Are my bichirs blind or con artists?

[Mighty Wizard]

Old topic, but it's interesting, so what the hell.

Polypterids don't have completely useless eyes, they have extremely good night vision for example, resulting from an almost identical mechanism to that of cats. This also makes their vision blurry, which makes them rely on other senses to a greater degree. The most obvious one is their very keen sense of smell. Their sense of smell however is far from enough, and they use their smell in conjunction with their other senses to catch prey and navigate their environment.

For example, they have a sophisticated lateral line system, used to detect changes in pressure, electrical impulses, and shockwaves in the water. In many ways it's like a sense of hearing, or a radar. Many have also proposed that Polypterids are in fact weakly electric fish, and indeed their heads are covered in electro-receptive pores. These are especially visible in Ropefish. Their lateral line system and electro-receptors is probably what enables them to effictively pinpoint and hunt fast fish. After all their sense of smell is, ultimately, dependant on the flow of water, and it would be almost impossible for them to hunt moving prey by using their noses alone.

 

[Hendre]

Interesting! Polys eyes are reflective, but my African knifefish have brighter (and bigger) eyes with a stronger glare against a torch. My syno has rather dull night eyes in comparison.

I think polys simply hone in on prey and gulp down everything in their path, usually patrolling the bottom for pellets. In nature it's said they can dig out insect larvae, likely electrosensory?

 

[Mighty Wizard]

Yes I have an ABK myself and it really does have huge eyes. I also understand that they have very good eyesight, and animals with big eyes, especially fish, usually do. This has often made me wonder about Polypterid eyesight actually, as some species have bigger eyes than others. My Polli for example has bigger eyes than my Delhezi, while they're actually not particularly smaller than on your "average fish", which makes me wonder how bad its eyesight can really be. Meanwhile Ropefish seem to have smaller eyes, yet their electro-receptors are more pronounced.

Bichirs probably use their sense of smell to locate buried prey like insects. Just like a proper dog, Bichirs can smell just the faintest trace of anything, trail it back to its source, no matter if it's buried, or very far away. My Delhezi is a bastard when it comes to sneaking up on the other inhabitants of the tank. There's this longfin Ancistrus in particular, who, in hindsight, I should have put in another tank. No matter where he hides, no matter how well, it's just a matter of time before the Del comes sneaking up behind him to take a bite out of his tail. I've actually made serious effort to remove the Ancistrus as he's obviously not having a good time in there, but he has become very very fast and the tank is heavily planted and furnished with all manner of caves, so I haven't been able. And to be perfectly honest I've grown somewhat apathic between all the attempts...

 

[Hendre]

Yes I have an ABK myself and it really does have huge eyes. I also understand that they have very good eyesight, and animals with big eyes, especially fish, usually do. This has often made me wonder about Polypterid eyesight actually, as some species have bigger eyes than others. My Polli for example has bigger eyes than my Delhezi, while they're actually not particularly smaller than on your "average fish", which makes me wonder how bad its eyesight can really be. Meanwhile Ropefish seem to have smaller eyes, yet their electro-receptors are more pronounced

My one sen runs away when he sees me coming close to the tank, I think that they're messing with us. I have 4 ABK, shining a torch on the tank is like a disco party haha

Interesting on the smell, my polys are always on the smelly BBS pellets in no time at all

 

[Mighty Wizard]

You can often see them lift their heads when they smell anything interesting. Goes for both food and new inhabitants of the tank, they'll smell it and then investigate. My Bichirs will also sometimes stop in their tracks as they sense someone else close by, possibly using their "radar", and then they'll bump carefully into them with their snouts, as if to smell exactly who is there.

I've found my Delhezi and sometimes my Ropes to be skittish at times, usually when the activity level in the tank is low, and especially if the living room is brightly lit as well. I think this is further proof that their eyes is more of a complimentary sense, like for example hearing is for Humans. You wouldn't hunt using your ears, meanwhile, if you heard a really loud bang right behind you, you wouldn't turn and look before you ran. I think this is the deal with Polys fleeing under a looming shadow. They can't see exactly what it is, only that it's huge and getting closer.

Also, if some of your polys are skittish, if you want to look at them without them fleeing, instead of turning the tank light off and using a flash light, turn off all lights in the room and only keep the tank light on. The fish inside won't see much beyond their own reflection in the glass, and will continue business as usual. Well mostly. My Snakehead usually tries to murder his own reflection, and my Polli sometimes, well, tries to bone with his reflection.

 

[twentyleagues]

I do think they can see better then we think. I can "call" my teug to the front of the tank by waving at him. I don't have to tap the glass. He just needs to be looking in my direction, wave my fingers at him and he comes right to the spot. He's not the only one that will do it, he will just do it almost every time.

 

[Hendre]

I do think they can see better then we think. I can "call" my teug to the front of the tank by waving at him. I don't have to tap the glass. He just needs to be looking in my direction, wave my fingers at him and he comes right to the spot. He's not the only one that will do it, he will just do it almost every time.

My WC is often glass surfing while I'm nearby hehe

Meanwhile my CB...

 

[twentyleagues]

My WC is often glass surfing while I'm nearby hehe

Meanwhile my CB...View attachment 1280873

That pic says it all! Proof, they can see!

 

[Mighty Wizard]

I do think they can see better then we think. I can "call" my teug to the front of the tank by waving at him. I don't have to tap the glass. He just needs to be looking in my direction, wave my fingers at him and he comes right to the spot. He's not the only one that will do it, he will just do it almost every time.

Haha, that's awesome. I suppose that's proof that their eyes are far from useless. I've always found the countless claims that Bichirs are nearly blind, rather dubious. After all, why would Polys hold on to their eyes for millions of years if they were useless? However it can't be ignored that pellets and other food items can fall right in front of them, without them seeing it.

One plausible answer would be that they are very far-sighted. Indeed many animals are short-sighted or far-sighted by default, and this might well be the case with Polys. This would explain how you can wave at them to make them come. Or how they can successfully charge another fish from the other side of the tank, as whatever electrical senses they possess probably isn't responsible for this alone.

That's such a cute little Senegal you have there Hendre, my Delhezi had a very similar piece of driftwood he'd poke his head out of when he was a baby. Your CB might be a little bit skittish, but at least he feels safe in the caves you've made for him(or her). I've found that the activity levels of my shy fish to be directly tied on the amount of plants and other hiding spots in the tank. After I stuffed my tank full of plants, all of my fish got super active, it really is as if they never sleep at all. I think that it's because no matter where they are in the tank, they're never far from dense vegetation, which seems to equal safety in their minds.

 

[Hendre]

I have wood and plants along my whole tank, a big piece of vine is the hangout of the ABK group and always hiding space when someone gets nippy. My tank is busy day and night and social behaviour of fish is awesome.