Decapod crustacea appear to utilize two overall strategies for excretion of anionic waste products and xenobiotics. One strategy utilizes a potent renal secretory system; the other utilizes both modest renal secretion and strong gut secretion (possibly aided by midgut gland conjugation). In crabs, the level of participation of the renal system in overall secretion is primarily determined by the location of an anion pump and a carrier protein.
The bladder of Cancer borealis,which strongly secretes the model organic anion, p-aminohippuric acid (PAH), has a serosal organic anion pump and a luminal facilitated carrier. The bladder of Cancer irroratus,which reabsorbs PAH from bladder urine, has a luminal organic anion pump and a serosal facilitated carrier.