catfish vs sharks

Waldo · Post by **Waldo** » 31 Dec 2003, 07:24

It's just a personal observation but my interest in catfish seems to dirive for my love of tiburon. I'm talking about the average slime run of the mill shark and catfish. These biological torpedoes have a lot in common, set aside the wiskers and extra opercula. Note the jaw structure, a flat, bottom based mandable. Also the fine scales, which seem to be a flaw until you see the fish swimming in there reflective fliud paterns unlike other fish. whats up with this, the list goes on. does anyone have anyinformation on why?

Sid Guppy · Post by **Sid Guppy** » 31 Dec 2003, 13:16

no it's all convergent evolution, and that's only speaking about the sharklike cats, such as Iridescent Sharks (Pangasius/Pangasiodon), Arius, Pims etc.

There's a truckload of cats out there that don't resemble sharks at all: Corydoras, Rubbernose Plecs, Whiptails, Clarias, Bumblebee-cats etc etc etc

The convergent evolution-thing is basically down to active swimmers in the open water all having the same shape (Dolphins, Sharks, big bony fish such as Arius-cats, Pangasius,Salmon, Tuna, Swordfish etc). Physics actually!

Once you get the scalpels out, put pieces under the microscope, dessect them, they're very very different!
a few facts:
Sharks (along with rays and such) belong to a whole different class of fish! they have catilage for bones, 4-7 gill-openings (depending on species), no swimbladder, small organs to detect electricity (Lorenzini?), teeth for scales (this is really true! a Shark's scales are essentially teeth....or teeth are "upscaled" scales)

catfishes are "bony fish", members of the great group of Ostariophysics, along with Characins (such as Neon Tetra and Piranha), Cyprinids (Carps, Loaches, Minnows etc) and American Knife-fishes. These all share a unique organ (Weber organ) that works more or less like an ear and is connected to the vertebrae behind the skull. ONLY this group of fishes possess this organ, although many other fish can hear quite well too.
NO catfish has true scales at all! although many have external armourplating.
Most catfish have fairly obvious whiskers, but not all (such as Ageneiosus, parasitic catfishes like Vandellia, some Loricariids etc).
Catfishes are all freshwaterfish or have freshwater ancestors (arius etc)

Sharks are all marine fish or have marine ancestors (Nicaragua Bullshark, Potamotrygon -Amazon Stingray etc)

Fiskars the Whiskers · Post by **Fiskars the Whiskers** » 31 Dec 2003, 16:06

The shark's sandpaper-like skin coverings are called denticles. In some places of the world, I've heard people use the skin as sandpaper, because it's so rough!

plesner · Post by **plesner** » 31 Dec 2003, 16:15

And I've been told that the sharkskin is so aerodynamically efficient that giving the surface of aeroplanes a similar structure has been given serious consideration. Should supposedly enable a decent improvement in fuel economy.

Post by **Rusty** » 31 Dec 2003, 16:32

Swim and wet suits for humans are now covered in projections based on denticles, and most of the swimmers at the Olympics will be wearing "fast skin". It works in a way similar to the dimples on a golf ball, reducing drag by disrupting the flow of water over your body.

Rusty

Waldo · Post by **Waldo** » 31 Dec 2003, 21:37

I think that it depends on which direction you rub the shark. -> towards the shark is aquadynamic with the least amount of friction, but moving your have from tail to head the "teeth" cling to you. About the swimsuits, I used to date a girl that was really into that stuff. She told me that there were little ruff spots that direct restirctions where they are needed, and that the idea did come from sharks. This is all too fascinating. I love learning this stuff!

S. Allen · Post by **S. Allen** » 01 Jan 2004, 00:06

but oddly enough rays have evolved, at least the freshwater species, denticles that are not hook-like, except along the dorsal surface of the tail, but really more rounded and pebbly, and in some species they stay towards the backside of the fish. the leopoldis I have have them from about midway on from the tip of it's disk to the back, and not to the margins of the disc, but mainly over where the internal organs cause the dorsal surface to rise a bit. It's got a slightly rough texture, but nothing sharp.

Suckermouth · Post by **Suckermouth** » 01 Jan 2004, 00:24

SG_Eurystomus, to be more accurate, sharks have scales for teeth. I know it's pretty much saying the same thing, but the teeth are modified scales, not the other way around.

Waldo · Post by **Waldo** » 01 Jan 2004, 11:21

so what your saying is scales came first? i don't know, it seems as though multiple cell organisms would have started with eating then armor.

michelle56 · Post by **michelle56** » 01 Jan 2004, 18:37

The Megatooth had teeth 7''!

spiny · Post by **spiny** » 01 Jan 2004, 21:13

Megatooth.. do you mean Carcharodon megalodon, the extinct relative of the Great White Shark Carcharodon carcharias? Scientists believe it was 2 or 3 times the size of the Great White...
Only the fossile tooth are found, because of the sharks lack of normal bones. The tooth was the size of a mans hand. I've got some fossil shark teeth (of a smaller species), and even if fossile, the tooth part is razorsharp and hard like porcelin, and the jawbone base are just like porous limestone... (fossils from Morocco).

