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A. Garm - One of the best experts on this subject based on the ideXlab platform.
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neuropeptide expression in the box jellyfish tripedalia Cystophora new insights into the complexity of a simple nervous system
2021Co-Authors: Sofie K D Nielsen, Thomas L Koch, Sofus H Wiisbye, Cornelis J P Grimmelikhuijzen, A. GarmAbstract:Box jellyfish have an elaborate visual system and perform advanced visually guided behaviors. However, the rhopalial nervous system (RNS), believed to be the main visual processing center, only has 1000 neurons in each of the four eye carrying rhopalia. We have examined the detailed structure of the RNS of the box jellyfish Tripedalia Cystophora, using immunolabeling with antibodies raised against four putative neuropeptides (T. Cystophora RFamide, VWamide, RAamide, and FRamide). In the RNS, T. Cystophora RF-, VW-, and RAamide antibodies stain sensory neurons, the pit eyes, the neuropil, and peptide-specific subpopulations of stalk-associated neurons and giant neurons. Furthermore, RFamide ir+ neurites are seen in the epidermal stalk nerve, whereas VWamide antibodies stain the gastrodermal stalk nerve. RFamide has the most widespread expression including in the ring and radial nerves, the pedalium nerve plexus, and the tentacular nerve net. RAamide is the putative neurotransmitter in the motor neurons of the subumbrellar nerve net, and VWamide is a potential marker for neuronal differentiation as it is found in subpopulations of undifferentiated cells both in the rhopalia and in the bell. The results from the FRamide antibodies were not included as only few cells were stained, and in an unreproducible way. Our studies show hitherto-unseen details of the nervous system of T. Cystophora and allowed us to identify specific functional groups of neurons. This identification is important for understanding visual processing in the RNS and enables experimental work, directly addressing the role of the different neuropeptides in vision.
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Gonadal cnidocytes in the cubozoan Tripedalia Cystophora Conant, 1897 (Cnidaria: Cubozoa).
2019Co-Authors: Sandra Helmark, A. GarmAbstract:Cubozoans have a complex lifecycle in many ways similar to the scyphozoan lifecycle. The sexual reproduction within cubozoans varies between species with one clade having copulation and internal fertilization and the release of planula larvae. This cubozoan clade, the family Tripedaliidae, includes three species, Copula sivickisi, Tripedalia Cystophora, and Tripedalia binata. In a recent study, it was suggested that in C. sivickisi cnidocytes play a new and important role during the sexual reproduction. Male derived cnidocytes anchor sperm packages to the female gonads and female derived cnidocytes protect the externalized embryo strand. Here, we have examined the gonads and gametes of T. Cystophora and our results reveal that the male produced spermatozeugmata have a high number of isorhiza type cnidocytes, which are transferred along with the sperm during copulation. This adds further support to our hypothesis that they are important for sperm anchorage. The female gonads are lacking cnidocytes all together showing that cnidocyte production is not just a default state of the epithelium in these animals.
