dear collegues Would you like to discuss the following arguments? Recently, Siddall et al (1995, see below) convincingly showed that the Myxozoa are not protozoans but cnidarians. Most interestingly, the molecular analysis showed a closer relationship to the only cnidarian genus that has an intracellular parasitic stage: Polypodium. Although not reliably resolvable at this stage, the clade (Myxozoa + Polypodium) did not cluster within the Hydrozoa but together with the only cubozoan species analyzed. Polypodium is currently seen as a member of the Hydrozoa, more precisely the Narcomedusae. However, the inclusion of Polypodium in the Narcomedusae is not based on any synapomorphies and is made only for lack of better solutions. Also the inclusion within the Hydrozoa is not supported by any synapomorphy. The medusa-like free phase of Polypodium has its gonads in the gastrodermis and not in the epidermis (Raikova 1994) (epidermal gonads are an autapomorphy of the Hydrozoa, see Schuchert 1993). It thus seems that the the clade (Polypodium + Myxozoa) is not closely related to the Hydrozoa and it probably constitutes a new class within the Cnidaria. The autapomorphy for this clade would be endocytic parasitisms (+support from 18S RNA sequence analysis). A new name for this clade could be:

Endocnidozoa.

The taxonomiy of the Cnidaria (in traditional Linnean way) would therefore look like as follows:

Phylum Cnidaria Subphylum Ametagenetica Class Anthozoa Subphylum Metagenetica Class Scyphozoa Class Cubozoa Class Hydrozoa Class Endocnidozoa

What do you think about this proposal? with kind regards, Peter

References: Raikova-E 1994: Life cycle, cytology, and morphology of Polypodium hydriforme, a coelenterate parasite of eggs of acipenserifom fishes. J. Parasitology 80: 1-22.

Schuchert-P 1993: Phylogenetic analysis of the Cnidaria. Zeitschrift fuer Zoologische Systematik und Evolutionsforschung 31(3): 161-173.

Siddall-M-E; Martin-D-S; Bridge-D; Desser-S-S; Cone-D-K 1995 : The demise of a phylum of protists: Phylogeny of Myxozoa and other parasitic cnidaria. Journal of Parasitology 81(6): 961-967

see also http://www.vims.edu/%7Emes/myxozoa/myxozoa.html

----------------------------------------------------------------------------- Peter Schuchert University of Basel Rheinsprung 9 CH-4051 Basel Switzerland fax 0041 61 267 34 57 tel 0041 61 267 34 78

http://www.unibas.ch/dib/zoologie/research/schuch.html

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