Growth and morphogenesis of the gastropod shell

Significance Mollusc shells are emblematic of the morphological diversity in nature. They are important models for understanding the evolution of form; they are all variations on the same basic geometrical groundplan, their shapes can be directly related to various adaptations, and they have an exquisite fossil record. Despite these advantages, the developmental mechanisms that control shell development are unknown. We examined cell division patterns in the shell-secreting epithelium and found striking asymmetries in proliferation rate and division orientation that correlate with key aspects of shell morphogenesis in two gastropods with different shell shapes. This work provides a foundation for understanding the cellular and developmental mechanisms that generate gastropod shell form and suggest how such mechanisms might evolve to generate new morphologies.