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PubMed1977

The fibrocartilage skeleton and related structures of the ventral pouch of balaenopterid whales.

The mandibular symphysis of rorqual whales, whales of the genera Megaptera and Balaenoptera, is characterized by a Y-shaped fibrocartilage structure that lies in the substance of the muscular ventral pouch of these animals. The stem of the structure joins with the symphysis and is usually indicated externally by an unfurrowed median strip of blubber that has been called the "cutwater" by earlier writers. The arms of the Y pass back and are superficially indicated in all rorqual whales as a ridge running parallel to the rami of the mandibles. This fibrocartilage skeleton of the pouch is most closely related to the mylohyoid muscle. The function of the fibrocartilage Y is probably linked with the jaw mechanics of these whales, but its precise function is otherwise not known.

Animals↗
PubMed1987

Anatomy of the heart of the beluga whale (Delphinapterus leucas).

The heart of the beluga whale (Delphinapterus leucas) is described from the dissection of seven specimens. As in most whales the heart is characterized by a transverse broadness and a flatness of the ventricles from one surface to the other and by an apex formed by both ventricles. Heart size parameters are used for comparison with parameters of other marine and land mammals. The heart width index (heart height/heart circumference) averages 31.3 in comparison to 28.7 for the Weddell seal and 39.0 for the felids. The right ventricle is relatively long and narrow with a mean length index (TS/heart height) of 64.7 and a mean breadth index (TP/heart height) of 38.7. These heart parameters are discussed in functional terms.

Animals↗
PubMed1988

Arterial and venous vasculature of the heart of the beluga whale (Delphinapterus leucas).

The arteries and veins of the heart of the beluga whale (Delphinapterus leucas) are described from the dissection of nine specimens. The arterial distribution is composed of the basic mammalian pattern of two major vessels, the left and right coronary arteries, which supply the cardiac tissue. The venous drainage is provided by three major systems which are the great, middle, and small cardiac veins. The vascular characteristics of the heart of the beluga whale are the marked sinuosity of both coronary arteries and their main branches, the numerous large interarterial anastomoses between major vessels, and the duplication of vessels in parallel branches. These characteristics are discussed in functional terms and correlated with the diving ability of the species.

Animals↗
PubMed1994

Noradrenergic and peptidergic innervation of lymphoid organs in the beluga, Delphinapterus leucas: an anatomical link between the nervous and immune systems.

The presence of peptidergic and noradrenergic sympathetic nerve fibers in specific compartments of both primary and secondary lymphoid organs of the rodent is well established. These nerve fibers directly contact lymphocytes and macrophages, as well as vascular and trabecular smooth muscle. We investigated the noradrenergic and neuropeptide-Y innervation of lymphoid organs in the cetacean, Delphinapterus leucas (beluga whale). The spleen, thymus, tonsil, gut-associated lymphoid tissue, and assorted lymph nodes were collected from five belugas, obtained during sanctioned hunts, and processed for catecholamine fluorescence histochemistry and for tyrosine hydroxylase and neuropeptide-Y immunocytochemistry. Innervation studies revealed fluorescent nerve fibers, tyrosine hydroxylase, and neuropeptide-Y positive nerve fibers in parenchymal lymphoid compartments, where they were closely associated with cells of the immune system, and in vascular and trabecular compartments. In lymphoid zones, tyrosine hydroxylase and neuropeptide-Y positive nerve fibers were observed in the periarteriolar lymphatic sheath and marginal zone of the spleen; in the outermost portion of the cortex, the corticomedullary zone, and medulla of the lymph nodes; in the parafollicular zones, and diffuse lymphocyte layer below the epithelium of the tonsil; in the outermost portion of some thymic lobules; and in the lamina propria of the gut. These findings are similar to those described for other mammals and substantiate an anatomical link between the nervous and immune systems in the beluga, whereby central nervous system activity may influence autonomic outflow to lymphoid organs and effect immunologic reactivity.

Animals↗
PubMed1994

Allometry of cetacean forelimb bones.

