Composition of the milks of the bottlenose dolphin (Tursiops trucatus) and the Florida manatee (Trichechus manatus latirostris)

Milk samples from four individual bottlenose (Tursiops truncatus) and two Florida manatees (Trichechus manatus latirostris) of known lactation stages were analyzed for protein, carbohydrate and lipid composition, as well as for activity levels of alpha-lactalbumin, the regulatory protein of lactose synthase. The milk from both species had relatively high protein and lipid levels, as reported previously for other marine mammals. The major proportion of the lipid was in the form of triglycerides. Dolphin milk contained an average of 2.2% neutral sugars, which was essentially all in the form of lactose, as determined by several criteria. Manatee milk samples contained 0.6% of neutral sugars, and a larger proportion (about 2%) of amino sugars. Lactose was not detected by enzymatic assay or paper chromatography, but HPLC analysis indicated the presence of low levels of lactose together with two components that were tentatively identified as oligosaccharides. alpha-Lactalbumin activity, determined by assay with bovine galactosyltransferase, was found in both dolphin and manatee milk. The level in dolphin milk was comparable with that found in bovine and other milk, but the level in the manatee was less than 10% of that in the dolphin.     

Anatomy and physics of the exceptional sensitivity of dolphin hearing (Odontoceti: Cetacea)

During the past 50 years, the high acoustic sensitivity and the echolocation behavior of dolphins and other small odontocetes have been studied thoroughly. However, understanding has been scarce as to how the dolphin cochlea is stimulated by high frequency echoes, and likewise regarding the ear mechanics affecting dolphin audiograms. The characteristic impedance of mammalian soft tissues is similar to that of water, and thus no radical refractions of sound, nor reflections of sound, can be expected at the water/soft tissue interfaces. Consequently, a sound-collecting terrestrial pinna and an outer ear canal serve little purpose in underwater hearing. Additionally, compared to terrestrial mammals whose middle ear performs an impedance match from air to the cochlea, the impedance match performed by the odontocete middle ear needs to be reversed to perform an opposite match from water to the cochlea. In this paper, we discuss anatomical adaptations of dolphins: a lower jaw collecting sound, thus replacing the terrestrial outer ear pinna, and a thin and large tympanic bone plate replacing the tympanic membrane of terrestrial mammals. The paper describes the lower jaw anatomy and hypothetical middle ear mechanisms explaining both the high sensitivity and the converted acoustic impedance match.     

Enamel Ultrastructure in Fossil Cetaceans (Cetacea: Archaeoceti and Odontoceti)

The transition from terrestrial ancestry to a fully pelagic life profoundly altered the body systems of cetaceans, with extreme morphological changes in the skull and feeding apparatus. The Oligocene Epoch was a crucial time in the evolution of cetaceans when the ancestors of modern whales and dolphins (Neoceti) underwent major diversification, but details of dental structure and evolution are poorly known for the archaeocete-neocete transition. We report the morphology of teeth and ultrastructure of enamel in archaeocetes, and fossil platanistoids and delphinoids, ranging from late Oligocene (Waitaki Valley, New Zealand) to Pliocene (Caldera, Chile). Teeth were embedded in epoxy resin, sectioned in cross and longitudinal planes, polished, etched, and coated with gold palladium for scanning electron microscopy (SEM) observation. SEM images showed that in archaeocetes, squalodontids and Prosqualodon (taxa with heterodont and nonpolydont/limited polydont teeth), the inner enamel was organized in Hunter-Schreger bands (HSB) with an outer layer of radial enamel. This is a common pattern in most large-bodied mammals and it is regarded as a biomechanical adaptation related to food processing and crack resistance. Fossil Otekaikea sp. and delphinoids, which were polydont and homodont, showed a simpler structure, with inner radial and outer prismless enamel. Radial enamel is regarded as more wear-resistant and has been retained in several mammalian taxa in which opposing tooth surfaces slide over each other. These observations suggest that the transition from a heterodont and nonpolydont/limited polydont dentition in archaeocetes and early odontocetes, to homodont and polydont teeth in crownward odontocetes, was also linked to a marked simplification in the enamel Schmelzmuster. These patterns probably reflect functional shifts in food processing from shear-and-mastication in archaeocetes and early odontocetes, to pierce-and-grasp occlusion in crownward odontocetes, with the implication of less demanding feeding biomechanics as seen in most extant odontocetes.     

