Our study shows that tool-using fish have a unique cerebral organization compared to other, non tool-using fish species.

What brain organization allows a fish to use a tool? In this study published in Communications Biology, researchers from the NeuroPSI institute (CNRS, Université Paris-Saclay) delved into tool use among fish, a behavior generally associated with primates, corvids and parrots possessing a large pallium (the pallium is another name for the cerebral cortex).
The researchers compared the different brain structures of several teleost fish species, particularly tool-using wrasses, and fish lacking this ability, such as zebrafish. The results reveal that, compared to other fish, wrasses show a significant hypertrophy of the pallium, as well as of the inferior lobe, a structure absent in mammals and birds. Furthermore, visualization of nerve fibers through a transparization technique followed by light sheet microscopy shows that wrasses have significant connectivity between the pallium and the inferior lobe. This abundant connectivity suggests a functional link between these structures.

These results highlight the crucial role of the pallium, common to both amniotes and fish, in intelligent behaviors such as tool use. However, in tool-using fish, another structure, the inferior lobe, specific to fish, seems to play an essential role. This difference in brain organization between fish and amniotes, despite a common ability to use tools, suggests distinct evolutionary paths for developing a brain adapted to this skill. Future studies will need to explore in greater depth the precise role of the inferior lobe in these behaviors.

Different ways of evolving tool-using brains in teleosts and amniotes. Pierre Estienne, Matthieu Simion, Hanako Hagio, Naoyuki Yamamoto, Arnim Jenett & Kei Yamamoto

Article published in Communications BiologyAccess to the manuscript