TRPV4 expression on lingual taste buds of larval, juvenile, and adult stages of gilthead sea bream (Sparus aurata)

The fish sensory system includes specialized organs that can perceive external mechanical and chemical sensory stimuli necessary for life and survival. The gustatory system is a chemosensory system that plays an essential role in identifying nutrients and avoiding harmful substances by detecting changes in chemical composition of the environment [1]. Taste buds, the morphofunctional units for taste perception, are observed in both aquatic and terrestrial vertebrates. They perceive and transduce gustatory stimuli using G protein-coupled receptors, signaling cascades, and a complex arrangement of ion channels, among which the TRP superfamily in some fish species and in mammals [2]. The gilthead seabream (Sparus aurata, Linnaeus, 1758) is considered one of the most important aquaculture species in the Mediterranean Sea [3]. At first feeding, the larval buccal cavity is functional but is structurally and functionally less complex than that of adults [4]. However, during the juvenile stage, larvae show dramatic changes in anatomy, physiology, and behavior [5,6]. The tongue of gilthead seabream is formed by an enveloping mucous membrane hosting taste buds, a musculature, and an osteo-fibrous skeleton [7]. Therefore, in the present study, we evaluated, by immunohistochemistry, the expression of TRPV4, a member of the TRP superfamily, in taste buds during different developmental stages. TRPV4 expression in the tongue was observed in all considered stages. Immunoreactivity for the TRPV4 antibody was detected mainly in taste bud sensory cells, epithelial cells, and nerve fibers of the connective tissue underlying the mucosa. The TRPV4 expression pattern was different depending on the morphological changes of the taste buds observed at the different examined stages.