BEHAVIORAL, ELECTROPHYSIOLOGICAL, AND MORPHOLOGICAL INVESTIGATIONS OF STATOCYST FUNCTION IN THE NUDIBRANCH MOLLUSC HERMISSENDA CRASSICORNIS

Laboratory-reared specimens of the nudibranch Hermissenda crassicornis (Eschscholtz, 1813) possess statocysts that contain either one, several, or a species-typical number of statoconia (150-200). The number of statoconia per statocyst is significantly related to the growth rate of the animal during its first month post-metamorphosis, with slower-growing individuals (<0.88 mm/day) tending to possess a single statoconium bilaterally. Laboratory-reared animals with statocysts containing a single statoconium exhibited significantly weaker conditioning effects as expressed by faster response latencies to enter an illuminated area one and two days following behavioral training as compared with laboratory-reared animals with more than one statoconium per statocyst. Rotation of the isolated nervous systems of preparations with a single statoconium revealed that caudal hair cells exhibited reduced depolarization and the hyperpolarization of Type B photoreceptors in response to rotation was absent. As the number o...