An immunohistochemical study on the gastrointestinal endocrine cells of three honeyeaters: Singing honeyeater (Meliphaga virescens), spiny-cheeked honeyeater (Acanthogenys rufogularis) and brown honeyeater (Lichmera indistincta)

The gastrointestinal endocrine cells of the singing honeyeater (Meliphaga virescens), spiny-cheeked honeyeater (Acanthogenys rufogularis) and brown honeyeater (Lichmera indistincta) were studied immunohistochemically with special reference to their degree of dependency upon nectar. The nine types of immunoreactive endocrine cells were detected in their gastrointestinal mucosa. Coexistence of motilin and serotonin in the same cells was confirmed in the pyloric region. In the duodenum and jejunum, a few peptide tyrosin tyrosin (PYY)-immunoreactive cells were detected. The clear difference in the distribution and frequency of the gastrointestinal endocrine cells among three types of honeyeaters, which differ in the degree of dependency upon the nectar, could not be confirmed. However, some differences were found that serotonin-, somatostatin- and gastrin-releasing peptide (GRP)-immunoreactive cells in the gizzard, gastrin-immunoreactive cells in the duodenum and jejunum, enteroglucagon-immunoreactive cells in the caeca and in the colon, and pancreatic glucagon-immunoreactive cells in the ileum of brown honeyeaters were more numerous (p < 0.05) than other two species