Chrysciova quinquecirrha, the common sea nettle infests the Chesapeake Bay waters during the summer season. This coelenterate causes a severe economic problem for this resort area because of the painful sting it iaflicts upon bathers who accidentally come in contact with its tentacles. These stings are thought to result from the injection of nematocyst threads and the introduction of a toxin in...

Athecate, pseudocolony-forming dinoflagellates have been classified within two genera of polykrikoids, Polykrikos and Pheopolykrikos, and different views about the boundaries and composition of these genera have been expressed in the literature. The photosynthetic polykrikoid Pheopolykrikos hartmannii, for instance, was originally described within Polykrikos and is now known to branch closely w...

In this review the history of discovery of siphonophores, from the first formal description by Carl Linnaeus in 1785 to the present, is summarized, and species richness together with a summary of world-wide distribution of this pelagic group within the clade Hydrozoa discussed. Siphonophores exhibit three basic body plans which are briefly explained and figured, whilst other atypical body plans...

Abstract Background Lineage-specific gene expansions represent one of the driving forces in evolutionary dynamics unique phylum traits. Myxozoa, a cnidarian subphylum obligate parasites, are evolutionarily altered and highly reduced organisms with simple body plan including cnidarian-specific organelles polar capsules (a type nematocyst). Minicollagens, group structural proteins, prominent cons...

The authors have previously found that mutant hydra strains showing various types of developmental defects can be isolated through sexual inbreeding of wild hydra. One such defective strain, called nem-4, contains virtually no stenoteles, one of the four types of nematocysts present in hydra, in its tentacles. However, stenoteles are present at a normal level in the body column of this strain, ...

The response of nematocytes in the anemone Stichodactyla haddoni to contact with complex organic compounds varies according to the 9ubstance concerned and in most cases according to the level of accompanying mechanical stimulation. Compounds with a proteinaceous moiety differ in their capacity to excite nematocytes, but usually tend to induce a stronger response than polysaccharides or lipids. ...