Obtainment of Two Monomorphic Nematocysts from <em>Nemopilema nomurai</em> (Cnidaria: Scyphozoa) and Comparative Analysis of the Biological Activities of their Contents

Nemopilema nomurai is a species of common large toxic jellyfish in China seas, and its tentacle tissues contain various types of nematocysts. However, the correlation between the morphology and function of nematocysts still remains unclear. In this study, we first obtained two monomorphic nematocysts with high-purity from N. nomurai, namely Anisorhizas and O-isorhizas, by density gradient centrifugation: the Anisorhizas is small and rod-shaped and the O-isorhizas is larger and spherical. Upon deionized water stimulation, O-isorhizas exhibited a stronger discharge capability than Anisorhizas. The nematocyst contents of Anisorhizas (AnC) and O-isorhizas (OnC) were extracted separately, and their composition and bioactivities were analyzed simultaneously. The protein bands by SDS-PAGE revealed similar distributions in AnC and OnC, except that the protein band distribution in OnC was more extensive. OnC showed stronger cytotoxicity, hemolytic activity, metalloprotease activity, and serine protease activity than AnC. In contrast, AnC exhibited a higher antioxidant activity and significant proinflammatory activity. Both AnC and OnC exhibited antimicrobial activities against certain marine pathogenic Vibrios. These results suggest that O-isorhizas, with the larger capsule capability, stronger discharge ability and toxicity, likely plays a major role in inducing toxic effects and tissue damage, while Anisorhizas, being smaller and less toxic, may undertake preferentially other functions, such as synergistic predation, environmental stress adaptation, and energy balance maintenance. This study provides insights into the morpho-functional relationship between various types of nematocysts, and also lays a foundation for further exploration of the functional diversity of nematocysts and the mechanisms underlying jellyfish envenomation.