Gut microbiomes are important determinants of animal health. In sentinel marine mammals where animal and ocean health are connected, microbiome impacts can scale to ecosystem-level importance. Mass mortality events affect cetacean populations worldwide, yet little is known about the contributory role of their gut bacterial communities to disease susceptibility and progression.
View Article and Find Full Text PDFToothed whales utilize specialized nasal structures such as the lipid-rich melon to produce sound and propagate it into the aquatic environment. Very little nasal morphology of mesoplodont beaked whales has been described in the literature, and the anatomy of the melon and associated musculature of Gervais' beaked whale (Mesoplodon europaeus) remains undescribed. Heads of three (n = 3) Gervais' beaked whales were examined in detail via dissection as well as computed tomography (CT) and magnetic resonance imaging (MRI).
View Article and Find Full Text PDFOdontocete cetaceans have undergone profound modifications to their integument and sensory systems and are generally thought to lack specialized exocrine glands that in terrestrial mammals function to produce chemical signals (Thewissen & Nummela, 2008). Keenan-Bateman et al. (2016, 2018), though, introduced an enigmatic exocrine gland, associated with the false gill slit pigmentation pattern in Kogia breviceps.
View Article and Find Full Text PDFThe cetacean vertebral canal houses the spinal cord and arterial supply to and venous drainage from the entire central nervous system (CNS). Thus, unlike terrestrial mammals, the cetacean spinal cord lies within a highly vascularized space. We compared spinal cord size and vascular volumes within the vertebral canal across a sample of shallow and deep diving odontocetes.
View Article and Find Full Text PDFMarine mammals are exposed to O-limitation and increased N gas concentrations as they dive to exploit habitat and food resources. The lipid-rich tissues (blubber, acoustic, neural) are of particular concern as N is five times more soluble in lipid than in blood or muscle, creating body compartments that can become N saturated, possibly leading to gas emboli upon surfacing. We characterized lipids in the neural tissues of marine mammals to determine whether they have similar lipid profiles compared to terrestrial mammals.
View Article and Find Full Text PDFWhaling has decimated North Atlantic right whales Eubalaena glacialis (NARW) since the 11th century and southern right whales E. australis (SRW) since the 19th century. Today, NARWs are Critically Endangered and decreasing, whereas SRWs are recovering.
View Article and Find Full Text PDFCompared with terrestrial mammals, marine mammals possess increased muscle myoglobin concentrations (Mb concentration, g Mb · 100g muscle), enhancing their onboard oxygen (O) stores and their aerobic dive limit. Although myoglobin is not homogeneously distributed, cetacean muscle O stores have been often determined by measuring Mb concentration from a single muscle sample () and multiplying that value by the animal's locomotor muscle or total muscle mass. This study serves to determine the accuracy of previous cetacean muscle O stores calculations.
View Article and Find Full Text PDFOn March 2, 2005 ~70 rough-toothed dolphins () mass stranded along mud flats and associated canals on the Atlantic Ocean side of Marathon Key, Florida. Forty-six were necropsied and placed into two groups for analysis: Group-1 animals ( = 34; 65%) that died prior to medical intervention and rehabilitative efforts and Group-2 animals ( = 12; 35%) that died in rehabilitation. Thirty-four animals were females (18 adults, 5 juvenile/subadult, 7 calves, and 4 of undetermined age) and 12 were males (6 adults, 4 juvenile/subadults, 1 calf, and 1 of undetermined age).
View Article and Find Full Text PDFGut microbiomes perform crucial roles in host health and development, but few studies have explored cetacean microbiomes especially deep divers. We characterized the gut microbiomes of stranded dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales to examine the effects of phylogeny and life stage on microbiome composition and diversity.
View Article and Find Full Text PDFThe locomotor muscle morphology of diving mammals yields insights into how they utilize their environment and partition resources. This study examined a primary locomotor muscle, the longissimus, in three closely related, similarly sized pelagic delphinids (n = 7-9 adults of each species) that exhibit different habitat and depth preferences. The Atlantic spotted dolphin (Stenella frontalis) is a relatively shallow diver, inhabiting continental shelf waters; the striped (Stenella coeruleoalba) and short-beaked common (Delphinus delphis) dolphins are sympatric, deep-water species that dive to different depths.
View Article and Find Full Text PDFA sphincter on the inferior vena cava can protect the heart of a diving mammal from overload when elevated abdominal pressures increase venous return, yet sphincters are reported incompetent or absent in some cetacean species. We previously hypothesized that abdominal pressures are elevated and pulsatile in fluking cetaceans, and that collagen is deposited on the diaphragm according to pressure levels to resist deformation. Here, we tested the hypothesis that cetaceans generating high abdominal pressures need a more robust sphincter than those generating low pressures.
