An Immunohistochemical Study of the Gastrointestinal Endocrine-Cells of the New Holland Honeyeater, Phylidonyris-Novaehollandiae

The gastrointestinal tract of the New Holland honeyeater, Phylidonyris novaehollandiae, was studied macroscopically, histologically and immunohistochemically. Although the honeyeater did not differ from other birds at the macroscopic and histological level, some interesting differences were revealed immunohistochemically. Eight types of immunoreactive endocrine cells were detected in the gastro- intestinal mucosa. The proventriculus and gizzard were characterised by the presence of serotonin-, somatostatin-, and gastrin-releasing polypeptide-immunoreactive cells. The pyloric region contained numerous gastrin- and motilin-immunoreactive cells as well as moderate numbers of somatostatin- immunoreactive cells. Along the length of the intestine, serotonin-immunoreactive cells were the dominant endocrine cells but small numbers of somatostatin-, gastrin-, enteroglucagon-, pancreatic glucagon- and neurotensin-immunoreactive cells were also found. Each had a different distribution pattern. The functional significance of these results remains to be resolved.