Evolutionary significance of the embryological development of the daphniid cladocerans Ceriodaphnia Dana, 1853 and Scapholeberis Schoedler, 1858 (Branchiopoda: Cladocera: Daphniidae).

The embryological development of Ceriodaphnia reticulata Dumont & Pensaert, 1983 and Scapholeberis rammneri Jurine, 1820 were investigated using scanning electron microscopy. A carapace spine did not develop and there was no fusion of the first antennae. These are apparent apomorphies of Daphnia Müller, 1785 , which suggests that the common ancestor of Daphniidae Straus, 1820 did not have a carapace spine during its embryological development, and its first antennae were short and separated during embryogenesis. Morphological evidence thus appears congruent with molecular interpretations showing that Scapholeberis Schoedler, 1858 is basal to other genera of Daphniidae, Ceriodaphnia being a sister taxon to Daphnia. [ABSTRACT FROM AUTHOR]