DHH, February 2007
This animal is roughly at mid L3 stage, and this TEM series covers the gonad primordium and developing vulval/uterine muscle precursor cells in transverse sections. 240 low power prints run anterior to posterior, with the prospective vulva centered near print # 127. A small set of high power prints concentrate on the anatomy of the ventral hypodermis (prospective vulva blast cells) and a second high power print set show the serial sections of chromatin organization inside a gonad primordium cell (cell #36).
Seven cells along the ventral midline are likely epithelial cells (hypodermis) that will give rise to vulval epithelium. Labelled in blue, with somata usually on the midline.
My inferred identities for “vulval” lineages
1A P4pp
1 P5pa
2 P5pp
3 P6pa
3 P6pp
4 P7pa
4 P7pp
Lying inward is the gonad primordium and germline precursors, whose cells are also labeled in blue. Many cells are probably somatic precursors to the uterus, spermatheca and gonad sheath, deriving from the MS lineages. MRC notes suggest that the more dorsal cell pairs will give rise to dorsal uterus, and the more ventral cells to ventral uterus.
Apparent germline precursors according to MRC notes:
10 - 21
and
38 - 47
Apparent somatic primordium cells
22 – 37
Anchor cell is #30 [see prints 119-133]
Lying laterally and closer to the bodywall are sex muscle precursor cells, for the vulval and uterine muscles, also marked in blue. These likely derive from M.vl and M.vr lineages. Note that the precursor cells already lie in close approximation to the lateral edges of ventral bodywall muscles, near where their daughters will later insert to the cuticle as mature muscles.
Y [on left]
Z [ on right]