Sensory cells in tunicates: insights into mechanoreceptor evolution

Area of Science:

• Evolutionary developmental biology (Evo-Devo)
• Comparative chordate sensory systems

Background:

• Tunicates are the sister group to vertebrates, providing a model for early chordate evolution.
• Their simple anatomy and early divergence from vertebrates predate vertebrate-specific genome duplications.
• Tunicate larvae exhibit basic swimming behaviors crucial for substrate selection during metamorphosis.

Purpose of the Study:

• To review two decades of research on tunicate mechanoreception.
• To explore the coronal organ's sensory cells as models for vertebrate hair cell evolution.
• To compare tunicate and vertebrate mechanoreception strategies at anatomical, cellular, and molecular levels.

Main Methods:

• Literature review of anatomical, cellular, and molecular studies on tunicate mechanoreception.
• Comparative analysis of tunicate sensory structures with vertebrate counterparts (inner ear, lateral line).
• Discussion of evolutionary significance within the Evo-Devo framework.

Main Results:

• Tunicates possess diverse mechanoreceptor structures, including primary and secondary sensory cells (coronal sensory cells).
• Coronal sensory cells show potential homology with vertebrate hair cells.
• Similarities and differences in mechanoreception strategies between tunicates and vertebrates have been identified.

Conclusions:

• Tunicate mechanoreception, particularly the coronal organ, is crucial for understanding the evolution of vertebrate sensory systems.
• Mechanoreception in tunicates provides key insights into sensory system evolution within chordates.
• This research highlights the intricate evolutionary pathways shaping chordate sensory systems.