From specialized skin to sensing whiskers to unique depth perception mechanisms to novel eyes and much, much more: The distinctive ways marine mammals interact with their world are explored in a Special Issue of the The Anatomical Record.

Abstract

The two authors of this editorial adore animals and have together watched many of them across the globe. We have seen huge bison in Yellowstone Park; magnificent moose and bouncing bears in the Grand Tetons; soaring eagles over the Moab landscape; prancing Belgian horses in, well, Belgium; happy (for a while) Iberian pigs in Seville; water buffalo and pandas in China; capybaras in Brazil; to kiwi, and even minuscule, glittering glow worms in New Zealand caves. We particularly watched with great glee (at least KA as JL was leaning over the rails most of the time) orcas off the coast of Vancouver. While being enthralled with all of nature's family, we usually observe them from the safety and security of dry land (or an occasional boat, unfortunately for JL); one of us (guess who?) is definitely not a “get in the water” type. KA, however, has splashed in the water with California gray whales, manatees in Florida, got caught in a giant, moving cloud of manta rays off the Great Barrier reef, and even stepped on a wobbegong shark! JL, on the other foot, has braved a few steps into the shallow Great Salt Lake, and hugged an old manatee or two, but that is about it. While we enjoy watching, and learning about, our marine friends from a distance, there are many water-enjoying (and stouter!) colleagues who spend a good amount of their lives in, or close to, the sea itself becoming intimate with its inhabitants. These hearty souls—and they are indeed strong of spirit and usually muscle as well as it is not easy to explore the world of marine animals up close—have brought much of their hidden world, particularly of our cousins, the marine mammals, nearer to the surface. As combination sea-explorers and anatomist/biologists, this pod of observer/scientists are providing extraordinary insight into the anatomy, physiology, and ethology that allows for the unique interface of marine mammals with their world. This Special Issue, “Marine Mammal Sensory Systems” is derived from a workshop entitled “Sensory Ecology in Marine Mammals” held as part of the World Marine Mammal Science Conference held in Barcelona, Spain, in pre-Covid 2019 (another world!). The workshop was planned, organized, and shepherded by Sherri Eldridge (Figure 1) with the assistance of Joy Reidenberg of the Icahn School of Medicine at Mount Sinai in New York and Frederike Hanke of the University of Rostock, Germany (Reidenberg & Hanke, 2022). Most tragically, Sherri died some months after the Symposium and during the write up phase of the manuscripts. JL was fortunate to meet and work with Sherri when The Anatomical Record served as a sponsor for the Workshop, its events, and planning for the segue to this Special Issue. To those of us who knew her, Sherri was a fascinating and ebullient “energizer” who added warmth, excitement, and enthusiasm to every encounter. She was actually a late arrival to the world of marine mammalogy, having only recently finished her PhD in 2018. Sherri was a Guest Investigator at The Woods Hole Oceanographic Institution at the time of her death, working in the laboratory of noted scientist Michael Moore under a recently received National Science Foundation Postdoctoral Research Fellowship. Prior to answering the lure of the sea, Sherri was an internationally acclaimed chef and cookbook author, having written over 30 well-known books (including one of JL's favorites, The New Americana Cookbook: A Heart-Healthy Excursion Through Regional Cuisines; Eldridge, 1997). She was, indeed, a Renaissance person of enormous depth; our world is much saddened by her absence. After Sherri's death, and as a tribute to her work and memory, her colleagues, Joy Reidenberg and Frederike Henke, took up the mantle of Guest Editing this Special Issue, and for that we are most grateful. A few words about them are in order. First, the new member of our Anatomical Record family, Professor Frederike Hanke is from the Institute of Biosciences, Neuroethology, of the University of Rostock. Professor Hanke is one really impressive scientist. Her interests are broad, yet revolve around her fascination with animals and their behaviors, specifically from the vantage point of understanding the intersection of vision and orientation in navigation in seals and cephalopods (do you know what the latter are…? word means “head foot” and relates to squid, octopuses, cuttlefish, and nautiluses). Along her path, she has studied everything from diminutive honeybees to sizeable bears and has spent considerable time braving the waters of the cold North Sea (see, e.g., Heinrich et al., 2020; Soto et al., 2020). Welcome onboard Professor Henke! Our second Co-Guest Editor is Joy Reidenberg, who is a frequent swimmer in the pages of The Anatomical Record and has published with us regularly (see below). Joy—we both know her too well for academic distance—is, like her brilliant colleagues above, also a “Renaissance” scientist/scholar/adventurer (you can see her often on television in series such as “Inside Nature's Giants”, Dance, 2009–2012; she has even recently illustrated a children's book on whales; Sieswerda & Reidenberg, 2021). She is a consummate comparative anatomist, with her prime items of desire being marine mammals, particularly cetaceans. Joy has literally grown up in our journal (Joy was JL's first graduate student, and they have been comparative anatomy sleuths together for years; indeed, her penchant for bringing rather large whales into their labs at Mount Sinai has had poor JL, the Center's Director, called to the Dean's office many a time!). Joy and KA share much in common as well, both enjoying communing with nature and its animal world and both in tormenting JL by their constant instructions to him about how to interact with animals in the wild. KA, for example, has delighted in telling JL (who is much the gullible city boy) how he should try to feed the bison at Yellowstone (KA's wife saved JL; KA was punished!), or what to do when approached by a male moose (JL did not leave the car for 2 days!). Joy, similarly, instructed JL some years back—just before he went swimming in the Gulf of Mexico—that she had seen sharks there during her morning swim and lectured him in detail on how to tell the difference between a shark's dorsal fin and that of a dolphin should he encounter such. If that failed, she gave added instructions on how JL should hit the shark squarely in the face when approached (JL went to the pool instead and has never swum in the Gulf). This wonderful Special Issue is a continuation of The Anatomical Record's long and proud tradition of publishing reports on the anatomy and function of marine mammals and how they interact with their world. Indeed, research published in our journal on our watery relatives goes back almost a hundred years, to work by Chinese anatomist Chi Ping who described the visceral anatomy of the then, poorly documented, porpoise (Ping, 1926a, 1926b); and, shortly thereafter, on the lungs and hypophysis of the porpoise by the renowned comparative anatomist George S. Wislocki, Professor and Chair of Anatomy at Harvard Medical School, and an enormous influence on the anatomical sciences sensu lato (Wislocki, 1940, 1942; Wislocki & Geiling, 1936). Detailing the sea of subsequent studies appearing in The Anatomical Record would entail a volume of its own; however, insight into the enormity of sea-going science appearing in our journal can be gleaned by reviewing some of the outstanding Special and Thematic Paper Issues on the topic in recent years. Most notably in this group is the now classic Special Issue, Guest Edited by the above comparative anatomist (and JL torturer) Joy Reidenberg, entitled “Anatomical Adaptations of Aquatic Mammals” that presented studies on the anatomy, evolution, and behavior of aquatic mammals ranging from manatees and dugongs to whales of all ilks (see Laitman, 2007; Laitman & Albertine, 2007; Reidenberg, 2007). This Special Issue contained many insights into the distinctive anatomy that has come to be that allows interaction with a watery environment. Some of particular note are: the studies by Mass and Suppin (2007) on the adaptive features of an aquatic mammal's eye; insights into the evolution of hearing in whales by Nummela et al. (2007); distinctiveness of the cetacean brain by Marino (2007); and the discovery underlying a low frequency sound source in mysticetes (baleen whales) by Reidenberg and Laitman (2007). The next collection of papers exploring the specialized anatomy of aquatic forms came as the result of a stranding of a rare gray whale calf off a California beach near San Diego in 2012. Due to the fortuitous occurrence of that year's American Association for Anatomy (AAA) Meeting being held at that time in San Diego, a ready and eager pod of anatomists was available to explore the anatomy of this individual and immediately left the meetings to take the opportunity (JL, as sitting President of the Association, was not allowed to go with the others by then Executive Director of the AAA; everyone got to explore a great opportunity from nature's bounty while JL presided over sessions and did budgets!). The observations from this opportunity, and subsequent dissections, appeared as a Thematic Papers Issue entitled “Anatomical Investigations of the California Gray Whale,” Guest Edited by Eric Ekdale of San Diego State University (Berta et al., 2015; Laitman, 2015; Laitman & Albertine, 2015). The occasion of The Anatomical Record's Board Meeting being held in the incomparable city of Vancouver, Canada, in July of 2017 afforded an opportunity to both explore the anatomy and ethology of nearby whales (and other extraordinary animals on land and in air). The results appeared in a Thematic Papers Issue entitled “North American Pacific Coastal Whales,” Guest Edited by noted anatomist A. Wayne Vogl of the University of British Columbia (Albertine et al., 2017; Vogl, 2017). Many of the nautical observations were afforded by a whale encounter that gave most (JL had a different view) the chance to see magnificent orcas in the Strait of Georgia off Vancouver Island. (Comment