Figure 1
From: Comparative muscle development of scyphozoan jellyfish with simple and complex life cycles
Scyphozoan life cycles. All animals are oriented oral down (the usual orientation for Chrysaora quinquecirrha polyps in nature) except ephyrae, which are oriented with the oral end facing the viewer. (A) Medusa development in the complex life cycle of C. quinquecirrha proceeds from a planula to a polyp with polyp cord muscle (red), to a strobila stage that liberates ephyrae, with circular muscle, radial muscle, and oral myoepithelial processes (red); picture scale bars are 1 mm. (B) Medusa development in P. noctiluca, by contrast, proceeds directly from a planula to an ephyra with circular muscle, radial muscle, and oral myoepithelial processes (red), left scale bar 300 μm, right scale bar (for ephyra only) 1 mm. In both species, ephyrae grow to medusae (with subumbrellar musculature (red)), which release eggs or sperm. (C) A simplified phylogeny of Pelagiidae, showing P. noctiluca nested within Chrysaora, based on [12]. * = mouth of polyps, ephyrae and developing P. noctiluca larvae.