Hairy and iridescent chaetae of the sea mouse <i>Aphrodita</i> (Annelida, Errantia)

Abstract

Abstract The bright iridescent chaetae of Aphrodita species have fascinated scientists for decades. The particular nanoscale substructure of these chitinous bristles resembles photonic crystals and manipulates the incident light in a way that results in spectacular structural coloration. Even though Aphrodita's chaetae have garnered great attention from the field of biomimetics, the few previous ultrastructural studies primarily focused on acicular chaetae that are much less iridescent than the thin capillary notochaetae. In this paper, we present new ultrastructural data on the chaetae of two species of Aphrodita and illustrate their formation process. Our results allow us to specify the prerequisite for iridescent chaetae. Aphrodita species are dorsally covered with a matted felt of intertwined chaetae, and we further discuss the evolution of feltage chaetae in Aphroditiformia. In addition to iridescent feltage chaetae, we also provide new insights into the chaeotogenesis of pilose chaetae. For the first time, our study shows that the hairy tips and ornamentation of the chaetae is formed by follicle cells alone and thus attribute a further role to this type of cells.

Topics & Concepts