title: Heart development in the spotted dolphin (Stenella attenuata).
abstract: Marine mammals show many deviations from typical mammalian characteristics due to their high degree of specialization to the aquatic environment. In Cetaceans, some of the features of limbs and dentition resemble very ancestral patterns. In some species, hearts with a clearly bifid apex (a feature normally present during mammalian embryogenesis prior to completion of ventricular septation) have been described. However, there is a scant amount of data regarding heart development in Cetaceans, and it is not clear whether the bifid apex is the rule or the exception. We examined samples from a unique collection of embryonic dolphin specimens macroscopically and histologically to learn more about normal cardiac development in the spotted dolphin. It was found that during the dolphin's 280 days of gestation, the heart completes septation at about 35 days. However, substantial trabecular compaction, which normally occurs in chicks, mice, and humans at around that time period, was delayed until day 60, when coronary circulation became established. At that time, the apex still appeared bifid, similarly to early fetal mouse or rat hearts. By day 80, however, the heart gained a compacted, characteristic shape, with a single apex. It thus appears that the bifid apex in the adult Cetacean heart is probably particular to certain species, and its significance remains unclear.
authors.affiliation: Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina 29425, USA. sedmera@musc.edu
authors.forename: David
authors.initials: D
authors.lastname: Sedmera
authors.forename: Ivan
authors.initials: I
authors.lastname: Misek
authors.forename: Milan
authors.initials: M
authors.lastname: Klima
authors.forename: Robert P
authors.initials: RP
authors.lastname: Thompson
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D002642:Chick Embryo; D003331:Coronary Vessels / Q000196:embryology / Q000502:physiology; D004289:Dolphins / Q000196:embryology* / Q000502:physiology; D005260:Female; D006321:Heart / Q000196:embryology* / Q000502:physiology; D006346:Heart Septum / Q000196:embryology; D006352:Heart Ventricles / Q000196:embryology; D006801:Humans; D051379:Mice; D009206:Myocardium / Q000166:cytology; D051381:Rats; D016276:Ventricular Function