Studies on the development of melanophores in in vitro cultured amphibian neural plates

Various parts of neural plates of Japanese newt (Cynops pyrrhogaster) neurula embryos were cultured alone in drops of culture media (Niu-Twitty's balanced salt solution or modified Leibovitz L-15 medium) with or without fetal calf serum (FCS). Although none of the parts gave rise to melanophores in a medium without FCS, some produced melanophores in a medium with FCS. The localization of melanophore-producing areas in the neural plates corresponded to that of Tada's (1944) findings. The assumption that FCS affects survival and development of melanophores is excluded, because neural fold cells do not require FCS to develop into melanophores. Therefore, there may be in FCS some factor which acts on the specialization of neural plate cells into melanophores. The results of this experiment suggest that this factor may be heat labile. The findings also indicate that FCS does not induce melanophores in gastrula ectoderm, but only affects neurula neural plate cells so as to give rise to melanophores.