Search publications of the members of the Royal Belgian institute of natural Sciences
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Valken voor iedereen. Hoe het grote publiek in Brussel de Slechtvalken op hun nest kan gadeslaan.
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The taxonomic status of the Venezuelan snakes Atractus matthewi and A. nororientalis (Serpentes, Colubridae)
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Morphological variation in Leptodactylus lutzi (anura, leptodactylidae) with description of its advertisement call and notes on its courtship behavior
- Prior to this study, Leptodactylus lutzi was known only from three localities in west-central Guyana. We refer here to a series of 60 additional specimens of L. lutzi collected in Kaieteur National Park, Mount Ayanganna, Mount Wokomung and the Merume Mountains in the Pakaraima Mountains region, substantially extending the known distribution of the species. We provide a revised diagnosis and an expanded description of L. lutzi discussing the extent of color-pattern variation in the species. Additionally, we describe its advertisement call and provide data on its reproductive biology. © 2007 Departamento de Ciências Biológicas.
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The genus Longidorus (Nematoda: Longidoridae) from Bohemia and South Moravia in the rhizosphere of fruit orchards and vineyards
- The occurrence and geographic distribution of the genus Longidorus was investigated during a nematological survey of Bohemia and South Moravia between 2003 and 2006. Soil samples were collected from 139 different fruit orchards and vineyards. Three Longidorus species (L. elongatus, L. euonymus and L. leptocephalus) were recorded. L. euonymus constitutes a new record for the Czech nematofauna. © 2007 Parasitological Institute of SAS.
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Modelling the relative impact of rivers (Scheldt/Rhine/Seine) and Western Channel waters on the nutrient and diatoms/Phaeocystis distributions in Belgian waters (Southern North Sea).
- The coastal areas of the Southern North Sea (SNS) experience eutrophication problems resulting from freshwater nitrogen (N) and phosphorus (P) inputs from rivers. In particular, massive blooms of Phaeocystis colonies occur in Belgian waters. In this region, water masses result from the mixing of Western Channel (WCH) waters transported through the Straits of Dover with nutrient-rich freshwater from the Scheldt, the Rhine and Meuse, the Seine, the Thames and other smaller rivers. However, the relative contribution of the WCH and each river to the inorganic nutrient pool and the impact on the phytoplankton community structure (diatoms and Phaeocystis) are not known. In order to effectively manage the eutrophication problems, it is necessary to know: (i) the relative contribution of the WCH and of each river impacting the region and (ii) the relative effect of a N and/or P nutrient reduction on the Phaeocystis blooms. To answer these questions, sensitivity tests (1% nutrient reduction) and nutrient reduction scenarios (50% nutrient reduction) have been performed with a three-dimensional (3D) coupled physical–biogeochemical model (MIRO&CO-3D). MIRO&CO-3D results from the coupling of the COHERENS 3D hydrodynamic model with the ecological model MIRO. The model has been set up for the region between 48.5°N, 4°W and 52.5°N, 4.5°E and run to simulate the annual cycle of carbon, inorganic and organic nutrients, phytoplankton (diatoms and Phaeocystis), bacteria and zooplankton (microzooplankton and copepods) in the SNS under realistic forcing (meteorology and river inputs) for the period 1991–2003. The relative contribution of the WCH waters and of the different rivers on the inorganic nutrient pool available for phytoplankton (diatoms and Phaeocystis) growth is assessed by decreasing by 1% the nutrient (dissolved inorganic nitrogen, DIN and inorganic phosphate, PO4) inputs from the WCH and from, respectively, the Scheldt (and smaller Belgian rivers), the Rhine/Meuse and the Seine (and smaller French rivers) [sensitivity tests]. The relative role of N and P reduction on the diatoms/Phaeocystis distribution is further explored by simulations with 50% reduction of the total (inorganic and organic) N and total P river inputs [nutrient reduction scenarios]. These scenarios allow assessing the impact of the expected 50% reduction of river nutrient inputs resulting from the implementation of nutrient reduction policy. Results of the sensitivity tests suggest that the impact of a 1% reduction of river nutrient inputs on surface nutrients (DIN and PO4) over the Belgian Exclusive Economic Zone (EEZ) area is similar for the Seine and the Scheldt, which are in turn greater than for the Rhine. However, a hypothetical 1% reduction of nutrient input from the WCH boundary would have a higher impact than for the Scheldt. The impact of nutrient reduction is higher for DIN than for PO4 whatever the river (contrary to the WCH). DIN is more sensitive to riverine nutrient reduction because the rivers are over enriched in DIN compared to PO4. The sensitivity tests suggest also that a PO4 river input reduction would result in a N:P increase and a DIN river input reduction would result in a N:P decrease but that a combined (PO4 and DIN) input reduction would reduce the N:P ratio at sea. From 50% nutrient reduction scenarios, model results suggest that a total P reduction would induce a significant decrease of diatoms and a small (coast) to negligible (offshore) decrease of Phaeocystis biomass. On the contrary, a total N reduction would induce a significant decrease of Phaeocystis biomass and a moderate increase of diatoms. When N and P river input reductions are combined, the model predicts a significant decrease of Phaeocystis biomass in Belgian waters and a significant decrease of diatom biomass in the coastal waters and a small increase offshore. A future management plan aiming at Phaeocystis reduction should thus prioritise N reduction.
