Deviating from the Norm: Peculiarities of Aplysia cf. californica Early Cleavage Compared to Traditional Spiralian Models.

Spiralia represents one of the main clades of bilaterally symmetrical metazoans (Bilateria). This group is of particular interest due to the remarkable conservation of its early developmental pattern despite of the high diversity of larval and adult body plans. Variations during embryogenesis are considered powerful tools to determine ancestral and derived characters under a phylogenetic framework.