Different ways of evolving tool-using brains in teleosts and amniotes

Area of Science:

• Comparative neuroanatomy
• Evolutionary biology
• Cognitive neuroscience

Background:

• Tool use in mammals and birds correlates with larger telencephalons and higher neuron counts.
• Certain teleost species, specifically wrasses, have independently evolved tool-using behaviors.
• Understanding the neural basis of tool use in diverse taxa can reveal convergent evolutionary pathways.

Purpose of the Study:

• To investigate the brain structure of tool-using wrasses and compare it with non-tool-using teleost species.
• To identify potential neural correlates associated with the evolution of tool-using behavior in teleosts.
• To explore the role of non-telencephalic brain structures in advanced cognitive functions.

Main Methods:

• Comparative analysis of brain morphology in tool-using wrasses and other teleost species.
• Examination of brain size, cellular composition, and fiber tract connectivity.
• Focus on the telencephalon and ventral midbrain structures.

Main Results:

• Tool-using wrasses possess significantly enlarged telencephalons and ventral forebrain/midbrain regions compared to other teleosts.
• This enlargement is attributed to expanded fiber tracts, not an increased proportion of neurons.
• A notable feature is the extensive connectivity between the pallium and the inferior lobe, a structure absent in amniotes.

Conclusions:

• The evolution of tool use in teleosts is associated with significant brain structural modifications, particularly in non-telencephalic areas.
• The enlarged and highly connected inferior lobe in tool-using wrasses may play a critical role in higher-order cognitive functions.
• These findings highlight the importance of non-telencephalic brain evolution in the emergence of complex cognition in teleosts.