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de novo transcriptome assembly of the cubomedusa tripedalia Cystophora including the analysis of a set of genes involved in peptidergic neurotransmission
2019Co-Authors: Sofie K D Nielsen, A. Garm, Thomas L Koch, Frank Hauser, Cornelis J P GrimmelikhuijzenAbstract:The phyla Cnidaria, Placozoa, Ctenophora, and Porifera emerged before the split of proto- and deuterostome animals, about 600 million years ago. These early metazoans are interesting, because they can give us important information on the evolution of various tissues and organs, such as eyes and the nervous system. Generally, cnidarians have simple nervous systems, which use neuropeptides for their neurotransmission, but some cnidarian medusae belonging to the class Cubozoa (box jellyfishes) have advanced image-forming eyes, probably associated with a complex innervation. Here, we describe a new transcriptome database from the cubomedusa Tripedalia Cystophora. Based on the combined use of the Illumina and PacBio sequencing technologies, we produced a highly contiguous transcriptome database from T. Cystophora. We then developed a software program to discover neuropeptide preprohormones in this database. This script enabled us to annotate seven novel T. Cystophora neuropeptide preprohormone cDNAs: One coding for 19 copies of a peptide with the structure pQWLRGRFamide; one coding for six copies of a different RFamide peptide; one coding for six copies of pQPPGVWamide; one coding for eight different neuropeptide copies with the C-terminal LWamide sequence; one coding for thirteen copies of a peptide with the RPRAamide C-terminus; one coding for four copies of a peptide with the C-terminal GRYamide sequence; and one coding for seven copies of a cyclic peptide, of which the most frequent one has the sequence CTGQMCWFRamide. We could also identify orthologs of these seven preprohormones in the cubozoans Alatina alata, Carybdea xaymacana, Chironex fleckeri, and Chiropsalmus quadrumanus. Furthermore, using TBLASTN screening, we could annotate four bursicon-like glycoprotein hormone subunits, five opsins, and 52 other family-A G protein-coupled receptors (GPCRs), which also included two leucine-rich repeats containing G protein-coupled receptors (LGRs) in T. Cystophora. The two LGRs are potential receptors for the glycoprotein hormones, while the other GPCRs are candidate receptors for the above-mentioned neuropeptides. By combining Illumina and PacBio sequencing technologies, we have produced a new high-quality de novo transcriptome assembly from T. Cystophora that should be a valuable resource for identifying the neuronal components that are involved in vision and other behaviors in cubomedusae.
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De novo transcriptome assembly of the cubomedusa Tripedalia Cystophora, including the analysis of a set of genes involved in peptidergic neurotransmission
2019Co-Authors: Sofie K D Nielsen, A. Garm, Thomas L Koch, Frank Hauser, Cornelis J P GrimmelikhuijzenAbstract:Abstract Background The phyla Cnidaria, Placozoa, Ctenophora, and Porifera emerged before the split of proto- and deuterostome animals, about 600 million years ago. These early metazoans are interesting, because they can give us important information on the evolution of various tissues and organs, such as eyes and the nervous system. Generally, cnidarians have simple nervous systems, which use neuropeptides for their neurotransmission, but some cnidarian medusae belonging to the class Cubozoa (box jellyfishes) have advanced image-forming eyes, probably associated with a complex innervation. Here, we describe a new transcriptome database from the cubomedusa Tripedalia Cystophora. Results Based on the combined use of the Illumina and PacBio sequencing technologies, we produced a highly contiguous transcriptome database from T. Cystophora. We then developed a software program to discover neuropeptide preprohormones in this database. This script enabled us to annotate seven novel T. Cystophora neuropeptide preprohormone cDNAs: One coding for 19 copies of a peptide with the structure pQWLRGRFamide; one coding for six copies of a different RFamide peptide; one coding for six copies of pQPPGVWamide; one coding for eight different neuropeptide copies with the C-terminal LWamide sequence; one coding for thirteen copies of a peptide with the RPRAamide C-terminus; one coding for four copies of a peptide with the C-terminal GRYamide sequence; and one coding for seven copies of a cyclic peptide, of which the most frequent one has the sequence CTGQMCWFRamide. We could also identify orthologs of these seven preprohormones in the cubozoans Alatina alata, Carybdea xaymacana, Chironex fleckeri, and Chiropsalmus quadrumanus. Furthermore, using TBLASTN screening, we could annotate four bursicon-like glycoprotein hormone subunits, five opsins, and 52 other family-A G protein-coupled receptors (GPCRs), which also included two leucine-rich repeats containing G protein-coupled receptors (LGRs) in T. Cystophora. The two LGRs are potential receptors for the glycoprotein hormones, while the other GPCRs are candidate receptors for the above-mentioned neuropeptides. Conclusions By combining Illumina and PacBio sequencing technologies, we have produced a new high-quality de novo transcriptome assembly from T. Cystophora that should be a valuable resource for identifying the neuronal components that are involved in vision and other behaviors in cubomedusae
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Ocular and extraocular expression of opsins in the rhopalium of Tripedalia Cystophora (Cnidaria: Cubozoa).
