Objectives:

To investigate the anatomic structure of the pancreas and the distribution of the islets in adult zebrafish.

Methods:

In situ immunofluorescent staining, electron microscopy, and serial paraffin-embedded sectioning with hematoxylin/eosin staining were applied.

Results:

The pancreas along the intestine included 4 relatively independent and concentrated lobes, in which 4 kinds of islets-principal islets, Brockmann bodies, diffusely existing islets, and single β-cell-were observed. Some islets contained both α and β cells, whereas some contained only β cells. The islet number in each adult zebrafish averaged 84.53�43.77; and the lower quartile, median, and upper quartile were 55.25, 70.50, and 112.00, respectively (n= 40). The different islets were differently distributed in the 4 pancreatic lobes with statistical significance (P< 0.05). Meanwhile, 3 kinds of secretory granules were found in the cytoplasm of different islet cells.

Conclusions:

According to the distinct distribution, concentration of the pancreas, and different contents of the islets within the pancreas, 4 lobes of the pancreas along the intestine-the gallbladder-spleen lobe, the middle lobe, the left lobe, and the ventral lobe-were identified in adult zebrafish.