Fine Structure of the Ephippium of Daphnia pulex (Crustacea: Cladocera)

The external surface of the ephippium of Daphnia pulex bears numerous, randomly distributed pits which are formed by the thickening of the brood chamber cuticle. The internal surface is covered by a thin amorphous sheet below which lies a polygonal matrix or lattice. In section, the wall of the ephippium is shown to be formed of several layers. The exterior is the thin epicuticle. The second or middle layer, the procuticle, is subdivided into an outer, thick laminated or banded region, a middle polygonal matrix of varying thickness, and an inner, thin, irregular lattice region. Innermost is an amorphous noncellular layer within which are observed bacteria-like particles. Comparisons are drawn with light microscope observations of the ephippium of Daphnia magna.