2014Co-Authors: Jan Bielecki, A. Garm, Alexander K. Zaharoff, Nicole Y. Leung, Todd H. OakleyAbstract:A growing body of work on the neuroethology of cubozoans is based largely on the capabilities of the photoreceptive tissues, and it is important to determine the molecular basis of their light sensitivity. The cubozoans rely on 24 special purpose eyes to extract specific information from a complex visual scene to guide their behavior in the habitat. The lens eyes are the most studied photoreceptive structures, and the phototransduction in the photoreceptor cells is based on light sensitive opsin molecules. Opsins are photosensitive transmembrane proteins associated with photoreceptors in eyes, and the amino acid sequence of the opsins determines the spectral properties of the photoreceptors. Here we show that two distinct opsins (Tripedalia Cystophora-lens eye expressed opsin and Tripedalia Cystophora-neuropil expressed opsin, or Tc-leo and Tc-neo) are expressed in the Tripedalia Cystophora rhopalium. Quantitative PCR determined the level of expression of the two opsins, and we found Tc-leo to have a higher amount of expression than Tc-neo. In situ hybridization located Tc-leo expression in the retinal photoreceptors of the lens eyes where the opsin is involved in image formation. Tc-neo is expressed in a confined part of the neuropil and is probably involved in extraocular light sensation, presumably in relation to diurnal activity.
D-e. Nilsson - One of the best experts on this subject based on the ideXlab platform.
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Contrast and rate of light intensity decrease control directional swimming in the box jellyfish Tripedalia Cystophora (Cnidaria, Cubomedusae)
2013Co-Authors: Ronald Petie, A. Garm, D-e. NilssonAbstract:Box jellyfish respond to visual stimuli by changing the dynamics and frequency of bell contractions. In this study, we determined how the contrast and the dimming time of a simple visual stimulus affected bell contraction dynamics in the box jellyfish Tripedalia Cystophora . Animals were tethered in an experimental chamber where the vertical walls formed the light stimuli. Two neighbouring walls were darkened and the contraction of the bell was monitored by high-speed video. We found that (1) bell contraction frequency increased with increasing contrast and decreasing dimming time. Furthermore, (2) when increasing the contrast and decreasing the dimming time pulses with an off-centred opening had a better defined direction and (3) the number of centred pulses decreased. Only weak effects were found on the relative diameter of the contracted bell and no correlation was found for the duration of bell contraction. Our observations show that visual stimuli modulate swim speed in T. Cystophora by changing the swim pulse frequency. Furthermore, the direction of swimming is better defined when the animal perceives a high-contrast, or fast dimming, stimulus.
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visual control of steering in the box jellyfish tripedalia Cystophora
2011Co-Authors: Ronald Petie, A. Garm, D-e. NilssonAbstract:Box jellyfish carry an elaborate visual system consisting of 24 eyes, which they use for driving a number of behaviours. However, it is not known how visual input controls the swimming behaviour. In this study we exposed the Caribbean box jellyfish Tripedalia Cystophora to simple visual stimuli and recorded changes in their swimming behaviour. Animals were tethered in a small experimental chamber, where we could control lighting conditions. The behaviour of the animals was quantified by tracking the movements of the bell, using a high-speed camera. We found that the animals respond predictably to the darkening of one quadrant of the equatorial visual world by (1) increasing pulse frequency, (2) creating an asymmetry in the structure that constricts the outflow opening of the bell, the velarium, and (3) delaying contraction at one of the four sides of the bell. This causes the animals to orient their bell in such a way that, if not tethered, they would turn and swim away from the dark area. We conclude that the visual system of T. Cystophora has a predictable effect on swimming behaviour.
