The cerebral (CG), pleuro-pedal (PPG) and visceral ganglia (VG) of mature females of the abalone, Nordotis discus R_EEVE, were respectively homogenized separately in filtered sea water, in tap water or in 0.6% NaCI solution in a concentration of one ganglion per 0.1 ml of the vehicle. The homogenates were injected 1, 2 or 3 times, once a day, in a constant amount of 0.1 ml per animal, into the head of prespawning females of 9.0-11.9 cm in shell length.
In groups of PPG-, PPG+VG- and VG-injected animals, ovaries exhibited a remarkable swelling and softening followed by a slight increase in mean body weight, possibly owing to an increased water content in the ovaries caused by the uptake of water. Moreover, they spawned a huge number of fertilizable eggs after 1 or 2 injections, which resulted in a loss in body weight. Conversely, a group of CG-injected animals showed a gain in mean body weight without revealing any notable change in the ovaries.
It seems likely that the visceral and pleuro-pedal ganglia may produce and release sub-stance(s) which induces spawning in the abalone, and that an uptake of water in the pre-spawning ovary might be physiologically significant for the execution of spawning.