Abstract

Two female Northern fur seals (Callorhinus ursinus) (NFS) and two female California sea lions (Zalophus californianus) (CSL) from the Mystic Marinelife Aquarium, the Smithsonian National Zoological Park, and Seneca Park Zoo died with similar clinical and pathologic findings. Livers showed necrosis and/or nodular regeneration with cirrhosis associated with high levels of iron within hepatocytes, Kupffer cells, and macrophages. Livers from these and other captive and wild otarids were compared histologically using hematoxylin and eosin stains and Prussian blue stain for iron. Histologic iron content was subjectively graded from 0-4+ with the following results: captive adult animals with histologic and gross lesions had levels of 3+ - 4+. Captive seal pups had levels from 1+ to 3+, and wild cases had levels from 0-2+.

Paraffin-embedded liver samples analyzed for iron and copper content by atomic absorption spectrophotometry varied from 10,700-27,000µg iron/g dry weight in captive adults. This compared with ranges of 364-872 µiron/g dry weight in wild harvested fur seals with histologically normal livers. Copper levels ranged from 6-193 µcopper/g dry weight in captive NFS and from 61-111 µcopper/g dry weight in wild harvested NFS with histologically normal livers.

Serum iron profiles from sixteen fur seals and three sea lions in adult females ranged from 72-341µg/dl of iron, with total iron binding capacity (TIBC), from 100-286µ/dl, and % saturation from 31-100%. In males and NFS pups, serum iron levels ranged from 77-162µ/dl; TIBC from 198-368µ/dl; and % saturation from 22-72%.

These data indicate that in captive female otarids iron accumulation is a pathologic process that may lead to hemochromatosis. Further evidence suggests that increased dietary bioavailability of iron may result from a higher proportion of fish fed than cephalopods in captive otarid diets.