Search publications of the members of the Royal Belgian institute of natural Sciences
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An estimate of the suspended particulate matter (SPM) transport in the southern North Sea using SeaWiFS images, in situ measurements and numerical model results
- A study is presented where satellite images (SeaWiFS), in situ measurements (tidal cycle and snapshot) and a 2D hydrodynamic numerical model have been combined to calculate the long term SPM (Suspended Particulate Matter) transport through the Dover Strait and in the southern North Sea. The total amount of SPM supplied to the North Sea through the Dover Strait is estimated to be 31.74×106 t. The satellite images provide synoptic views of SPM concentration distribution but do not take away the uncertainty of SPM transport calculation. This is due to the fact that SPM concentration varies as a function of tide, wind, spring-neap tidal cycles and seasons. The short term variations (tidal, spring-neap tidal cycle) have not been found in the satellite images, however seasonal variations are clearly visible. Furthermore the SPM concentration in the satellite images is generally lower than in the in situ measurements. The representativness of SPM concentration maps derived from satellites for calculating long term transports has therefore been investigated by comparing the SPM concentration variability from the in situ measurements with those of the remote sensing data. The most important constraints of satellite images are related to the fact that satellite data is evidence of clear sky conditions, whereas in situ measurements from a vessel can be carried out also during rougher meteorological conditions and that due to the too low time resolution of the satellite images the SPM concentration peaks are often missed. It is underlined that SPM concentration measurements should be carried out during at least one tidal cycle in high turbidity areas to obtain representative values of SPM concentration. © 2007 Elsevier Ltd. All rights reserved.
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Antrobathynella stammeri (Jakobi, 1954) : The first record of bathynellacea (Crustacea : Syncarida) in Belgium
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Fossil bear bones in the Belgian Upper Paleolithic: The possibility of a proto bear-ceremonialism
- This paper examines several fossil bear bones from Upper Paleolithic deposits recovered from Belgian caves. The bones exhibit traces of ochre. The paper examines the archaeological and archaeozoological data in detail, comparing the finds with other sites containing fossil bear remains and identifying patterns suggesting purposeful staining of bear bones. These patterns are compared with ethnographic examples of bear ceremonialism. On the basis of similarities found in these analyses, the authors argue that a proto bear-ceremonialism existed during the Upper Paleolithic. © 2007 by the Board of Regents of the University of Wisconsin System.
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Spiniferaphonte, a new genus of Laophontidae (Copepoda: Harpacticoida), with notes on the occurrence of processes on the caudal rami
- A new genus and species of Laophontidae, Spiniferaphonte ornata n. gen., n. sp., is described from the coast of Kenya. The new genus is closely related to Laophontina and Wellsiphontina as shown by the following synapomorphies: a denticulate operculum, a sexually dimorphic P4 exopod (reduced chaetotaxy of the ultimate segment in the male), and the absence of sexual dimorphism in the P2 and P3 endopods. The two-segmented exopod of P1 and the presence of a seta on the endopodal part of the male P5 are plesiomorphies indicating that the new genus represents a separate lineage within this group. The proposal of the new genus Spiniferaphonte is supported by the following autapomorphies: three smooth setae on the female P5 exopod and a robust, dorsally bent, and strongly sclerotised caudal seta V. Within the Laophontidae, it is striking that the presence of distinct, thorn-like processes on the caudal rami is limited to interstitial genera. Distinct processes on the proximal segments of the antennule and a proximally thickened caudal seta V also appear to be associated with this interstitiality. These structures may play a role in the movement and the anchoring of the animals in their interstitial habitat.
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Revision of the genus Tapholeon Wells, 1967 (Copepoda, Harpacticoida, Laophontidae)
- To date, only two species are known in the laophontid genus Tapholeon Wells, 1967 (Copepoda, Harpacticoida). In the present contribution, a redescription of the type species T. ornatus Wells, 1967, based on the type material, is provided. Furthermore, two new species are described from the coast of Kenya, T. inconspicuus sp. nov. and T. tenuis sp. nov. Two species, formerly attributed to Asellopsis Brady and Robertson, 1873 (namely A. arenicola Chappuis, 1954 and A. chappuisius Krishnaswamy, 1957), are allocated to Tapholeon based on the absence of sexual dimorphism in the swimming legs P2-P4. The former of the two species is redescribed based on additional material from the Comoros. An updated generic diagnosis and a key to the six species of Tapholeon are included. © 2007 Taylor & Francis.
