Nephrolithiasis in a giant Pacific octopus Enteroctopus dofleini

Managed care of cephalopods can be complicated by numerous factors including infectious and non-infectious disease, environmental stressors, and anatomic and physiological changes associated with senescence. The current report describes a unique case of nephrolithiasis in a senescent, >2 yr old female Pacific octopus Enteroctopus dofleini housed in a public aquarium. Clinical signs included generalized external pallor, inappetence progressing to anorexia, lethargy, and a slow healing mantle abrasion over a period of a year. Due to the animal's declining condition, humane euthanasia was elected. At necropsy, multiple, small, approximately 1-5 mm diameter crystalline deposits were reported throughout all sections of the renal appendages. Histopathology identified a large crystal expanding and rupturing a focal tubule, causing necrosis, ulceration, and hemocytic infiltration. Crystalline stone analysis revealed that the nephrolith was composed of 100% ammonium acid urate. Additional changes to the digestive gland included marked atrophy with fibrosis correlated to the animal's history of hyporexia/anorexia secondary to senescence. To our knowledge, this is the first report of nephrolithiasis in E. dofleini.