Revision of the genus Chrysaora Péron & Lesueur, 1810 (Cnidaria: Scyphozoa)

Abstract

Revision of the scyphozoan genus Chrysaora Péron & Lesueur, 1810 was undertaken from observations on museum material (Brazil, Europe, and USA), on living specimens in nature, and on life-cycles of some species cultured under laboratory conditions. A total of 168 museum lots, some of them having many medusae, were inspected. Included amongst these were nine type specimens. The genus comprises 13 valid species (Chrysaora achlyos, C. chinensis, C. colorata, C. fulgida, C. fuscescens, C. hysoscella, C. lactea, C. melanaster, C. pacifica, C. pentastoma, C. plocamia, and C. quinquecirrha), one species inquirenda (Chrysaora caliparea), and two doubtful species (C. kynthia and C. wurlerra). Differentiation of species is based mostly on tentacle number, shape of radial septa, order of tentacle development, colouration, and measurements of nematocysts. We resurrect C. chinensis for specimens from southeast Asia. Chrysaora pacifica is considered valid and distinct from C. melanaster based on tentacle number and nematocyst complement. Mediterranean specimens assigned to C. hysoscella are hermaphroditic and thereby considered distinct from those of C. fulgida from west Africa. Chrysaora achlyos (northeast Pacific) and C. plocamia (southeast Pacific and southwest Atlantic) are geographically isolated but morphologically identical, being distinguished only by colour pattern. The recently described C. southcotti is considered a junior synonym of C. pentastoma. The Australian C. kynthia and C. wurlerra, here considered nomina dubia, merit further study. Our phylogenetic hypothesis indicates that the genus Chrysaora forms a monophyletic group, with C. colorata, C. plocamia, and C. achlyos having a basal position in the phylogeny. Species with more than 24 tentacles (formerly assigned to the genus Dactylometra) form a clade with a derived position.