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Statoblast ultrastructure and genetic identity of Pectinatella magnifica population, based on COI gene, from three different watersheds in Korea

Pectinatella magnifica, one of the most common freshwater bryozoans in the world, is an indicator species of eutrophic waters. This species was a major source of concern in 2014 in Korea due to uncertainty surrounding its toxicity to humans and the aquatic biota. Few studies of its morphology and of its physiological characteristics have been conducted in Korea. To investigate the ultrastructural features and molecular phylogeny of P. magnifica, we used scanning electron microscopy (SEM) analysis and the molecular approach with mitochondrial cytochrome c oxidase subunit I gene (COI) sequence data from 20 colonies in three watersheds. Our morphological analysis of colonies and statoblasts indicates that this species has distinct taxonomic features, including a couple of white spots on the lophophora, a red pigmented mouth, and multiple statoblasts bearing hooked spines. The ultrastructure of the statoblasts, including the annular surface features, pore morphology, and inner chamber distribution, was confirmed using SEM. All of the newly generated P. magnifica COI sequences were identical to one another, regardless of geographic location. The application of a maximum likelihood analysis showed the phylogenetic position and the sister relation with Cristatella mucedo. The results of this molecular analysis of P. magnifica in Korea using a barcode gene provide a means to reliably classify this species. This study, which is the first of its kind, also contains detailed information on the morphology and phylogenetic relationships of P. magnifica.