Species-dependent variation in the dendritic stratification of apparently homologous retinal ganglion cell mosaics in two neoteleost fishes

Large retinal ganglion cells of the marine neoteleost Bathymaster derjugini were labeled with horseradish peroxidase and studied in flatmounts. Four t ypes formed regular, independent mosaics, of which three (biplexiform, alph a-a, alpha-c) resembled those in several other teleosts. The fourth (alpha- ab) appeared novel in one significant respect. Whereas we originally descri bed similar cells in another neoteleost, Oreochromis spilurus, as monostrat ified in sublamina b of the inner plexiform layer, these were very clearly bistratified in a and b. Detailed re-analysis of our Oreochromis flatmounts showed that the difference is of one degree only: many Oreochromis cells d o send fine dendrites into a. These observations strengthen the evidence th at all four mosaics are homologous across a wide range of fishes, and clear away an obstacle to our earlier proposals that the alpha-a, alpha-ab and a lpha-c mosaics of fishes, frogs, and perhaps other nonmammalian jawed verte brates too, may all be homologous. (C) 1999 Elsevier Science Ltd. All right s reserved.