Species Description: Phyllorhiza punctata is a large jellyfish with a rounded and somewhat flattened gelatinous bell that is clear or possibly tinted brown with many small white crystalline refractive spots close to the surface (Graham et al. 2003, Perry and Larsen 2004). As is characteristic of members of Order Rhizostomae, the bell margin lacks tentacles and the central mouth area is ringed by eight highly dichotomous (branching) oral arms that each bear 14 lappets (flaps of tissue) and become fused near their bases (Graham et al. 2003, Omori and Kitamura 2004). Within its native range and in certain introduced localities, symbiotic zooxanthellae reside in the tissue of the animal, giving these jellyfish a brownish tint.
Potentially Misidentified Species: In the IRL region, potential exists for confusion with the moon jelly Aurelia aurita based on size similarity, but the two species are markedly different in appearance otherwise. In other parts of the world, Phyllorhiza co-occurs with other mastigiid jellyfish which are similar in appearance, including several species belonging to the genus Mastigias.
Regional Occurrence: P. punctata is a coastal and estuarine jellyfish whose wide native distribution includes Australia and much of the Indo-Pacific including the Philippine archipelago (Heeger et al. 1992). Regionally, populations of P. punctata have persisted within a few isolated Caribbean lagoon systems (e.g., Puerto Rico) for at least four decades. More recently, established populations have been reported in Brazil (Haddad and Nogueira 2006). For the last several years, an established population has existed in the Gulf of Mexico which may become extraordinarily dense under favorable environmental conditions (Graham et al. 2003).
IRL Distribution: Spotted jellyfish were first collected from the IRL and identified in June, 2001. St. Johns River Water Management District scientists encountered two specimens in the IRL proper near the Melbourne causeway in Brevard County. One of these was collected and transported to Harbor Branch Oceanographic, Fort Pierce, where it was positively identified as P. punctata. In light of the explosive population of this species in the Gulf of Mexico the previous year, the occurence of P. punctata prompted boat and/or aerial surveys of the central IRL between Vero Beach and State Road 520 in Cocoa to estimate the size of the population. Approximately 10-12 individuals were spotted by the aerial survey. Survey leader W.M. Graham of Dauphin Island Sea Lab, Alabama, estimated the actual population at that time to be approximately ten times that number, based on extensive survey experience gained while following the Gulf of Mexico population explosion (W.M. Graham, personal communication).
Age, Size, Lifespan: Phyllorhiza punctata is a large jellyfish whose average adult bell width is approximately 35 cm (Perry and Larsen 2004). Very large individuals nearly twice that diameter have also been reported from Gulf of Mexico specimens (Graham et al. 2003).
Abundance: An explosive summer P. punctata bloom, followed by a winter/spring decline or disappearance has occurred in Brazil every year since a population became established around 2001. The reasons for these fluctuations are unknown (Haddad and Nogueira 2006). A similar exponential population explosion occurred in 2000 in the Gulf of Mexico, although subsequent seasonal blooms have not been as large.
Reproduction: Scyphozoans have a life cycle that can be broadly divided into two parts: a free-living medusa (the "jellyfish stage") and an attached, sessile polyp stage. Sexes are separate in the medusae and these produce haploid gametes that combine through external fertilization to form free-swimming planula larvae. Planulae search out suitable settlement sites and leave the water column to assume a sessile benthic existence. Thse scyphistomae then give rise to new offspring in the form of free-swimming medusae. Immature medusae, called ephyrae, detach from the ends of the sessile scyphistomae in a process termed strobilation. Ephyrae develop into mature medusae over a period of usually several weeks (Rupert et al. 2004).
Embryology: In a Western Australia P. punctata population study, Rippingale and Kelly (1995) noted the presence of small (< 2 cm diameter) medusae and ephyrae in early summer. In Brazil, the presence of all size classes of P. punctata in late winter and spring suggested a prior period of continuous ephyrae release synchronized to seasonal high water temperatures and extended photoperiod (Haddad and Nogueira 2006).
Temperature: Although not rigorously examined, a link between abnormally warm weather and P. punctata regional population explosions has been suggested (Haddad and Nogueira 2006).
Salinity: Though some degree of euryhaline tolerance is expected in an estuarine inhabitant, there is some evidence that low salinities negatively impact the ability of P. punctata to thrive. Rippingdale and Kelly (1995) report the absence of the species from Western Australia estuary study sites during low salinity periods following heavy rains, and also its return when higher salinity conditions returned in the summer months. Graham et al. (2001), suggest that the lack of photosynthetic zooxanthellae in Gulf of Mexico Phyllorhiza specimens might be the result of hyposalinity stress.
Trophic Mode: Like most members of Phylum Cnidaria, the tentacles of Phyllorhiza are equipped with stinging cells called cnidocytes. Within these cells are stinging organelles called nematocysts. When discharged, nematocysts can immobilize small prey items that are subsequently ingested. Nematocysts are also used as a defense mechanism. The planktonic egg and larval stages of several fish species (including commercially important species such as red snapper in the Gulf of Mexico) are probably important as prey items.
Additionally, throughout its native range and much of its introduced range, P. punctata also harbor endosymbiotic zooxanthellae within their bell. In a relationship analogous to that of reef-building tropical corals and their resident zooxanthellae, primary production of the photosynthetic zooxanthellae likely fulfills a large proportion of the nutritional needs of the host jellyfish (Garcia and Durbin 2003). The invasive Gulf of Mexico P. punctata populations were/are unusual in that they lacked endosymbiotic zooxanthellae (Graham et al. 2003). Zooplanktivory was/is the sole trophic mode of these populations which, nonetheless, attained high population numbers.
