The Ogasawara Islands are remote oceanic islands located approximately 1,000 km south of mainland Japan and investigations of their fauna are essential for understanding the processes underlying the assembly of oceanic island biotas. Despite this importance, knowledge of several terrestrial invertebrate groups remains remarkably limited, including millipedes, which constitute a major component of soil macrofauna. Previous studies on the millipede fauna of the Ogasawara Islands have been sporadic and, to date, only ten identified species had been recorded from the archipelago. Field surveys conducted between 2023 and 2026 on Ototo-jima, Ani-jima, Chichi-jima and Haha-jima Islands revealed five species of polydesmid millipedes: Prosopodesmus jacobsoni Silvestri, 1910; P. panporus Blower Cryptocorypha ornata (Attems, 1938); Dyskolonius uniramus (Attems, 1938) (Pyrgodesmidae); and Solaenaulus butteli (Carl, 1922) (Opisotretidae). All five species represent new records for both Japan and the Ogasawara Islands. Reexamination of specimens previously reported as Prosopodesmus sinuatus from the Ogasawara Islands revealed that they were misidentified and actually belong to Cryptocorypha ornata . Furthermore, the previous record of Solaenaulus sp. from Chichi-jima Island was identified as S. butteli , based on detailed sketches of the gonopods. In addition, we partially examined and compared the postembryonic development of Prosopodesmus species, a genus known for intrageneric polymorphism in the number of body rings in adult males. Based on these observations, we discuss potential heterochronic shifts in sexual maturation amongst species and between sexes.
Chiyoda et al. (Wed,) studied this question.