by JL, turn away KA: For the record, it should be noted that KA—who is a fine photographer who is not allowed to display his photographs in his home, long story—profusely illustrated his above article, including photos from his granddaughter, but has refused to allow JL to publish his closeup wildlife photography! Comment by KA: JL's “wildlife” was of a “stuffed” bear in Yellowstone!) Yet another opportunity to explore and gain insight into the interface of anatomy and the aquatic world arose out of a unique conference in May of 2016 funded in part by The Anatomical Record and held in an institution not usually associated with active whale biology: the Icahn School of Medicine at Mount Sinai in the middle of Manhattan, the home base for Joy Reidenberg and JL. Some 50 comparative anatomists, whale biologists, brain, and upper respiratory tract experts, converged for 2 days of in-depth presentations, discussions, and dissections of the extraordinary collection of material housed at the Center for Anatomy and Functional Morphology. Thanks to Joy's ever enthusiastic collecting (and JL's ability to explain to the deans that any odors were not related to his center) a large sample of many cetaceans, including (rather difficult to house) mysticetes, were housed. This extraordinary conference resulted in a Thematic Papers Issue entitled “Mysticete anatomy and evolution,” Guest Edited by our ever-energetic Joy Reidenberg (Laitman & Albertine, 2019; Reidenberg, 2019). Notable among some of the insights in this issue were observations on features of how marine mammal lungs respond to underwater blast dynamics (Fetherston et al., 2019); detailed comparative study of the semiaquatic moose nasal complex and how this sheds light on the evolution of ancestral cetaceans (Marquez et al., 2019); and a comparison of the nostrils in the hippopotamus and mysticetes as a means to understand both their function and evolutionary relationships (Maust-Mohl et al., 2019). (This meeting was very successful in decanting JL's cold rooms and freezers of considerable material; you-know-who has already restocked them!) While the above recounting gives some insight into the extensive history of publications on aquatic and marine mammals, it should be noted that The Anatomical Record has also extensively investigated the other part of this special issue, the mechanisms by which mammals sense their environment. This has been a thread weaving through our journal both by focused Special Issues and independent reports. Some examples of the former can be found in: the Special Issue, “Evolution of the Special Senses in Primates,” Guest Edited by expert comparative anatomists Nathanial Dominy and Callum Ross, both of the University of Chicago, and our own Associate Editor, Tim Smith (who doubles as a magnificent artist whose work has often graced our covers) of Slippery Rock University (Dominy et al., 2004; Laitman, 2004); a most sweet-smelling Special Issue on “The Vertebrate Nose: Evolution, Structure, and Function,” Guest Edited by frequent contributors Blaire Van Valkenburgh of the University of California, Los Angeles, Brett Craven of Pennsylvania State University, and that Timothy Smith fellow again (Laitman, 2014; Laitman & Albertine, 2014; Van Valkenburgh et al., 2014); and two extraordinary Special Issues loudly broadcasting cutting-edge science exploring balance, hearing, and olfaction: “The Anatomy and Biology of Hearing and Balance: Cochlear and Vestibular Implants” and “Novel Stem Cell and Gene Therapies for Hearing, Balance and Olfaction,” both Guest Edited by anatomist extraordinaire and long-time contributor and supporter of the journal, Thomas Van De Water, now Professor Emeritus of the University of Miami Miller School of Medicine (Laitman, 2012; Laitman & Albertine, 2012, 2020; Van De Water, 2012, 2020). While we land mammals get the lion's share of biological attention (we do control the press!), the fact remains that over 70% of our planet is covered by water and some 95% of that in the realms of the great oceans and seas. And living therein are a host of mammalian relatives that we know relatively little about. Indeed, there are likely many more species of aquatic animals, including our mammalian kin, that we have not as yet even met. While learning about how mammals interact with their world is, of course, of fascinating zoological and ethnological interest, it is also an imperative in our world today. Environmental abuse and global warming are tsunamis of destruction that put so many species at perpetual risk. Our oceans and seas are becoming polluted both by human detritus and the effects of increasing traffic and sound assault. It is, in the end, our responsibility as guardians of the future of our home, to understand how aquatic beings interact with their world via unique adaptations so that we may understand more fully the damage that we do. It is toward furthering this important acquisition of knowledge that this Special Issue of The Anatomical Record is devoted. We hope that the studies within will both enhance your understanding of our marine cousins and inspire your efforts to care and protect their future (Figure 2).