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Validation of the 3D biogeochemical model MIRO&CO with field nutrient and phytoplankton data and MERIS-derived surface chlorophyll a images.
- This paper presents results obtained with MIRO&CO-3D, a biogeochemical model dedicated to the study of eutrophication and applied to the Channel and Southern Bight of the North Sea (48.5°N–52.5°N). The model results from coupling of the COHERENS-3D hydrodynamic model and the biogeochemical model MIRO, which was previously calibrated in a multi-box implementation. MIRO&CO-3D is run to simulate the annual cycle of inorganic and organic carbon and nutrients (nitrogen, phosphorus and silica), phytoplankton (diatoms, nanoflagellates and Phaeocystis), bacteria and zooplankton (microzooplankton and copepods) with realistic forcing (meteorological conditions and river loads) for the period 1991–2003. Model validation is first shown by comparing time series of model concentrations of nutrients, chlorophyll a, diatom and Phaeocystis with in situ data from station 330 (51°26.00′N, 2°48.50′E) located in the centre of the Belgian coastal zone. This comparison shows the model's ability to represent the seasonal dynamics of nutrients and phytoplankton in Belgian waters. However the model fails to simulate correctly the dissolved silica cycle, especially during the beginning of spring, due to the late onset (in the model) of the early spring diatom bloom. As a general trend the chlorophyll a spring maximum is underestimated in simulations. A comparison between the seasonal average of surface winter nutrients and spring chlorophyll a concentrations simulated with in situ data for different stations is used to assess the accuracy of the simulated spatial distribution. At a seasonal scale, the spatial distribution of surface winter nutrients is in general well reproduced by the model with nevertheless a small overestimation for a few stations close to the Rhine/Meuse mouth and a tendency to underestimation in the coastal zone from Belgium to France. PO4 was simulated best; silica was simulated with less success. Spring chlorophyll a concentration is in general underestimated by the model. The accuracy of the simulated phytoplankton spatial distribution is further evaluated by comparing simulated surface chlorophyll a with that derived from the satellite sensor MERIS for the year 2003. Reasonable agreement is found between simulated and satellite-derived regions of high chlorophyll a with nevertheless discrepancies close to the boundaries.
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Macro- and megabenthic assemblages in the bathyal and abyssal Weddell Sea (Southern Ocean)
- The assemblages inhabiting the continental shelf around Antarctica are known to be very patchy, in large part due to deep iceberg impacts. The present study shows that richness and abundance of much deeper benthos, at slope and abyssal depths, also vary greatly in the Southern and South Atlantic oceans. On the ANDEEP III expedition, we deployed 16 Agassiz trawls to sample the zoobenthos at depths from 1055 to 4930 m across the northern Weddell Sea and two South Atlantic basins. A total of 5933 specimens, belonging to 44 higher taxonomic groups, were collected. Overall the most frequent taxa were Ophiuroidea, Bivalvia, Polychaeta and Asteroidea, and the most abundant taxa were Malacostraca, Polychaeta and Bivalvia. Species richness per station varied from 6 to 148. The taxonomic composition of assemblages, based on relative taxon richness, varied considerably between sites but showed no relation to depth. The former three most abundant taxa accounted for 10-30\% each of all taxa present. Standardised abundances based on trawl catches varied between 1 and 252 individuals per 1000 m2. Abundance significantly decreased with increasing depth, and assemblages showed high patchiness in their distribution. Cluster analysis based on relative abundance showed changes of community structure that were not linked to depth, area, sediment grain size or temperature. Generally abundances of zoobenthos in the abyssal Weddell Sea are lower than shelf abundances by several orders of magnitude. © 2007 Elsevier Ltd. All rights reserved.