Prenatal development of the integument in Delphinidae (Cetacea: Odontoceti)

The prenatal development of epidermis, dermis, and hypodermis was studied in embryos of different ago of two delphinid species (Stenella attenuata, Delphinus delphis), using light and transmission electron microscopical methods. The delphinid embryo is covered by a multilayered tissue formed by four different epidermal generations (periderm, stratum intermedium-I, str. intermedium-II, str. spinosum) produced by the str. basale. The first layer appears at about 40–50 mm of body length, the second type (s.i.-I) about 60–160 mm, and the third type (s.i.-II) is present at 160–500 mm. The first spinosal cells are produced at 225–260 mm body length; thenceforth, the epidermis increases continuously in thickness. Epidermal ridge formation begins about 400–mm body length. The development of the dermis is characterized by the early production of thin connective tissue fibers (40- 70-mm body length) and simultaneously the cutaneuous muscle matures in structure. Vascular development intensifies between embryos of 150–225 mm, and collagen production increases markedly in fetuses of 225–260-mm length. These events are paralledled by an increase in dermal thickness. The first elastic fibers can be recognized in the skin from the abdomen at about 600-mm body length. The development of the hypodermis is marked by very rapid and constantly progressing growth, beginning about 60-mm body length. The first typical fat cells appear in animals of 360–400 mm. Regional differences are obvious for all skin layers with regard to the flippers, where structural maturation proceeds more rapidly than in dorsal or abdominal regions. © 1995 Wiley-Liss, Inc.     

Evolution of cranial telescoping in echolocating whales (Cetacea: Odontoceti)

Odontocete (echolocating whale) skulls exhibit extreme posterior displacement and overlapping of facial bones, here referred to as retrograde cranial telescoping. To examine retrograde cranial telescoping across 40 million years of whale evolution, we collected 3D scans of whale skulls spanning odontocete evolution. We used a sliding semilandmark morphometric approach with Procrustes superimposition and PCA to capture and describe the morphological variation present in the facial region, followed by Ancestral Character State Reconstruction (ACSR) and evolutionary model fitting on significant components to determine how retrograde cranial telescoping evolved. The first PC score explains the majority of variation associated with telescoping and reflects the posterior migration of the external nares and premaxilla alongside expansion of the maxilla and frontal. The earliest diverging fossil odontocetes were found to exhibit a lesser degree of cranial telescoping than later diverging but contemporary whale taxa. Major shifts in PC scores and centroid size are identified at the base of Odontoceti, and early burst and punctuated equilibrium models best fit the evolution of retrograde telescoping. This indicates that the Oligocene was a period of unusually high diversity and evolution in whale skull morphology, with little subsequent evolution in telescoping.     

Purification and characterization of the major whey proteins from the milks of the bottlenose dolphin (Tursiops truncatus), the Florida manatee (Trichechus manatus latirostris), and the beagle (Canis familiaris)

The major whey proteins of the milks of the dolphin, manatee, and beagle were purified by gel filtration and ion exchange chromatography and characterized and identified by molecular weight determination, amino acid analysis, N-terminal sequencing, and activity measurements. The major whey protein components from all three species were found to be monomeric beta-lactoglobulins. These proteins were all active in binding retinol. Dolphin milk contained two beta-lactoglobulins (designated 1 and 2) which showed a slight difference in molecular weight and considerably divergent N-terminal sequences, whereas the other milks only contained a single form of beta-lactoglobulin. alpha-Lactalbumins were purified from dolphin and dog milks and were active in promoting lactose synthesis by bovine galactosyltransferase. The dolphin protein had an N-terminal sequence more similar to ruminant alpha-lactalbumins than to those known from other species. Although alpha-lactalbumin activity has been detected in manatee milk at low levels, the corresponding protein was not isolated. In addition, dog milk was found to contain high levels of lysozyme (greater than 1.0 mg/ml), which were identified by activity and sequencing. The functional and evolutionary implications of these results are discussed.     

