The anatomical record under the sea: A history of reporting findings on the biology, adaptations, and evolution of mammals that inhabit a watery world

The Anatomical Record has a long and robust history of reporting findings on the anatomy, embryology, adaptations, and evolution of our wettest mammalian relatives. Ranging from reports on the largest baleen whales to riverine manatees to other reports on fur seals to porpoises, the anatomy of those relatives that ventured back to the waters has been exquisitely documented within our pages. Keeping with that tradition is this month's special issue, “The anatomical adaptations of aquatic mammals,” guest edited by comparative anatomist and water-world aficionado Dr. Joy Reidenberg. Within the pages of this special issue will be found a pelagic cornucopia of the latest science and issues confronting those at the forefront of aquatic anatomy, as well as providing us with a “Jules Verne-esque” window onto the use of state-of-the-art tools and approaches used to address some long-standing questions on how these remarkable relatives came to be.

This journal has long been a leader in uncovering the anatomy and function below the waves and, indeed, some of our brightest lights have put their scalpels and microscopes to the task. Particularly notable in this regard have been the following: the elegant and insightful comparative studies by George B. Wislocki, renown Professor and Chair of Anatomy at Harvard Medical School (and the mentor and stimulator of many anatomists, such as Editor Emeritus of this journal, John Ladman) on the hypophysis in mysticete whales (Wislocki and Geiling, 1936), on comparisons of the hypophysis among elephants, manatees, and hyraxes (Wislocki, 1940), on the ovary of humpback whales (Demsey and Wislocki, 1941), and on the lungs in porpoises (Wislocki, 1942); studies by the Chinese anatomist Chi Ping, on the visceral and testicular anatomy of the Yangtze River porpoise (Ping, 1926a, b); a study by one of the greatest embryologists of his day, Leslie B. Arey, on the seal liver (1932); the work by Oldham and colleagues on the hypophysis of the manatee (Oldham et al., 1938); the comparative study by Grafflin and Geiling on the thyroid gland in whales (1942); studies on the anatomy and physiology of the reproductive system of fur seals by Enders, Pearson, and colleagues (Enders et al., 1946; Pearson and Enders, 1951); the study by Zeek on the fascinating occurrence of the double trachea in penguins and sea lions (Zeek, 1951); the comparative study on cardiac anatomy, pathology, and coronary circulation of whales by the eminent anatomist Raymond C. Truex (Truex et al., 1961); work by the Japanese anatomist Kinziro Kubota on the variation in dentition among pinnipeds (Kubota and Togawa, 1964) and on the comparative anatomy of the fur seal tongue (Kubota, 1968); the exquisitely detailed study by Galliano and colleagues on the cervicothoracic arterial system of the bottlenose dolphin (1966); the study by Sinha and Conaway on the ovary of the sea otter (1968); Morita and colleagues examination of the carotid body in the weddel seal (1970); comparative studies on the arteriovenous anastomoses in the skin of seals by Molyneux and Bryden (1978; Bryden and Molyneux, 1978); the study by noted Yale orthopedist John Ogden and colleagues on the cervical spine in pilot whales (1981); and the series of studies by Haldiman, Henk, Abdelbaki, and colleagues on the respiratory system and other features of the rare bowhead whale (Henry et al., 1983; Abdelbaki et al., 1984; Haldiman et al., 1984, 1985; Henk and Haldiman, 1990).

The past few decades have been particularly fruitful for The Anatomical Record, with researchers continuing explorations into the often difficult-to-acquire aquatic material, but now also adding in-depth insights into both functional morphology and frequently introducing visualizations of structures through advancements in imaging technologies. Notable in this regard have been the following: comparative studies on the cranial base, hyoid, and upper respiratory structures of toothed whales by Reidenberg and Laitman (1987, 1988, 1994); extensive comparative analyses by Rommel and coworkers on an array of animals, including observations on the cetacean uterus, and reproductive organs of phocid seals (Rommel et al., 1993, 1995) and, especially, their groundbreaking work on the various organ systems of the Florida manatee (Reynolds and Rommel, 1996; Rommel and Reynolds, 2000; Rommel et al., 2001); the study by James and colleagues (1995) on the impulse conduction system in the sperm whale heart; the embryological examination by the Dutch anatomist van der Shoot on the fetal development of the cetacean gubernaculum (1995); work by the Spanish team of Calzada and Aguilar on the development of the flipper in the striped dolphin (1996); the description of the heart of the fetal bowhead whale by Tarpley and colleagues (1997); the extensive, magnetic resonance imaging analyses of whale brains, and interpretations of how they got to be so intricate, by Marino and colleagues (Marino et al., 2001, 2004a, b; Ridgeway et al., 2002); the detailed examination of the muscles of the eye of the bowhead whale by Zhu and colleagues (2000); the immunohistochemical analysis of immune cells in the skin of the Atlantic bottlenose dolphin by Zabka and Romano (2003); assessments of neocortical cell numbers in the mysticete brain by the Danish team of Eriksen and Pakkenberg (2007); and the recently published, extraordinarily insightful and probing studies on the complexity of the whale brain cortex, and how the cells therein may have evolved, by Hof and coworkers (2005; Hof and Van der Gucht, 2007).

As evidenced from the luminaries and probing science in the partial list above, The Anatomical Record has long been, and, continues to be, a prime forum for the communication of new findings and challenging hypotheses on the anatomy, physiology, and evolution of our aquatic kin. This special issue is a most appropriate torch to carry this tradition proudly into our journal's second century.