The life cycle of Gastroblasta raffaelei (Cnidaria, Hydrozoa, Leptomedusae, Campanulariidae) and a review of the genus Gastroblasta

Abstract

The genus Gastroblasta was proposed by Keller in 1883 for a campanulariid medusa from the Red Sea, G. timida, with round umbrella, multiple radial canals and multiple manubria. A second species, G. raffaelei, with elliptic umbrella, multiple manubria and radial canals, and a great tendency to fission, was subsequently described from the Mediterranean Sea by Lang in 1886. A third species with multiple manubria was described by Mayer in 1900 from Tortugas: Multioralis ovalis (currently ascribed to Gastroblasta). The complete life cycle of a species of Gastroblasta, whose polyp stage was collected inside sponges from the Ligurian Sea and the Ionian and Adriatic Seas, is described. The first stage of medusa development is a typical Clytia with four radial canals and four tentacles, then the medusa becomes similar to G. ovale, to subsequently acquire the typical morphology of G. raffaelei. The species G. timida and G. raffaelei are considered as valid representatives of the genus, sharing the characters of multiple manubria and radial canals. The medusa of G. ovale has a diagonal canal system, instead of multiple radial canals, sharing with Gastroblasta the presence of multiple manubria only: it is proposed to resurrect the genus Multioralis to accommodate it.