Auditory evoked potentials in the West Indian manatee (Sirenia:Trichechus manatus)

Summary Potentials evoked by clicks and tone pips were recorded by fine wires inserted extracranially in four West Indian manatees (Trichechus manatus) in air. Sounds were delivered via padded ear phones.Averaging a few thousand trials at 20/s reveals early peaks at N5.4 (vertex negativity to a frontal reference, at 5.4 ms), P7.6, N8.8, P9.5 — probably equivalent to waves IV and VII of the typical mammalian auditory brainstem response (ABR). Averaging 100 trials at <4/s suffices to reveal a complex sequence of later peaks including N25, P80, N150 and P190; consistent smaller peaks are visible when several hundred trials are averaged.Using tone pips with a rise and fall time of 2–5 ms the carrier frequency becomes important. Evoked potential wave forms are not the same at different frequencies, bringing out the fact that frequency is not a scalar that can be compensated for by intensity. Therefore the method was not used to obtain audiograms; however the largest EPs occur in the range of 1–1.5 kHz. EPs are found up to 35 kHz; almost no evoked potential is discernible at 40 kHz but the undistorted intensity available was limited. This is in reasonable agreement with the theoretical expectation for the upper limit of behavioral hearing from Heffner and Masterton based on head size and aquatic medium.Among several ear phone placements, that over the external auditory meatus was the most effective, but only slightly so. The external canal is presumably fluid or tissue filled and sound enters over a large area.Comparing data for two species on the most effective range of frequencies and the power spectra of their vocalizations,T. manatus is lower thanT. inunguis in both respects.The results show the utility and limitations of the method of recording extracranial evoked potentials to sounds, especially for large and valuable animals under makeshift conditions.Abbreviations ABR auditory brainstem response - AEP averaged evoked potentials - EMG electromyogram - F frontal sinuses - V vertex     

Erythropoiesis and granulopoiesis in the West Indian manatee, Trichechus manatus (Mammalia: Sirenia)

The West Indian manatee, Trichechus manatus, has amedullary, pachyostotic long bones. Since marrow cavities of the long bones typically are the locations of hemopoiesis in adult mammals, the manatee has evolved an alternative primary site of hemopoiesis. Histological examinations of spleens, livers, kidneys, and vertebral bodies indicate that the last-named location is the main site of erythropoiesis and granulopoiesis in T. manatus. This conclusion is based on the presence in the vertebrae of bone-marrow-containing diagnostic cell types including erythroblasts, megakaryocytes, and myelocytes, which are the precursor cells of erythrocytes, platelets, and granular leukocytes, respectively. No developing lymphocytes were found, so that the location of lymphopoiesis remains unknown.     

The primary structure of the hemoglobin of the Brazilian manatee (Trichechus inunguis, Sirenia)

The hemoglobin of the Brazilian Manatee (Trichechus inunguis, Sirenia) consists of one component. We present the primary structures of the alpha- and beta-chains which have been separated by chromatography on carboxymethyl-cellulose CM-52. The sequences have been determined by automatic Edman degradation with the film technique, using the native chains, tryptic peptides and the C-terminal prolyl-peptide obtained by acid hydrolysis of the Asp-Pro bond of the alpha-chains. Compared to the corresponding human chains we found 27 substitutions in the alpha- as well as in the beta-chains. Three heme contacts and four alpha 1/beta 1 contacts between the subunits are affected by exchanges. The hemoglobin of Trichechus inunguis is compared with those of Elephas maximus, Loxodonta africana, and Procavia habessinica and the monophyletic origin of the superorder Paenungulata is discussed.     

The heart of the dugong (Dugong dugon) and the west indian manatee (Trichechus manatus) (Sirenia)

Thirty-eight dugong (Dugong dugon) hearts and 28 Florida manatee (Trichechus manatus) hearts were obtained from stranding programs in Australia and the United States. In addition to a double ventricular apex, a feature that has astonished scientists since the eighteenth century, the hearts of both animals have a double subvalvular conus and a dorsal left atrium. The heart lies in a vertical plane at right angles to that of the completely dorsal, symmetrical lungs. The dugong heart has a deeper interventricular cleft and a more conical left ventricle. The latter features may be part of a general morphological trend toward specialization for a more energetic aquatic existence. The presence of a bulbous ascending aorta in the manatee but not in the dugong is without explanation.     

