Intracellular purine deposits in the gecarcinid land crab Gecarcoidea natalis

The terrestrial crab Gecarcoidea natalis stores large amounts of purine in the body. The major component of the purine deposits is urate (85% of the total purines). The other 15% is comprised of hypoxanthine, guanine, and xanthine. Microscopy studies reveal that these urate deposits are located intracellularly in spongy connective tissue cells throughout the body. Urate exists as numerous membrane-bound crystals 1 μm in diameter. Vesicles thought to represent urate vesicles at various stages of development are also present in the cytoplasm of the cell. Few organelles are visible in the urate storage cells, and it is unlikely that the urate is synthesized on site. Crabs (N = 2) fed a high-nitrogen diet have greater numbers of urate storage cells at more connective tissue sites, and the cells are larger (36.3 ± 1.8 μm (mean ± SE) and 44.0 ± 1.4 μm (mean ± SE)) and contain more urate than urate storage cells in animals collected from the field (N = 3) or maintained in the laboratory on a low-nitrogen diet (N = 1). The mean diameter of urate storage cells in animals fed a diet low in nitrogen and field-collected animals ranges from (13.5 ± 0.5 μm (SE) - 22.3 ± 1.0 μm (SE)). This histological study supports a strong correlation between purine accumulation and the nitrogen content of the diet.