LIFE HISTORY OF THE CANNONBALL JELLYFISH,STOMOLOPHUS MELEAGRISL. AGASSIZ, 1860 (SCYPHOZOA, RHIZOSTOMIDA)

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Abstract
Stages in the life history of the scyphozoan S. meleagris from the planula to the newly liberated ephyra were raised in the laboratory and are described for the 1st time. After swimming actively for 2-5 days, the ciliated planula larvae settled and scyphistoma morphogenesis occurred. Fully developed scyphistomae were cone-shaped and bore a whorl of about 16 tentacles around a dome- or knob-shaped proboscis. Podocyst formation was the only observed method of asexual reproduction in cultures of scyphistomae maintained for 1 mo. Strobilation began as soon as 9 days after scyphistoma morphogenesis and occurred in scyphistomae with as few as 8 tentacles. The strobilation process, completed in about 3.5 days at 25.degree. C, was not accompanied by any noteworthy color changes. Most strobilae produced 2 ephyrae each, although the number varied from one to three. Some scyphistomae began to strobilate a 2nd time within a week after completion of an initial round of strobilation. Newly liberated ephyrae possessed a normal complement of 8 lappet pairs and 8 rhopalia. They were morphologically similar to, yet distinguishable from, ephyrae of the related species Rhopilema verrilli. None of the examined stages of S. meleagris contained algal symbionts.

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