Random Thought

[jag51186]

So, I've been wondering for awhile now...how do fish recognize others of their species??

To elaborate, it is often told and retold on here that cory cats need six plus per species to be comfortable. How do they recognize the differences in each other?? Especially the albino corys, which are technically of a specific species (paleatus??). So, are you required to have six albino, or could you mix them them in with a group of the common form??

Just random thoughts.

 

[Baccus]

I guess you could also say how does a fish know who is Arther and who is Martha? When not all fish species are diamorphic. I have kept Albino corys with normal peppered corys and the two types definantely showed a preference to their own kind. Perhaps it was because the albinos where derived from bronze corys which some how the fish picked up on from cues we couldnt see. Or perhaps it was simply because the peppereds and albinos where not used to the other colour.
Always keep in mind fish see in different colour spectrums to us and catfish especially have inhanced senses of smell, so perhaps when we see something that looks the same (or should be the same according to species) the fish actually see and smell something entirely different to what they know themselves to be.

 

[Akasha72]

if we are basing this on cories I'll add my experience. I have peppered (8 of them) bronze (5) panda's (6) and Melini (3) cories. My bronzes live on the left side of the tank all by themselves in their own species group. My peppered live on the right side but they mix themselves in with the panda's. The melini are so small I rarely notice where they are but last night when my panda's were spawning and playing the melini's were with them zooming around and playing. The spawning was kept within the panda group - I was careful to check that as I've been told on planet catfish that they can interbreed - but the melini's seem to think they are panda's. 
 
Now the panda cory and the melini cory look the same from the front - both have the black patch over the eyes. The only difference really is the black stripe that the melini's have down their back and into their tail. Could it be that the panda's and melini think they are the same species? Is it that they so closely related that they don't know they are different? I can't answer that because they can't tell me!!
 
One thing I will add is that cories behave similar to shoaling species. When under stress the species doesn't matter they just huddle together for safety .... try chasing 22 cories around with a net and that becomes obvious!

 

[Byron]

This is a very complicated subject, and way beyond my level of understanding.  But I have picked up some bits over the years.
 
Fish like all animals are born with algorithms implanted into their brain.  These involve sight certainly, but likely other senses too.  And they can be surprisingly acute.  Studies have proven that a guppy will avoid eating its own offspring, while eagerly gobbling up the offspring of another guppy in the same tank.  Scientists believe that some fish can distinguish their own siblings, which avoids interbreeding in the wild.  Other studies have shown that fish prefer to hunt with specific other fish of their species when it has been to their advantage in the past.  Male guppies have been shown to ignore females they have previously mated with and select others, probably for the purpose of spreading their distinctive genes further afield, something that we now know drives the evolution of new species.
 
Eyesight is a major factor, as scientific studies have shown.  Images from the eyes are transmitted to the brain, and the optic lobe is the largest part of a fish's brain.  Studies have shown that fish can be "tricked" into recognizing another member of the species or a predator in the shape and colour but made of wood or plastic placed outside the tank.  
 
Smell and chemical reception also plays into this.  Fish release pheromones and allomones that are sufficiently distinctive to be read by other fish for a number of different purposes.  Fish of the same species pick up the pheromones, and these can signal food, danger, spawning, stress, etc.  They affect behavioural and physiological responses in the receiver.  Other species pick up the allomones, which benefit the originator but not the receiver; these are primarily used as a form of defense.  The sense of smell in fish is quite strong; corys for example can smell food in the sand when they cannot see it.  I always feed my fish from the side of the tank (length-wise) closest to the filter return so the current carries the scent down-tank, and this makes a difference so obviously the fish are picking it up.
 
Byron.

 

[TallTree01]

Something I've noted in my years of keeping tetras is that it's not all based on eyesight. A while back, I had 2 groups of tetras, Cardinal tetras and x Ray tetras. There was always 2 distinct groups of the species and they very rarely shocked together. One of the cardinal fish lost both eyes over a few years ( he was the only one. I guess unlucky? ). He still managed to stay with his Cardinal shoal as well as the ones with eyes did.

 

[jag51186]

All interesting info! Thanks guys!

 

[Baccus]

Something I've noted in my years of keeping tetras is that it's not all based on eyesight. A while back, I had 2 groups of tetras, Cardinal tetras and x Ray tetras. There was always 2 distinct groups of the species and they very rarely shocked together. One of the cardinal fish lost both eyes over a few years ( he was the only one. I guess unlucky? ). He still managed to stay with his Cardinal shoal as well as the ones with eyes did.

Your Cardinal was probably making full use of its other less understood supersense, its lateral line. This line allows fish to stay in perfect spacing from each other and avoid obsticles. As for feeding the activity and smell the other fish created in the shoal would have let it know food was available, how it actually managed to injest the food may have been down to luck of a opertune snap.