Introduction

The family Rhizostomatidae contains the genera Eupilema Haeckel, 1880, Rhizostoma Cuvier, 1800 and Rhopilema Haeckel, 1880. Of these, only Rhopilema has been reported in Australian waters, and only very rarely.

The group is easily identified by having scapulets on the upper portions of the oral arms, which are coalesced in the proximal portion only; the distal portion of the oral arms are three-winged, and they usually have a terminal club. Eupilema is characterised by lacking filaments, clubs or other appendages on the oral arms. Rhizostoma is characterised by having small scapulets and a short manubrium, a single club-like terminal appendage, no clubs or filaments, and typically with a ring canal. Rhopilema is characterised by having large scapulets and a long manubrium, a large terminal club, numerous clubs or filaments, and typically lacking a ring canal.

Stiasny (1921: 168) studied specimens from Japan and concluded that the species is probably a damaged form of Rhopilema escuelnta; however, it is possible that he did not have the right species to begin with: Eupilema scapulare is from the Sunda Archipelago and Sumatra, whereas R. esculenta is from Japan. The validity of the genus Eupilema was questioned by Kramp (1970: 15), who believed it to be obsolete based on Stiasny's conclusions. However, the genus was considered valid by Pagès and his colleagues (1992), who added a new species to Haeckel's genus.

Diagnosis

Scapulatae with mouth-arms coalesced in proximal portion only; without a primary mouth opening; rnanubrium with a complicated canal system; distal portion of arms three-winged, usually with a terminal club.

Diagnosis References

Kramp, P.L. 1961. Synopsis of the medusae of the world. Journal of the Marine Biological Association of the United Kingdom 40: 1-469 [377]

General References

Kramp, P.L. 1970. Zoogeographical studies on Rhizostomeae (Scyphozoa). Videnskabelige Meddelelser fra Dansk Naturhistorisk Forening i Kjøbenhavn 133: 7–30

Pagès, F., Gili, J.M. & Bouillon, J. 1992. Medusae (Hydrozoa, Scyphozoa, Cubozoa) of the Benguela Current (southeastern Atlantic). Scientia Marina 1-64

Stiasny, G. 1921. Studien über rhizostomeen. Capita Zoologica 1(2): viii + 179, 5 pls

History of changes

• Rhopilema Haeckel, E. 1880. System der Acraspeden. Zweite Halfte des System der Medusen. Jena : G. Fischer. [596].

  Type species:

   Rhopilema rhopalophora Haeckel, 1880 by subsequent designation, see Mayer, A.G. 1910. Medusae of the World. Vol. 1 and 2, The Hydromedusae. Vol. 3, The Scyphomedusae. Washington, D.C. : Carnegie Institution 735 pp., 76 pls. [reprinted by A. Asher & Co., 1977] [704].

Distribution

States

Northern Territory, Queensland

Extra Distribution Information

Widely distributed: Madagascar, USA, British Indian Ocean Territory, China (People's Republic), Hong Kong, India, Malaysia, Philippines, Thailand. Egypt, Japan

IMCRA

Central Eastern Shelf Transition (39)

Distribution References

Diagnosis

Rhizostomatidae with large scapulets and long manubrium; mouth-arms with numerous clubs or filaments and usually with a large terminaI club; usually without a ring canal; canal network broad with numerous fine meshes; inter-rhopalar canals wide.

Diagnosis References

Kramp, P.L. 1961. Synopsis of the medusae of the world. Journal of the Marine Biological Association of the United Kingdom 40: 1-469 [379]

Notes

Species identification in the genus Rhopilema is primarily based on number and shape of velar lappets, presence or absence of radial grooves in the margin of the exumbrella, manubrium length, size and shape of terminal clubs on the oral arms, and arrangement and form of other oral arm appendages.

History of changes

• Rhizostoma hispidum Vanhöffen, E. 1888. Untersuchungen ueber Semaeostome und Rhizostome Medusen. Bibliotheca Zoologica, Stuttgart 1(3): 51 pp., 6 pls, 1 map [32].

Generic Combinations

• Rhopilema hispidum (Vanhöffen, 1888). —
  Maas, O. 1903. Die scyphomedusen der Siboga-Expedition. Siboga-Expeditie 11(livr. 10): 1–91, pls 1–12

Distribution

States

Northern Territory

Extra Distribution Information

Rhopilema hispidum was reported in Australian waters by Williamson et al. (1996), from the Northern Territory. It was subsequently found again in Darwin Harbour by Gershwin (unpublsihed notes, 2004). Elsewhere in the world, it has been reported from various localities throughout the Indo-Pacific (see Kramp 1961).

Ecological Descriptors

Carnivorous, epipelagic, estuary, marine, neritic.

Diagnosis

250-340 mm wide, exumbrella with numerous small, sharp-pointed, conical projections; in each octant about eight velar lappets, oblong, rounded; mouth-arms terminate in a large club-shaped appendage with a faceted, swollen end, other club-shaped appendages between the mouths on the three wings.

Diagnosis References

Kramp, P.L. 1961. Synopsis of the medusae of the world. Journal of the Marine Biological Association of the United Kingdom 40: 1-469 [380]

Notes

Rhopilema hispidum is easily distinguished by its whitish bell with numerous fine red dots, and thick, elongate pyramidal appendages on the oral arms, which may be reddish in colour.

The species was originally described into the genus Rhizostoma, and was moved to the genus Rhopilema by Maas (1903), where it has remained stable. The species R. verrucosa Kishinouye from Japan was thought by Mayer (1910) to be conspecific, as was the species R. visayana Light (1914b) from the Philippines (Stiasny 1921).

General References

Kramp, P.L. 1961. Synopsis of the medusae of the world. Journal of the Marine Biological Association of the United Kingdom 40: 1-469

Mayer, A.G. 1910. Medusae of the World. Vol. 1 and 2, The Hydromedusae. Vol. 3, The Scyphomedusae. Washington, D.C. : Carnegie Institution 735 pp., 76 pls. [reprinted by A. Asher & Co., 1977]

Stiasny, G. 1921. Results of Dr. E. Mjöbergs Swedish scientific expeditions to Australia, 1910-13. XXX. Scyphomedusen. Kongliga Svenska Vetenskaps-Academiens Nya Handlingar, Stockholm 62(2): 1–12, text-figs

Williamson, J., Fenner, P., Burnett, J. & Rifkin, J. (eds) 1996. Venomous and Poisonous Marine Animals: a medical and biological handbook. Sydney, Australia : NSW University Press 800 pp.

History of changes