As a result of chlorpyrifos treatment in this sensitive period, a compact extralarval cap, largely comprised of pigmented cells, formed at the animal pole, and the blastocele, indeed the larva itself, was correspondingly diminished because of both cell extrusion and compaction.
At even lower chlorpyrifos concentrations (2.5-5 [micro]M), there was no extrusion of cells from the blastocele. Instead, the pigmented cells that arose 5-6 hr after addition of chlorpyrifos accumulated inside the larva (Figure 5B), rather than in an external cap.
Some of these embryos remained normal at the mid-blastula 2 stage (category 0), whereas others exhibited anomalies: inhibition of hatching, precocious appearance of mesenchyme cells in the blastocele, and extrusion of some cells to the perivitelline space (Figure 7C, 8A).