Why Are Corys Considered Scalless?

[guppy fan]

I have read that corys are considered scalless fish, but it looks like they have scales everwhere exept thier faces. If they don't have scales than what do they have?

 

[poopsydrew]

I believe they are actually "armormed plates" not scales, meaning they have a different makeup and shape than fishes with regulars scales. You can see the "plates" are long and and barred. Maybe someone in the science field could describe it more in depth.

Drew

 

[guppy fan]

Are they more vulnerable than fish wiht scales?

 

[CFC]

Catfishes with scutes (thats the proper term for the armour plates) tend to be less vulnerable to skin based parasites and diseases than scaled and scaleless fish, indeed they are most often the last fish in the tank to become infected with Ich or fungus problems.

 

[guppy fan]

Is it just salt then, that thier scutes are more sensative to than scaled fish?

 

[Inchworm]

Hi guppy fan

You asked a very good question!

What CFC said is correct. But, despite their "armor plates," they are vulnerable to predation by larger and more aggressive fish.

Corys are non-aggressive and peaceful. While their hard scutes are a protection, they are still a small fish that is unable to defend itself from attack except by blending into a larger group and hoping for the best.

 

[andywg]

Is it just salt then, that thier scutes are more sensative to than scaled fish?

Nope. The salt issue with cories is to do with their osmoregulation being evolved for soft water with no appreciable salt content.

Dissolved salt in the water does not burn the skin of scaleless fish.

 

[Inchworm]

Hi guppy fan

When corys are kept in salted water they absorb some of it through their skin. This then must be eliminated from their systems through their kidneys and other organs. Since they do not come from areas that have naturally salted water, they have not evolved with the ability to cope with this heavy load, and this additional work will eventually result in premature death.

BTW, salt, if used for short term medicinal treatment, will not harm them. It's having a salt content in the water for an extended period of time that causes trouble.

 

[guppy fan]

Thanks for the info gys. Now that I know what salt actually does to my cories I will stop puting it in my water. I hope it hasn't damaged them to much!

 

[andywg]

When corys are kept in salted water they absorb some of it through their skin. This then must be eliminated from their systems through their kidneys and other organs. Since they do not come from areas that have naturally salted water, they have not evolved with the ability to cope with this heavy load, and this additional work will eventually result in premature death.

Actually, the vast majority of the salt uptake will occur at the gills and not the gills. The fact that the fish has scales or not is pretty immaterial for its salt tolerance (one needs only to look at eels or the marine catfish families to see that). In fact, since a cory is a freshwater fish, I would expect it will lose salt through its skin as osmosis will result in the salt passing from the higher concentrated body of the fish to the lower concentrated water around it.