Comparative embryology of Delphinapterus leucas, Balaena mysticetus, and Stenella attenuata (Cetacea: Mammalia).

Embryogenesis of cetaceans (whales, dolphins, porpoises) is well known in Stenella attenuata, the pan-tropical spotted dolphin, based on a remarkably complete and well-studied series prenatal ontogenetic stages. Our study expands understanding of cetacean embryology by adding two additional cetacean taxa: the beluga whale (Delphinapterus leucas, Odontoceti), and the bowhead whale (Balaena mysticetus, Mysticeti). We identify key features that characterize these taxa at specific stages and highlight heterochrony between the odontocetes and mysticetes. A presomitic Delphinapterus embryo is also described. This study therefore applies the Carnegie staging system to two more cetacean taxa and forms a framework for future research on cetacean developmental genetics and modeling of fetal growth. This article is protected by copyright. All rights reserved.