Ossicular density in golden moles (Chrysochloridae)

Area of Science:

• Paleontology
• Zoology
• Mammalogy

Background:

• The middle ear ossicles are crucial for hearing in mammals.
• Golden moles (Chrysochloridae) are unique African mammals with adaptations to fossorial life.
• Seismic communication is a potential sensory modality in fossorial mammals.

Purpose of the Study:

• To investigate the physical properties of middle ear ossicles in golden moles.
• To determine the density and internal structure of the malleus in Eremitalpa granti.
• To explore the functional implications of ossicle density for seismic vibration detection.

Main Methods:

• Density measurements using the buoyancy method.
• High-resolution computed tomography (HR-CT) for internal structure analysis.
• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy for phosphorus content.

Main Results:

• The malleus density of Eremitalpa granti (2.44 g/cm3) is exceptionally high among terrestrial mammals.
• Other golden mole species do not exhibit unusually dense ossicles.
• Increased density in Eremitalpa mallei is linked to reduced vascularization and high mineralization.
• Subspecies of Eremitalpa granti show significant differences in malleus size and shape.

Conclusions:

• The high malleus density in Eremitalpa granti likely enhances inertial bone conduction for detecting seismic vibrations.
• This adaptation may reduce the need for extensive skull modifications to accommodate a large malleus.
• Morphological variations in malleus between E. granti subspecies suggest potential functional divergence.