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Temporal properties of the lens eyes of the box jellyfish Tripedalia Cystophora
2010Co-Authors: Megan O’connor, D-e. Nilsson, A. GarmAbstract:Box jellyfish (Cubomedusae) are visually orientating animals which posses a total of 24 eyes of 4 morphological types; 2 pigment cup eyes (pit eye and slit eye) and 2 lens eyes [upper lens-eye (ule) and lower lens-eye (lle)]. In this study, we use electroretinograms (ERGs) to explore temporal properties of the two lens eyes. We find that the ERG of both lens eyes are complex and using sinusoidal flicker stimuli we find that both lens eyes have slow temporal resolution. The average flicker fusion frequency (FFF) was found to be approximately 10 Hz for the ule and 8 Hz for the lle. Differences in the FFF and response patterns between the two lens eyes suggest that the ule and lle filter information differently in the temporal domain and thus are tuned to perform different visual tasks. The data collected in this study support the idea that the visual system of box jellyfish is a collection of special purpose eyes.
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The ring nerve of the box jellyfish Tripedalia Cystophora
2007Co-Authors: A. Garm, Y. Poussart, L. Parkefelt, P. Ekström, D-e. NilssonAbstract:Box jellyfish have the most elaborate sensory system and behavioural repertoire of all cnidarians. Sensory input largely comes from 24 eyes situated on four club-shaped sensory structures, the rhopalia, and behaviour includes obstacle avoidance, light shaft attractance and mating. To process the sensory input and convert it into the appropriate behaviour, the box jellyfish have a central nervous system (CNS) but this is still poorly understood. The CNS has two major components: the rhopalial nervous system and the ring nerve. The rhopalial nervous system is situated within the rhopalia in close connection with the eyes, whereas the ring nerve encircles the bell. We describe the morphology of the ring nerve of the box jellyfish Tripedalia Cystophora as ascertained by normal histological techniques, immunohistochemistry and transmission electron microscopy. By light microscopy, we have estimated the number of cells in the ring nerve by counting their nuclei. In cross sections at the ultrastructural level, the ring nerve appears to have three types of neurites: (1) small “normal”-looking neurites, (2) medium-sized neurites almost completely filled by electron-lucent vacuoles and (3) giant neurites. In general, only one giant neurite is seen on each section; this type displays the most synapses. Epithelial cells divide the ring nerve into compartments, each having a tendency to contain neurites of similar morphology. The number and arrangement of the compartments vary along the length of the ring nerve.
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The lens eyes of the box jellyfish Tripedalia Cystophora and Chiropsalmus sp. are slow and color-blind
2007Co-Authors: A. Garm, M. M. Coates, R. Gad, J. Seymour, D-e. NilssonAbstract:Box jellyfish, or cubomedusae, possess an impressive total of 24 eyes of four morphologically different types. Compared to other cnidarians they also have an elaborate behavioral repertoire, which for a large part seems to be visually guided. Two of the four types of cubomedusean eyes, called the upper and the lower lens eye, are camera type eyes with spherical fish-like lenses. Here we explore the electroretinograms of the lens eyes of the Caribbean species, Tripedalia Cystophora , and the Australian species, Chiropsalmus sp. using suction electrodes. We show that the photoreceptors of the lens eyes of both species have dynamic ranges of about 3 log units and slow responses. The spectral sensitivity curves for all eyes peak in the blue-green region, but the lower lens eye of T. Cystophora has a small additional peak in the near UV range. All spectral sensitivity curves agree well with the theoretical absorbance curve of a single opsin, strongly suggesting color-blind vision in box jellyfish with a single receptor type. A single opsin is supported by selective adaptation experiments.
Ian A Van Altena - One of the best experts on this subject based on the ideXlab platform.
