Ampullae of lorenzini and its uses in potamotrygon/paratrygon

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Nov 10, 2009
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Im trying to create some sort of experiment to see if in fact potamotrygon and paratrygon rays do still use the electroreseptors that mother nature has left them with.

unlike their cousins around the world the potamotrygons ampullae of lorenzini pores are alot smaller perhaps they evolved this way because they are now exclusive to freshwater and no longer need.but potamotrygon do infact still have the electroreseptory system and some people think they no longer use it?
Than theirs the paratrygon species of rays.they have evolved a way larger disc on the front and smaller eyes.apparentley these guys evolved from potamotrygon??? their eyes are about 1/10th the size or smaller than their potamotrygon relatives and inhabit muddy sandy areas where they can ambush prey.some how if the paratrygon evolved from potamotrygon its eyes have got smaller for some reason ,alot smaller??But the amazon is very muddy for many months of the year and for the paratrygon to rely on just smell and its tiny eyes seems unlikely. This subspecies has evolved a completely different shaped disc like and apple ,flat across the front and more disc size in front of its eyes.most about 1/3 of its disc is infact infront if its mouth and eyes. why would a paratrygon evolve smaller eyes and a way larger disc infront of its head if they do no longer have use of their highly evolved ampullae of lorenzini electroreseptor system???? Perhaps this is why this species of ray only ever really readily excepts live foods ??? it needs to use its sixth sense to feed??ive tried feeding the same fish dead and they will not take .i know rays are opportunists and will probably never hesitate to eat dead rotting fish on the bottom of the amazon river floor,maybe with alot of training mine in captivity will be trained to take prepaired foods? i think the paratrygon are alot like the mekong river rays ambush preditors that pateintly wait and pick up electricty created by all living creatures that pass over in murky muddy waters.

what im getting at here is that i want to create some sort of experiment at home to see if the paratrygon and potamotrygons i have react to electricty living things give off and not just relying on smell.all my pota rays have never shown any signs of using this briliant eveolutionary system. it kinda doesnt make sense that the rays worked millions of years to get the ampullae of lorenzini system just to no longer use it? their has been studies done on potamotrygon ampaulle of lorenzini vs salt water cousins and the pores are alot deeper and larger on the saltwater rays vs the freshwater exclusive rays.but they still have it! Now is it possible electricty is easier to pick up in sof acidic water vs very hard water? the electro conductivity of saltwater is way off the charts higher than amazon river water. perhaps the potamotrygons sytem has evolved for use in soft acidic water where electricty is much easier detected or is its less easier detected??

to many variables i think because the rays still use smell and eyes? does anybody know anything about this .i think paratrygon still infact use this system thats whay they evolved a larger disc maybe more room for more pores?i dont know ?i would love somebody to share any data they have on this subject.
 
Well my first experiment was to use a fluorocarbon fishing line and replicate a minnow with a piece of shrimp and jig it around in the tanks.the 7 potamotrygon would not touch it but could see it moving and smell it.
The paratrygons would only get annoyed by it? One actually slammed a minnow down while I was trying this.these guys can definitely distinguish real from fake.

I feel like the rays knew it was fake. They seen it move but wouldnt take it for some reason.i pulled the pieces of shrimp off the hook and the same ray ate it with out hesitation , probably because it wasn't swimming. The fishing line I used is the best most invisible line on the market also ,used by tournament anglers it's like $30 for one spool
 
I once had an internal digital thermometer. I removed it as my scobinas and hystrix kept attacking it, knocking it of the glass..

My current P14´s and BD´s love to pounce metal forks (used to sink down greens for my B. xanthellus).

I do not know how effecitve their sense of electroreception is, but it is most definitely there.

As to why the pores are smaller, their pray may yield a possible answer. Many stingrays feed largly on insects. I feel that electroreception my not bet much of a help in that kind of hunting.
 
