Abundant mitochondrial DNA variation and world-wide population structure in humpback whales.

Hunting during the last 200 years reduced many populations of mysticete whales to near extinction. To evaluate potential genetic bottlenecks in these exploited populations, we examined mitochondrial DNA control region sequences from 90 individual humpback whales (Megaptera novaeangliae) representing six subpopulations in three ocean basins. Comparisons of relative nucleotide and nucleotype diversity reveal an abundance of genetic variation in all but one of the oceanic subpopulations. Phylogenetic reconstruction of nucleotypes and analysis of maternal gene flow show that current genetic variation is not due to postexploitation migration between oceans but is a relic of past population variability. Calibration of the rate of control region evolution across three families of whales suggests that existing humpback whale lineages are of ancient origin. Preservation of preexploitation variation in humpback whales may be attributed to their long life-span and overlapping generations and to an effective, though perhaps not timely, international prohibition against hunting.

Population characteristics of DNA fingerprints in humpback whales (Megaptera novaeangliae).

Humpback whales exhibit a remarkable social organization that is characterized by seasonal long-distance migration (> 10,000 km/year) between summer feeding grounds in high latitudes and winter calving and breeding grounds in tropical or near-tropical waters. All populations are currently considered endangered as a result of intensive commercial exploitation during the last 200 years. Using three hypervariable minisatellite DNA probes (33.15, 3'HVR, and M13) originally developed for studies of human genetic variation, we examined genetic variation within and among three regional subpopulations of humpback whales from the North Pacific and one from the North Atlantic oceans. Analysis of DNA extracted from skin tissues collected by biopsy darting from free-ranging whales revealed considerable variation in each subpopulation. The extent of this variation argues against a recent history of inbreeding among humpback whales as a result of nineteenth- and twentieth-century hunting. A canonical variate analysis suggested a relationship between scaled genetic distance, based on similarities of DNA fingerprints, and geographic distance (i.e., longitude of regional subpopulation). Significant categorical differences were found between the two oceanic populations using a multivariate analysis of variance (MANOVA) with a modification of the Mantel nonparametric permutation test. The relationship between DNA fingerprint similarities and geographic distance suggests that nuclear gene flow between regional subpopulations within the North Pacific is restricted by relatively low rates of migratory interchange between breeding grounds or assortative mating on common wintering grounds.

Crassicaudosis: a parasitic disease threatening the health and population recovery of large baleen whales.

This communication briefly reviews knowledge of the systemic disease caused by Crassicauda boopis in blue whales (Balaenoptera musculus), fin whales (B. physalus) and humpback whales (Megaptera novaeangliae). Infections with this giant nematode characteristically incite a chronic inflammatory reaction of the blood vessels which drain the kidneys. In this critical location, the parasite-induced lesion can cause complete vascular occlusion and kidney failure. Whale calves and juveniles typically suffer the heaviest parasite burdens following transplacental infection of the developing whale foetus. There is also probable whale-to-whale transmission post-partum, involving urinary contamination of the environment with C. boopis eggs and larvae. The frequency of the infection can exceed 95%. Haematological findings suggest that systemic pathological effects are typical at the population level. Gradual development of occlusive lesions in the renal veins appears to correlate with a major peak in natural mortality at about one year of age. To date, all findings support the conclusion that premature death caused by C. boopis infection is potentially a major impediment to population recovery of affected whale species. This suggests the interesting possibility of actively encouraging the population recovery of three species of large baleen whales. Such a restoration effort would entail remotely-deployed anthelminthic therapy administered, at sea, to infected whale cows and calves.

Influence of seasonal migration on geographic distribution of mitochondrial DNA haplotypes in humpback whales.

Humpback whales (Megaptera novaeangliae) migrate nearly 10,000 km each year between summer feeding grounds in temperate or near-polar waters and winter breeding grounds in shallow tropical waters. Observations of marked individuals suggest that major oceanic populations of humpback whales are divided into a number of distinct seasonal subpopulations which are not separated by obvious geographic barriers. To test whether these observed patterns of distribution and migration are reflected in the genetic structure of populations, we looked for variation in the mitochondrial DNA of 84 individual humpback whales on different feeding and wintering grounds of the North Pacific and western North Atlantic oceans. On the basis of restriction-fragment analysis, we now report a marked segregation of mitochondrial DNA haplotypes among subpopulations as well as between the two oceans. We interpret this segregation to be the consequence of maternally directed fidelity to migratory destinations.

Genital papillomatosis in sperm whale bulls.

