Freshwater jellyfish in northern temperate lakes: Craspedacusta sowerbii in British Columbia, Canada

Freshwater jellyfish species of the genusCraspedacustapurportedly originated from the Yangtze River catchment area, China, and have now been observed on all continents except Antarctica. Sightings ofC. sowerbiiin the Pacific regions of Canada were compiled to document some of the northernmost records of this species in the Americas. Species identification has been difficult in the past. Therefore, field collection of specimens was carried out on southern Vancouver Island. The morphology was described macro- and microscopically as well as molecularly using mitochondrial and nuclear markers. Collected hydromedusae from British Columbia (BC) did not deviate morphologically fromC. sowerbiispecimens from other continents, but molecular analyses support the idea of 2 main widely distributed lineages hidden under similar morphological features (i.e. a species complex). Through a community science approach, an understanding of the extent ofC. sowerbiidistribution in western and southern BC (present in 24 lakes from as early as 1990) has been established. Results showed that the number of sightings increased considerably in the period after 2010. Recent increases in sightings ofC. sowerbiiin BC and worldwide could be indicative of a climate warming-related range extension or growing public awareness and/or increased observational efforts. Even after more than 120 yr ofCraspedacustaresearch, much about their biology and ecology remains unknown, which motivated us to compile a list of knowledge gaps based on an extensive literature survey.