TRANSFER AND TISSUE-SPECIFIC ACCUMULATION OF CYTOPLASMIC COMPONENTS IN EMBRYOS OF CAENORHABDITIS-ELEGANS AND RHABDITIS-DOLICHURA - INVIVO ANALYSIS WITH A LOW-COST SIGNAL ENHANCEMENT DEVICE

The pattern of autofluorescence in the two free-living soil nematodes Rhabditis dolichura and Caenorhabditis elegans has been compared. In C. elegans, during later embryogenesis the prospective gut cells develop a typical bluish autofluorescence as seen under UV illumination, while in Rh. dolichura a strong autofluorescence is already present in the unfertilized egg. Using a new, low-cost signal enhancement device, we have been able to follow in vivo the dramatic change in the pattern of autofluorescence during embryogenesis of Rh. dolichura. Autofluorescent material accumulates progressively in the gut primordium and disappears completely from all other cells. To investigate whether such an accumulation of cytoplasmic components also takes place in the C. elegans embryo, we labeled the cytoplasm of the egg with the fluorescing tracer dyes Lucifer Yellow (LY) or Rhodamine 6G (R6G). While LY appears to bind to yolk and progressively accumulates in the developing gut primordium, R6G does not show any such binding and remains equally distributed over all cells. Measurements in early and late stages indicate a significant increase in the volume of the gut cells during embryogenesis, while the embryo as a whole does not grow. Moreover, in cleavage-blocked 2-cell stages after development overnight, a reversal of cell size relationship to the benefit of the gut precursor cell takes place. In summary, our observations suggest a previously unknown massive transfer of yolk components in the nematode embryo from non-gut cells into lysosomes of the gut primordium, where they are further metabolized during postembryonic development.