Examination of 31 male sperm whales (Physeter catodon) caught off the western coast of Iceland revealed three cases of genital papillomatosis involving the unsheathed penis. One subadult and two sexually mature bulls were affected. Gross lesions resembled papillomas common in terrestrial mammalian species. Transmission electron microscopy of these lesions revealed nonenveloped intranuclear virus particles 28-40 nm in diameter and round to hexagonal in shape. In two cases immunoperoxidase staining was negative for group-specific papillomavirus antigen. These findings indicate that the spectrum of animal species affected with virus-associated genital papillomatosis includes at least one globally distributed species of the order Cetacea (whales, dolpins, and porpoises).

Unusual multisystemic pathology in a sperm whale bull.

This report describes an unusual combination of lesions and apparent behavioral abnormalities in a sexually mature sperm whale bull taken in whaling operations off Iceland. Lesions included heavy combative scarring of the head, grossly roughened and thickened skin on the lower left flank, cutaneous maculae, genital papillomatosis, partial duodenal obstruction by plastic debris, colo-rectal obstruction by ambergris, cystic degeneration of the right kidney, and a deeply ulcerative gastric nematodiasis. Sealskin was found in the stomach. Gross and histopathologic observations suggested that the disease complex in this animal may have been related both to habitat degradation and health risks naturally associated with its ecology and age.

Serum chemistry and evidence of renal failure in the North Atlantic fin whale population.

Serum electrolytes, urea nitrogen, creatinine, albumin and globulin were studied in fin whales (Balaenoptera physalus) caught by commercial whalers in the North Atlantic (Denmark Strait area). Blood samples were obtained by catchment or cardiac puncture within 5-15 min of death and analyzed using automated spectrophotometric methods and flame photometry. Osmolality was determined for two serum samples by a vapor pressure method. Linear regressions determined for each measured serum variable vs. chase time suggested that pursuit of the whales prior to capture had no substantive effect on measured serum chemistry. As in other cetaceans, serum sodium, chloride, urea nitrogen and osmolality were distinctly higher in the fin whale than in terrestrial mammals. The total concentration of serum proteins, however, was 1.4-1.8 g/dl lower, on average, than reported in small toothed whales, and was similar to that of domesticated animals. One animal in this population showed alterations in serum chemistry which were consistent with renal failure.

Taxonomy and distribution of a Crassicauda species (Nematoda: Spirurida) infecting the kidney of the common fin whale (Balaenoptera physalus Linné, 1758).

Nematode parasites were found in the kidney of common fin whales (Balaenoptera physalus Linné, 1758) captured in the North Atlantic Ocean (Denmark Strait area). These were identified as Crassicauda boopis Baylis, 1920, on the basis of morphologic and morphometric descriptions of this species' posterior end. The cephalic end of this parasite was described for the first time, however, and was indistinguishable from that of Crassicauda pacifica Margolis and Pike, 1955, a species whose posterior portion is unknown. It was also found that the eggs, size, host, and site of infection of both C. boopis and C. pacifica are indistinguishable. This established the synonymy of C. boopis with the more recently named taxon, C. pacifica. In light of previous descriptions of Crassicauda infections in balaenopterids, this implied that C. boopis should at present be considered a renal parasite of fin whales, and perhaps other rorquals, throughout the world's oceans.

Interdigitative coupling of presumptive hematopoietic stem cells to macrophages in endocloned marrow colonies.

Hematopoietic marrow colonies were studied ultrastructurally to investigate stromal cell-hematopoietic cell interactions during early hematopoiesis. An elaborate interdigitative coupling of mature marrow macrophages to morphologically undifferentiated colony cells is described. This coupling was found in undifferentiated and granulocytic colonies and established a physical linkage of the macrophage and undifferentiated cell. The spaces between the coupled cells contained an electron-dense material and appeared to be modified by the uptake or release of cytoplasmic vesicles of the macrophage. Based on available evidence that hematopoietic stem cell proliferation is controlled at a local, or stromal, level, and the finding that this interaction occurs in very early hematopoietic colonies, it is suggested that interdigitative couplings represent a mechanism of stem cell regulation. In addition, the observations indicate macrophages to be actively involved with the lodgement of morphologically undifferentiated hematopoietic cells in the marrow space.

Anatomy and vasculature of a minke whale heart.

