Abstract

Regeneration of the chelae has been studied in the Australian freshwater crustacean, Cherax destructor, by characterising the ultrastructure, sarcomere length and myofibrillar protein composition of the muscle tissue at different stages of limb formation. Pristine chelae of the yabby are symmetrical and are composed of two major fibre types that can be distinguished by their greatly different sarcomere length. These different fibre types can also be distinguished by differences in their myofibrillar protein composition. Short-sarcomere fibres differed from longsarcomere fibres in the paramyosin isoforms, a 75K unidentified protein and in troponin I and troponin T isoforms. Papillae contained large amounts of an 88K protein, most likely a haemolymph protein, while most of the major myofibrillar proteins found in the pristine muscle fibres were absent. No ordered muscle structure was observed in the papillae. Muscle fibres isolated from fully segmented but non functional regenerating chelae (closed dactyl) expressed many protein isoforms common to both long- and short-sarcomere fibres. In ultrastructure, these fibres had the characteristic structural features of short-sarcomere fibres but had atypically long sarcomere lengths. Once the claw became functional through the release of the dactyl from the propus after ecdysis, the protein profiles and ultrastructure of the muscles were indistinguishable from those found in pristine claws.

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