Virginia Institute of Marine Science
The sea nettle, Chrysaora quinquecirrlza (Desor, 1848) , is locally abundant during summer along the east coast of the United States from southern New England to Florida. The venomous medusa stage of this species is a significant pest and a negative economic factor, particularly in the Chesapeake Bay region.
In common with many other cnidarians, C. quinquecirrha undergoes an alternation between polyp and medusa stages in its life history. While the medusa population dies off annually, the sessile polyp or scyphistoma stage may remain active all year and is potentially perennial (Truitt, 1939). The scyphistoma is capable of asexual reproduction, most commonly through podocyst formation. These cysts are also resistant to adverse environmental conditions. Given favorable conditions the scyphistomae undergo strobilation, a process leading to the production of free swimming ephyrae. The proximal portion of the polyp remaining after strobilation undergoes renewed growth, returning the scyphistoma to normal size and morphology. It is then capable of continued asexual reproduction and perhaps repeated strobilation. The ephyrae develop rapidly into medusae, which are dioecious. Fertilization results in a free-swimming planula larva, which settles on a firm substrate and develops into the scyphistoma, thereby completing the life cycle.
While the morphological details of strobilation in C. quinquecirrha have been described (Littleford, 1939; Cones, 1969), little is known about the ecology and seasonal dynamics of the process. The only relevant field data available to date on strobilation in this species were based on collections of ephyrae by Cargo and Schultz (1966, 1967). The present study was undertaken to determine (1) when strobilation begins and ends in nature; (2) the percentage of polyps strobilating at a given time; (3) the number of ephyrae produced per strobila, as observed throughout the season; (4) whether a given polyp will strobilate more than once a season under field conditions.
Calder, Dale R., Strobilation Of The Sea Nettle, Chrysaora Quinquecirrha, Under Field Conditions (1974). Biological Bulletin, 146(3), 326-334.