The heart from a 4-m-long minke whale (Balaenoptera acutorostrata) was studied to determine the details of its anatomy and to consider cardiac adaptations to diving. The volume fraction (Vvc) of capillaries in the wall of the left ventricle was determined at different levels from base to apex and at different depths from epi- to endocardium using a light microscopic stereologic technique. Typical of cetaceans, this minke whale heart was distinctly flattened dorsoventrally. A moderator band, characteristic of ungulate hearts, spanned the right ventricle. The right and left atrioventricular valves were tricuspid and bicuspid, respectively. The right coronary artery supplied the dorsal and right lateral myocardium. The left coronary artery supplied the ventral and left lateral myocardium. An anastomosis between the dorsal and ventral interventricular arteries occurred in the dorsal interventricular groove. Stereologically, a decreasing transmural gradient in Vvc was identified between the epicardium and the subepicardium at 15 cm from the apex. Our results, however, did not reveal any significant deviations in the pattern of capillary distribution in the wall of the left ventricle between this baleen whale and terrestrial mammals. Measurements of the heart, great vessels, coronary vasculature, and ventricular walls are also given, and they suggest a physiologic and adaptive right ventricular hypertrophy. Based on these and other observations, we propose that the relatively great thickness of the right ventricle and the distinctive shape of the cetacean heart are adaptations to the hemodynamic changes and collapse of the thorax associated with apneic diving.

A model of intramedullary hematopoietic microenvironments based on stereologic study of the distribution of endocloned marrow colonies.

Hematopoietic colonies were studied in the marrow of alternate fraction-irradiated mice by light microscopic stereology to investigate the microenvironmental organization of marrow. Separate analyses of the relative colony cell density of undifferentiated, granulocytic, erythrocytic, and macrophage colonies in four marrow zones were carried out at 3, 4, and 5 days postirradiation (PI) for all colonies, all periarterial colonies, and all non-periarterial colonies. The results demonstrate a differential colony cell distribution that does not appear to be due to a preferential distribution of certain colony types around arteries. Undifferentiated colony cells showed a consistent predilection for endosteal and periarterial regions, with the majority of colony cells occurring along bone. Erythrocytic colony cells proliferated initially in intermediate and central marrow zones and along arteries. Granulocytic colony cells occurred in all areas at 3 days PI, but increased in density along bone thereafter. Macrophage colony cells occurred in all zones at 4 days PI, but at 5 days were concentrated in subosteal and central regions. Macrophage colonies also occurred periarterially. To explain these findings and the organization of normal bone marrow, we present a detailed model of the microenvironmental organization of intramedullary hematopoiesis. This model portrays the stroma as engendering distinct microenvironments for stem cell replication, stem cell commitment, and early progenitor cell proliferation.

Studies on the organization and regeneration of bone marrow: origin, growth, and differentiation of endocloned hematopoietic colonies.

Hematopoietic colonies were studied by light microscopy in the marrow of alternate fraction x-irradiated mice (C576J/B1) to investigate the microenvironmental organization of marrow and identify early hematopoietic cell-stromal cell interactions. Undifferentiated colonies (UC) were detected at 3 days postirradiation, showed a marked predilection for bone surfaces, and disappeared as differentiated colonies developed. Some UC occurred along marrow arteries. Neutrophilic granulocyte colonies (GC) occurred in all areas at 3 days but grew rapidly only subosteally. Few eosinophilic colonies (GCe) occurred. Erythrocytic colonies (EC) appeared at 4 days as dispersed populations of motile cells within a localized area of marrow; these tended to proliferate initially in intermediate and central marrow zones. Macrophage colonies (M phi C) of two "subtypes" were detected, peaking in relative frequency at 4 days. These appeared active in stromal repair and monocytopoiesis. Megakaryocyte colonies (MC) originated along bone and differentiated away from bone. From 3-5 days, the frequency of GC greater than UC greater than M phi C much greater than MC approximately equal to GCe. All colony types except UC, M phi C, and central GC increased in size and became mixed in differentiation by 12-14 days. For several weeks, however, erythropoiesis concentrated toward central areas, whereas granulopoiesis and thrombopoiesis concentrated along bone. Some mixed colonies showed an abrupt transition from erythrocytic, centrally, to granulocytic, subosteally. These results were interpreted as evidence that in x-irradiated marrow: (1) hematopoietic microenvironments (HMs) for stem-cell proliferation and commitment to differentiation, with the possible exception of HMs determining erythroid differentiation, occur in endosteal and periarterial regions; (2) a proliferative and/or chemotactic stimulus to erythroid progenitors exists in intermediate and central marrow regions; and (3) some subosteal regions may exclude erythropoiesis, or preferentially support nonerythroid differentiation. Elaborate associations occurred between macrophages and early UC, GC, and EC, but not MC hematopoietic cells. UC and GC often associated with osteoclasts. Reticular and other fibroblastic cells associated with the cells of all colony types.