Anatomy of the cecum of the West Indian manatee,Trichechus manatus (Mammalia,Sirenia)

Summary The anatomy of the cecum of the West Indian manatee (Trichechus manatus) is described at the macroscopic and microscopic levels. The cecum possesses a voluminous corpus ceci with two lateral outpocketings; two diverticulae (cecal horns) extend from the corpus at the vicinity of the ileocecal junction. An ampulla ceci is found distal to the corpus ceci, the two compartments communicating via a wide-opened orifice. The most striking microscopic finding is the mucosal covering of a keratinized stratified squamous epithelium overlying the crypts of Lieberkühn.An attempt is made to interpret the morphological observations in terms of the functional digestive process in the manatee, giving alternative suggestions concerning the significance of the cecum and colon in the nutritional status of the manatee.Abbreviations A Ampulla ceci - CC Corpus ceci - CH Cecal horns - I Ileum - C Colon The present investigation was supported by a grant from the Deutsche Forschungsgemeinschaft (La 325/7-1)The author is greatly indebted to the members of the Fish and Wildlife Service, Sirenia Project, Gainesville Station, Gainesville Florida: special thanks are extended to Dr. Thomas O'Shea for organizing this undertaking, to Cathy A. Beck and Robert K. Bonde for their generous hospitality, for allowing the author to participate in the salvaging project, which they carried out with great efficiency, and for help in collecting the material. Without this aid, this study could not have been completed     

Severe Karenia brevis red tides influence juvenile bottlenose dolphin (Tursiops truncatus) behavior in Sarasota Bay,Florida

Harmful algal blooms (HABs) are natural stressors in the coastal environment that may be increasing in frequency and severity. This study investigates whether severe red tide blooms, caused by Karenia brevis, affect the behavior of resident coastal bottlenose dolphins in Sarasota Bay, Florida through changes to juvenile dolphin activity budgets, ranging patterns, and social associations. Behavioral observations were conducted on free‐ranging juvenile dolphins during the summer months of 2005–2007, and behavior during red tide blooms was compared to periods of background K. brevis abundance. We also utilized dolphin group sighting data from 2004 to 2007 to obtain comparison information from before the most severe recent red tide of 2005 and incorporate social association information from adults in the study area. We found that coastal dolphins displayed a suite of behavioral changes associated with red tide blooms, including significantly altered activity budgets, increased sociality, and expanded ranging behavior. At present, we do not fully understand the mechanism behind these red tide‐associated behavioral effects, but they are most likely linked to underlying changes in resource availability and distribution. These behavioral changes have implications for more widespread population impacts, including increased susceptibility to disease outbreaks, which may contribute to unusual mortality events during HABs.     

Digesta passage rates in the Florida manatee (Trichechus manatus latirostris)

The Florida manatee, Trichechus manatus latirostris (Sirenia: Trichechidae), is an herbivorous marine mammal found within coastal areas throughout the state of Florida, which feeds on both fresh and salt water sea grasses. Manatees, like other Sirenians, are a tropical species with little tolerance for water temperatures below 20°C, rely on a relatively poor nutritional food source, and have a low metabolic rate. Although manatees are hindgut fermenting herbivores, they are very efficient at extracting nutrients from the plants on which they feed. Slow passage rates of digesta have been suggested to be a factor in this increased efficiency. Two studies monitored the digesta passage times and mixing of particulate digesta within the manatee digestive tract using MicroGrits colored corncob grit as a fecal marker. Fecal samples were collected subsequently from four manatees in Study 1 and 3 manatees in Study 2, grit pieces removed, counted, and measured. The digesta passage times ranged from 6 and 10 days in Study 1, and 4.3 and 8.3 days in Study 2, supporting data presented in previous studies. When two different colored markers were administered on sequential days, minimal to no mixing was seen in recovered feces, suggesting that the digesta from a given day traveled through the tract as a bolus. Less than 1% of the marker fed was recovered and we hypothesize that perpendicular folds of the large intestine may be the major contributing factor, with pieces being retained and eventually digested. Zoo Biol 26:503–515, 2007. © 2007 Wiley‐Liss, Inc.     

