Stick Insect Sperm (Phasmatodea) With Mammalian-Like Basal Bodies

Stick insect sperm exhibit a remarkable modification of the basal body, characterized by the expansion of the proximal region and the incorporation of amorphous, unstructured material. This atypical architecture parallels transformations observed in mammalian sperm, where the distal centriole transitions into splayed microtubules of variable length. Despite their structural irregularity, these modified centrioles enable zygotic centrosome formation, likely relying on a large permissive recruitment domain of specific proteins. Therefore, atypical centrioles may represent a sort of assembly platform, rather than providing a defined basal scaffold as observed in other systems. Basal stick insects possess canonical cylindrical centrioles, whereas higher stick insects show increasing basal body complexity. This trend mirrors mammalian sperm evolution, suggesting structural parallels of the basal bodies, presumably enhancing mechanical support to the sperm neck during flagellar motion.