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Whole-genome shotgun sequencing of mitochondria from ancient hair shafts
- Although the application of sequencing-by-synthesis techniques to DNA extracted from bones has revolutionized the study of ancient DNA, it has been plagued by large fractions of contaminating environmental DNA. The genetic analyses of hair shafts could be a solution: We present 10 previously unexamined Siberian mammoth (Mammuthus primigenius) mitochondrial genomes, sequenced with up to 48-fold coverage. The observed levels of damage-derived sequencing errors were lower than those observed in previously published frozen bone samples, even though one of the specimens was >50,000 14C years old and another had been stored for 200 years at room temperature. The method therefore sets the stage for molecular-genetic analysis of museum collections.
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The archaebacterial communities in Antarctic bathypelagic sediments
- 16S ribosomal DNA clone library analysis was performed to assess archaeal diversity within three surficial sediment samples obtained from the bathypelagic zone (depth: 2165-3406 m) of the Weddell Sea, Antarctica. The nearly complete 16S rDNA gene (1440 bp) was obtained for 146 clones and 46 phylotypes were defined. The majority of the sequences (99\%) formed three clusters within the Marine Group I Crenarchaeota. The most important cluster, with 78.8\% of the clones, included Candidatus Nitrosopumilus maritimus, a mesophilic archaeon able to oxidize ammonia. The most important subgroup in that cluster was the APA4-0cm subgroup (with 62.3\% of the clones). This subgroup might represent important Crenarchaeota in the functioning of the bathypelagic sedimentary ecosystems of the Weddell Sea because it dominated the clone libraries in all sampling stations, and was found in sediments separated by very large geographic distances. Only one clone grouped within the Euryarchaeota. This euryarchaeal clone could not be affiliated with any of the previously defined clusters and might represent a novel euryarchaeal lineage. © 2007 Elsevier Ltd. All rights reserved.
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Phylogenetic relationships and classification of the Malagasy pseudoxyrhophiine snake genera Geodipsas and Compsophis based on morphological and molecular data
- Based on a specimen found at Montagne d'Ambre in northern Madagascar morphologically agreeing with Compsophis albiventris Mocquard, 1894, we report on the rediscovery of this enigmatic snake genus and species and its molecular phylogenetic relationships. Compsophis albiventris, considered to be the only representative of its genus and unreported since its original description, bears strong morphological similarities to species of Geodipsas Boulenger, 1896. A molecular phylogeny based on DNA sequences of three mitochondrial and nuclear genes (complete cytochrome b, fragments of 16S rRNA and c-mos) in Compsophis albiventris and three Geodipsas species corroborated close relationships between C. albiventris and Geodipsas boulengeri, and showed that the genera Compsophis and Geodipsas together form a monophyletic unit. Despite the general similarities, morphological data and chromatic features support the existence of two species groups, corresponding to Compsophis and Geodipsas. We consequently consider Geodipsas as a subgenus of Compsophis and transfer all species currently in Geodipsas into the genus Compsophis. Copyright © 2007 Magnolia Press.
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Conodont-based graphic correlation of upper Givetian-Frasnian sections of the Eastern anti-atlas (Morocco)
- A high-resolution correlation of ten upper Givetian-Frasnian sections spread over the different facies environments of the Eastern Anti-Atlas (Morocco) is established using graphic correlation. The measured stratigraphic ranges of eighty-five conodont taxa have been assembled into a chronostratigraphic framework. The developed regional composite subdivides the Frasnian into 501 composite standard units (CSU) based on the original thickness of the reference section (Bou Tchrafine). This is a higher resolution than obtained by the classic biozone correlation. Based on the conodont data available for this correlation project, the jamieae and Lower rhenana zones could not be recognised in the sections.
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Non-marine Chersodromia Walker from Southeast Asia and Papua New Guinea (Diptera, Empidoidea, Hybotidae)
- Two small species of Chersodromia Walker are described from lowland rain forest in Papua New Guinea and Thailand: C. flavicaput sp. nov. (Papua New Guinea, Thailand) and C. obscura sp. nov. (Thailand). The species are almost completely white, except for the contrastingly black eyes. Although the eyes touching on the face and wing venation suggest affinities with Nanodromia Grootaert, the extended gena, bristling on the apical half of the hind tibia and structure of the male genitalia indicate inclusion in Chersodromia. The new species represent the first non-marine Chersodromia reported from Southeast Asia and Papua New Guinea. Copyright © 2007 Magnolia Press.
