COLOR CODE FOR P2M
Aug. 30, 2012
This wild type mid L1 larval hermaphrodite was prepared for Sulston and Horvitz for study of postembryonic cell fates in the early larval stages. According to MRC notes, the animal was grown at 20oC, hatching at about 7 PM on the day of egg-laying, then fixed the next morning at 11:50 AM, when blast cells “V3 and V5 are in prophase”. A sister animal was fixed several hours earlier, when the Q2 daughters were still quite close together (I am guessing this may have been the animal now called “L1Q”). The original TEM prints for P2M were accompanied by a drawing of the layout of seam cell and ventral hypodermis positions as seen from a lateral aspect, and a series of quick sketches made by Nomarski imaging during the L1 animal’s development to show the relative positions of all nuclei seen from a lateral aspect, similar to the more polished drawings in Figure 4 of the paper. By comparing the final sketch to the TEM series, Horvitz and Sulston could interpret the cell fates for known cell lineages.
The P2M animal is sectioned transversely, except that the tail tip is bending almost lengthwise. The cell bodies of many epithelial cells are marked, including the lateral and ventral hypodermis, and the seam cells.
See: J.E. Sulston and H.R. Horvitz (1977) Post-embryonic cell lineages of the nematode Caenorhabditis elegans. Dev. Biol. 56: 110-156.
According to the paper, EM images may have been prepared or annotated by Donna Albertson, Lois Edgar, John White, and Nichol Thomson.
Color code annotations follow the original MRC notes
Seam Cells marked as left / right pairs:
Lateral Hypodermis marked as left / right pairs:
A cell body has divided, but still joined by bridge
Central (mesodermal) cells
24 INT cell
left lateral cells
right lateral cells
1 phasmid cell
3 phasmid cell
10 phasmid cell