It is incredible that the Sharks are mostly unchanged since from an age before the dinosaurs. Perfect designed then.

Beware of the shark...

The sharks tooth are also lined up in rows in the jaw, ready to grow into position if one tooth are lost or damaged.

I've seen several sharks, and the skin in several species might rip your skin off.

The origin of the fishes are really exciting, as aquatic life have lived in their habitats for a far longer time than the later landbased organisms!

Waldo · Post by **Waldo** » 01 Jan 2004, 23:36

thats what i was thinking when i started this topic, it seems as though catfish might have started out as freshwater shark. Speaking of which., is there such a thing?

Post by **Silurus** » 01 Jan 2004, 23:43

Comparing a catfish and a shark is like comparing a cow and a salmon. If you go back far enough, they share a common ancestor, but they are not really that closely related.

michelle56 · Post by **michelle56** » 02 Jan 2004, 03:31

but they are not really that closely related.

exactly!

Sharks-Cartilaginous fish(sharks,rays,eagle-rays,manta rays and horned sharks(Chondrichthyes).

Catfish-Bony Fish(catfish,angelfish,clownfish,etc(Osteichthyes).

Lamprey-Jawless Fish(hagfish,and lamprey(Agnatha).

they share a common ancestor

Darwin's finches are good eamples of a common Fringilid ancestor.

Waldo · Post by **Waldo** » 02 Jan 2004, 07:02

ok how about this, what are some of the lifespans. which will live longer. I would assume sharks would but thats just an opinion.

michelle56 · Post by **michelle56** » 02 Jan 2004, 23:42

Sharks mate only rarely and have a relatively small number of babies at a time. Consequently, they can't replenish their population quickly. Sharks also have fairly long lifespans -- on average, sharks live 25 to 30 years, and some sharks live 100 years or more

Post by **Rusty** » 03 Jan 2004, 00:34

michelle56 wrote:Sharks mate only rarely and have a relatively small number of babies at a time. Consequently, they can't replenish their population quickly. Sharks also have fairly long lifespans -- on average, sharks live 25 to 30 years, and some sharks live 100 years or more

You know, copying and pasting from a website without giving credit isn't very ethical. It's called plagiarism, which is a big no no.

Rusty

S. Allen · Post by **S. Allen** » 03 Jan 2004, 00:52

There are sharks that find their way into freshwater, bull sharks being the most notable, being found in lakes in nicaragua if memory serves me right, as well as rivers in north america occasionally. I'm not aware of any truly freshwater(restricted to only freshwater that is) shark. There are a few sawfish said to inhabit freshwater, even an episode of TFH(I think) with Bleher holding one on the cover, and just about every sawfish listed in Freshwater Rays by Ross and Schafer shows as found in both salt and fresh waters. If you want information on rays, there seem to be freshwater sightings on most continents.

Waldo · Post by **Waldo** » 03 Jan 2004, 07:07

holy moly, thats a lot of years. I was just doing some research on the sturgeon, as for some reason i thought i had heard it was a type of shark. well it's not unfortunatly, but what an odd fish. they live for decades and can grow larger the an RV. wow, I want an aquarium to hold one of them.

wait i would have to feed it dead catle. hmmm.

S. Allen · Post by **S. Allen** » 03 Jan 2004, 20:06

Sturgeons are a whole other cup of tea, but I believe that some species are protected due to overfishing. There are 3 listed in Axelrod's atlas, the typical 30 foot max beluga sturgeon, a whiptail sturgeon he lists as maxing out at 60cm, and one other that is listed as 1.25 meters max size. They are probably not reasonable fish to keep, you'd at very least need a chiller, as temps listed are 18C, and I haven't the foggiest who'd even sell live ones, nor even any general info on keeping them.

Post by **Barbie** » 03 Jan 2004, 20:55

You'd be sad to know I've seen them for sale in Walmarts then

Barbie

kateswan · Post by **kateswan** » 03 Jan 2004, 21:57

Sturgeon for sale at WalMart? OMG!

I'm fortunate to live in place where you can still see sturgeon passing
through the river to spawn. A local group raises and plants babies
in an effort to revive them in our inland lakes just off Lake Michigan.

Want to see pictures?
http://www.indianrivermi.com/fish01.html

Kathy S

Waldo · Post by **Waldo** » 03 Jan 2004, 23:14

how is that possible. you tell the fish and wildlife it's in the interest of science and you can get away with murder. that brings up another question. I know some fish like the channel catfish are native to the US and that we have them in our rivers. are there local fisheries around that catch them or farms?

Post by **Silurus** » 03 Jan 2004, 23:41

Channel catfish (that are eaten) are farmed.

Waldo · Post by **Waldo** » 04 Jan 2004, 05:10

hmm, wow drag me out in the street and shoot me.

I just thinks thats dandy. do you know where?

Post by **Silurus** » 04 Jan 2004, 14:43

Mostly in the south, with Alabama, Arkansas, Louisiana and Mississippi being the largest producers.