Cyst morphology of European branchiopods (Crustacea, Anostraca, Notostraca, Spinicaudata, Laevicaudata)

A comparative analysis of cyst (= resting egg) size and shell architecture by scanning electron microscopy is reported in 40 species of "large branchiopods", belonging to 21 genera from all the families inhabiting inland waters of Europe. This paper follows one on the geographic distribution of the European branchiopods where 72 species and sub-species belonging to 22 genera and 13 families were listed (BRTEK & THIÉRY, 1995). Particular attention has been paid to cyst shape and morphology of the external shell surface. The results are discussed in the light of existing literature. When the taxonomic value of the external shell surface pattern shows its limits, the combination size/surface pattern seems more useful, being sometimes species-specific, while in other cases (such as in Branchipus, Tanymastix, Cyzicus, Imnadia) it appears to reflect taxonomic relationships of higher rank. In other cases, a third character, the structure of the cyst envelope, observable in fractured cysts, must be taken into acount to separate cysts (as in Artemia and Branchinectella). "large branchiopods" eggs can provide new taxonomic information that is useful in the definition of natural groups.