Abstract
The small box jellyfish Copula sivickisi was collected from the Ryukyu Archipelago, southern Japan, in June 2011, in order to observe its early life history, including polyp formation and metamorphosis. Fertilization occurred internally. Fertilized eggs were packed in an embryo strand with nematocysts and released into the water from the female’s manubrium. Blastulae developed into planulae bearing about 30 larval ocelli within two days, and then settled and metamorphosed into primary polyps. Primary polyps developed into adult polyps within 40 days, and both polyp stages could actively detach to change location by creeping on the central part of their body. Adult polyps formed cysts at temperatures below 20°C, which when favorable conditions retuned (above 28°C), excysted from the capsules within a week. Budding occurred in adult polyps, and buds were released two days after the commencement of budding. Metamorphosis of a whole polyp into a single medusa occurred within 10 days. Juvenile medusae were distinguished from those of other cubozoans by the pattern of nematocyst warts on the exumbrella and the adhesive pads on the apex. The developmental features of C. sivickisi resemble most closely those of T. cystophora among the cubozoans. The similarities in all early life stages of both species support recent molecular results.
