Comparative analysis of the tardigrade feeding apparatus: adaptive convergence and evolutionary pattern of the piercing stylet system

A thorough analysis of the cuticular parts of tardigrade feeding apparatuses was performed in order to provide a more complete understanding of their evolution and their potential homologies with other animal phyla (e.g. Cycloneuralia and Arthropoda). The buccal-pharyngeal apparatuses of eight species belonging to both Eutardigrada and Heterotardigrada were studied using light and scanning electron microscopy. The possible convergent evolution of several structures of the buccal-pharyngeal apparatus (e.g. ventral lamina, pharyngeal tube, wide buccal tube without buccal crown, buccal lamellae) was analysed and discussed.