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1.
Sequence variation at the major histocompatibility complex DRB loci in beluga (Delphinapterus leucas) and narwhal (Monodon monoceros) 总被引:2,自引:2,他引:0
The variation at loci with similarity to DRB class II major histocompatibility complex loci was assessed in 313 beluga collected from 13 sampling locations across North
America, and 11 narwhal collected in the Canadian high Arctic. Variation was assessed by amplification of exon 2, which codes
for the peptide binding region, via the polymerase chain reaction, followed by either cloning and DNA sequencing or single-stranded
conformation polymorphism analysis. Two DRB loci were identified in beluga: DRB1, a polymorphic locus, and, DRB2, a monomorphic locus. Eight alleles representing five distinct lineages (based on sequence similarity) were found at the
beluga DRB1 locus. Although the relative number of alleles is low when compared with terrestrial mammals, the amino acid variation found
among the lineages is moderate. At the DRB1 locus, the average number of nonsynonymous substitutions per site is greater than the average number of synonymous substitutions
per site (0.0806 : 0.0207, respectively;P<0.01). Most of the 31 amino acid substitutions do not conserve the physiochemical properties of the residue, and 21 of these
are located at positions implicated as forming pockets responsible for the selective binding of foreign peptide side chains.
Only DRB1 variation was examined in 11 narwhal, revealing a low amount of variation. These data are consistent with an important role
for the DRB1 locus in the cellular immune response of beluga. In addition, the ratio of nonsynonymous to synonymous substitutions is similar
to that among primate alleles, arguing against a reduction in the balancing selection pressure in the marine environment.
Two hypotheses may explain the modest amount of Mhc variation when compared with terrestrial mammals: small population sizes at speciation or a reduced neutral substitution
rate in cetaceans.
Received: 15 July 1997 / Revised: 24 March 1998 相似文献
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Narwhal (Monodon monoceros) liver and kidney cytosol were fractionated by gel chromatography, anion-exchange chromatography and electrophoresis. Cadmium was associated largely with low molecular weight proteins, while mercury was associated also with high molecular weight proteins, but apparently not because of saturation of the metallothionein mechanism. Eight different electrophoretic bands, four of which were metalloproteins, were found under the "metallothionein" peak. Anion-exchange chromatography yielded five metal peaks while further fractionation on G-50 gave two peaks, one containing almost pure metallothionein (Mt-1) and the other a metalloprotein having twice the molecular weight of metallothionein. Mt-2 was observed, at a much lower concentration than Mt-1, in liver but not kidney. 相似文献
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Murray M. Humphries 《Marine Mammal Science》2012,28(4):649-665
The behavioral and environmental context of animal calls provides insights into their functions. Narwhals are a highly vocal species and, like other social cetaceans, rely on acoustic signals to communicate. We characterize and categorize narwhal whistles and pulsed calls, as well as investigate variation in these calls under different contexts (behavior, herd, and year) using recordings made during the month of August 2006–2008, in Koluktoo Bay (72°04′N, 80°32′W). We detected similarities among whistles but not pulsed calls that were produced under a similar behavioral context. Both whistles and pulsed calls recorded within the same herd were more similar than whistles and pulsed calls recorded within different herds. We did not find any type of whistle to be associated with a specific behavior although some acoustical features might be behavior specific. Both whistles and pulsed calls show properties that are consistent with the hypothesis that narwhals produce group‐ or individual‐specific calls. 相似文献
5.
Population estimates are important for the development of management plans of harvested species and thereby ultimately important for species sustainability. Aerial surveys are one of the methods used in preparing population estimates. For marine mammals, aerial population surveys require that animal biology is understood in order to account for availability bias. Availability bias in this case derives from animals that are invisible to the survey due to diving behavior. In order to understand diving behavior of the Northern Hudson Bay narwhal (Monodon monoceros), nine whales were tagged with satellite tracking devices in the Repulse Bay, Nunavut area in August 2006 (n = 5) and 2007 (n = 4). Of specific interest was time at depth of 0–2 m of water, the depth at which studies have shown that whales could be distinguished at the species level during an aerial survey. The proportion of time spent in 0–2 m of water can then be used to correct the population estimate from aerial survey. This research found that narwhals spent approximately 32 % of their time at the surface where they would be available to be seen by an aerial survey. This paper provides raw data that can be used to correct population survey estimates. 相似文献
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A simplified population equation for Monodon Pnonoceros shows that current estimates of the values of the life history variables are inconsistent with the hypothesis of a stationary population. Instantaneous adult mortality must be less than 0,10/yr, not the published estimate of 12–13%/yr, for accepted values of the other variables to be consistent with stationarity. For sustainable harvest, permissible exploitation rates are no larger than 3–4%/yr, and instantaneous natural mortality must then be well below 10%/yr. Present uncertainty in the values of survival rates, both of adults and young, contributes twice as much to uncertainty in population growth rate as does uncertainty in reproductive rates. 相似文献
