Fig. 1From: Duplication of spiralian-specific TALE genes and evolution of the blastomere specification mechanism in the bivalve lineagea, b Diagram displaying the typical early development of equal-cleaving species (a, e.g., limpet) and bivalves (b) from the egg stage to the 16-cell stage. c Diagram displaying typical polar lobe formation during early bivalve development. pl polar lobeBack to article page