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bioactive α β conjugated 3 keto steroids from the australian brown alga Cystophora xiphocarpa
2021Co-Authors: Ian P Holland, Yuhanis Mhd Bakri, Jennette A Sakoff, Diana Zaleta Pinet, Cheri Motti, Ian A Van AltenaAbstract:Abstract As part of our ongoing study of the specialised metabolites present in brown algae belonging to the Cystophora genus, eight new steroids including three pairs of diastereoisomers were isolated from Cystophora xiphocarpa (Harvey) (Sargassacea, Fucales). The metabolites identified by standard spectrometric methods are (16S,22S)-16,22-dihydroxyergosta-4,24(28)-dien-3-one and (16S,22R)-16,22-dihydroxyergosta-4,24(28)-dien-3-one, (16S,22S,24R)-16,22,24-trihydroxyporifera-4,28-dien-3-one and (16S,22S,24S)-16,22,24-trihydroxystigma-4,28-dien-3-one along with (16S,22S,24E)-16,22-dihydroxystigma-4,24(28)-dien-3-one and (16S,20S)-16,20-dihydroxyergosta-4,24(28)-dien-3-one. (16S,22S,24E)-16,22-Dihydroxystigma-4,24(28)-dien-3-one possessed the most potent cytotoxicity of the steroids in this series with cell growth inhibitions of GI50 8.7 ± 0.7 μM against colon cancer HT29, GI50 5.6 ± 0.8 μM against the breast cancer line MCF-7 and GI50 4.5 ± 0.2 μM against the ovarian cancer cell line A2780. (16S,22R)-16,22-dihydroxyergosta-4,24(28)-dien-3-one was found to be active against the ovarian cancer cell line A2780 with a GI50 of 6.2 ± 0.1 μM.
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chemical investigation of seven australasian Cystophora species new chemistry and taxonomic insights
2010Co-Authors: Damian W Laird, Sarah A Bennett, Baohong Bian, Benjamin Sauer, Kathleen Wright, Victoria Hughes, Ian A Van AltenaAbstract:Chemical investigation of seven species from the brown algal genus Cystophora collected throughout Australia and New Zealand resulted in the isolation of two new compounds, 9,10-farnesylacetone epoxide (1) from Cystophora moniliformis and 1′-(2′,4′,6′-trihydroxyphenyl)-13-hydroxyoctadeca-6Z,9Z,11E,15Z-tetraen-1-one (12) from Cystophora scalaris, and 16 others that have been previously reported. Structures were elucidated using spectrometric methods, particularly 1D and 2D NMR spectroscopy. Taxonomic implications of the chemical findings are discussed including the possibility that 1 may be an intra-specific marker for the Western Australian population of C. moniliformis, and that 12 may be diagnostic for populations of C. scalaris from New Zealand waters.
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pycnanthuquinone c an unusual 6 6 5 tricyclic geranyltoluquinone from the western australian brown alga Cystophora harveyi
2007Co-Authors: Damian W Laird, Rachel Poole, Maria Wikstrom, Ian A Van AltenaAbstract:Chemical investigation of the Western Australian marine brown alga Cystophora harveyi resulted in the isolation of the new linearly fused 6,6,5-tricyclic compound pycnanthuquinone C (1), in addition to four previously reported geranyltoluquinol derivatives. Structures were elucidated by interpretation of spectrometric data. Compounds with the same cyclic skeleton as 1 have been reported to be useful drug leads for the treatment of type 2 diabetes, while compounds 4 and 7 are known constituents of Chinese medicinal herbs. A biosynthetic scheme encompassing all of the geranyltoluquinol derivatives isolated from C. harveyi is proposed.
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tetraprenyltoluquinols from the brown alga Cystophora fibrosa
2006Co-Authors: Damian W Laird, Ian A Van AltenaAbstract:Six cyclised tetraprenyltoluquinols and five stereoisomers with the previously reported amentol skeleton have been isolated from the lipophilic extract of the South African brown alga Cystophora fibrosa. Structures and relative stereochemistry were determined using spectrometric techniques, particularly 1D and 2D NMR, and molecular modelling experiments. The compounds isolated appear to be enantiomeric to compounds with the same skeleton isolated from brown algae of the genus Cystoseira collected in northern Africa and the Mediterranean Sea. The isolation of tetraprenyltoluquinols with the amentol skeleton from this alga suggests that C. fibrosa should be moved from the genus Cystophora into the Cystoseira.
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four new compounds from the australian brown alga Cystophora brownii
1998Co-Authors: Baohong Bian, Ian A Van AltenaAbstract:Two new steroids, (20S)-3β,20-dihydroxyergosta-5,24(28)-dien-16-one (7) and 3β-hydroxyergosta-5,24(28)-dien-16-one (9), and two new diastereoisomeric meroditerpenes, compounds (10) and (11), † have been isolated from the brown alga Cystophora brownii (Cystoseiraceae). Their structures were elucidated by one- and two-dimensional n.m.r. and other spectrometric and chemical methods.
