The tongue of the Surinam caiman (a reptilian species) was studied by light
microscopy including immunohistochemistry for protein gene product 9.5 (PG
P 9.5), and transmission electron microscopy. The connective tissue immedia
tely under taste buds housed a cluster of cells immunoreactive for PGP 9.5.
These cells synapsed on nerves, and their cytoplasm contained characterist
ic granules of 90 nm in the mean diameter, glycogen particles, and bundles
of intermediate filaments. In light of these ultrastructural features, they
were identified as Merkel cells. The Merkel cells were also surrounded by
Schwann cells. These findings indicate that the present Merkel cell-neurite
-Schwann cell complex is comparable to the avian Merkel corpuscle. On the b
asis of the granule localization in the cytoplasm, the caiman Merkel cell w
as presumed to be involved in not only mechanoreception but also endocrine
or paracrine functions.