Fig. 4. Mesoderm development following manipulation of LvDelta levels. (A-C) Gastrulation morphology in living embryos; (D-F) Immunostaining of blastula stage embryos with SMC1 (green), a marker for non-skeletogenic mesoderm, and CAD-1 (red), which labels cell boundaries. (A,D) In control embryos, SMCs ingress from the archenteron during gastrulation. SMC1-positive cells are evident in the central region of the vegetal plate at the mesenchyme blastula stage. (B,E) Following injection of LvDelta morpholino, gastrulation is delayed and few SMCs ingress from the archenteron. SMC1 immunostaining shows that there are few prospective mesodermal cells in the vegetal plate (one SMC1-positive cell is visible in this embryo). (C,F) Following injection of LvDelta mRNA, the archenteron produces excessive numbers of SMCs and the vegetal plate contains greatly increased numbers of SMC1-positive cells.