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Evidence for early cat taming in Egypt
- The remains are described of a young small felid found in a Predynastic burial at Hierakonpolis, Upper Egypt. Osteometric and zoogeographical arguments indicate that the specimen, dated to around 3700 B.C. on the basis of the associated pottery, belongs to Felis silvestris. In the same cemetery several other animal species, both wild and domestic, have been found. The left humerus and right femur of the cat show healed fractures indicating that the animal had been held in captivity for at least 4-6 weeks prior to its burial. We believe that this pathology suggests early cat taming more convincingly than a buried cat recently reported from Neolithic Cyprus (7500 B.C.). Such taming events were probably part of the processes that eventually led to the domestication of Felis silvestris. However, the absence of the cat in Predynastic and Early Dynastic depictions and its rare attestation in the archaeozoological record indicates that domestic status had not yet been attained during those early periods. Other species that were also held in captivity by Ancient Egyptians probably never became domesticated because they had one or more characteristics that prevented it. © 2007 Elsevier Ltd. All rights reserved.
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The Upper Miocene of the southern North Sea Basin (northern Belgium): A palaeoenvironmental and stratigraphical reconstruction using dinoflagellate cysts
- Organic-walled palynomorph assemblages from the Kasterlee Formation in northern Belgium provide new insights into the Late Miocene depositional history and palaeoenvironments of the southernmost North Sea Basin. Ranges of key dinoflagellate cysts constrain the unit between 7.5 and 5.32 Ma, that is, a latest Tortonian to Messinian age. The palynomorph assemblage is characterized, amongst others, by Geonettia clineae, an opportunistic species that thrives in mesotrophic, coastal embayments with a low sediment influx. This environmental setting is corroborated by the notable presence of Gramocysta verricula, a species with preference for shallow marine environments. The occurrence of species of the fresh water green alga Pediastrum indicates manifest river discharge in a near-shore environment or embayment. The coastal depositional environment mirrored by the palynomorphs of the Kasterlee Formation succeeds the distinct transgressive and fully marine environments of the underlying Diest Formation in the Campine area. The results from the palynological study, combined with lithological and geophysical data, show that both Upper Miocene formations are two distinct depositional cycles separated by an erosional or regressive phase. The upper boundary of the Kasterlee Formation is correlated with the Me2 sequence boundary at 5.73 Ma. The Kasterlee Formation is herein formally moved from the Lower Pliocene series to the Upper Miocene series. The coastal environment, probably characterized by a shoaling phase, recorded at the border of the southern North Sea Basin, matches the global record of regressive phases in Messinian sedimentary sequences, which are linked to cooling and increasing global ice volume. © 2006 Cambridge University Press.
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An integrated modelling approach for the management of clam farming in coastal lagoons
- The development of shellfish farming was analyzed with a coupled watershed and 3D biogeochemical model for the Sacca di Goro coastal lagoon (Northern Adriatic Sea, Italy). Sacca di Goro is the second site in Europe for the production of the Manila clam (Tapes philippinarum). Different scenarios were identified and analyzed, considering clam productivity under different environmental conditions, namely with and without macroalgal blooms. In addition, the influence of climatic variability - dry, average and wet years - was assessed. Model simulations indicated that macroalgal blooms have an important negative impact on clam productivity due to the risk of anoxia and subsequent clam mortality. Furthermore, simulation results evidenced that meteorological conditions also affect clam productivity, especially in a dry year due to a shortage of food supply. © 2007 Elsevier B.V. All rights reserved.
