When the 4 blastomere pairs of an 8-cell stage tunicate embryo are dissociated, each forms most of the structures it wou
Tunicate embryos at the eight-cell stage exhibit predominantly autonomous development, as dissociated blastomere pairs still differentiate into most tissues normally derived from them, reflecting segregation of determinants like macho-1 for muscle. However, notochord and nervous system lineages deviate from this rule, failing to form in isolation and requiring cell-cell interaction between animal and vegetal partners. Inductive signals involving FGF and BMP antagonism from presumptive notochord precursors influence neighboring ectoderm. Therefore most lineages demonstrate autonomous specification, while notochord and neural fate exemplifies conditional specification dependent on extrinsic instructive communication for proper induction.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 4: Tunicates and Conditional Specification of Notochord.