Associated Species: None described.
Invasion History: P. punctata was recorded only from Indo-Pacific waters prior to the 1950s. In 1955, an Atlantic basin population was discovered in Brazil (Haddad and Nogueira 2006). A large population there persisted briefly in coastal waters off the southern half of the country but disappeared within a few years. At the time, the organism was identified as Mastigias scintillae, another mastigiid jellyfish similar in appearance to Phyllorhiza (Moreira 1961, in Haddad and Nogueira 2006).
Three decades later, around 1991, a second established population of P. punctata was reported from Brazil, this time off of the northeastern coastline (Silveira and Cornelius 2000). Ten years later (2001), evidence pointed to a new southern population of this non-indigenous jellyfish (Fuller 2005, Haddad and Nogueira 2006). This population may be the result of a natural range extension of the established northern population, or alternatively, accidental transport by the shipping industry, or perhaps an irruptive event within an extant cryptic population. Regardless of the mechanism, Haddad and Nogueira (2006) believe that P. punctata is now widespread in Brazil, occurring in both northern and southern waters. Since 2001, the established P. punctata population in Brazil undergoes a large summer bloom, and then declines and disappears the subsequent winter and spring (Haddad and Nogueira 2006).
An established population of spotted jellyfish in a mangrove lagoon in Bonqueron Bay, Puerto Rico was reported by Cutress (1973). The first report of the animal in U.S. waters dates to California in 1981 (Carlton and Geller 1993). These Phyllorhiza invasions pale in magnitude to one recorded in the northern Gulf of Mexico off Louisiana, Alabama and Mississippi in the summer of 2000. At that time, an estimated 10 million P. punctata medusae invaded the region and persisted at very high numbers between June and September before rapidly declining (graham et al. 2003). Interestingly, despite the magnitude of the population explosion, northern Gulf of Mexico P. punctata entirely lacked symbiotic zooxanthellae.
In 2001, P. punctata was identified from collected specimens occurring in Florida in the central Indian River Lagoon near the city of Melbourne. Aerial and boat-based surveys undertaken at that time revealed only a handful of individuals. Even fewer individuals were detected the following year, and no irruptive events have been detected subsequent to this.
Natural ocean circulation patterns may have been sufficient to transport P. punctata up into the northern Gulf of Mexico from established Caribbean Sea populations, as has occurred in other species (Graham 1998). Circulation set up by the Loop Current (part of the Gulf Stream; a warm ocean current in the Gulf of Mexico that flows northward between Cuba and the Yucatan Peninsula) and eddies spun off from it may have effected such transport (Johnson et al. 2004). The precise mechanisms of invasion in each of the above cases remain a matter of speculation.
Invasions into new locales may occur via attachment of the sessile polyp stages to ship hulls or other submerged and towed structures. Larson and Arneson (1990) have proposed hull-fouling as the likely dispersal method transporting spotted jellyfish between the Pacific Ocean and the Caribbean Atlantic. Transport of free-swimming stages in ballast water has probably also led to some of the invasions (Carlton and Geller 1993). Passage of vessels through the Panama Canal probably facilitated introduction from the Pacific into the Atlantic basin (e.g., Graham et al. 2003, Bolton and Graham 2004). The fact that the first documented occurrence of the species in Brazil dates back to 1955 suggests that P. punctata was first transported between ocean basins at least 50 years ago (Silveira and Cornelius 2000) Putative transport routes and vectors may be critically examined through comparative molecular or morphological analyses among various populations. In fact, a recent comparative molecular study by Bolton and Graham (2004) concluded that the Brazillian population examined was not Phyllorhiza, but rather a member of genus Mastigias.
Potential to Compete with Natives: Non-native jellyfish species like P. punctata have the capacity to compete with native species for food resources. To what extent such competition occurs is unknown, as are its ecological ramifications. P. punctata may also compete with other taxa for food resources (see below).
Possible Economic Consequences of Invasion: Direct negative economic impact of the 2000 Gulf of Mexico P. punctata population explosion included several million dollars of fishery losses, primarily due to net damage. Some evidence also points to a greater than 25% reduction in the northern Gulf of Mexico white shrimp (Penaeus setiferus) harvest at that time, attributable to competition between the shrimp and jellyfish for food resources. (Graham et al. 2003). Predation on pelagic fish eggs and bivalve larvae was also pronounced (Graham et al. 2003).
References: Bolton T.F. and W.M. Graham. 2004. Morphological variation among populations of an invasive jellyfish. Marine Ecology Progress Series 278:125-139.
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Fuller P. 2005. Phyllorhiza punctata. Nonindigenous Aquatic Species Database, Gainesville, FL. Available online.
Garcia J.R. and B. Durbin. 1993. Zooplanktivorous predation by large scyphomedusae Phyllorhiza punctata (Cnidaria: Scyphozoa) in Laguna Joyuda. Journal of Experimental Marine Biology and Ecology 173:71-93.
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Silveira F.L. and P.F.S. Cornelius. 2000. New observations on medusae (Cnidaria, Scyphozoa, Rhizostomae) from the northeast and south Brazil, Acta Biologica Leopoldensia 22:9-18.