white fish in caves

[Cave_Troll]

so are all the white cave fish i've been videoing a seperate population who have lost their pigment over generations, or if you raise a fish from an egg in darkness will it never bother developing pigment?

 

[droid]

It's an evolutionary thing.

If it's not needed it evolves out. I think it's an evolutionary advantage to lose eyes and pigment if ou don't need them as it saves energy needed to make them. Only a marginal advantage but has an effect over millennia.

 

[Antwan]

Depends on the fish, trout have a photo reactive pigment that retreats into the centre of the cells making them pinkey white but after a few days back in the sun they return to normal colours

 

[droid]

Afraid I was thinking of Mexican Cave fish, Antwan....I can assure you they don't change colour. Whether that's lack of melanophores or lack of switching mechanisms I don't know.

 

[Samouse1]

There have been Mexican cave fish (Astyanax mexicanus) kept in the aquarium hobby for quite a while so they're well documented, and they develop eyes as fry, then lose them. They can also interbreed with surface species and produce fertile offspring, as the blind fish are just another morph of the same species, so they're quite interesting.

 

[Cave_Troll]

so is there a sub species in this cave?

 

[Samouse1]

In this species yes. This probably means that the cave morph populations only washed in recently and haven?t evolved into a seperate species. There will be other fish species that are solely cave dwelling.

 

[Cave_Troll]

This is in Ilam by the way. where the surface river is the overflow for this section of the River Manifold

 

[Samouse1]

Ah sorry didn't get that. Unsure, would probably have to be collected to have a good look at

 

[droid]

I have kept Astyanax in the past, fascinating to watch them navigate a tank. It's not learning because if you change the rocks round they're still fine.

There's an interesting debate above as to what constitutes a 'species'. guess it depends on whether you're  a 'splitter' or a 'lumper' 

 

[Cave_Troll]

Its a through trip from one bit of the river to another, so i'd expect things to be swept in all time time, so could be fry/eggs being swept in or it could be a static population

i caught a video of one of them eating something at the weekend. either that or it went from sitting there hapily to having a fit with it's face buried in the sand and back again.