Family CASSIOPEIDAE Tilsius, 1831

Museums

Regional Maps

Introduction

The family Cassiopeidae in the modern context contains only a single genus, Cassiopea. In the past, Haeckel (1880) recognised three genera: Toreuma Haeckel, 1880, with 8 rhopalia; Polyclonia Brandt, 1837 with 12 rhopialia; and, Cassiopea Péron & Lesueur, 1810, with 16 rhopalia. However, the arrangement of Haeckel (1880) has not been adopted by subsequent authors.

Cassiopea medusae are widespread throughout the tropics and sutropics of the world. In Australian waters, four described and two undescribed species have been recorded.

Like many rhizostomes, cassiopeids have algal symbionts (zooxanthellae), from which they gain some of their nutrition. It has been estimated that up to 169% of the host's demands may be satisfied by their zooxanthellae (Verde & McCloskey, 1998). Species of Cassiopea are one of the most distinctive of all jellyfish groups, having the unusual habit of spending their time 'upside down' (i.e., exumbrella downward), only occasionally swimming normally for brief periods. Cassiopea medusae are basically quiet farmers, that are usually found in shallow pools where there is ample sunlight for their zooxanthellae and also where they gently pulsate oxygenated water over the zooxanthellae. Most have only a mild sting, but a few species are capable of delivering quite a painful and persistent sting.

Identification of Cassiopea species is primarily based on the number of rhopalia and lappets, the cross section shape and branching patterns of the oral arms, the arrangement of clubs and filaments amongst the oral arms, and colour patterns.

Diagnosis

Kolpophorae with subumbrellar muscles in fearher-like arcs. Radial canals usually about twice as many as rhopalia (more or less than 32). Without or with faintly indicated ring canal. With four completely separated subgenital cavities. Subgenital ostia small, round. Stomach circular. Arm disk octagonal, with four primary canals.

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 [348]

General References

Haeckel, E. 1880. System der Acraspeden. Zweite Halfte des System der Medusen. Jena : G. Fischer.

Verde, E.A. & McCloskey, L.R. 1998. Production, respiration, and photophysiology of the mangrove jellyfish Cassiopea xamachana symbiotic with zooxanthellae: Effect of jellyfish size and season. Marine Ecology Progress Series 168: 147–162

History of changes