SPONTANEOUS LESIONS DETECTED IN THE COMMON COTTON-FARED MARMOSETS (CALLITHRIX-JACCHUS)

Spontaneous lesions in the common cotton-eared marmosets (Callithrix j acchus), which were maintained in our laboratory or were purchased fro m a commercial breeder, were examined histopathologically. There were 39 males and 22 females, between the ages of 7 to 100 months. The most interesting finding noted was extramedullary hematopoiesis, which was observed in the mesenteric lymph nodes, spleen, liver, kidney, adrena l gland, and cerebral choroid plexus. Megakaryocytes were frequently o bserved in the blood vessels of the alveolar wall of the lung. It is i mportant to distinguish extramedullary hematopoiesis which occurs acci dentally from that induced by repeated blood sampling or that resultin g from administration of chemicals. Extramedullary hematopoiesis was e asily distinguishable from inflammation or hematopoietic neoplasms, be cause of the various cellular elements present, including megakaryocyt es. In the weak and dead animals, enterocolitis was found at a high fr equency. Other common findings included thymic involution, prominent v acuolation of liver sinusoidal cells, which were probably Ito-cells, a nd basophilic changes in the renal tubular epithelium. The liver and t he kidney are frequently affected by toxic effects of chemicals. There fore, it is important to distinguish the toxic changes from the sponta neous ones. Proliferation of apocrine glands in the cervical skin was an interesting finding; however, neither inflammatory change nor cellu lar atypia was noted in this structure. Although its function is uncle ar, this structure may be a marmoset-specific tissue.