Article: Symbiotic relationships between ectoprocts and gastropods, and ectoprocts and hermit crabs in the French Jurassic

Certain gastropods from the Pierre Blanche de Langrune (Upper Bathonian) at Lion-sur-Mer, Calvados, France, have been encrusted by a succession of ectoproct zoaria. After the death of the gastropods, the vacated shells, with their encrustations, have been occupied by hermit crabs. Abrasion of the shell during locomotion of the crabs produces flat areas near the shell aperture, and discontinuities in the ectoproct colony growth. The relationship between the ectoproct and the inhabitant of the shell is considered to be one of true symbiosis.