On the biology of<i>Aurelia aurita</i>(L.) 1. Release and growth of<i>Aurelia aurita</i>(L.) ephyrae in the Gullmar Fjord, Western Sweden, 1982–83

123

Outbreaks of jellyfish are reported worldwide, yet the environmental factors that control the sizes of jellyfish populations are not well understood. The scyphomedusan Chrysaora quinquecirrha occurs in the mesohaline portion of Chesapeake Bay each summer. Population sizes of the medusae show dramatic annual variations that are correlated with salinity and temperature. We measured the total numbers of ephyrae and polyps produced by benthic polyps of C. quinquecirrha in laboratory experiments lasting 42 d, and found that temperature (15. 20, 25°C) was not a statistically significant factor at low salinities (5 to 20P:m); however, ephyra production increased significantly with increasing temperature at high salinities (20 to 35%). Conversely, each 5°C decrease in temperature delayed strobilation (ephyra production) by about 1 wk. Salinity significantly affected the numbers of ephyrae and polyps produced in all experiments. Ephyra and polyp production was lower at both low (

Section: Mar Ecol Prog Sermentioning

confidence: 99%

Section: Mar Ecol Prog Sermentioning

confidence: 99%

Temperature, salinity and food effects on asexual reproduction and abundance of the scyphozoan Chrysaora quinquecirrha

Purcell¹,

White²,

Nemazie³

et al. 1999

123

“…All these results show dependence of polyp metamorphosis and reproduction on temperature. The success of asexual reproduction is dependent not only on the strobilation process, but also on the number of ephyrae released (Hernroth & Grondahl 1983). A maximum of 5 or 6 ephyrae are formed per strobila of Rhopilema nomadica under optimal conditions (Lotan et al 1992).…”

Section: Strobilation and Vitality Of Rhopilema Nomadicamentioning

confidence: 99%

“…The life cycle of scyphozoans includes a benthic polyp stage that reproduces asexually and releases ephyrae, and a planktonic medusa stage that reproduces sexually. Optimal strobilation of Aurelia aurita on the Swedish coast was observed during autumn, when zoo-0 lnter-Research 1994 Resale of full article not permitted plankton biomass peaked (Hernroth & Grondahl 1983, 1985. Strobilation of Rhopilema esculenta in China, though dependent on nutrition, was delayed or inhibited when water temperature fell below 15 "C (Chen & Ding 1984, Chen et al 1985.…”

Section: Introductionmentioning

confidence: 99%

Synchronization of the life cycle and dispersal pattern of the tropical invader scyphomedusan Rho-pilema nomadica is temperature dependent

Lotan¹,

Fine²,

Ben-Hillel³

1994

During the last decade, an Indo-Pacific scyphomedusa, Rhopilema nomadica, penetrated the eastern Mediterranean. Annual blooms of the medusa near the Israeli coast were observed during the summer months of the years 1989 to 1992. R. nomadjca migrated northward from the Israeli coast towards Lebanon and Syria and has not been found elsewhere in the Mediterranean. Temperature dependence of the metamorphosis of R. nornadica polyps into strobila was studied in the laboratory. Rapid strobilation occurred between 18 and 20°C and a decline of strobilation was observed when the temperature was raised to 24 or 26OC. When water temperature was below 16"C, polyps did not strobilate, and below 13 "C, polyps did not feed, resulting in a gradual loss of polyp vitahty. Con~parison of the temperature regime in the Levant Basin and the dependence of polyp strobilat~on on temperature suggest that the spring rise in water temperature causes a rapid strobilation, whereas winter and summer water temperatures inhibit or diminish reproduction. Laboratory studies support the possibility that synchronization and annual occurrence of R. nomadica is controlled by seasonal changes in water temperature regimes, leading to rapid strobilation and release of ephyrae during springtime. The sensitivity of the polyps to low temperatures enables us to predict that the future dispersal of Rhopilerna nornadica may be limited to the eastern Mediterranean. This study emphasizes the importance of the effect of 1 abiotic factor on the physiology and the migration pattern of R. nomadica. This can be a good model for understanding the behavior and limiting factors of Indo-Pacific jellyfish migrating into non-tropical seas.

“…As controls, glass slides that had been completely cleared of polyps were used. The PVC plates were then transferred to a submerged rack at 7 m depth (see Hernroth & Grondahl 1983 for rack description). The plates were randomly assigned to positions within the settling rack.…”

Section: Methodsmentioning

confidence: 99%

Evidence of gregarious settlement of planula larvae of the scyphozoan Aurelia aurita: an experimental study

Gröndahl¹

1989

Evidence of gregarious settlement of planula larvae of the scyphozoan Aurelia aurita: an experimental study F. GrondahlKristineberg Marine Biological Station, S 4 5 0 34 Fiskebackskil, Sweden ABSTRACT: Laboratory and field experiments investigated whether the aggregated distribution of polyps of the scyphozoan Aurelia aurita is a result of attraction by the established polyps on the planula larvae, i. e. gregarious recruitment. Planula larvae showed an increased rate of metamorphosis in the presence of established A. aun-fa polyps in laboratory experiments. Petri dish experiments showed that the planula larvae were attracted to established polyps. If the polyps were replaced by mimics (sandgrains), no such attraction was observed. Transplant experiments in the field tested whether different densities of 4-d old established A. aurita polyps could affect the recrmtment of conspecific planula larvae. A significant treatment effect was observed, viz. a positive correlahon to initial polyp density. Results are interpreted as suggesting that the planula larvae of AureLia aurita show gregarious behaviour. This is the first report of gregarious behavlour in the class Scyphozoa.