This study examines the allometric scaling relationships of the cetacean humerus, radius, and ulna. Bone lengths and diameters were measured for 20 species of odontocete and three species of mysticete cetaceans, representing eight of the nine extant cetacean families. The scaling of individual bone proportions (bone length vs. cranio-caudal diameter, bone length vs. dorso-ventral diameter), and of individual bone dimensions against estimated body mass, are compared to models of geometric and elastic similarity. The geometric similarity model describes the scaling relationship of bone length vs. cranio-caudal diameter and body mass vs. cranio-caudal diameter for the humerus only; geometric similarity also describes the scaling relationship of body mass vs. bone length for all three bones. None of the scaling relationships fits the elastic similarity model. The scaling relationships of bone length vs. dorso-ventral diameter for all three bones, and bone length vs. cranio-caudal diameter for the radius and ulna, exhibit negative allometry, indicating that large bones are less robust than small bones. Negative allometry of structural support elements has not been previously described for terrestrial mammals or plants. The high relative swimming speeds of small delphinids may generate sufficient stresses to require more robust bones relative to those of larger whales.

Animals↗
PubMed1995

A role for airborne particulates in high mercury levels of some cetaceans.

In a study of 25 Tursiops truncatus and two Globicephala macrorhynchus examined by necropsy, abundant HgSe was found in both the liver and in the respiratory system (lung and hilar lymph nodes). In the liver HgSe was consistently associated with the cell-breakdown pigment lipofuscin, whereas in lung and hilar lymph nodes it was consistently associated with particulates consisting of partially graphitic soot and silicates. This supports earlier suggestions that in the liver HgSe may be a storage end product of Hg metabolism, while adding the new suggestion that in the respiratory system HgSe may be inhaled, preformed in combustion emissions.

Air Pollutants↗
PubMed2001

Can diving-induced tissue nitrogen supersaturation increase the chance of acoustically driven bubble growth in marine mammals?

The potential for acoustically mediated causes of stranding in cetaceans (whales and dolphins) is of increasing concern given recent stranding events associated with anthropogenic acoustic activity. We examine a potentially debilitating non-auditory mechanism called rectified diffusion. Rectified diffusion causes gas bubble growth, which in an insonified animal may produce emboli, tissue separation and high, localized pressure in nervous tissue. Using the results of a dolphin dive study and a model of rectified diffusion for low-frequency exposure, we demonstrate that the diving behavior of cetaceans prior to an intense acoustic exposure may increase the chance of rectified diffusion. Specifically, deep diving and slow ascent/descent speed contributes to increased gas-tissue saturation, a condition that amplifies the likelihood of rectified diffusion. The depth of lung collapse limits nitrogen uptake per dive and the surface interval duration influences the amount of nitrogen washout from tissues between dives. Model results suggest that low-frequency rectified diffusion models need to be advanced, that the diving behavior of marine mammals of concern needs to be investigated to identify at-risk animals, and that more intensive studies of gas dynamics within diving marine mammals should be undertaken.

Animals↗
PubMed1996

Support for interordinal eutherian relationships with an emphasis on primates and their archontan relatives.

Current knowledge about mammalian interordinal relationships is growing rapidly; thus this contribution is an attempt to summarize the past 5 years of this literature. We have focused on the recent controversies in mammalian phylogenetics including hypotheses concerning the monophyly of Archonta, the diphyly of Chiroptera, and the polyphyly of Rodentia. All of these issues have been proposed recently, challenging these phylogenetic hypotheses. We have attempted to include all of the comprehensive analyses of eutherian mammal systematics with an emphasis on morphological and molecular data sets where discrete characters are listed so they could be compiled and used in support of interordinal relationships. Particular attention is given to determining which of the living eutherian orders is the closest relative to primates. In reviewing relationships among the mammals, we have focused on collating all of the available evidence so that one could know where each of the specific data sets is in support of the various relationships.

Animals↗
PubMed1996

Epidemiological analysis of persistent organochlorine contaminants in cetaceans.

