 The ammonia diffuses down its concentration gradient into the urine or into the blood, where it gets pumped through the branchial hearts and diffuses out the gills.The excretion of ammonia by "O. vulgaris" makes them ammonotelic organisms.Aside from ammonia, a few other nitrogenous waste products have been found to be excreted by "O. vulgaris" such as urea, uric acid, purines, and some free amino acids, but in smaller amounts.