The ampullae of lorenzini in Potamotrygon stingrays are innervated and functional. However they have lower sensitivity and as you mentioned the canals are shallower than in their marine living relatives. This is probably due to the lower conductance of the freshwater river systems compared to the highly conductive sea environment. The sensitivity seem to be in the range of electrosensitive teleost fish of the same river systems, accruing to studies. Paratrygon rays share a common ancestor with the Potamotrygon rays, their ancestors got landlocked in south america some 30-20 million years ago (different sources states a bit older time point), and probably have lived in the same river systems since. This would suggest that their ampullae of lorenzini also is less sensitive than the ones of their marine relatives. There are some info in the scientific literature about this if you have access to pubmed, web of science or google scholar.

/David
 
This is probably due to the lower conductance of the freshwater river systems compared to the highly conductive sea environment.
/David

Ah ofc. That makes perfect sense.

Very informative post!
 
This is what I'm trying to figure? Softer water is less conductive so why would they evolve smaller?
What if like alot of us now keep them in fresh water that is very conductive like a 200-300uS or even highers 400-500 Tds?

You'd think that would Definatley mess them up? They have evolved to sense electricity in soft water 10-30uS than we throw them into liquid Rock water? This is what they evolved away from its in a way kinda like taking them back in time a million years or more.This maybe why paratrygon don't do well captive, the shape and body structure of these species clearly shows me they have evolved this shape for one reason. More room on the front of the disc where the ampaulle or lorenzini system is? Flower and tiger too? They also have a different longer disc from anus to front of disc.

Perhaps this is a very over looked reason why we experience deaths ect... Stress due to them never agreeing with our hard fresh water.this would stress the ray for sure.rays only do good when not stressed as you all know ,but what about these very sensitive species like the paratrygon that more than likely have a way more advanced ampaulle of lorenzini electro.. System!
 
Maybe flower/tiger antenna and paratrygon are not all that sensitive. They are by far rarest to find in captivity long term.im sure theirs also alot more contributing factors to stress than hard water and them stressing out because they no longer can hunt the way they once did in the wild.

I wonder what the effects of hard fresh water really is on pota/para rays lorenzini system???? And if theirs a tolerance ? And where it is?
 
This is an interesting topic. I know that I feed a mix of prepared foods and live for my elasmos for the very reason of keeping them stimulated by the electrical signals put off by the live prey. They aren't specifically picking up ONLY prey though. Anything living in the water is something they'll pick up on - including other tankmates.
 
Very cool subject but I what I'm not really understanding is if electricity flows easier in salt water compared to freshwater then why would the AOL be smaller in freshwater species unless they are evolving not to use them anymore but in the same time I also agree why would a ray develop like the apple rays if it wasn't to have an increased amount of these receptors. I've never really fed live except for worms so I haven't had first hand knowledge on thier reactions. I'll have to do a little reading on this as it is a pretty interesting subject.
 
Salt water is hard. Conducts electricity better.ever wonder why so many people survive electric eels? Amazon river water is almost pure water which means it does not conduct electricity well.hard water contains salt and other ions which carry current ect...
So their ampaulle of lorenzini pores are shrinking ? Why?
Water does not conduct electricity well in amazon which is about 5-20uS .many people use a Tds meter to read hardness of water but Tds meter is just a general idea not exact measure. You need a ec meter to test hardness of water accurately. It measures ions In the water giving you and exact measure of the electric conductivity of fluids ie.. Hardness. Tds meter is not accurate.

Anders maybe right about what they are feeding on?it maybe just so much easier now they are in the amazon.Remember they didn't migrate into freshwater for nothing?

But I maybe misunderstanding how ampaulle of lorenzini detect electric fields created by all living things.maybe hardness of water makes it harder for ampaulle of lorenzini to detect eletric fields?or that would defy science $u4k? Maybe they are just way crazier preditors In salt water with a way better electro reciptive hunting system .

Alot of fish are electroreciptive .ampaulle of lorenzini is just the name science gave to elasmos advanced system. I don't know if any other fishes systems have been named ? Probably not many as sharks are most famous. We are just lucky rays are related or we would know almost nothing about them.

Perhaps they use a different form of electroreciption now being in almost pure water . Maybe there is something we do not know the evolved
 
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