are plecos jawless fish????

[mangopleco]

im doing a science project on jawless fish, cartilaginous fish and bony fish and i want 2 know if plecos a jawless fish can u help me???

[MatsP]

Absolutely not jawless. I'm not sure what fish are jawless, but plecos are definitely bony fish with jaws.

I'll post a link to Nathan Lujan's dissertation, which has very nice pictures of jaw-bones of the fish.

--
Mats

[Suckermouth]

No they are not. Plecos have jaws.

The jawless fishes ("Agnatha") are a mish-mash of unrelated groups, including the hagfish and lampreys, as well as numerous extinct groups. If it's alive today and it's not a species of hagfish or lamprey, then it's not jawless. By contrast, both cartilaginous fishes (Chondrichthyes) and bony fishes (Osteichthyes) form distinct groups. Plecos (family Loricariidae) are a group of fishes from the bony fish group. Just about any other fish that has a sucker is a bony fish, such as suckers (Catostomidae), naked suckermouth catfishes (Astroblepidae), and the African suckermouth catfishes (various genera in Mochokidae).

[Back]

Jaws yes - but while evolving the suckermouth they have kind of lost most or all of the, what we would consider "traditional" gaping jaw function. That makes them supeficially lamprey lookalikes in the mouth region. They also remind of the Ordovician and Devonian Ostracoderms which where jawless fish.

Anyone know if the Pl*co jaw still have some function?
I'd guess attachment for muscular functions in getting food transported backwards and maybe for pumping water to the gills but that's as mentioned just guessing.

[MatsP]

If you are into "heavy duty fish technicals", this is for you, and explains pretty well how the jaw and teeth work in a pleco.
Nathan Lujan's PhD dissertation:
http://etd.auburn.edu/etd/bitstream/han ... tation.pdf
.

Of course, just looking at the pictuers will show the jaw bone structure.

--
Mats

[Suckermouth]

Jaws yes - but while evolving the suckermouth they have kind of lost most or all of the, what we would consider "traditional" gaping jaw function. That makes them supeficially lamprey lookalikes in the mouth region. They also remind of the Ordovician and Devonian Ostracoderms which where jawless fish.

Anyone know if the Pl*co jaw still have some function?
I'd guess attachment for muscular functions in getting food transported backwards and maybe for pumping water to the gills but that's as mentioned just guessing.

Pleco jaws are in fact even more complex than the typical jaw system, and definitely more complex than the related catfishes such as callichthyids and trichomycterids. This is seen in many species that need to eat encrusting things, such as in the angelfishes, butterflyfishes, and tangs. By no means are pleco jaws non-functional. Pleco jaw muscles are still necessary for both food acquisition and respiration (as you note), which is typical of jaws/throat muscles of other fishes, as well as maintaining suction. This is a moot point, however, as lampreys have similar functionality without jaws.

[sidguppy]

a long time ago, someone called Hoedemann had his ownb theory on this very subject

he was convinced that the similarities in shape and armorplating of Plecostomus and Cephalaspis weren't caused by convergent evolution (both are bottomdwelling fish with larger enemies all around), but caused by the Pleco's being direct descendants of that Agnata instead of bony fishes

he was also fairly convinced that the plating in Callichthyids was also a primitive characteristic and inherited from the armorplated toothless fish from the Ordovician, Silurian and Devonian.


it does resemble a pleco, for a bit

but it's convergent evolution, not a direct descendant.

the jaws of a pleco are easily visible when it's cleaning the glass


the only jawless fish around today are the hagfish and the lamprey


hagfish, a scavenger


two lamprey on this unfortunate salmon; a carnivore/parasite/bloodsucker

[apistomaster]

The unfortunate Salmonid beset upon by several blood sucking lamprey is actually Salmo trutta, The native Brown Trout of Europe but one that has become well established across much of the United States and Canada and has become a "naturalized citizen". Widely respected by fly fishermen as being more difficult to fool than the native North American species of trout. In many waters where they coexist in equal numbers with Rainbow Trout, the catch ratio runs about 8 or 9 Rainbows per every Brown trout caught. Because they are less rarely caught than the rainbows, there are always some very large old brown trout present which have switched from eating aquatic insects to eating 8-12 inch Rainbows or even mice and shrews dumb or unfortunate enough to have to swim at night when the largest Brown trout are most actively hunting. I night fish for them using "Bunny Flies". A "Fly" tied from strips of Rabbit skin with fur about 6 inches long.

[Back]

Pleco jaws are in fact even more complex than the typical jaw system, and definitely more complex than the related catfishes such as callichthyids and trichomycterids. This is seen in many species that need to eat encrusting things, such as in the angelfishes, butterflyfishes, and tangs. By no means are pl*co jaws non-functional. Pleco jaw muscles are still necessary for both food acquisition and respiration (as you note), which is typical of jaws/throat muscles of other fishes, as well as maintaining suction. This is a moot point, however, as lampreys have similar functionality without jaws.

Thanks. Interesting.
I imagined they would be in some sort of use but not to what extent.
Especialy since evolution tends to take advantage of existing body parts and adjust their use.

That's why I asked. There are (and there where) suckermouth(ish) fish that had to deal with similar problems without the jaw thus having "similar" mouth/throuth functions based on other constructions.

Evolutionary stuff is some sort of side kick thing so I'm my self a suckermouth (sorry for that one ) when it comes to looking up this sort of facts.

[Back]

If you are into "heavy duty fish technicals", this is for you, and explains pretty well how the jaw and teeth work in a pl*co.
Nathan Lujan's PhD dissertation:
http://etd.auburn.edu/etd/bitstream/han ... tation.pdf
.

Of course, just looking at the pictuers will show the jaw bone structure.

--
Mats

Just got it downloaded. Lovely paper indeed.
Thanks!
So far I've just been skimming through.
Requires a printout and some hours in a comfortable chair next to the aquarium.

Edit:
One more thing since lampreys have been mentioned.
We sometimes have them alive in our lawn on early September mornings.
It was a mystery at first.
After a while we learned that our cat carried them home and just left them there.
Just 50 meters away we have a river where lampreys come up to spawn in the autumns. However they are unfortunatelly stopped 100 meters downstreams (from our house) by a powerplant. Below the dam there are a few people fishing them and I think the cat simply steals one or two every now and then.
I know that lampreys can "walk" short distances when they're trying to reach upstreams waters but I don't think that's how they get caught by the cat.
They seems to cope being out of the water for quite some time. We've had some of them in tanks just briefly for the children to see before letting them go back into the river.

[MatsP]

Just got it downloaded. Lovely paper indeed.
Thanks!
So far I've just been skimming through.
Requires a printout and some hours in a comfortable chair next to the aquarium.

I think even Nathan would agree that it's probably best if it's not a too comfortable chair, or you'll fall asleep! ;)

--
Mats