# The distribution and chemosensory responses of pharyngeal taste buds in the sea lamprey Petromyzon marinus

## TL;DR

This study explores taste buds and chemosensory responses in the pharynx of sea lampreys, revealing their distribution and activity.

## Contribution

The study provides new insights into the chemosensory system of sea lampreys, a basal jawless vertebrate.

## Key findings

- Taste buds and axons were found at all six lateral pharyngeal locations in sea lampreys.
- The rostral pharyngeal region had more and larger taste buds compared to the caudal region.
- Taste receptor cells responded similarly to various chemicals across all pharyngeal regions.

## Abstract

Little is known about the chemosensory system of gustation in sea lampreys, basal jawless vertebrates that feed voraciously on live prey. The objective of this study was to investigate taste bud distribution and chemosensory responses along the length of the pharynx in the sea lamprey. Scanning electron microscopy and immunocytochemistry revealed taste buds and associated axons at all six lateral pharyngeal locations between the seven pairs of internal gill pores. The most rostral pharyngeal region contained more and larger taste buds than the most caudal region. Taste receptor cell responses were recorded to sweet, bitter, amino acids and the bile acid taurocholic acid, as well as to adenosine triphosphate. Similar chemosensory responses were observed at all six pharyngeal locations with taste buds. Overall, this study shows prominent taste buds and taste receptor cell activity in the seven pharyngeal regions of the sea lamprey.