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

Abstract

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.

Stranding events provide indirect insights into the seasonality and persistence of jellyfish medusae (Cnidaria: Scyphozoa)

“…More likely is that sharp thermal variations within such estuarine / coastal environments may themselves trigger multiple releases of ephyrae, as shown for the giant jellyfish Nemopilema nomurai (>2 m bell diameter) under laboratory conditions (Kawahara et al, 2006). Indeed, it is well established that thermal elevation is one of the triggers inducing strobilation in rhizostome jellyfish (Kawahara et al, 2006), as previously reported for Cephea cephea (Sugiura, 1966), Rhopilema esculentum (Chen and Ding, 1983) and Rhopilema nomadica (Lotan et al, 1994). As the scyphistoma of rhizostome jellyfish (Nemopilema nomurai) are capable of asexual reproduction for >1.5 years (Kawahara et al, 2006) the notion of protracted and repeated ephyrae release in the Irish Sea is certainly possible, although bespoke investigations of this claim are clearly required.…”

Temperature effects on asexual reproduction rates of scyphozoan species from the northwest Mediterranean Sea

“…Survival of C. tuberculata polyps from the Mar Menor was 100% at 16°C, but all polyps at lower temperatures (2, 4, and 9°C) died in B32 days (Prieto et al, 2010). Polyps of Rhopilema nomadica Galil, Spanier & Ferguson, 1990 from Mediterranean waters off Israel (16-28°C) survived at temperatures between 11 and 26°C, but did not feed below 13°C (Lotan et al, 1994). Similar results were reported for Rhopilema esculentum Kishinouye 1891 polyps (Chen et al, 1985).…”

“…Differences in strobilation of A. aurita polyps from Germany at 14-15°C (100% of polyps from the Baltic Sea, Kiel strobilated vs. 5-6.5% from the North Sea, Helgoland) and in the numbers ephyrae Lotan et al (1994) 24-26 ND *3…”

“…Most of the analyses to date show high medusa abundances in warm years: Aurelia aurita and Cyanea spp. in the Irish Sea (1994( , Lynam et al, 2011, and in the North Sea west of Denmark (1971( -1986( , Lynam et al, 2010. Regional differences in climate effects on medusa abundances are due to incursions of cool oceanic water that enhance Aurelia aurita and Cyanea lamarckii populations in the northern part of the North Sea, which is opposite to association of those species with warm conditions in the southern part (1971( -1986( , Lynam et al, 2010.…”

The solitary ascidian Herdmania momus: native (Red Sea) versus non-indigenous (Mediterranean) populations

“…Since the opening of the Suez Canal in 1869, more than 300 Red Sea species of algae, invertebrates and fish have entered the Mediterranean through the canal (Safriel and Ritte 1986;Spanier and Galil 1991;Barash and Denin 1992;Lotan et al 1994;Golani 1998;Galil 2000). For example, the invasive jellyfish Rhopilema nomadica appears in mass swarms along the Mediterranean coasts of Israel every summer, causing severe damage to coastal fishing, tourism and coastal installations (Spanier and Galil 1991).…”