The sensory dorsal organs of crustaceans

摘要: The cuticle of crustaceans bears numerous organs, which the functions many are unknown. One these, sensory dorsal organ (SDO), is present in a wide diversity taxa. Here we critically review variability, ultrastructure, distribution, and possible function this enigmatic cuticular organ. Previous data complemented by new observations on larvae adults various malacostracans. SDO composed four sensors arranged as corners square, centre occupied gland. Pores or pegs surrounding central complex may also form part arrangement external aspect five main elements varies greatly, but apparently has little impact their ultrastructural organisation. gland associated with particularly thin cuticle. Each sensor contains outer dendritic segments made single large cell. It not yet known what cell secretes. innervated from tritocerebrum therefore belongs to third cephalic segment. A similar organ, here called posterior SDO, been repeatedly observed more posteriorly carapace. resembles greater number (usually six, up ten) only two segments. Eumalacostraca, Hoplocarida, Phyllocarida. Some branchiopods possess ‘dorsal organ’ resembling both ion-transporting typical group. This indicate common origin for these functionally distinct groups organs. New support hypothesis that homologous lattice complexes thecostracans. However, relationship between hump calanoid copepods remains unclear. No correlation can be demonstrated presence particular ecological biological trait. In fossils, most convincing examples SDO-like organs found some Late Cambrian arthropods Alum Shale southern Sweden. They suggest related might have non-crustacean arthropods. distribution extant fossil strongly suggests originated early history group, crucial functioning organisms. except knowing chemoreceptors given functional probably exists them gland, about function. description freshwater carideans, easily reared laboratory, opens way behavioural physiological experiments undertaken could prove determination