What distinguishes the protostome cleavage pattern?

The cleavage pattern in protostomes is characterized by spiral and determinate cleavage. In spiral cleavage, the embryonic cells divide at an angle to the axis of the embryo, resulting in a distinct arrangement of cells that is twisted. This arrangement is crucial as the fate of these cells is already determined at the early stages of development, which is referred to as determinate cleavage. In other words, the developmental pathway of each cell is set early on, leading to a specific structure in the resulting organism.

Additionally, this cleavage pattern distinguishes protostomes from deuterostomes, where indeterminate cleavage occurs. In indeterminate cleavage, the fate of the cells remains flexible for a longer period, allowing for a greater potential for developmental variation. In summary, the unique features of spiral and determinate cleavage define the embryonic development pattern in protostomes.