Distribution and Morphological Features of Taste Buds in the Zebrafish, Danio rerio

Histological and immunohistochemical study of gilthead seabream tongue from the early stage of development: TRPV4 potential roles

BACKGROUND

Taste buds, the morphofunctional units for taste perception, transduce gustatory stimuli using G protein-coupled receptors, and a complex arrangement of ion channels, among which TRPV4, a member of the TRP superfamily. Studies on taste buds development on gilthead seabream are unknown, and the TRPV4 expression on fish taste cells studies were conducted only on zebrafish.

METHODS

In our study, we have investigated the histological features of the gilthead seabream tongue dorsal surface from the earliest stage of development using Masson trichrome with aniline blue staining. Additionally, TRPV4 expression pattern was studied by means of immunohistochemical labeling and quantitative RT-PCR.

RESULTS

We have recorded for the first time on gilthead seabream lingual dorsal surface the presence of, stage specific, three types of taste buds: type I, type II and type III in larvae, juvenile and adults respectively. At 40 days post hatching, taste buds were mature-looking. TRPV4 expression was detected in a subpopulation of taste cells of larvae, juveniles, and adults. Furthermore, TRPV4 was expressed in the basal epithelial cells of the tongue at the larvae and juvenile stage, while this expression pattern was more diffused within all the epithelial cell layers on the adult.

CONCLUSION

Our findings presume a taste sensory role of TRPV4 in the three stage-specific taste buds and oral epithelia of gilthead seabream. In addition to its sensory role on the epithelial cell layers, we hypothesize that TRPV4 is implicated in epithelial cells differentiation and membrane protection.

Gustatory ultrastructures of an amphihaline migratory fish hilsa Tenualosa ilisha

This study was conducted with the tongue samples of different life stages of hilsa, that is, adult Marine hilsa, adult Riverine hilsa, and Riverine juvenile hilsa, respectively. Three types of taste buds (Types I, II, and III based on their elevation from the epithelium at different levels) of the tongue, which may be to ensure full utilization of the gustatory ability of the fish were rocorded. Presence of specific taste buds indicate that the fish hilsa dwells in turbid waters with a possible preference toward diatom like planktonic food source. Enhanced expression of taste receptors (T1R1 and T1R3) and associated stimulatory G-proteins subunits on tongue also indicate occurrence of amino acid like substances that guided sensory cues for feeding by this fish. A firm regularity or stringency of the free surface of the epithelial cells may be attributed to compactly arranged microridges. These structures protect against physical abrasions potentially caused during food manoeuvring and swallowing. In our present observations, the surface architectures of the tongue of hilsa are discussed within the background of migratory adaptation of the species in the context of feeding and habitat preferences.

Food and Feeding of Fishes. What Do We Need to Know?

Unrevealing food and feeding habits of fishes is the centre of research in aquatic biology, ecology, conservation biology and fisheries. The current practice in feeding ecology of fish accredits it as descriptive ecology, relying primarily on the information of their diet, directly through gut analysis or indirectly by computing some diet based indices. Such methods often mislead in the understanding of the true feeding behaviour of organisms need for more reliable and functional approach. The main objective of feeding ecology is to evaluate feeding behaviour of fish. Recent developments in tools and techniques of analytical research is an opportunity to take up more reliable details by formulating affordable methodical design for recording, modulating and designing suitable approaches for better explanation of the feeding biology in fish.