First record of the hydromedusa Dichotomia cannoides (Leptothecata, Dipleurosomatidae) in the Red Sea

The leptomedusa Dichotomia cannoides is reported for the first time from the Red Sea, extending its known distribution beyond the western Atlantic and western Pacific Ocean. Five specimens were documented in the northern Gulf of Aqaba, and one was collected for molecular analysis. In situ photography was used to extract diagnostic characters and natural habitus. DNA barcoding of the mitochondrial COI gene showed 98.03% identity with D. cannoides from Florida. Phylogenetic analysis confirmed its placement within D. cannoides, distinct from related leptothecate taxa. This finding increases the number of Leptothecata species recorded in the region to 15. The delayed detection of D. cannoides in the Red Sea may be due to its small size, limited seasonality or a recent introduction via ballast water or hull fouling. The species remains known only from its medusa stage. We further discuss how environmental DNA may help uncover its life cycle and those of other hydrozoans.