Fish May Not Have Evolved Gills to Breathe

Fish May Not Have Evolved Gills to Breathe (via BoingBoing)



In order to keep from shriveling like your fingers in the bathtub, fish must constantly exchange ions, such as sodium and potassium, with the water. Larval fish can exchange ions through their skin, and early fish likely used rudimentary gill structures known as branchial baskets. But when the salinity of the water changes rapidly--as happened when fish invaded freshwater habitats--fish would have needed a much more efficient way of exchanging ions with their environment. That means large, complex gills.

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The team placed the rainbow trout larvae in a box with two compartments: one for the head, where gills develop, and one for the tail. Clarice Fu, then a graduate student at the University of British Columbia in Canada, measured ion and oxygen levels at both ends of the larvae. After about 15 days, gills were exchanging more ions than the tail was. It took another 10 days or so for the same thing to happen with oxygen ... Greg Goss, a biologist at the University of Alberta in Canada, says the study has made him much more confident in the hypothesis that gills evolved to exchange ions. But he'd still like to know which genes turn on first--those involved in oxygen exchange or those involved in ion exchange.

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This kinda makes sense and explains a few things to me.

First, you need to ask the right questions to get the right answers. To ask the right questions you need to know A LOT. I know, pretty vague, but let me dive in here a bit. Things are very rarely as simple as they appear. The process of natural selection has been taking place over millions of years within the context of millions of variables.

Now, I'm not going to tell you anything you haven't heard before, but the process of folding to increase surface area for absorption is really something special. This growth through 'branching' and folding (I'm not even going to start on the fibonacci sequence here yet.. ) is something quite special. Who could forget villi?



Both villi and gills are a great and efficient way to expand with minimal resource investment. Form often equals function... or at least originally? Things end up doing multiple things.

Leading from that, (Second,) it seems that these scientists are basing their 'what came first (evolutionary)' hypothesis on 'what comes first'. As in, since the process of ionization happens first in development, gene expression, and function, it therefore must have been the basis for the actual form of the resulting product. Is this right? It makes sense, but doesn't necessarily account for the whole story.

Anyway, this is all rather trivial in a sense.. but, I'm happy reinforcing those two ideas. I mean, some things take a long motherfucking time, tonnes of shit fails, and tonnes of shit, because it initially succeeds, grows and adapts into something more.