Parallel And Divergent Morphological Adaptations Underlying The Evolution of Jumping Ability in Ants

Area of Science:

• Evolutionary Biology
• Biomechanics
• Insect Morphology

Background:

• Jumping is a rare locomotory specialization in ants, with limited understanding of its underlying morphological adaptations.
• Existing knowledge shows variation in leg and body part engagement during jumps across different ant genera.

Purpose of the Study:

• To investigate the morphological adaptations for jumping behavior in ants.
• To compare locomotory musculature between jumping and non-jumping ant relatives.
• To determine if jumping relies solely on muscle contraction or involves elastic recoil.

Main Methods:

• Utilized X-ray micro-CT and 3D morphometrics to compare muscle structures.
• Analyzed size-specific muscle volumes and muscle architecture (PCSA, fiber length, pennation angle).
• Compared hind leg length relative to body length.

Main Results:

• Jumping ants exhibit 3-5 times larger trochanter depressor muscles (scm6) and reduced coxal remotor muscles (scm2) in middle/hind legs.
• Increased muscle volume in jumping ants is primarily due to larger Physiological Cross-Sectional Area (PCSA), not fiber length.
• Hind legs are proportionally longer in jumping ants.

Conclusions:

• Increased investment in jumping-specific musculature is a key adaptation separating jumping from non-jumping ants.
• Direct muscle contractions appear sufficient for jumping performance in most studied species.
• Morphological adaptations for jumping in ants are both common and idiosyncratic across genera.