Conflicts with fisheries and intentional killing of freshwater dolphins (Cetacea: Odontoceti) in the Western Brazilian Amazon

We report three cases of conflicts with fishing activities of freshwater dolphins Inia geoffrensis and Sotalia fluviatilis in the Western Brazilian Amazon. The animals presented several cuts produced by perforating and cutting objects, especially on the dorsum, sides and flukes. The wounds were probably caused by harpoons and machetes, gear commonly used by local inhabitants for fishing and agricultural practices in the Amazon. The carcasses had not been subsequently used in any way, which suggests that the animals were not killed for consumption. Conflicts with fishermen and persistent cultural taboos may have led to the deaths. These records are an indication of a growing situation of conflict with fishing activities that should be taken into consideration in the conservation policy planning of aquatic mammals in the Amazon.     

Struvite calculus in the vagina of a bottlenose dolphin (Tursiops truncatus)

On 27 January 2000, a struvite calculus was observed in the vagina during necropsy of a 138-cm-long female bottlenose dolphin (Tursiops truncatus) collected from the Stono River, South Carolina (USA). Vaginal calculi have been reported in other species of cetaceans but not in bottlenose dolphins. Urinary tract infection might have been an underlying cause of the calculus. While urinary tract inflammation was not detected by light microscopic evaluation of sections of the urinary tract, it is conceivable that sufficient time had lapsed following voiding of the calculus through the urethra for urinary tract infection to have resolved. To further define the prevalence and significance of urolithiasis, prosectors of dead stranded marine mammals are encouraged to closely observe their urinary and genital tracts for calculi and to submit them for quantitative analysis.     

Conflict and reconciliation behavior trends of the bottlenose dolphin (Tursiops truncatus)

Wild bottlenose dolphin (Tursiops truncatus) populations display societal structures characterized by numerous and frequent changes in group composition, complex social relationships, and high levels of cooperation, attributes also observed in human and nonhuman primate cultures. Maintaining social relationships under such elemental conditions can frequently create conflict—and the opportunity for reconciliation—among group members. The conflict and reconciliation behavior patterns of the chimpanzee (Pan troglodytes) have been studied extensively; trends are well‐documented in the wild and in captivity. Apparent cultural similarities have prompted several analogous studies on wild and captive bottlenose dolphins. This research attempted to corroborate previous efforts by analyzing the social behavior of seven captive bottlenose dolphins to determine the effects of sex and age on the frequency of conflict and reconciliation, and to investigate the incidence of consolatory behavior within the group. A total of 3,428 interactions involving focal animals, 414 of which were conflict episodes, were documented during 261 hr of videotaped observations. Although the sample size precluded meaningful statistical evaluation of the influence of sex on conflict and reconciliation, participant age was a significant determinant of conflict frequency. Conversely, age did not impact frequency of reconciliation, which only occurred after 18% of all conflict interactions. Little to no definitive evidence of consolation was apparent within the study group. While results partially support the findings of previous dolphin reconciliation research, extensive behavioral studies of wild populations should be conducted before generating broad comparisons between human terms and nonhuman behavioral interactions. Zoo Biol 29:567–585, 2010. © 2009 Wiley‐Liss, Inc.     

Gross and microscopic anatomy of the kidney of the West Indian manatee, Trichechus manatus (Mammalia: Sirenia)

Examination of the gross and microscopic anatomy of the kidney of the West Indian manatee, Trichechus manatus, revealed that: (1) the medulla is about 6 times thicker than the cortex; (2) juxtamedullary glomeruli have a mean diameter 1.3 times greater than that of cortical glomeruli; (3) juxtamedullary glomeruli have 1.7 times as much volume as cortical glomeruli; (4) there are about twice as many cortical glomeruli as juxtamedullary glomeruli per square millimeter of cortical tissue, and (5) the vasa recta are closely juxtaposed to the thin loops of Henle in the outer medulla. Many of these results suggest an enhanced urine-concentrating ability in this species.