Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!decwrl!argosy!freeman From: freeman@argosy.UUCP (Jay R. Freeman) Newsgroups: sci.bio Subject: Re: jellyfish classification Message-ID: <1354@argosy.UUCP> Date: 31 May 91 01:15:55 GMT References: <91150.145201U33695@uicvm.uic.edu> Sender: news@argosy.UUCP Reply-To: freeman@cleo.UUCP (Jay R. Freeman) Organization: MasPar Computer Corporation, Sunnyvale, CA Lines: 30 I'm sure someone will hollar if I am wrong, so I will venture that the vaguely bell-shaped, betentacled marine entities commonly called "jellyfish" are indeed single animals; but that their life cycle is complicated: Many of them exhibit alternation of generations, in which the immediate adult offspring of a jellyfish may look like something else entirely, and may be one or another form of sessile, colonial critter. In such cases, it is not until these colonial forms' offspring reaches adulthood that another generation of "jellyfish" emerges. Not all jellyfish exhibit strict alternation of generation. The phylum (cnidaria) which includes these animals also includes corals, which are largely colonial and have no free-living adult stage, and sea anemones, which if not strictly colonial are often found in groups, and which also have no free-living adult stage. Also in the phylum are assorted free-living colonial animals, like the Portugese Man O'War (_Physalia_). Each Portugese Man O'War is a colony of separate individual animals of the same species, but having many different shapes; that is, the species is polymorphic. When people speak of a "colonial jellyfish", critters like these are probably what they had in mind, although they do not look like jellyfish -- there's no "bell" -- and they behave somewhat differently -- they float at the surface rather than immersed. -- Jay Freeman