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On a new species and genus in the Cypridini (Crustacea, Ostracoda, Cyprididae) from South Africa, with a phylogenetic analysis of the tribe and a discussion on the genus concept in this group
- The present paper describes Mnementh brennei n. sp. n. gen., a new non-marine ostracod species and genus from temporary wetlands in the Western Cape Province (South Africa). The new genus is the fifth in the subfamily Cypridinae and a phylogenetic analysis using morphological characters demonstrates that it is most closely related to its putative sister taxon Pseudocypris. Apart from this cluster, the phylogenies are not at all robust and this is to all probability due to the incongruent (mosaic) evolution amongst the different characters in valve and soft part modules. Implications of such incongruent evolution of characters for the concept of genera in this group are discussed. © 2007 Taylor & Francis.
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Ostracodology in time and space: Looking back on fifteen International Symposia on Ostracoda, and the times in between
- Fifteen International Symposia on Ostracoda (ISO) have been organized between 1963 and 2005, each of them followed by one or more proceedings volumes. In the present study, 906 titles presented at the occasion of one of these fifteen symposia were evaluated regarding their prevailing and their secondary theme or method, thus obtaining a retrospective on the history of ostracod research between ISO1 and ISO15. This review may help in moving ostracodology into the 21st century. © 2007 Springer Science+Business Media B.V.
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On Afrocypris barnardi G. O. Sars, 1924 (Ostracoda), a second giant ostracode with additional appendages
- Afrocypris barnardi G. O. Sars, 1924, a giant temporary pool ostracode from South Africa, is here redescribed, based on new material. It is only the second time that this species has been found. The present morphological analyses show that the copulatory appendages of both sexes have unusual characteristics. In the female, at least three paired appendage-like structures (R-appendages) are associated with the Female Reproductive Organ (FRO). This is the second time that such structures are described from non-marine ostracodes, Liocypris grandis (G. O. Sars, 1924) having six pairs of such structures. The male copulatory organs have a Penile Attachment uniting the proximal sides of both hemipenes, and in Afrocypris barnardi an asymmetrical, finger-like structure is associated with this PA. The discovery of female R-appendages in a second species strengthen the interpretation of these structures as (part of) true appendages, and reinforces the hypothesis that the FRO is homologous to more than one ancestral somite. However, it remains unclear how many body segments are involved in the origin of the FRO, and three, five, or even six somites are all possible. In addition, these R-appendages can be ancestral, atavistic, or even apomorphic. The position of the two taxa with such appendages in a phylogeny of the Cyprididae as a whole will constitute a test to discriminate between these three possibilities. © 2007 Koninklijke Brill NV.
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Plumage characteristics and return rate of one-year-old tropical Roseate Terns
- We report an unusually high return rate (16\%) of one-year-old Roseate Terns (Sterna dougalli) to their natal colony on Aride Island, Seychelles, in 2005. Detailed accounts of these birds are provided in terms of timing of arrival, breeding status, and plumage characteristics, and compared with those of two other age classes (2-year-olds and 3 to 6 year-olds) in the same colony and with temperate populations. One-year-old individuals returned on average three weeks later than older birds and did not attempt to breed. Their immature plumage dress ('portlandica phase') differed from their one-year-old temperate counterparts, with most birds showing several characteristics of adults in full breeding plumage, such as red bill and red legs, long tail-streamers, and absence of a dark carpal bar. Contrary to expectations from temperate studies, nonbreeding two-year-old individuals did not retain any characteristic of the portlandica plumage, and were virtually inseparable from breeding adults. The ad hoc return rate of Roseate Tern one-year-olds found in this particular year is high compared to recapture/resighting data from colonies in temperate areas, but is comparable to observations made at other tropical (Caribbean) breeding colonies. Altogether, these findings suggest that tropical Roseate Terns are prone to return to their natal site earlier than their temperate counterparts, and show a more rapid acquisition of the adult plumage. This may be especially the case in years of good food supply conditions, since the 2005 event coincided with the two (2004-2005) of highest marine productivity recorded in the vicinity of Aride Island over the 1997-2005 period.
