Zebrafish adult pigment stem cells are multipotent and form pigment cells by a progressive fate restriction process

Skin pigment pattern formation is a paradigmatic example of pattern formation. In zebrafish, the adult body stripes are generated by coordinated rearrangement of three distinct pigment cell‐types, black melanocytes, shiny iridophores and yellow xanthophores. A stem cell origin of melanocytes and iridophores has been proposed although the potency of those stem cells has remained unclear. Xanthophores, however, seemed to originate predominantly from proliferation of embryonic xanthophores. Now, data from Singh et al. shows that all three cell‐types derive from shared stem cells, and that these cells generate peripheral neural cell‐types too. Furthermore, clonal compositions are best explained by a progressive fate restriction model generating the individual cell‐types. The numbers of adult pigment stem cells associated with the dorsal root ganglia remain low, but progenitor numbers increase significantly during larval development up to metamorphosis, likely via production of partially restricted progenitors on the spinal nerves.     

Individual differences in the ability to discriminate the direction of spontaneous changes in peripheral finger temperature

Spontaneous fluctuations of .1° C in peripheral finger temperature were recorded for a 30-minute baseline period in 10 subjects. Those meeting specified criteria of temperature fluctuations were then asked to judge the direction of change in computer-detected temperature fluctuations of .1° C, first without feedback, then with feedback (knowledge of results). Only 1 subject produced convincing evidence of ability to make directional judgments at better than chance level, though more training with feedback might have benefited other subjects. The theoretical significance of these results for the relationship between discrimination and voluntary control is discussed.This research was supported by a grant from the Australian Research Grants Scheme.