First detection of taste buds in a chimaeroid fish (Chondrichthyes: Holocephali) and their Gi-like immunoreactivity

The mucosa covering the tongue of the Chimaera monstrosa has been investigated with histological and immunohistochemical methods allowing to describe, for the first time, gustatory structures (taste buds) in this subclass of cartilaginous fish. G-protein-alpha-subunit-inhibitory-like (Gi-like) immunoreactivity has been detected in the taste buds of C. monstrosa, as described in other vertebrates. In order to gain confidence on the antiserum used, able to recognize three Gi proteins in mammals, alignments of the antigenic sequence in mammals and other vertebrates were performed. The data were used for a research of putative genes in the genome of the holocephalan Callorhinchus milii, to date the only cartilaginous fish with a sequenced genome; the highlighted sequences could suggest the presence of all three genes (gnai1, gnai2 and gnai3) in holocephalans. The sequences of the predicted proteins present a high identity with the mammalian proteins.