A guideline to nematocyst nomenclature and classification, and some notes on the systematic value of nematocysts

Cnidocyst nomenclature is based on the structure of the tubule and its arma ture as viewed in the light microscopy (LM). Investigations utilising optic ally improved LM and scanning electron microscopy have revealed some errors in the interpretation of the fine structure of tubules and armature of nem atocysts. Categories of nematocyst have been modified, therefore, to incorp orate observations made with new visualising techniques. Isorhizas are defi ned as nematocysts whose tubule is of uniform or nearly uniform thickness p roximal to the midpoint, while b-mastigophores are nematocysts with a rod-s haped encapsulated shaft and a prominent armature on the everted shaft. The category of amastigophores is retained but redefined as p-amastigophores F or the V-shaped notch at the base of encapsulated shaft. The trirhopaloids are found to be similar to the birhopaloids. Mesobasic is redefined as an i ntermediate length of discharged shafts between micro- and macrobasic. Asto mocnidae is redefined as entangling nematocysts and stomocnidae as penetran ts.