Sabine Hauperich - One of the best experts on this subject based on the ideXlab platform.
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fucophlorethols from the brown algae sargassum spinuligerum and Cystophora torulosa
1997Co-Authors: Karl-wemer Glombitza, Michael Keusgen, Sabine HauperichAbstract:Abstract The brown alga Sargassum spinuligerum contains a variety of fuhalols. In addition to these compounds, a number of fucophlorethols were isolated in the form of their peracetylated derivatives and identified by means of spectral analysis. The following phlorotannins were identified: the known, fucophlorethol-B octa-acetate, fucodiphlorethol-B, -D and -F deca-acetate, hydroxyfucodiphlorethol-A undeca-acetate, bisfucotriphlorethol-A pentadeca-acetate, hydroxybisfucophlorethol-A hexadeca-acetate, bisfucotetraphlorethol-A heptadeca-acetate and the new, dihydroxyfucotriphlorethol-A and -B tetradeca-acetate, bisfucopentaphlorethol-B nonadeca-acetate, chlorobisfucopentaphlorethol-A nonadeca-acetate, difucodiphlorethol-A trideca-acetate and fucodifucotetraphlorethol-A icosa-acetate. Bisfucotriphlorethol-A pentadeca-acetate, chlorobisfucopentaphlorethol-A nonadeca-acetate and fucodifucotetraphlorethol-A icosa-acetate were also isolated from the brown alga, Cystophora torulosa .
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phlorotannins from the brown alga Cystophora torulosa
1997Co-Authors: Karl-wemer Glombitza, Sabine HauperichAbstract:Abstract A number of phlorotannins were isolated at their peracetyl derivatives and identified by means of spectral analysis. The new compounds belong to the class of hydroxylated branched fucophlorethols and bisfucophlorethols lacking a 1,2,3-triphenoxy-5-acetoxybenzene moiety.
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Phlorotannins from the brown algae Cystophora torulosa and Sargassum spinuligerum.
1997Co-Authors: Karl-wemer Glombitza, Sabine Hauperich, Michael KeusgenAbstract:Phlorotannins often have various toxic effects against a large number of organisms. From the ethyl acetate fraction of the ethanolic extract of the brown alga Cystophora torulosa 33 phlorotannins were obtained. Twenty of them are described in this report: phlorethols and fuhalols, and fucophlorethols and hydroxyfucophlorethols. Seven of them were isolated for the first time. New phlorotannins bearing additional hydroxy groups belong to the hydroxyfucophlorethols. NMR- and MS-data were used for structural elucidation. Several of the substances described for C. torulosa occur in Sargassum spinuligerum as well.
Tore Haug - One of the best experts on this subject based on the ideXlab platform.
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Age-dependent prevalence of anti-Brucella antibodies in hooded seals Cystophora cristata
2013Co-Authors: Ingebjorg Helena Nymo, Morten Tryland, Geoffrey Foster, Tore Haug, Anne Kirstine Frie, Rolf Rødven, Jacques GodfroidAbstract:Investigations of hooded seals Cystophora cristata have revealed high prevalences of Brucella-positive seals in the reduced Northeast Atlantic stock, compared to the increasing North- west Atlantic stock. This study evaluated the relation between Brucella-serostatus in seals in the Northeast Atlantic stock and age, sex, body condition and reproduction. Bacteriology documented which animals and organs were B. pinnipedialis positive. No relationship was observed between Brucella-serostatus and body condition or reproductive traits. Pups ( 1 yr old, the mean prob- ability of being seropositive decreased with age, with no seropositives older than 5 yr, indicating loss of antibody titre with either chronicity or clearance of infection. The latter explanation seems to be most likely as B. pinnipedialis has never been isolated from a hooded seal >18 mo old, which is consistent with findings in this study; B. pinnipedialis was isolated from the retropharyngeal lymph node in 1 seropositive yearling (1/21, 5%). We hypothesize that this serological and bacte- riological pattern is due to environmental exposure to B. pinnipedialis early in life, with a subse- quent clearance of infection. This raises the question of a reservoir of B. pinnipedialis in the hooded seal food web.
