Abstract
The brachiopod shell is closed by 2 pairs of adductor muscles. The striate adductors are twitch-type muscles causing quick incomplete closure; they are activated by single depolarizations, fatigue rapidly and cannot be tetanized. The smooth adductors are activated by repetitive depolarizations and do not respond to single stimuli; they contract slowly and develop tetanic tension at a low stimulatin frequency (10 Hz). The patterns of muscle activation and the conduction pathways in response to mechanical stimulation are described. Several types of reflex including a closing reflex and a resistance reflex were identified. [Species studied were Terebratalia transversa and Terebratulina unguicula].

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