Does phosphate cause stunting?
- Thread starter slipknottin
- Start date
Hmmm. Had to think about that for a bit. I would guess that there wouldn't be much interference between the two, because they use separate cellular transport systems. Plus, Ca is largely absorbed from the food in the gut. Since FW fish don't drink, there wouldn't be water from the tank coming into the gut.
I am reminded as I poke around the literature that freshwater is a lousy source of electrolytes. Almost everything has to come from food.
I am reminded as I poke around the literature that freshwater is a lousy source of electrolytes. Almost everything has to come from food.
Yes, but, the increased concentration of PO4 may bind Ca, decreasing available Ca for absorption, or making uptake more difficult. Maybe, anyway. I don't know how strong the CaPO4 bond would be. My instincts tell me that it wouldn't be very strong and that the uptake of free Ca would tend to pull the equilibrium back to the free ionic form. But, you never know. Perhaps the binding makes it kinetically more difficult, even though thermodynamically it all comes out in the wash?
Calcium Phosphate is insoluble at normal pH. It's one reason that the addtion of Ca(OH)2 (kalkwasser) to marine tanks reduces phosphate. It precipitates out as CaHPO4.
But it will be more soluble in the acidic environment of the gut.
After a little more hunting, I found that I was wrong about Ca intake. Most FW fish take it up through the gills from the water, using specialized cells called "chloride cells." The mechanisms for pumping Ca into the blood are quite interesting, and different from how the same transport happens in the gut.
Under circumstances of low external Ca, they will take it in via the food, though.
So, if PO4 rises high enough to precipitate the available Ca, then the fish will be forced to rely on Ca in the food. Is there a metabolic cost to this, I have no idea. There is probably an answer in the aquaculture literature, but I don't have time to pursue it right now.
But it will be more soluble in the acidic environment of the gut.
After a little more hunting, I found that I was wrong about Ca intake. Most FW fish take it up through the gills from the water, using specialized cells called "chloride cells." The mechanisms for pumping Ca into the blood are quite interesting, and different from how the same transport happens in the gut.
Under circumstances of low external Ca, they will take it in via the food, though.
So, if PO4 rises high enough to precipitate the available Ca, then the fish will be forced to rely on Ca in the food. Is there a metabolic cost to this, I have no idea. There is probably an answer in the aquaculture literature, but I don't have time to pursue it right now.
