Integration of ecological and genetic approaches is a particularly powerful strategy to identify natural population diversity and structure over different timescales. To investigate the potential ...occurrence of population differentiation in long-finned pilot whales Globicephala melas in the North Atlantic, both biogeochemical (fatty acids and stable isotopes) and genetic (mitochondrial DNA) markers were analyzed in animals from 4 regions within the North Atlantic: the northwestern Iberian Peninsula, the United Kingdom, the Faroe Islands and the United States of America. Genetic data revealed strong regional levels of divergence, although analysis of molecular variance revealed no differentiation between the northeastern and northwestern Atlantic. Results from biogeochemical tracers supported previous dietary studies, revealing geographic and ontogenetic dietary variation in pilot whales. Fatty acids revealed ecological differentiation between all regions analyzed, while stable isotopes showed an overlap between some sampling regions. These results suggest that both ecological and genetic factors may drive the levels of pilot whale differentiation in the North Atlantic. The ecological differentiation observed may be related to the exploitation of different foraging niches (e.g. oceanic vs. coastal), which can be highly influenced by prey distributions or oceanographic phenomena. Genetic differentiation may result from historical or contemporary processes or even limited dispersal mediated through the social structure displayed by this species and potential foraging specialization. These results highlight some problems when assessing population structure across multiple markers and the ecological vs. evolutionary timescales over which differences may accumulate. Notwithstanding, the data provide preliminary information about pilot whale diversity and stocks in the North Atlantic, giving essential baseline information for conservation plans.
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In 1940 Scholander proposed that marine mammals have stiffened upper airways that would stay open and receive air from highly compressible alveoli during diving. However, this idealized ...alveoli–up system would tend to underestimate the importance of tracheal collapse or the role of the trachea at pressure. There are little data available on the structural and functional adaptations of the marine mammal respiratory system. Although biomechanical and pressure‐associated changes have been measured, the aim of this research is to investigate the microscopic tracheal characteristics of five different species of diving mammals, specifically focusing on elastic fibers and distances of cartilage overlap. Our histological measurements have revealed the presence of “slip features” in both pinniped and cetacean tracheas. These “slip features” are characterized by partial or incomplete cartilaginous rings, which, at pressure, will overlap maintaining constricted airways. This finding lends evidence for pressure‐induced collapse and re‐inflation of the trachea. In some cases, more than one “slip feature” is present per tracheal ring, perhaps allowing for more rapid and effective compression. There is great variation in the anatomy of the “slip feature” between cetacean and pinniped, as some truly overlay one another and others are separated by elastic fibers, connective tissue and smooth muscle. There also seems to be a significant difference between the quantity of elastic fiber in pinniped species versus cetacean species, for example cetaceans tended to have more elastic fibers, perhaps correlating to deeper dive depths or higher ventilatory rates.
Determining how intra-specific genetic diversity is apportioned among natural populations is essential for detecting local adaptation and identifying populations with inherently low levels of extant ...diversity which may become a conservation concern. Sequence polymorphism at two adaptive loci (MHC DRA and DQB) was investigated in long-finned pilot whales (Globicephala melas) from four regions in the North Atlantic and compared with previous data from New Zealand (South Pacific). Three alleles were resolved at each locus, with trans-species allele sharing and higher levels of non-synonymous to synonymous substitution, especially in the DQB locus. Overall nucleotide diversities of 0.49 ± 0.38% and 4.60 ± 2.39% were identified for the DRA and DQB loci, respectively, which are relatively low for MHC loci in the North Atlantic, but comparable to levels previously described in New Zealand (South Pacific). There were significant differences in allele frequencies within the North Atlantic and between the North Atlantic and New Zealand. Patterns of diversity and divergence are consistent with the long-term effects of balancing selection operating on the MHC loci, potentially mediated through the effects of host-parasite coevolution. Differences in allele frequency may reflect variation in pathogen communities, coupled with the effects of differential drift and gene flow.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
For marine mammals, the ability to tolerate apnea and make extended dives is a defining adaptive trait, facilitating the exploitation of marine food resources. Elevated levels of myoglobin within the ...muscles are a consistent hallmark of this trait, allowing oxygen collected at the surface to be stored in the muscles and subsequently used to support extended dives. In mysticetes, the largest of marine predators, details on muscular myoglobin levels are limited. The developmental trajectory of muscular myoglobin stores has yet to be documented and any physiological links between early behavior and the development of muscular myoglobin stores remain unknown. In this study, we used muscle tissue samples from stranded mysticetes to investigate these issues. Samples from three different age cohorts and three species of mysticetes were included (total sample size = 18). Results indicate that in mysticete calves, muscle myoglobin stores comprise only a small percentage (17-23%) of conspecific adult myoglobin complements. Development of elevated myoglobin levels is protracted over the course of extended maturation in mysticetes. Additionally, comparisons of myoglobin levels between and within muscles, along with details of interspecific differences in rates of accumulation of myoglobin in very young mysticetes, suggest that levels of exercise may influence the rate of development of myoglobin stores in young mysticetes. This new information infers a close interplay between the physiology, ontogeny and early life history of young mysticetes and provides new insight into the pressures that may shape adaptive strategies in migratory mysticetes. Furthermore, the study highlights the vulnerability of specific age cohorts to impending changes in the availability of foraging habitat and marine resources.