The ontogeny of the pancreas in macropodid marsupials

Abstract

The development of the endocrine pancreas in kangaroos was examined histologically with tissue from three kangaroo species, the red kangaroo Megaleia rufa, the euro Macropus robustus erubescens, and the grey kangaroo Macropus giganteus. The relative size of the pancreas of the pouch young was found not to differ significantly from that of adults. Stages of pancreatic development were described from the frequency of the occurrence of the pancreatic epithelial ducts and the B or insulin-secreting cells, while the development and distribution of the A2 or glucagon-producing cells was also observed. In pouch young of less than 22 days of age the pancreas is dominated by ductular epithelial and undifferentiated pancreatic cells. From days 42 to 97 of pouch life B endocrine cells tend to be concentrated together and ductular tissue encroaches into areas previously dominated by connective tissue. After 120-135 days the first A2 cells are apparent and are usually located at the periphery of the islets, which now take on a distinctive appearance as the acinar tissue expands and separates them. After 135 days of pouch life A2 cells outnumber B cells; the endocrine tissue assumes an adult appearance after 150-160 days. The major difference between the development of pancreatic tissue in foetal sheep and pouch-young kangaroo is the prolonged dominance of connective tissue and the slow development of endocrine tissue in the former.