View Article and Find Full Text PDFFlorida manatees (Trichechus manatus latirostris) possess an unusual suite of adaptations to accommodate both a fully aquatic lifestyle and an herbivorous diet, including a low metabolic rate and a very limited thermoneutral zone. Their relatively high lower critical temperature of around 20 °C suggests strong sensitivity to cold, thereby limiting their distribution to tropical and subtropical waters. "Cold stress syndrome" affects and kills Florida manatees every year during intense or prolonged cold weather, posing one of the major threats to manatees.
View Article and Find Full Text PDFThe giant (>3 m) parasitic nematode Crassicauda magna infects kogiid whales, although only 3 studies to date have provided detailed descriptions of these worms, all based upon fragmented specimens. These fragments were found within the neck region of kogiids, an unusual anatomic site for this genus of parasites. C.
View Article and Find Full Text PDFInternal pressures change throughout a cetacean's body during swimming or diving, and uneven pressures between the thoracic and abdominal compartments can affect the cardiovascular system. Pressure differentials could arise from ventral compression on each fluke downstroke or by a faster equilibration of the abdominal compartment with changing ambient ocean pressures compared with the thoracic compartment. If significant pressure differentials do develop, we would expect the morphology of the diaphragm to adapt to its loading.
View Article and Find Full Text PDFMammals host diverse bacterial and archaeal symbiont communities (i.e. microbiomes) that play important roles in digestive and immune system functioning, yet cetacean microbiomes remain largely unexplored, in part due to sample collection difficulties.
View Article and Find Full Text PDFMesoplodont beaked whales are extreme divers, diving for over 45 mins and to depths of over 800 m. These dives are of similar depth and duration to those of the giant sperm whale (Physeter macrocephalus) whose body mass can be 50 times larger. Velten et al.
View Article and Find Full Text PDFAn unusual mortality event (UME) involving primarily common bottlenose dolphins Tursiops truncatus of all size classes stranding along coastal Louisiana, Mississippi, and Alabama, USA, started in early 2010 and continued into 2014. During this northern Gulf of Mexico UME, a distinct cluster of perinatal dolphins (total body length <115 cm) stranded in Mississippi and Alabama during 2011. The proportion of annual dolphin strandings that were perinates between 2009 and 2013 were compared to baseline strandings (2000-2005).
View Article and Find Full Text PDFCetaceans are protected worldwide but vulnerable to incidental harm from an expanding array of human activities at sea. Managing potential hazards to these highly-mobile populations increasingly requires a detailed understanding of their seasonal distributions and habitats. Pursuant to the urgent need for this knowledge for the U.
View Article and Find Full Text PDFOdontocete echolocation clicks are generated by pneumatically driven phonic lips within the nasal passage, and propagated through specialized structures within the forehead. This study investigated the highly derived echolocation structures of the pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales through careful dissections (N = 18 K.
View Article and Find Full Text PDFIn 1940, Scholander suggested that stiffened upper airways remained open and received air from highly compressible alveoli during marine mammal diving. There are few data available on the structural and functional adaptations of the marine mammal respiratory system. The aim of this research was to investigate the anatomical (gross) and structural (compliance) characteristics of excised marine mammal tracheas.
View Article and Find Full Text PDFEuthanasia of stranded large whales poses logistic, safety, pharmaceutical, delivery, public relations, and disposal challenges. Reasonable arguments may be made for allowing a stranded whale to expire naturally. However, slow cardiovascular collapse from gravitational effects outside of neutral buoyancy, often combined with severely debilitating conditions, motivate humane efforts to end the animal's suffering.
View Article and Find Full Text PDFBlubber has been used for decades to monitor exposure of marine mammals to persistent organic pollutants (POPs). However, little is known about POP variability as a function of blubber depth and across the body of the animal. Remote blubber biopsy sampling (e.
View Article and Find Full Text PDFPost-mortem examination of dead and live stranded beach-cast pinnipeds and cetaceans for determination of a cause of death provides valuable information for the management, mitigation and prosecution of unintentional and sometimes malicious human impacts, such as vessel collision, fishing gear entanglement and gunshot. Delayed discovery, inaccessibility, logistics, human safety concerns, and weather make these events challenging. Over the past 3 decades, in response to public concern and federal and state or provincial regulations mandating such investigations to inform mitigation efforts, there has been an increasing effort to objectively and systematically investigate these strandings from a diagnostic and forensic perspective.
View Article and Find Full Text PDFWhen a marine mammal dives, breathing and locomotion are mechanically uncoupled, and its locomotor muscle must power swimming when oxygen is limited. The morphology of that muscle provides insight into both its oxygen storage capacity and its rate of oxygen consumption. This study investigated the m.
View Article and Find Full Text PDFUnited States and Canadian governments have responded to legal requirements to reduce human-induced whale mortality via vessel strikes and entanglement in fishing gear by implementing a suite of regulatory actions. We analyzed the spatial and temporal patterns of mortality of large whales in the Northwest Atlantic (23.5°N to 48.
View Article and Find Full Text PDF