Chrysaora species

Morandini, André C. & Marques, Antonio C., 2010, Revision of the genus Chrysaora Péron & Lesueur, 1810 (Cnidaria: Scyphozoa) 2464, Zootaxa 2464, pp. 1-97 : 63-74

Chrysaora species outbreaks/blooms and bioinvasions

Several factors in the life cycle, development, and ecology of a species may favor its invasion or create an outbreak/bloom ( Boero & Bouillon 1994; Kremer 2001; Parsons & Lalli 2003; Secord 2003; Kremer et al. in press). Some of these factors may be contrasted with the biology of the species of pelagiid medusae.

Jellyfish outbreaks/blooms is a major topic in the biology of scyphomedusae ( Mills 2001; Purcell 2005; Xian et al. 2005; Purcell et al. 2007; Uye 2008). Recent reviews and compilations (Dawson & Hamner 2009; Hamner & Dawson 2009) depicting the evolution of outbreaks/blooms/swarms among semaeostomes and rhizostomes failed in giving accurate information on representatives of the family Pelagiidae , for which no species was discussed in relation to blooms. In fact, literature records exist of large aggregations of some pelagiid species, viz. Pelagia noctiluca in Irish ( Doyle et al. 2008) and Mediterranean ( Goy et al. 1989) waters; Chrysaora achlyos in southern California ( Martin et al., 1997); C. caliparea (as Dactylometra quinquicirrha ) in southeastern India ( Masilamoni et al. 2000); C. fulgida in the Benguela current ( Sparks et al. 2001; Lynam et al. 2006); C. lactea (as C. quinquecirrha ) in the Gulf of Mexico (Graham 2001); and C. melanaster in the Bering Sea ( Brodeur et al. 2002, 2008b) [the report of Sanderia malayensis in the Yangtze estuary by Xian et al. (2005) is here considered doubtful, because there is no voucher specimen deposited in any collection (author’s information) and the image illustrating the article is a specimen of Cyanea ]. At least another species of pelagiid is known to have large aggregations, C. plocamia in Argentina and Peru (H.W.

Mianzan and J. Quiñones pers. comm.). Apparently, the only well documented outbreak/bloom is that of C. melanaster in the Bering Sea ( Brodeur et al. 2008b); all other species have no historical data to present a clear panorama and to draw conclusions whether these aggregations are related to the biological cycle of the species.

Biological invasions (see Carlton & Geller 1993; Falk-Petersen et al. 2006) are also an important topic in the biology of gelatinous zooplankton, well known for their ability to colonize new habitats. Although there are some reports of outbreaks or population increases related to pelagiid medusae, real cases of bioinvasions including species of the family are not known, and it seems that polyps/medusae of Chrysaora are not prone to invade and colonize new habitats (see Malej & Malej Jr 2004). In general, this lack of ability in establishing new populations in different environments makes the biogeographical history of the species of Pelagiidae very stable, with few events of dispersal. This may be seen and contrasted with the biogeographic distribution of the species (see discussion below).

Distributional patterns of the Chrysaora species

Species of the genus Chrysaora occur in all oceans (see Mayer 1910; Kramp 1961; Larson 1986; 1990; Wrobel & Mills 1998; Mianzan & Cornelius 1999; Gershwin & Collins 2002; Gershwin & Zeidler 2008). Sometimes several species co-exist in the same area, occasionally geographic distributions of species overlap, and in other case species occupy neighbouring areas.

The west coast of the USA has records of several species of Chrysaora , some of them sympatric. These species are very similar morphologically (cf. Wrobel & Mills 1998), resulting in considerable confusion about their taxonomy. These medusae occur in large numbers on coasts of North America, but few specimens are available in collections (see list of examined material). This makes comparisons among the species somewhat “weak”, because large series of specimens are not available for study. To correct and clarify information in the literature, and avoid propagating confusion, we tried to base our conclusions and proposals exclusively on characters observed in available and studied material, although data from literature reports were necessary for a major understanding of the taxonomy of the group. We present below a geographical synthesis of the species based on our taxonomic conclusions.

Five species of Chrysaora ( C. fulgida , C. hysoscella , C. lactea , C. plocamia , and C. quinquecirrha ) are recognized in the Atlantic Ocean. Chrysaora fulgida is restricted to west African waters, occurring southwards to Mauritania and reaching the coast of South Africa. Chrysaora hysoscella is endemic to northeast Atlantic waters (Mediterranean and North Seas). Chrysaora lactea occurs in the Caribbean region ( Agassiz & Mayer 1898), Gulf of Mexico, Panama, Colombia, Brazil, Uruguay, and Argentina. Chrysaora plocamia is known from waters of south Argentina, but it also occurs in the southeastern Pacific. The only species on the east coast of the USA is C. quinquecirrha ( Larson 1976) , and there are no reliable published records (see above) of the species south of the state of Georgia ( USA).