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Gas bubbles in marine mammals entangled and drowned in gillnets have been previously described by computed tomography, gross examination and histopathology. The absence of bacteria or autolytic ...changes in the tissues of those animals suggested that the gas was produced peri- or post-mortem by a fast decompression, probably by quickly hauling animals entangled in the net at depth to the surface. Gas composition analysis and gas scoring are two new diagnostic tools available to distinguish gas embolisms from putrefaction gases. With this goal, these methods have been successfully applied to pathological studies of marine mammals. In this study, we characterized the flux and composition of the gas bubbles from bycaught marine mammals in anchored sink gillnets and bottom otter trawls. We compared these data with marine mammals stranded on Cape Cod, MA, USA. Fresh animals or with moderate decomposition (decomposition scores of 2 and 3) were prioritized. Results showed that bycaught animals presented with significantly higher gas scores than stranded animals. Gas composition analyses indicate that gas was formed by decompression, confirming the decompression hypothesis.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Microbes are now well regarded for their important role in mammalian health. The microbiology of skin - a unique interface between the host and environment - is a major research focus in human health ...and skin disorders, but is less explored in other mammals. Here, we report on a cross-population study of the skin-associated bacterial community of humpback whales (Megaptera novaeangliae), and examine the potential for a core bacterial community and its variability with host (endogenous) or geographic/environmental (exogenous) specific factors. Skin biopsies or freshly sloughed skin from 56 individuals were sampled from populations in the North Atlantic, North Pacific and South Pacific oceans and bacteria were characterized using 454 pyrosequencing of SSU rRNA genes. Phylogenetic and statistical analyses revealed the ubiquity and abundance of bacteria belonging to the Flavobacteria genus Tenacibaculum and the Gammaproteobacteria genus Psychrobacter across the whale populations. Scanning electron microscopy of skin indicated that microbial cells colonize the skin surface. Despite the ubiquity of Tenacibaculum and Psychrobater spp., the relative composition of the skin-bacterial community differed significantly by geographic area as well as metabolic state of the animals (feeding versus starving during migration and breeding), suggesting that both exogenous and endogenous factors may play a role in influencing the skin-bacteria. Further, characteristics of the skin bacterial community from these free-swimming individuals were assembled and compared to two entangled and three dead individuals, revealing a decrease in the central or core bacterial community members (Tenacibaculum and Psychrobater spp.), as well as the emergence of potential pathogens in the latter cases. This is the first discovery of a cross-population, shared skin bacterial community. This research suggests that the skin bacteria may be connected to humpback health and immunity and could possibly serve as a useful index for health and skin disorder monitoring of threatened and endangered marine mammals.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Assessment of body condition is critical for examination of live and dead dolphins. Using live and dead stranded and dead bycaught short-beaked common dolphins (Delphinus delphis) from New England ...waters, a simple, practical body condition scoring (BCS) system was developed that has utility for all delphinid species. Using photographs, a non-invasive, 4-point visual scale was created based on anatomical landmarks which are indicative of body condition and emaciation. The consistency of using this BCS system was tested via a blind study with five trained and experienced stranding responders independently scoring a subset of D. delphis cases (n=30) using photo documentation only, and results showed a significant level of agreement among observers. Specific morphometric data relating to body condition were analyzed to determine parameters which, in association with the clinical evaluation of the animal, may be indicative of potential success after release during a live stranding event. Results showed a significant difference in length-to-girth ratios in both the axilla and anterior dorsal fin regions between animals which were released (mean for axilla: single stranded 1.75, mass stranded 1.76; mean for dorsal fin: single stranded 1.79, mass stranded 1.76) and those that died or were deemed unreleasable and euthanized (mean for axilla: single stranded 2.03, mass stranded 1.99; mean for dorsal fin: single stranded 1.99, mass stranded 1.87). Future studies are needed to validate the BCS system and its ability to predict such morphometric parameters and relative health. Use of this BCS system will allow for consistency in determining body condition in delphinid species, thus enabling stranding response agencies to better compare data relating to health and nutritional status in these animals.
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