Muscle phenotype remains unaltered after limb autotomy and unloading

Area of Science:

• Crustacean muscle physiology
• Muscle plasticity and adaptation
• Biochemistry of muscle contraction

Background:

• Loss of chelipeds (claws) in crustaceans leads to significant atrophy of the anterior levator muscle.
• Understanding muscle phenotype changes under altered mechanical load is crucial for muscle biology.

Purpose of the Study:

• To investigate if the loss of mechanical load from chelipeds affects the muscle phenotype of the anterior levator muscle in crayfish.
• To compare protein profiles of levator muscles under different conditions of limb presence and regeneration.

Main Methods:

• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to analyze total protein and actomyosin fractions.
• Comparison of levator muscles from crayfish with functional regenerate limbs, limb buds (papilla stage), normal contralateral limbs, and pristine animals.

Main Results:

• No significant differences in protein profiles were observed among levator muscles with functional regenerate limbs, limb buds, or normal contralateral limbs.
• The total protein profile of the levator muscle is distinct from fast (L) and slow (SEL) abdominal muscles.
• The myosin heavy chain profile of the levator muscle resembles that of slow phenotype muscles.

Conclusions:

• Mechanical load does not appear to influence the phenotype of the crayfish anterior levator muscle.
• Continued muscle activation via intact innervation or maintained passive tension may preserve muscle phenotype during atrophy.