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Effects of annual changes in primary productivity and ocean indices on breeding performance of tropical roseate terns in the western Indian Ocean
- We assessed the influence of inter-annual changes in primary productivity and local, regional and large scale ocean indices on the breeding parameters of roseate terns Sterna dougallii on Aride Island, Seychelles, western Indian Ocean. Productivity (chicks per breeding pair), timing of breeding and clutch and egg sizes were monitored annually for 8 yr and correlated with local ocean productivity (denoted by Sea-viewing Wide Field-of-view Sensor, SeaWiFS, estimates of chlorophyll concentration, CC), sea surface temperature and indices recording the status of the Indian Ocean Dipole and of El Niño. The rate of increase in CC between mean laying date and CC peak value was positively related to roseate tern productivity and mean clutch size over the 1998 to 2005 study period. Colony productivity seemed also to be influenced by the Multivariate El Niño Index. In most years, the breeding phenology of roseate terns corresponded to the local increase in CC around Aride, and failure to adjust timing of reproduction to the timing of the phytopankton bloom decreased the probability of breeding success. This is the first study showing that a tropical seabird species is sensitive to inter-annual variations in the intensity and timing of the phytoplankton bloom, which should be connected to annual variations in the availability of its main fish prey (juvenile goatfishes). Overall, these patterns indicate that the reproduction of this top marine predator is dictated by the temporal variability in oceanographic conditions. We suggest that CC data available over the world's oceans may be a useful tool to develop models predicting the fate of colonies of inshore feeding seabirds when other, more conventional, monitoring methods cannot be used. © Inter-Research 2007.
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Rhipicephalus appendiculatus and R. zambeziensis (Acari: Ixodidae) from Zambia: A molecular reassessment of their species status and identification
- The closely related species Rhipicephalus appendiculatus and R. zambeziensis co-occur in a wide area in Zambia. In this area, specimens of both species have been collected on the same individual host at the same time. In addition, specimens that are morphologically intermediate between R. appendiculatus and R. zambeziensis have been found in this area. These observations cast some doubt on the species status of R. appendiculatus and R. zambeziensis. Because the two taxa have varied influences on the epidemiology of East Coast fever (ECF), a cattle disease for which they act as vectors, it is essential that their taxonomic status is clarified and their identification is accurate. Therefore a phylogenetic analysis of nucleotide sequences of the ITS2 and a fragment of the mitochondrial 12S rDNA was performed to reassess the specific status of both taxa. This revealed two well supported clades coinciding with R. appendiculatus and R. zambeziensis as two separate species. In order to facilitate species identification a PCR-RFLP diagnostic assay was developed based on BauI digestion of the ITS2 gene. This assay produced clear diagnostic banding patterns for the two species and is applicable over a wide range of both species' distribution. © 2007 Springer Science+Business Media B.V.
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Genetic variation in Rhipicephalus appendiculatus (Acari: Ixodidae) from Zambia: Correlating genetic and ecological variation with Rhipicephalus appendiculatus from eastern and southern Africa
- Based on their ecology, Rhipicephalus appendiculatus ticks from eastern and southern Africa have been divided into three groups. We investigated how two geographic genetically differentiated stocks of R. appendiculatus from the southern and the eastern provinces of Zambia, representing two ecological groups, i.e., southern African and transition groups, respectively, genetically compare to stocks from east Africa (Rwanda) and southern Africa (Zimbabwe and South Africa). The ITS2 and two mitochondrial genes segments, 12s rDNA and COI, were used in the investigations. The ITS2 tree did not show support for differentiation into any groups, while the two mitochondrial genes trees (12s rDNA and COI) showed two genetically differentiated groups: an east African genetic group which included specimens from Rwanda and the plateau area of the eastern province of Zambia, and a southern African genetic group represented by specimens from South Africa, Zimbabwe and specimens collected on the fringes of the eastern province plateau in the Nyimba district of Zambia. This suggests that the two geographically differentiated stocks of the southern and eastern provinces of Zambia might be part of two wider geographic genetically differentiated R. appendiculatus groups that extend beyond Zambia. Stocks of "transition" ecology (eastern province) belong to the east African genetic group and the differences in ecology within this genetic grouping may be due to genetic polymorphism, phenotypic plasticity, and other local factors.
