Worm Breeder's Gazette 7(1): 46

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More on Panagrellus redivivus Nongonadal Cell Lineages

P. Sternberg, B. Horvitz

Figure 1

We've finished determining the P.  redivivus postembryonic 
nongonadal cell lineages.  The postembryonic nongonadal increases in 
nuclear number in P.  redivivus (P.r.) and C.  elegans (C.e.) are as 
[See Figure 1]
The additional blast cells in P.  redivivus are two intestinal cells 
and a rectal cell K2 (a.k.a.  K') and a tail ectoblast T3.  Four cells 
present in both sexes divide only in the males of both species.  Most 
of the additional cells generated in P.  redivivus are derived from 
the lateral hypodermal precursors (V1-V6).  The extra deaths of the P. 
redivivus female are found in the M and P lineages.  There is 
variability in the lateral hypodermal lineages in P.  redivivus.  The 
male tails of P.  redivivus and C.  elegans differ substantially in 
gross morphology: C.  elegans, but not P.  redivivus, males have a 
bursal fan; the spicules are shaped differently; and P.  redivivus has 
14 knob-like caudal papillae rather than 18 elongated caudal papillae (
rays).  In P.  redivivus males, each V6 cell generates four caudal 
papillae precursors (Rn cells) and T1 and T2 each generate three Rn 
cells.  In C.  elegans, each V5 generates one, each V6 generates five 
and each T cell generates three Rn cells.  The Rn sublineage is 
identical in the two species.  The lineages of the male-specific blast 
cells (B, Y, U and F) differ only by one extra round of cell division 
in the F lineage and certain division axes in the B, Y and F lineages. 
As homologous structures in the two species have essentially the same 
number of cells, the morphological differences are probably caused by 
differences in the morphogenetic programs of lineally equivalent cells.

Figure 1