Males that drop a sexually selected weapon grow larger testes

Area of Science:

• Evolutionary biology
• Animal behavior
• Sexual selection

Background:

• Sexually selected traits, like weapons, are costly and may trade off with other traits.
• Some species can autotomize (drop) weapons to escape danger, offering a unique experimental opportunity.

Purpose of the Study:

• To investigate if losing a sexually selected weapon (hind limb) in Narnia femorata males leads to increased testes investment.
• To assess the impact of weapon loss on offspring production and fertilization success.

Main Methods:

• Experimental manipulation of hind limb autotomy in male Narnia femorata.
• Measurement of testes size in males with and without hind limbs.
• Quantification of offspring production and hatching success in pairs involving males with and without hind limbs.

Main Results:

• Males that lost a hind limb grew significantly larger testes compared to controls.
• Hind-limb autotomy did not lead to enlargement of other nearby traits.
• Females paired with males lacking a hind limb showed 40% lower egg hatching success.
• Males missing a hind limb produced 42% more viable offspring than intact males.

Conclusions:

• Experimental evidence demonstrates males compensate for natural weapon loss by increasing testes investment.
• Loss of a hind-limb weapon can lead to greater fertilization success in viable offspring, despite reduced hatching success.
• This study highlights a complex trade-off between weapon investment and postcopulatory success in Narnia femorata.