Selection on vocal output affects laryngeal morphology in rats

Area of Science:

• Evolutionary biology
• Comparative anatomy
• Bioacoustics

Background:

• Laryngeal morphology is often shaped by vocalization needs.
• The specific structural impacts of selection for distinct vocal behaviors are not well understood.
• This study examines how breeding for ultrasonic vocalizations affects larynx structure.

Purpose of the Study:

• To investigate the effects of selective breeding for increased ultrasonic calling in pups on adult rat larynx morphology.
• To determine the structural and acoustic consequences of altered vocal behavior selection.

Main Methods:

• Utilized microCT scans for 3D modeling and mineralized cartilage volume comparison.
• Employed clearing and staining with microscopy to analyze internal laryngeal structure.
• Conducted histology and microscopy for cellular structure assessment.
• Applied scanning energy dispersive X-ray spectroscopy for element composition analysis.

Main Results:

• Rats bred for higher pup ultrasonic calling rates exhibited shorter vocal folds in adulthood.
• The high-ultrasound lineage showed increased thyroid cartilage mineralization compared to the low-ultrasound lineage.
• Vocal fold length differences correlated with variations in low-frequency calls between the rat lines.

Conclusions:

• Selection for vocal behavior demonstrably influences laryngeal morphology.
• Increased thyroid cartilage mineralization in the high-ultrasound group may reinforce the larynx during vocalization.
• These morphological changes have direct acoustic consequences, highlighting the interplay between behavior and anatomy.