HOMOLOGOUS NEURONS CONTROL MOVEMENTS OF DIVERSE GILL TYPES IN NUDIBRANCH MOLLUSKS

A comparison of central neurons controlling circumanal gill movements in 5 species of dorid nudibranch molluscs with those known to control movements of the dorsal gill tufts in the dendronotid nudibranch Tritonia, suggests that the neurons controlling these two gill types are homologous. Four symmetrical pairs of neurons, 2 in the pleural ganglia and 1 each in the cerebral and pedal ganglia, were found to control the circumanal gills in the dorids; three of these pair (pedal and pleural) correspond to similar neurons in Tritonia. In Triopha carpenteri, a dorid nudibranch having dorsal tufts as well as circumanal gills, the same neurons control both types of gill. The common neural control of dorsal tufts and circumanal gills revealed here, coupled with the widely observed conservatism in neural evolution, supports the hypothesis that these two gill types have a common evolutionary origin. © 1979 Springer-Verlag.