Two blastomeres show Acetylcholinesterase activity. Summary Diagram of Muscle cell lineages in Ascidians. Blastomere B4.1 demonstrates autonomous specification of muscle cells. 13-6 illustrates segregation of cytoplasmic determinants for muscle, endoderm, and epidermis during cleavage in Ascidians. Mollusc embryos develop into trochophore larva and veliger larva before assuming their adult form.
Some molluscs display an unusual cell behavior during cleavage.
Polar lobe formation. Polar lobe cytoplasm is incorporated in the CD blastomere after the first cleavage division, and then into the D blastomere after the second cleavage division. Blastomere isolation experiment demonstrates autonomous specification. Isolated presumptive trochoblast cells develop cilia at the same time as trochoblast cells do in the intact embryo. Loss of Function experiment.