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Causes of variability in diatom and Phaeocystis blooms in Belgian coastal waters between 1989 and 2003: A model study.
- Massive blooms of Phaeocystis colonies usually occur in the Belgian coastal zone (BCZ) between spring and summer diatom blooms but their relative magnitude varies between years. In order to understand this interannual variability, we used the biogeochemical MIRO model to explore the link between diatom and Phaeocystis blooms and changing nutrient loads and meteorological conditions over the last decade. For this application, MIRO was implemented in a simplified 3-box representation of the domain between the Baie de Seine and the BCZ. MIRO was run over the 1989–2003 period using actual photosynthetic active radiation (PAR), seawater temperature and riverine nutrient loads as forcing. The water mass residence time was calculated for each box based on a monthly water budget estimated from 1993–2003 water flow simulations of the three-dimensional hydrodynamical model COHSNS-3D. Overall MIRO simulations compare fairly well with nutrient and phytoplankton data collected in the central BCZ but indicate the importance of the hydrodynamical resolution frame for correctly describing the extremely high nutrient concentrations and biomass observed in the BCZ. Analysis of model results suggests that while interannual variability in diatom biomass depends on both meteorological conditions (light and temperature) and nutrient loads, Phaeocystis blooms are mainly controlled by nutrients. Further sensitivity tests with varying N and P loads suggest that only N reduction will result in significantly decreased Phaeocystis blooms without negative affects on diatoms, while P reduction will negatively affect diatoms. Moreover, Atlantic nutrient loads play such a great role in BCZ enrichment that reduction of Scheldt nutrient loads only is not sufficient to significantly decrease phytoplankton blooms in the BCZ. It is concluded that future nutrient reduction policies aimed to decrease Phaeocystis blooms in the BCZ without impacting diatoms should target the decrease of N loads in both the Seine and the Scheldt rivers.
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Dispersal mechanisms in amphipods: A case study of Jassa herdmani (Crustacea, Amphipoda) in the North Sea
- Jassa herdmani (Walker 1893), a tube-building amphipod typical of hard substrates, was found in large densities on shipwrecks from the Belgian part of the North Sea, in association with the hydrozoan Tubularia indivisa. In this area, shipwrecks only represent the source of hard substrates in an environment dominated by soft sediments. Nevertheless, the long-distance dispersal of Jassa species has never been investigated. Therefore, we tested the hypothesis of dispersal with currents, by investigating the behaviour of J. herdmani in the laboratory. Size distribution revealed that newly released juveniles (1 mm) predominated throughout the year and the lower frequency of the size class 1-3 mm indicates a high mortality or a dispersal at this life stage. Individuals of J. herdmani may initiate actively the transport by tidal or surface currents by swimming to the surface of the water or by floating at the surface, as suggested by behaviours noted in the laboratory. The reaction of the amphipods to a current was investigated in the laboratory. We could not detect any sexual function associated with drifting and there was also no preponderance of a size class in the drifting individuals. When testing different substrates, we observed a significant influence of the substrate type on the frequency at which drifting occurred: J. herdmani showed a better adherence on T. indivisa compared to other substrates. Finally, the amphipod showed also a preference for its host compared to other substrates, which suggests a possible detection mechanism. © 2007 Springer-Verlag.
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Isolation and characterization of polymorphic microsatellite markers in Galapagos prickly pear (Opuntia) cactus species: Primer note
- The Opuntia (prickly pear) genus contains over 200 species. Six of them are endemic to the Galapagos archipelago. Although these cacti are 'keystone' species of the Galapagos' semi-arid ecosystem, they have never been studied in detail. Because of their current threatened status and their important role in the ecosystem, we developed 16 microsatellite markers to study the population genetic structure of some of these species. These markers display a high level of polymorphism with numbers of alleles per locus ranging from six to 53. Results also revealed possible polyploidy in these cacti. © 2006 The Authors.
