STROBILATION OF THE SEA NETTLE, CHRYSAORA QUINQUECIRRHA, UNDER FIELD CONDITIONS

¹ Virginia Institute of Marine Science, Gloucester Point, Virginia 23062

1. A 12-month study of strobilation in the sea nettle, Chrysaora quinquecirrha, was conducted under natural conditions in the field. Observations were made in a creek of the Chesapeake Bay system where scyphistomae of C. quinquecirrha were known to occur and where medusae are normally abundant each year.

2. Strobilation was seasonal in occurrence, beginning in April and lasting until early October.

3. Maximum rates of strobilation occurred during May and June. Instead of a single sustained peak during this period, strobilation was protracted into a series of pulses that coincided with periods of increasing tidal amplitude, suggesting a semilunar periodicity. Although strobilation continued into October, the percentage of polyps strobilating after June was relatively low.

4. The number of ephyrae produced per strobila varied from one to 16, with a mean of five and a mode of four. The mean number of ephyrae per strobila was higher in spring than during summer.

5. Observations on individual scyphistomae attached to petri dishes confirmed that repeated strobilation can occur in polyps of C. quinquecirrha in nature.

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