Information is provided to test the hypothesis that organochlorines introduced into the environment since the early 1940s could threaten the reproductive potential of baleen whales and other cetaceans. Comparisons are made using data on the role of organochlorines in a model system, the Great Lakes region of North America, and in model animals, including humans, pinnipeds, and other wildlife. DDT and PCB are used as model organochlorines with the caveat that there may be thousands of other chemicals in the environment also involved. Improved sensitivity in analytical quantification of synthetic chemicals in biological tissue has been accompanied by an increase in knowledge about biochemical processes that control development and function. The effects described in this review are the result of disrupted gene expression, not damage to the gene. The mechanisms of action of the organochlorines reveal their ability to affect developing organisms at very low concentrations during critical life stages: embryonic, fetal, and early postnatal. Exposure during early development can disrupt the organization of the endocrine, reproductive, immune and nervous systems, effecting irreversible damage that may not be expressed until the individuals reach adulthood. The recent discovery that human sperm count is declining worldwide at a rate of 1 x 10(6) sperm/(mL.yr) suggests common exposure to estrogen-like chemicals during prenatal and early postnatal development. This raises concern for other top predator species that also share the same exposure. Periods of intense feeding followed by long periods of fasting are common among species of baleen whales. This unique strategy places the embryonic and nursing calves in vulnerable positions, because under both situations maternal blood levels are elevated as a result of absorption from food intake or as a result of mobilization as fat is metabolized. Estimates of Toxic Equivalents (TEQs) based on the occurrence of four PCB congeners (118, 183, 153, 180) in sigma PCB reported in whales are highest for St. Lawrence belugas and Faroe Island long-finned pilot whales. This conservative approach reveals that some whale species are within the range of enzyme-induced TEQs at which effects have been associated with adverse health effects in other aquatic species. The epidemiological approach was used for analysis because it was developed to handle multiple exposure scenarios in which direct causal links are virtually impossible to isolate. The analysis includes the tenets of timeorder, strength of association, specificity of cause and effect, consistency, coherence, and predictive performance.

Animals↗
PubMed1992

Evolution of the common cetacean highly repetitive DNA component and the systematic position of Orcaella brevirostris.

The common cetacean highly repetitive DNA component was analyzed with respect to its evolution and value for establishing phylogenetic relationships. The repeat length of the component, which is tandemly organized, is approximately 1750 bp in all cetaceans except the delphinids, in which the repeat length is approximately 1580 bp. The evolution of the component was studied after sequencing the component in different odontocetes representing the Delphinidae (delphinids), Monodontidae (narwhals), and Ziphiidae (beaked whales). The evolution of this component is very slow, and comparisons showed that sequence divergence among species corresponds closely to their generally accepted phylogenetic relationships and that the component evolves in a concerted manner. The phylogenetic information obtained in this study identified the Irrawaddy dolphin (Orcaella brevirostris) as a delphinid and did not support a close relationship of this species with the Monodontidae.

Animals↗
PubMed1993

The sequence-immunology correlation revisited: data for cetacean myoglobins and mammalian lysozymes.

Quantitative microcomplement fixation tests employing rabbit antisera were done to compare immunologically 13 cetacean myoglobins and 15 mammalian lysozymes c of known amino acid sequence. In both cases there was a strong correlation between immunological distance (y) and percent sequence difference (x), as had been found for several other globular proteins. For myoglobin the relationship could be described by y = 10.5x and for lysozyme by y = 8.5x. The coefficients in both of these equations are appreciably higher than the values of 5.1-6.9 reported for three other vertebrate globular proteins (bird lysozyme c, mammalian ribonuclease, and mammalian serum albumin), and they imply that rabbit antisera to mammalian myoglobins and lysozymes are more sensitive to evolutionary substitutions. A strong inverse correlation (r = -0.95) was found when the slope of the line relating y to x for these five data sets was plotted against the percent sequence difference between the rabbit's own protein and the proteins immunized with. Specifically, the cetacean myoglobins on average differ in amino acid sequence from rabbit myoglobin by less than 13% and exhibit the steepest slope (10.5), while bird lysozyme sequences differ by nearly 40% from rabbit lysozyme and exhibit the shallowest slope (5.1).

Amino Acid Sequence↗