Long tubules of tentacular nematocysts in the moon jellyfish <i>Aurelia coerulea</i> (Semaeostomeae, Scyphozoa, Cnidaria) from Tanabe Bay, Pacific coast of southern Japan

We collected 43 medusae of Aurelia coerulea from Tanabe Bay, Wakayama, Japan, and measured the tubule lengths 1,613 nematocysts at different growth stages: ephyra, juvenile, subadult, adult. The median for ephyrae, juveniles, subadults, adults were 72, 51, 79, 58 µm, respectively. No in or subadults exceeded 200 µm length. In tentacles 15 adults, we detected with exceeding µm. average proportion long tubules was 9.1% bell diameters 110 mm more, contrast to only 1.0% less than mm. Among examined, there two groups modes 54 230 Nematocysts short-tubule group composed microbasic euryteles small isorhizas, whereas long-tubule euryteles. These can potentially penetrate not large planktonic crustaceans but also human skin. growth-related intra-species variation length could modify degree envenomation humans.