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Holocene sedimentary evolution and palaeocoastlines of the Lower Khuzestan plain (southwest Iran)
- The Holocene sequence of the Lower Khuzestan plain in southwest Iran has been investigated in the context of coastal evolution and relative sea-level change. A literature review about the coastal evolution of the Shatt-el Arab region with respect to relative sea-level changes is provided. The sedimentary succession in undisturbed hand-operated cores and temporary outcrops is described and facies are identified on the basis of lithology, sedimentary structures and macrofossils. Four main sedimentary environments are interpreted from the Holocene sedimentary record of the plain: brackish tidal flat, clastic coastal sabkha, brackish-freshwater marsh and fluvial plain. The study of the vertical and spatial distribution of sedimentary facies, their environmental interpretation especially with respect to the relationship to tide levels is done for five different zones in the plain. Chronological control is provided by radiocarbon dates. On the basis of this analysis, palaeogeographical reconstructions of the Lower Khuzestan plain, and the northern extension of the Persian Gulf were made for different points in time between 8000 and 450 cal BP. This study shows that during the early and middle Holocene, the Lower Khuzestan plain was a low-energy tidal embayment under estuarine conditions. During the initial sea-level rise of the early Holocene, the coastline rapidly transgressed across the shelf, and drowning of a major valley resulted in the development of extended tidal flats. Deceleration of sea-level rise after approximately 5500 cal BP, together with probably more arid conditions, allowed coastal sabkhas to extend widely and to aggrade while the position of the coastline remained relatively stable. Continued deceleration of sea-level rise initiated the progradation of the coastline from ca. 2500 cal BP. The effect of sediment supply by the rivers became more important than the effect of relative sea-level rise. The Karun megafan developed under a descelerating rate of sea-level rise, controlling the avulsive shifting of the rivers Karkheh and Jarrahi and their loci of sediment input. Moreover, in this study it is suggested that a Holocene RSL highstand, above the present-day sea level, as suggested by previous workers, did not occur. © 2007 Elsevier B.V. All rights reserved.
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The gynogenetic reproduction of diploid and triploid hybrid spined loaches (Cobitis: Teleostei), and their ability to establish successful clonal lineages - On the evolution of polyploidy in asexual vertebrates
- Polyploidisation is assumed to have played a significant role in the evolution of hybrid asexual lineages. The virtual absence of natural asexual systems in which more than a single ploidy level successfully establishes successful independent clonal lineages is generally explained by the strong effects of polyploidisation on fitness. Experimental crosses were made between diploid and triploid asexual Cobitis elongatoides x C. taenia hybrids (female) and both parental spined loach species (male). Genotyping of the progeny using allozymes and multilocus DNA fingerprinting, along with flow cytometric measurement of ploidy level, demonstrated the occurrence of gynogenetic reproduction in both female biotypes. The incorporation of the sperm genome occurred in some progeny, giving rise to a higher ploidy level, but the rate of polyploidisation differed significantly between the diploid and triploid females. These outcomes are consistent with the existence of developmental constraints on tetraploidy, which determine the rarity of tetraploids in natural populations. No cases of ploidy level reduction were observed. Since diploid and triploid hybrid populations occur where the lack of potential progenitor excludes the possibility of de novo origin, it is probable that both diploid and triploid females can establish successful clonal lineages. Spined loaches represent a unique example, among asexual vertebrates, where more than one ploidy level can establish persistent clonal lineages, which are reproductively independent of one another. © 2007 Springer Science+Business Media, Inc.
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Phylogeography of western Palaearctic reptiles - Spatial and temporal speciation patterns
- A phylogeographic analysis of eight species complexes of European reptiles was performed using different molecular methods. While mitochondrial genes (mainly cytochrome b sequences) enabled conclusions about phylogeography and differentiation, additional application of bisexually inherited markers provided information about speciation stages. As species with similar distribution patterns in southern and Central Europe were selected, matching phylogeographic patterns are useful for drawing general conclusions:(1)The species complexes are in different stages of speciation. In some cases, cryptic species were detected.(2)Highest genetic diversity occurs in southern Europe, the Near East and the Caucasus, regions corresponding with glacial refuges in the Iberian, Apennine and Balkan Peninsulas as well as in Turkey and the Caucasus. Often, several microrefugia must have existed in close neighbourhood. Additional microrefugia were located in southern France and in the Carpathian Basin.(3)North Africa and the Middle East did not serve as glacial refuges for Central or northern European lineages and are typically inhabited by independent clades.(4)Evidence for multiple range retractions and expansions, which were postulated for the times of Pleistocene climatic oscillations, could be found in the Balkans, but in Central Europe their traces have been wiped out by the last glacial. Only the Holocene invasion has left imprints in the genomes from this area.(5)Central and northern Europe were recolonized from Balkan and Pontic refugia in the Holocene.(6)Groups from the Iberian and Apennine Peninsulas rarely conquered other regions. This limitation can be attributed to the barrier function of the Pyrenees and the Alps. © 2007 Elsevier GmbH. All rights reserved.