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Further evidence for geographic differentiation in R. appendiculatus (Acari: Ixodidae) from Eastern and Southern provinces of Zambia
- Studies in the biology, ecology and behaviour of R. appendiculatus in Zambia have shown considerable variation within and between populations often associated with their geographical origin. We studied variation in the mitochondrial COI (mtCOI) gene of adult R. appendiculatus ticks originating from the Eastern and Southern provinces of Zambia. Rhipicephalus appendiculatus ticks from the two provinces were placed into two groups on the mtCOI sequence data tree. One group comprised all haplotypes of specimens from the Eastern province plateau districts of Chipata and Petauke. The second group consisted of a single haplotype of specimens from the Southern province districts and Nyimba, an Eastern province district on the fringes of the valley. This variation provides additional evidence to the earlier observations in the 12S rDNA and ITS2 data for the geographic subdivision of R. appendiculatus from Southern province and Eastern province plateau. The geographic subdivision further corresponds with differences in body size and diapause between R. appendiculatus from these geographic areas. The possible implications of these findings on the epidemiology of East Coast fever (ECF) the disease for which R. appendiculatus is one of the vectors are discussed. © 2007 Springer Science+Business Media B.V.
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Conodont biostratigraphy of shallow marine Givetian deposits from the Radom-Lublin area, SE Poland
- Detailed conodont data were obtained from 66 samples in 9 deep wells representative of three palaeogeographic regions of the Mid Devonian epicontinental basin of southeastern Poland: (1) the elevated part of the East European Platform representing the basin margin, (2) the Lublin Graben with a larger proportion of open marine systems, (3) the Radom Area characterized by more offshore, purely marine deposition and larger subsidence rates in the Radom Area. The 1344 specimens collected were assigned to 8 genera: Icriodus, Polygnathus, Ancyrodella, Belodella, Mehlina, Neopanderodus, Pandorinellina and Skeletognathus, and 38 taxa of species or subspecies rank. The vertical distribution of the conodont assemblages studied in particular sections is highly irregular and discontinuous with many barren intervals controlled by less suitable palaeocological conditions, mostly representing restricted and/or very shallow-water facies. We found only a single index species characteristic of deeper marine facies, as applied in the standard conodont zonation. Therefore the biostratigraphic interpretation also takes into account the total range of all taxa found in particular samples, established after a critical analysis of adequately published total ranges of these taxa. The stratigraphic ranges of the following taxa were modified: Icriodus arkonensis arkonensis, I. a. walliserianus, I. eslaensis, I. platyobliquimarginatus, I. subterminus, I. aff. I. subterminus, Polygnathus ansatus, P. latifossatus, P. linguiformis linguiformis, P. timorensis and P. varcus. As a result of the stratigraphic analysis of the conodont assemblages we distinguished five zones in the Givetian of the studied area, i.e. the rhenanus/varcus, ansatus, hermanni, norrisi (=lower part of Lower falsiovalis Zone) zones, and also two informal units, the subterminus and insita faunas. We documented the co-occurrence of I. subterminus and P. latifossatus which supports the earlier supposition of Rogers (1998) that the Lower subterminus Fauna may partly correspond to the Lower hermanni Zone.
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Detecting algae blooms in European waters
- A near real-time algal bloom detection service has been developed for European waters. Daily chlorophyll a data from Envisat/MERIS and Aqua/MODIS are compared to a predefined threshold map to determine whether an algal bloom has occurred. The design of the threshold map takes account of two factors. Firstly, over European waters regional differences in typical and extreme levels of chlorophyll a span two orders of magnitude. A concentration, e.g. 2 μg/1, that would be considered as a bloom concentration in one region could correspond to a relatively low concentration in another region. Secondly, the errors in satellite chlorophyll a can be significant in coastal waters effectively giving an artificial background level in satellite images. To account for these two factors a threshold map has been designed using satellite chlorophyll a data from a previous year, with separate threshold maps for each sensor to take account of sensor-specific bias. This threshold is defined here as the top 10\% level of a previous year's chlorophyll a data. The results of algal bloom detection in various regions are analysed in terms of bloom timing, duration and strength. Differences between the performance for the MERIS and Aqua sensors are also discussed.
