PAH excretion in two species of cancroid crab Cancer irroratus and C. borealis

C. W. Holliday and D. S. Miller To determine the characteristics of p-aminohippuric acid (PAH) excretion in Cancer irroratus and C. borealis, crabs were given a single injection of radiolabeled PAH and polyethylene glycol (PEG), and serum, urine, tissue, and seawater concentrations of each were measured over the next 6 days. In both species, PEG clearances averaged 5-10 ml serum/day; serum PAH concentrations fell exponentially after a 1-day equilibration period. In C. irroratus, urine PAH rose over the first 2 days and then fell; during days 2-6, mean urine PAH averaged two to four times mean serum PAH. In C. borealis, urine-to-serum ratios for PAH were 20-40 during days 2-6. PAH-to-PEG clearance ratios exceeded unity in both species, with ratios in C. borealis about three to six times those in C. irroratus. Tissue distribution data showed that C. irroratus midgut gland accumulated up to 50% of injected PAH, with gland-to-serum concentration ratios of 15-45; in this species, stomach fluid-to-serum PAH concentration ratios averaged 87, and nonurinary routes accounted for more than half of excreted PAH. In C. borealis, midgut gland-to-serum ratios never exceeded 2, and the urinary routes accounted for all excreted PAH. Thus, in C. irroratus, injected PAH accumulated in the midgut gland, with slow excretion through renal and nonrenal routes; in C. borealis, PAH remained in hemolymph, and only the renal route of excretion was utilized.