use of ligatures), and the Google test reveals a preference for that form in a ratio of almost 30:1. It’s hardly a shock that words wholly restricted to scientific discourse should show unusual orthographic conservatism, but it remains an intriguing phenomenon.

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