"warm-blooded" FW fish?

[slipknottin]

are there any "warm-blooded" freshwater fish?

not neccissarily ones you would want to or could keep... just wondering if they exist.

[Wippit Guud]

Not freshwater.

And only 2 in marine - Tuna and Mackerel.
Basically, really really big fish.

[slipknottin]

arent some sharks? ie. great white, mako... etc.

i wonder why there are no FW ones? There are cold FW bodies of water such as the great lakes and stuff... weird

[Wippit Guud]

Heh, wasn't looking for sharks... looks like the shortfin mako and the longfin mako are, as is the great white, but it's not a continuous warm-bloodedness... they raise their temps when hunting to get a speed increase. They're called endotherms. Mammals are homeotherms, continuous heat.


(and you can tell that Wip is bored at work)

[OrionGirl]

You are not the first to wonder...

http://www.bio.davidson.edu/people/midorcas/animalphysiology/Lectures/1999/6/index.htm

Good info!

[slipknottin]

ohhh. good link.

[Wippit Guud]

Looks like threshers are too... still haven't found a FW fish...

[FishmasteR2002]

No fish is really warm blooded like we mammals are. The mackerel sharks( Mako, Great White, etc. ) use metabolic heat to raise their temperatures up to 25 degrees F more than the temp. of the water. Tunas use the same "technology" as well. They have red heat producing muscles under all the white muscles.

The reason these fish have these features is because warmer muscles move faster and work harder, hence why the tuna is one of the fastest fish in the ocean. The mackerel sharks on the other hand use this metabolic heat for stamina. Sharks( well most sharks anyway... nurse sharks do not need to move to breathe ) need to always be moving to breathe. They do not have muscles on their gills like normal fish so they are always in constant movement to pass water over their gill slits. If a Great White shark stops moving it will drown. They even sleep while they swim. This is why sharks need the extra heat, so their muscles can keep going all the time.

The sharks have small viens in their muscles which pass next to small arteries. The veins carry warm unoxygenated blood to the gill slits from the muscles. The atreries then carry cold oxygenated blood back to the muscles. These atreries and veins are very close to one another. They are called the "Rete Mirable". The warm blood carried by the veins warms the colder oxygenated blood going to the muscles. Warm blood means warm muscles which means better operation. I hope this helps.
:)

PS- There is no such thing as a FW warm blooded fish. All fish are cold blooded, other than the ones mentioned above, which are not really warm blooded they just tricked nature. They cannot hold a constant temperature so they are not considered warm blooded.

[val]

Fishmaster,

You know, the line about sharks always needing to move has been shown as not always true. There was a big Discovery show about hammerheads 4-5 years ago and they found some warm water shoal, ouside of Mexico I think, where 100s of hammerheads were sleeping. Maybe sleeping isn't the right word, but they were motionless and the announcers were stunned by the discovery. Has this finding been confirmed, do you know...

Val

[OrionGirl]

Sharks need to keep moving unless they are in water that is moving and has a high oxygen level. There are several places where this super oxygenated water enters the ocean, and sharks congregate in this areas and hang out. The movement of the incoming water tends to be erosive, resulting in caves.

[ewok]

this is an interesting thread/thought......

i never heard of anything like this personally though, i think fish by definition means cold-blooded....

[Wippit Guud]

I bet the definition of fish once included: cannot fly, and: cannot walk across land. Not to mention: cannot breathe air, but we all know a bunch that do that.

Why should warm-blooded be so weird?

[Slappy*McFish]

What about salmon?....they are a fresh/salt water fish. Not sure if they have the ability to raise their body temp though, but it seems they would during spawning runs.