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Mating ecology of beluga (Delphinapterus leucas) and narwhal (Monodon monoceros) as estimated by reproductive tract metrics
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Trish C. Kelley Robert E. A. Stewart David J. Yurkowski Anna Ryan Steven H. Ferguson 《Marine Mammal Science》2015,31(2):479-500
Narwhal and beluga whales are important species to Arctic ecosystems, including subsistence hunting by Inuit, and little is understood about their mating ecology. Reproductive tract metrics vary across species in relation to mating strategy, and have been used to infer mating ecology. Reproductive tracts from beluga and narwhal were collected between 1997 and 2008 from five beluga stocks and two narwhal stocks across the Canadian Arctic. Tract length for males and females, relative testes mass for males, and tusk length for male narwhal were measured. We assessed variation relative to species, body size, stock, maturity, and season. Significant variation was found in testes mass across month and stock for beluga, and no significant difference between stock or date of harvest for narwhal. Beluga had significantly larger testes relative to body size than narwhal, suggesting they were more promiscuous than narwhal. A significant relationship was found between narwhal tusk length and testes mass, indicating the tusk may be important in female mate choice. No significant differences were found between narwhal and beluga reproductive tract length for males or females. The mating systems suggested for narwhal and belugas by our results mean the two species may respond differently to climate change. 相似文献
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Cortney A. Watt Barbara E. Stewart Lisa Loseto Thor Halldorson Steven H. Ferguson 《Marine Mammal Science》2020,36(1):103-115
Counting growth-layer groups (GLGs) in teeth is one of the most precise and widely accepted methods for aging marine mammals. Male narwhals have a large erupted tusk that can be used for aging, but this tusk is often difficult or expensive to obtain from hunters and most females do not display the tusk; thus, alternative methods for narwhal aging are needed. In this study, we aged narwhals by counting annual GLGs in embedded tusks and by measuring the change in the ratio of D- and L-enantiomers of aspartic acid in the eye lens nucleus that occurs as the animal ages (the aspartic acid racemization [AAR] technique). Absolute age estimates were estimated for seven tusks aged ≤15 yr. Estimated age was a significant predictor of aspartic acid D/L ratios with a racemization rate (Kasp) of 9.72 × 10−4/year ± 2.28 × 10−4 and a (D/L)0 of 3.46 × 10−2 ± 1.78 × 10−3 (r2 = 0.74). Results from our study, which included more younger GLG-aged animals than previously evaluated, confirms AAR can be used to generate age estimates for narwhals. 相似文献
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Rapid changes in sea ice cover associated with global warming are poised to have marked impacts on polar marine mammals. Here we examine skeletal muscle characteristics supporting swimming and diving in one polar species, the narwhal, and use these attributes to further document this cetacean's vulnerability to unpredictable sea ice conditions and changing ecosystems. We found that extreme morphological and physiological adaptations enabling year‐round Arctic residency by narwhals limit behavioral flexibility for responding to alternations in sea ice. In contrast to the greyhound‐like muscle profile of acrobatic odontocetes, the longissimus dorsi of narwhals is comprised of 86.8%± 7.7% slow twitch oxidative fibers, resembling the endurance morph of human marathoners. Myoglobin content, 7.87 ± 1.72 g/100 g wet muscle, is one of the highest levels measured for marine mammals. Calculated maximum aerobic swimming distance between breathing holes in ice is <1,450 m, which permits routine use of only 2.6%–10.4% of ice‐packed foraging grounds in Baffin Bay. These first measurements of narwhal exercise physiology reveal extreme specialization of skeletal muscles for moving in a challenging ecological niche. This study also demonstrates the power of using basic physiological attributes to predict species vulnerabilities to environmental perturbation before critical population disturbance occurs. 相似文献
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《Seminars in cell & developmental biology》2013,24(5):507-513
Cell cycle exit and acquirement of a postmitotic state is essential for the proper development of organs. In the present review, we examine the role of the cell cycle control in the sensory epithelia of the mammalian inner ear. We describe the roles of the core cell cycle regulators in the proliferation of prosensory cells and in the initiation and maintenance of terminal mitosis of the sensory epithelia. We also discuss how other intracellular signalling may influence the cell cycle. Finally, we address the question of whether manipulations of the cell cycle may have the potential to create replacement cells for the damaged inner sensory epithelia. 相似文献
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?ystein Wiig Mads Peter Heide-J?rgensen Kristin L. Laidre Eva Garde Randall R. Reeves 《Polar Biology》2012,35(1):63-71
We analyzed variation in nine non-metric and eight metric variables in the skulls of 132 narwhals (Monodon monoceros) from five localities in Greenland (Inglefield Bredning, Melville Bay, Uummannaq, Disko Bay, and Scoresby Sound) and one
in the eastern Canadian Arctic (Eclipse Sound). Metric variables were used to compare the combined Disko Bay and Uummannaq
samples with the samples from Inglefield Bredning and Scoresby Sound using three different multivariate techniques for each
sex. None of the results were significant. Seven of the non-metric variables were independent of age and sex and were used
in comparing samples from the six localities. No differences were found among the four localities in West Greenland, but differences
were found in two of the non-metric variables between the combined West Greenland sample and the one from Scoresby Sound.
