Cockroach homologs of praying mantis peripheral auditory system components

Area of Science:

• Entomology
• Evolutionary Biology
• Bioacoustics

Background:

• Insects possess diverse auditory structures, with praying mantids featuring a unique midline ear.
• The evolutionary origins of insect hearing, particularly the transition from non-auditory to auditory structures, remain incompletely understood.

Purpose of the Study:

• To identify the cuticular metathoracic structures in earless cockroaches homologous to peripheral auditory components in praying mantids.
• To define the cuticular transition from earless to eared hearing in Dictyoptera.

Main Methods:

• Comparative morphological analysis of cuticular structures in cockroaches and praying mantids.
• High-speed video analysis of metathoracic structures during coxa movement in cockroaches.
• Histological examination of the Nerve 7 chordotonal organ and associated cuticular elements.

Main Results:

• Earless cockroaches exhibit socketed hairs and the Nerve 7 chordotonal organ in the metathorax, homologous to mantis auditory structures.
• The lateral ventropleurite (LVp) in cockroaches shares structural similarities with mantis auditory chamber walls and facilitates chordotonal organ stimulation.
• The mantis ear likely evolved from the cockroach LVp through enlargement, medial shift, and rotation, potentially at the cost of proprioception.

Conclusions:

• The study identifies homologous structures and elucidates the evolutionary pathway of auditory organ development in Dictyoptera.
• The findings suggest that the evolution of hearing in mantids involved modification of existing cuticular structures, with potential trade-offs in sensory function.