Cubozoa: Systematics

Systematic Relationships within Cubozoa

Cubozoans have yet to be the subjects of a published phylogenetic analysis. However, UCMP graduate student Lisa-ann Gershwin is working on just such an analysis as part of her dissertation. Until she finishes this project, we are presenting a phylogenetic representation of the current classification scheme for Cubozoa.

Systematics of Cubozoa

There are two main groups of cubozoans, Chirodropidae and Carybdeidae. The two groups are relatively easy to tell apart. In carybdeids, each tentacle is connected to a single pedalium. Usually there are four pedalia each with a tentacle, however, in Tripedalia species, each corner of the bell has two or three tentacles each connected to a single pedalium. Chirodropids always have four pedalia, one at each corner, with multiple tentacles. Are you ready for the test?

The Phylogenetic Position of Cubozoa

The phylogenetic position of Cubozoa within
Cnidaria has been the subject of a great deal of debate. Classically, cubozoans were viewed as a subgroup of the "true jellyfish" or Scyphozoa (as shown to the left below).

Alternative Hypotheses for the Phylogenetic Position of Cubozoa

However, when it was observed that the cubozoan polyp and life cycle were rather different than those of scyphozoans, Cubozoa was placed on its own. Some scientists have proposed that cubozoans are the closest living relatives of scyphozoans, as shown in the middle above. Still others have argued that Cubozoa is more closely related to Hydrozoa (as shown to the right). Post-doctoral researcher and former UCMP graduate student, Allen G. Collins is presently working on this question and its evolutionary implications.

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

Moore, S. J. 1988. A new species of cubomedusan (Cubozoa: Cnidaria) from northern Australia. The Beagle, Records of the Northern Territory Museum of Arts and Sciences 5, 1-4.

Southcott, R. V. 1956. Studies on Australian cubomedusae, including a new genus and species apparently harmful to man. Austr. J. Mar. Freshw. Res. 7, 254-280.

Southcott, R. V. 1967. Revision of some Carybdeidae (Scyphozoa: Cubomedusae), including a description of the jellyfish responsible for the "Irukandji syndrome". Australian J. Zool. 15, 651-671.

Sources for Phylogenetic Position of Cubozoa:
Salvini-Plawen. 1978. On the origin and evolution of the lower Metazoa. Z. zool. Syst. Evolut. -rforsch. 16, 40-88.

Thiel, H. 1966. The evolution of the Scyphozoa, a review. In Cnidaria and their Evolution (ed. W. J. Rees), pp. 77-117. London: Academic Press.

Uchida, T. 1929. Studies on the Stauromedusae and Cubomedusae, with special reference to their metamorphosis. Jap. Jour. Zool. 2, 103-193.

Werner, B. 1973. New investigations on systematics and evolution of the class Scyphozoa and the phylum Cnidaria. Publications of the Seto Marine Biological Laboratory 20, 35-61.