Evolution of Fish

[BoroughGal]

If things evolve to benefit them, such as animals blending in to their natural environment so as not to be hunted etc, why do some of the deep sea fishes have such bright colouring when it's too dark to see them anyway?? And some cave fishes are white with no eyes (so I'm told)... why would their colouring be of any benefit to them when, because it's so dark there, they've evolved without eyes?? Thanks.

[Woodstock]

There was a programme on only last week which I managed to catch only part of - I think it was set in the Amazon River - and they happened to mention that the brightly coloured tropical fish there were so coloured so that they could find each other.  Can't help with the white eyeless fish though.

[trilobite]

The white 'colouring' of cave fish is a lack of pigment, (similar to albinoism), rather than an 'attempt' to be white. It may not be a primary selective trait (ie the pigment-less fish originally survived in greater numbers than the pigmented members of its species due to another trait it possessed, rather than it being a question of body colouring.)

'Blind' cave fish are evolved from sighted fishes, so it's not a case of having evolved without eyes, rather a case of having either 'lost' them or that they no longer function. In the small number of cave species that have no eyes, there are often residual organs; and the cavities within the skull, (the orbits) indicate that the species' ancestor did originally have eyes.

I'm not sure which deep sea fish are brightly coloured, but many are capable of bio-luminescence where specialised cells synthesise chemicals that 'glow in the dark', (others hold cultures of bio-luminescent bacteria in specialised sacs) - these features may be brightly coloured or irridescent in daylight, but this is coincidental and not the intended purpose, which is to attract mates / prey in conditions of low or no light.

[BoroughGal]

Thanks a lot for your answers... appreciate it.

[smorodina]

�Evolution� is actually random mutation. If the mutation trait benefits the animal its offspring, if they continue with the mutation, may survive better than animals without the trait. If the mutation is a disadvantage, it is likely that its offspring will not survive. If the trait has no advantage or disadvantage, it may very well continue if the animal is otherwise well-suited to its environment. So bright colours in a dark-dwelling creature could be a random factor that has no disadvantage

[BoroughGal]

Yep, I guess that makes sense...  thank you....!

[Dreddnaught]

I'm sure i heard while watching the making of the bbc series Blue Planet, that the reaason the deep see fish are to wonderful in colour is the light they use while filming.

If its what I'm thinking of, the vivid rainbow like colours on the fish etc was caused by the "red light" the crew used. I'm sure it said red light was the best light to use at a depth where normal light just doesnt really do much.

Or I could be talking out of my Arsene Wenger......

[Dreddnaught]

Just read my post and realised its sounds a bit fuzzy.

what I mean by red light is that they ussed the red spectrum of light for filming, and thats what caused the wonderfuil colours on the fish.

if you saw the fish in regular lighting conditions, they wouldnt look like that.

[Chillum]

bad fish-fashion has a lot to answer for.

[BoroughGal]

Don't worry, I've alerted the "Fish Fashion Police"!

[brachiopod]

> Don't Worry, I've alerted the "Fish Fashion Police"! <

Would that be Finny and Piranha from 'What Not To Wear'?