Biology question (1 Viewer)

[asiangamer01]

Ok, so my biology teacher and I were arguing over the type of nitrogenous waste fish excrete. He said that freshwater fish excrete ammonia, whereas saltwater fish excrete urea. But then I was like both types of fish mainly excrete ammonia, no matter the environment.

So, can someone please clarify who is right and who is wrong?

Thanks

 

[anomalousdecay]

I think this will answer your question:

http://www.marietta.edu/~mcshaffd/aquatic/sextant/excrete.htm

Organisms with less fresh water available, such as some marine organisms and all terrestrial organisms, are not as likely to waste water excreting nitrogen one atom at a time. They will often invest some energy to convert the ammonia into urea, which is less toxic, has two nitrogen atoms, and therefore takes less water to excrete. Because it is less toxic, it can be allowed to accumulate in the blood to some extent, and many organisms have specialized organs to remove urea and other wastes from the blood and excrete them. Urea is commonly used as an excretory product in vertebrates, and is rarely used in invertebrates. Some organisms, such as sharks and snails, allow urea to accumulate in their blood to help with overall osmotic balance. Sharks, for instance, use urea in the blood to make them hyperosmotic in relation to seawater, thus they tend to gain water from the ocean and do not have to worry about dehydration.

 

[BLIT2014]

Hagfishes can be exposed to extreme conditions within the cavities of the carcasses upon which they feed including very high CO2, low O2 (anoxia/hypoxia), low pH, and elevated ammonia. Yet we know virtually nothing about how these animals produce, let alone get rid of nitrogenous wastes. We do know that under standard laboratory conditions they excrete primarily ammonia, with trace amounts of urea (Walsh et al., 2001b).

http://www.mhhe.com/biosci/genbio/raven6b/graphics/raven06b/other/raven06_58.pdf (page 3)
Evolution of the Vertebrate Kidney. Freshwater bony
fish produce a dilute urine and marine bony fish produce an
isotonic urine. Only birds and mammals can retain so much..

From the sounds of it, would depend whether your talking about
(marine)Cartilaginous Fish or Marine Bony Fish
but for the sake of HSC bio course, I think its assumed marine fish excrete urea, whilst freshwater excrete ammonia.

 

[DepressedPenguino]

Hagfishes can be exposed to extreme conditions within the cavities of the carcasses upon which they feed including very high CO2, low O2 (anoxia/hypoxia), low pH, and elevated ammonia. Yet we know virtually nothing about how these animals produce, let alone get rid of nitrogenous wastes. We do know that under standard laboratory conditions they excrete primarily ammonia, with trace amounts of urea (Walsh et al., 2001b).

http://www.mhhe.com/biosci/genbio/raven6b/graphics/raven06b/other/raven06_58.pdf (page 3)
Evolution of the Vertebrate Kidney. Freshwater bony
fish produce a dilute urine and marine bony fish produce an
isotonic urine. Only birds and mammals can retain so much..

From the sounds of it, would depend whether your talking about
(marine)Cartilaginous Fish or Marine Bony Fish
but for the sake of HSC bio course, I think its assumed marine fish excrete ammonia, whilst freshwater excrete urea.
water that they produce a concentrated urine. So go with what your teacher is telling you.

Ehh I am sure that freshwater fish excrete mainly ammonia and marine fish excrete mainly urea.

 

[faisalabdul16]

Freshwater fish excrete ammonia not urea

 

[obliviousninja]

Can comfirm the last two posts.

Freshwater = need to conserve water so it is concentrated in the form of ammonia