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long term trends in reproductive and demographic parameters of female northwest atlantic hooded seals Cystophora cristata population responses to ecosystem change
2012Co-Authors: Anne Kirstine Frie, Garry B. Stenson, Tore HaugAbstract:More than 2500 ovaries were collected from Northwest Atlantic hooded seals (Cystophora cristata (Erxleben, 1777)) in the period 1956–2006 during moulting (data blocks: 1956–1960, 1970–1972, 1978), ...
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Estimation of hooded seal (Cystophora cristata) pup production in the Greenland Sea pack ice during the 2005 whelping season
2008Co-Authors: Arnt-børre Salberg, Tore Haug, Kjell Tormod NilssenAbstract:In March 2005 aerial surveys were carried out to estimate pup production of Greenland Sea hooded seals, Cystophora cristata in three whelping patches using photographic strip transects. The majority of whelping occurred 17–23 March and surveys were carried out on 24 March. The temporal distribution of births and estimated proportion of solitary bluebacks present within the survey area were used to correct the abundance estimates. The total estimated pup production (15,250 pups, s.e. = 3,470; CV = 22.8%) was lower than an estimate from a comparable study in 1997. The current estimate is considered to be negatively biased, as it is uncorrected for pups born outside the whelping concentrations. Population modeling suggests a substantial decline with subsequent stabilization at a lower level for Greenland Sea hooded seals in recent decades. It is suggested that future research on the population explore possible factors (e.g. reduced fertility, predation, food shortage, disease, reductions in ice cover) that may have contributed to the apparent prevailing low abundance.
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Diets of hooded seals (Cystophora cristata) in coastal waters and drift ice waters along the east coast of Greenland
2007Co-Authors: Tore Haug, Kjell Tormod Nilssen, Lotta Lindblom, Ulf LindstrømAbstract:Abstract To provide data on the diets of hooded seals (Cystophora cristata) in the Greenland Sea, seals were collected for scientific purposes on expeditions conducted in the pack ice belt east of Greenland in September/October 1999, 2002 and 2003 (autumn), July/August in 2000 (summer), and February/March in 2001 and 2002 (winter). The results from analyses of stomach and intestinal contents from captured seals revealed that their diet was comprised of relatively few prey taxa. The squid Gonatus fabricii and polar cod (Boreogadus saida) were particularly important, whereas capelin (Mallotus villosus) and sand eels (Ammodytes spp.) occasionally contributed more. These four prey items constituted 60–97% of the diet biomass. Gonatus fabricii was the most important food item in autumn and winter, whereas polar cod dominated the summer diet, with important contributions from G. fabricii and sand eels. The latter was only observed on the hooded seal menu during the summer period, whereas polar cod, which was an...
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Panmictic population structure in the hooded seal (Cystophora cristata).
2007Co-Authors: David W. Coltman, Tore Haug, G. B. Stenson, M. O. Hammill, Corey S. Davis, Tara L. FultonAbstract:Two putative populations of hooded seals (Cystophora cristata) occur in the North Atlantic. The Greenland Sea population pup and breed on the pack ice near Jan Mayen ('West Ice') while the Northwest Atlantic population is thought to pup in the Davis Strait, in the Gulf of St. Lawrence (the 'Gulf'), and off southern Labrador or northeast Newfoundland (the 'Front'). We used microsatellite profiling of 300 individuals at 13 loci and mitochondrial DNA sequencing of the control region of 123 individuals to test for genetic differentiation between these four breeding herds. We found no significant genetic differences between breeding areas, nor evidence for cryptic nor higher level genetic structure in this species. The Greenland Sea breeding herd was genetically most distant from the Northwest Atlantic breeding areas; however, the differences were statistically nonsignificant. Our data therefore suggest that the world's hooded seals comprise a single panmictic genetic population.