A major shortcoming of the analysis based on metric data was the small sample size from several of the areas, which resulted
in low statistical power. Genetic as well as environmental factors could explain the differences detected here between narwhals
living along the west and the east coasts of Greenland. 相似文献
15.
The mechanical properties of the tissues of the tusk of a narwhal Monodon monoceros , their histological arrangement, and the gross anatomy of the tusk were examined. The histology of the tusk shows various toughening mechanisms. The tusk tissues are of low stiffness, but are very tough, suiting the tusks for loading on impact, but not for longitudinal loading. These mechanical properties suggest the possible functions of the tusk, namely to be long in order to be sexually attractive, while being tough in order to withstand 'testing' blows from other males. 相似文献
16.
Mhatre AN Stern RE Li J Lalwani AK 《Biochemical and biophysical research communications》2002,297(4):987-996
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Autosomal dominant optic atrophy (adOA) is the most common form of hereditary optic neuropathy. The majority of cases are
associated with mutations in the OPA1 gene. A few cases of adOA are known to be associated with moderate progressive hearing loss. To gain insight into the pathogenesis
of this hearing loss, we performed expression analyses of OPA1 in the rat auditory and vestibular organ. In cochlear tissue,
several splice variants of OPA1 were detected, which are also expressed in retinal tissue. OPA1 mRNA and protein was found in the hair cells and ganglion
cells of the cochlea and vestibular organ. In ganglion cells, OPA1 mRNA and protein was already detectable at birth, whereas
in the organ of Corti OPA1 mRNA and protein was up-regulated after birth and reached mature-like expression level during the
onset of hearing. Comparison of an antibody directed to the mitochondrial marker protein HSP60 with antibodies directed to
different amino acid stretches of OPA1 revealed a sub-cellular distribution of OPA1 in areas of significant density of mitochondria.
The data suggest that defects in OPA1 cause hearing disorders due to a progressing metabolic disturbance of hair and ganglion
cells in the inner ear.
Stefanie Bette and Ulrike Zimmermann contributed equally to this work. 相似文献
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We report the immunolocalization of aquaporins (AQPs) 1, 4, and 6 in the human auditory and vestibular endorgans. A rapid
protocol was applied to audiovestibular endorgans microdissected from postmortem human temporal bones from six subjects (ages
ranging from 75 to 97 years) with no history of audiovestibular disease. Temporal bones were fixed in formalin, and the endorgans
were immediately microdissected. Cryostat sections were obtained from audiovestibular endorgans and were subjected to double-immunohistochemical
staining with antibodies against AQPs and several cellular markers. In the human cochlea, AQP1 immunoreactivity was localized
to the fibrocytes of the spiral ligament and the sub-basilar tympanic cells; AQP4 immunoreactivity was localized to the outer
sulcus cells, Hensen’s cells, and Claudius’ cells; AQP6 immunoreactivity was localized to the apical portion of interdental
cells in the spiral limbus. In the vestibular endorgans (macula utriculi and cristae), AQP1 was localized to fibrocytes and
blood vessels of the underlying stroma and trabecular perilymphatic tissue; AQP4 immunoreactivity was localized to the basal
pole of vestibular supporting cells; AQP6 was localized to the apical portion of vestibular supporting cells. Cochlear and
vestibular hair cells and nerve fibers were not immunoreactive for any AQP. Supporting cells were identified with antibodies
against glial fibrilar acidic protein. Nerve fibers and terminals were identified with antibodies against neurofilaments and
Na+K+ATPase. The high degree of conservation of AQP expression in the human inner ear suggests that AQPs play a critical role in
inner ear water homeostasis.
The National Institutes of Health (grants AG09693-10, DC005224, 00140-02, and DC05187-01) supported this work. 相似文献
20.
Summary Reserpine and guanethidine produce a highly significant reduction in electron density of the synaptic bars in the sensory cells of the bullfrog labyrinth. When amphetamine is administered simultaneously with guanethidine, the density of the synaptic bars is similar to those of untreated frogs. p-Chloramphetamine has no significant effect upon the electron density of synaptic bars. These observations are discussed in the light of what is known of the biological effects of these drugs, and are taken to indicate that the synaptic bars could be intracellular storage sites for a monoamine that mediates the synaptic contacts between the sensory cells and afferent nerve fibres. It is suggested that the monoamine involved is a catecholamine.Both of us thank Mrs. J. Birch and Miss J. Sutcliffe for their technical assistence. One of us (M. P. O.) was supported by a U.S. National Research Council Senior Research Associateship (1967–1968) during the earlier phase of this work, and we are both indebted to the Italian Consiglio Nazionale delle Ricerche for a grant (No. 69.01697.119.3) which financed the latter stages of this study. 相似文献