Phyllorhiza punctata von Lendenfeld , 1884 ( Scyphozoa : Rhizostomeae : Mastigiidae ) reappeared off the Mediterranean coast of Israel

A shoal of the Australian spotted jellyfish, Phyllorhiza punctata, native to the southwestern Pacific, was spotted on July 27, 2009 off the Mediterranean coast of Israel. Several recent records suggest that the vessel-transported species may have established a reproducing population.

Phyllorhiza punctata von Lendenfeld, 1884 is indigenous to the tropical western Pacific (Graham et al. 2003), and was not recorded outside the Indo-Pacific Ocean until the mid 20 th century.In the 1950s a large but short-lived population of a new species, Mastigias scintillae Moreira, 1961, which later was considered synonymous with P. punctata, was described off southern Brazil (Mianzan and Cornelius 1999;Migotto et al. 2002;Haddad and Nogueira 2006).By the early 1970s P. punctata was established within a few isolated Caribbean lagoon systems (Cutress 1973), and in 1981 it was reported off California (Larson and Arneson 1990).In 1991 it reappeared off Bahia in northern Brazil (Silveira and Cornelius 2000), and subsequently spread northwards to Ceará and southwards to Santa Catarina (Haddad and Nogueira 2006).In the Gulf of Mexico it was first recorded in 1993.A massive population explosion occurred in the summer of 2000 off Alabama, Mississippi, and Louisiana, spreading in the following summer to the Indian River Lagoon, Florida (Graham et al. 2003), but no irruption have been detected since.The fishery losses of that invasion were estimated at several million dollars, primarily due to net damages, a significant reduction in the shrimp harvest and predation on pelagic fish eggs and bivalve larvae (Graham et al. 2003).The native habitat of P. punctata is in tropical western Pacific estuaries and lagoons (Rippingale and Kelly 1995).Tolerant of a wide range of salinity and temperature, it has flourished when introduced to bodies of water of fluctuating salinities and temperatures and high productivity (Garcia and Durbin 1993).Phyllorhiza punctata harbors endosymbiotic zooxanthellae throughout its native range and in certain introduced localities, giving the bell a brownish tint.The photosynthetic zooxanthellae likely fulfill a large proportion of its nutritional needs (Garcia and Durbin 2003).However, the population in Gulf of Mexico lacked endosymbiotic zooxanthellae, making it wholly zooplanktivorous (Graham et al. 2003).
The first record of P. punctata in the Mediterranean Sea dates back to 1965, and consists of a single specimen collected off the coast of Israel (Galil et al. 1990).In 2005 and 2006 P. punctata ephyrae and medusae were collected off Lefkada Island on the Ionian coast of Greece, but the population has apparently occurred there for a number of years (Abed-Navandi and Kikinger 2007).
In July 2009, 8 specimens (bell diameter 15-24 cm) were collected by a bottom trawler off Ashdod, Israel at water depth of 20 m (31º48.2'N,34º36.7'E),and 4 specimens (bell diameter 13-17 cm) at depth of 40 m (31º49.4'N,34º33.2'E).The specimens are deposited in the National Collections of Natural History at Tel Aviv University (TAU Co 34567) (Figures 1 and  2).Four of the specimens display mature gonads.Examination of the collections revealed an earlier unpublished specimen collected intertidally off Shikmona (lat.32º49.3'N,long.34º57' E) (TAU Co 34568), in January 2005, following a winter storm (Figures 3 and 4), and two specimens (bell diameter 12, 13.5 cm) collected off Kiryat Yam, Haifa Bay (lat.32º50.7'N,long.34º38'E), 14 October 2006 (TAU Co 34569).Whereas the earliest specimen contained zooxanthellae, the later specimens were all devoid of zooxanthellae, and either pale or dark blue in colour.The sea surface salinity of the coastal waters of the southern Levantine Sea in the summer months tops 39.5 PSU (I.Gertman, pers.comm.), and the temperature -31.5ºC (L.Raskin, pers.comm.), whereas in December it drops to 17ºC.The upper layer, to depth of 100 m, is mixed in most winters, whereas during the remainder of the year a sharp halocline and thermocline begins at 10 m depth.
In 2006, 13,000 merchant vessels made 252,000 calls at Mediterranean ports and an additional 10,000 vessels transited through the sea (REMPEC/WG.29/INF.9).With the exception of the South Pacific and the Northeast Pacific "… the Mediterranean is connected by considerable sea trade with most global regions."(CIESM 2002: 6).An increase in shippingrelated invasions was noted in recent publications: one fifth of the alien species recorded in the Mediterranean have been primarily introduced by vessels (Galil 2009).The rise was attributed to the growth in shipping volume throughout the Mediterranean, changing trade patterns that result in new shipping routes, improved water quality in port environments, augmented opportunities for overlap with other introduction vectors, and rising awareness and research effort (CIESM 2002;Galil 2006).Though the inbound commercial traffic arrives through the Straits of Gibraltar (81%) and the Suez Canal (19%), the native range of vesseltransported alien taxa recorded in the Mediterranean is most commonly the Indo-Pacific Ocean (30%), pantropical (17%), and the Indian Ocean (15%).However, the native range is not necessarily the area of origin of the Mediterranean populations as propagules may have been introduced from established alien populations elsewhere (secondary introductions).Phyllorhiza punctata may have been transported via vessels arriving from tropical western Atlantic ports (8% of the Gibraltar inbound vessels originate in Caribbean, Gulf of Mexico and Central American ports) (CIESM 2002), or in the fouling of vessels arriving from Southeast Asia through the Suez Canal.It is widely believed that transportation of the sessile polyp stages on ship hulls or drilling rigs is the likely dispersal method (Larson and Arneson 1990;Bolton and Graham 2004).The occurrence of P. punctata near Ashdod and Haifa, next to the two largest harbours along the Mediterranean coast of Israel, suggests that it is indeed plausible.
The bipartite life history of P. punctata, with an asexually reproducing benthic polyp and a sexually reproducing pelagic medusa, allows it to remain cryptic for extended periods and irrupt when environmental variables are opportune.The presence of sexually mature specimens throughout the year (January, July, October) indicates the presence of an established population.