Abstract
Polyps of Chrysaora pacifica were found on sediments sampled from the sea bottom in Sagami Bay near the mouth of the Sagami River on 26 June 2009; they were identified from released ephyrae in the laboratory. This is the first record of wild polyps of C. pacifica. Polyps and/or podocysts were found from five among the six stations. They were found on 25 shells (2.5–9.2 cm in width, 1.6–5.3 cm in height) and on 22 stones (1.5–8.0 cm in width, 1.3–5.0 cm in height). The shells with polyps were mostly from the dead clam Meretrix lamarckii. Polyps and podocysts were mostly found on the concave surface of bivalve shells, or in hollows of the stones. The number of polyps and podocysts per shell ranged between 0–52 (median = 9) and 0–328 (median = 28); and those per stone were 1–12 (median = 2) and 0–26 (median = 1.5). The number, especially of podocysts, was much greater on shells than on stones. On a convex substrate they can easily be removed by being hit with other substrates during dredging and washing, and such a process may also occur in natural conditions. They were induced to strobilate and release ephyrae by decreasing the temperature from 22–23°C to 5–10°C.