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Effects of mating, breeding system and parasites on reproduction in hermaphrodites: Pulmonate gastropods (Mollusca)
- There are approximately 20 000 pulmonate gastropod species that are all hermaphroditic and (with a few exceptions) can act in both (i.e., male and female) sexual roles. Life history traits such as growth (rate), age at first reproduction, fecundity, fertility, future survival and offspring survival are highly variable within pulmonate species, even among individuals of the same population. Here, we review some aspects of reproduction (availability of partners, size-dependent sex allocation, courtship, (multiple) mating, sperm longevity/viability, social facilitation), breeding system (selffertilisation, outcrossing or mixed) and parasitism that may influence an individual's reproductive success and therefore account for part of the intraspecific variation in life history traits. A literature study showed that fecundity, fertility and/or growth are significantly affected by: i) the mating group size through changes in interference competition (e.g., crowding), breeding system and sex allocation; ii) individual body size with larger individuals producing more eggs than smaller individuals; iii) mating whereby female fitness may be positively or negatively affected; iv) social facilitation whereby female fitness is positively affected by the presence of conspecifics; v) the breeding system including the phenomena of inbreeding and outbreeding depression; and vi) parasites that may suppress or stimulate reproduction, especially egg-laying, in parasitised individuals. Moreover, multiple mating and multiple paternity seem very common in pulmonates. Interestingly, several of the above-mentioned aspects seem to interact or even act synergetically. Although many aspects of life history variation in pulmonate gastropods are still poorly understood which makes it difficult to draw general conclusions, pulmonates offer ample opportunities to study the evolution of major topics in evolution and life history strategies. Indeed, there is a growing number of basommatophoran and stylommatophoran model species, experimental setups and molecular, histological and histochemical techniques that are used to test current hypothesis on sex allocation, sexual selection (sexual conflict, sperm competition or cryptic female choice), the evolution of breeding systems and host-parasite interactions which will yield much information for the study of life history strategies as well. © Koninklijke Brill NV 2007.
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Metallothionein gene and protein expression as a biomarker for metal pollution in natural gudgeon populations
- Gudgeons (Gobio gobio) from historically Cd and Zn contaminated sites in Flanders (Belgium) were found to be resistant to elevated Cd levels. In previous work, this increased resistance was largely explained by increased metallothionein (MT) expression. Recently, environmental cleanup efforts resulted in a significant decrease in Cd concentrations in the surface water. In this study, we evaluated the use of hepatic metal and metallothionein (MT) concentrations as biomarkers of metal exposure before and after the cleanup. Hepatic MT mRNA levels were determined after the environmental metal levels decreased in order to assess the applicability of MT gene expression as an environmental biomarker in natural fish populations. Our data show that both metallothionein protein and gene expression have the potential to be sensitive biomarkers for metal exposure. Significant correlations were found (a) among accumulated metal concentrations and both MT protein and mRNA levels, and (b) between MT protein and mRNA levels. However, our data illustrated that while MT protein and gene expression give a quantitative picture of metal load at a single time point, quantitative information in natural populations cannot always be obtained when different time points (including different years) are compared, since MT gene and protein expression are affected by many other factors in addition to the metal load. Furthermore, the result of the environmental cleanup was reflected in a decrease of hepatic Cd concentrations. Zn remained the most important factor determining MT concentrations. Finally, two differently sized MT mRNAs were amplified to test the hypothesis that 3′-UTR length can offer a protective advantage in conditions of environmental stress. Our data provided no evidence to support this hypothesis. In contrast, the ratio of the long mRNA variant relative to total MT mRNA was surprisingly constant, and independent of exposure history. © 2007 Elsevier B.V. All rights reserved.
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First record of the rotifer Lecane shieli Segers and Sanoamuang, 1994 from Australia
- The monogonont rotifer Lecane shieli is recorded for the first time from Australia (Bora Channel in the Macquarie Marshes, New South Wales: 30.65872° S/147.53 144° E). Until recently, L. shieli was known only from Thailand, where the species was first described. This Australian record of a Thai 'endemic' is interesting in considering possible dispersal and biogeographical distribution.
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Stefania evansi (Groete Creek carrying frog): Froglet carrying