Based on the observed specimens and distributional data, there are no sympatric species of Chrysaora in the Atlantic Ocean. Nevertheless, patterns of distribution of species may vary with time and environmental factors, although these data are presently not available. Samples from Caribbean and Gulf of Mexico waters, and northwest African waters, may reveal areas of sympatry between some of the species.

Ten species are discussed here from the Pacific Ocean ( C. achlyos , C. chinensis , C. colorata , C. fuscescens , C. kynthia , C. melanaster , C. pacifica , C. pentastoma , C. plocamia , and C. wurlerra ). Several of them occur in the northeast Pacific. Chrysaora achlyos is known from California ( USA) and northern Mexico, C. colorata occurs in California, C. fuscescens is distributed from California northwards to Washington ( USA), and the more northerly C. melanaster ranges from the Bering Sea (Alaska) to Oregon ( USA). On the other side of Pacific, C. chinensis is recorded in the China Sea, Philippines, and Indonesian waters, and C. pacifica is endemic to waters around Japan. It is possible that other species (probably C. chinensis and C. melanaster ) reach Japanese waters, but further collections and confirmation will be necessary. As noted above, C. plocamia is reported in southeastern Pacific waters ( Peru, Chile), but also in the southwestern Atlantic ( Argentina). The recently described species C. kynthia , C. pentastoma and C. wurlerra are distributed in waters of south and southeastern Australia ( Gershwin & Zeidler 2008).

Apparently the only known species occurring in the Indian Ocean is C. caliparea . There are some records of Chrysaora medusae from east Africa and India which we believe to be related to this little-known species. There are no published records of Chrysaora medusae in the Red Sea and Arabian Gulf.

Scattered records of dubious identity or validity exist. Péron & Lesueur (1810) described C. pentastoma and C. hexastoma in Australia, but the descriptions are so poor that they cannot be assigned to any species (see comments in C. pentastoma ). Gershwin & Collins (2002: 128) mentioned two undescribed species from Australia (one of them, C. sp. #1, formally described later as C. kynthia , see Gershwin & Zeidler 2008: 4). Another questionable record is that of Vannucci & Tundisi (1962) based on a specimen collected at the Argentinean Antarctic station (Puerto Melchior) and identified as C. hysoscella . This material was not inspected and the identity cannot be confirmed. Larson (1986) wisely mentioned the specimen and regarded it as an unidentified Chrysaora species. Here we propose that it might have been a specimen of C. plocamia .

Distribution and Phylogeny. Our working phylogenetic hypothesis ( Fig. 96) presents additional and interesting biogeographical information (based on the plotting of the species of Chrysaora in the tree topology). In general, it must be considered that the distribution of species of Chrysaora is restricted to coastal areas (related to the continental slope), most probably due to the presence of a polypoid stage and its need in colonize hard substrates to complete its life cycle.

Geographically, the basal part of tree is represented by a paraphyletic group of species ( C. colorata , C. achlyos , C. plocamia , C. melanaster and C. fuscescens ) distributed along the Pacific coast of the Americas. However, C. plocamia also occurs in the southwestern Atlantic, a distribution probably related to particular hydrographic circulation patterns (see under species ‘systematic remarks’). The origin of this paraphyletic group, and consequently that of the ancestor of Chrysaora , might be hypothesized in the Pangaean coasts of the Panthalassic Ocean basin (Late Permian Period, 290–250 Mya). Such early origin is plausible when compared to the present knowledge of the existence of major medusozoan clades, all with at least Cambrian origins ( Cartwright et al. 2007). During the Triassic period (200 Mya), with the separation of Laurasia and Gondwana, the Proto-Caribbean Sea and North Atlantic established a connection with the former Panthalassic Ocean. At this period of time an ancestral species might have invaded these ocean basins giving origin to the species C. hysoscella and the Chrysaora clade with 40 tentacles. During the late Cretaceous period (94 Mya) the 40-tentacle clade of Chrysaora split into two groups, one eastward in the Tethys Sea (giving origin to C. chinensis and C. pacifica ), and the other paraphyletic or monophyletic Atlantic group splitting into eastern ( C. fulgida ) and western ( C. lactea , central and south Atlantic; C. quinquecirrha , north Atlantic) groups.