74 research outputs found
Current and historic gene flow of the sand goby <i>Pomatoschistus minutus</i> on the European Continental Shelf and in the Mediterranean Sea
No full textPhylogeographical patterns of the sand goby Pomatoschistus minutus (Gobiidae, Teleostei) were studied by means of sequence and single-stranded conformational polymorphism analysis of a 283-bp fragment of the cytochrome b locus of the mtDNA. A total of 228 individuals sampled at 13 sites throughout the species's distributional range revealed a moderate level of diversity and a low but significant level of overall genetic differentiation at all but one site. The goby sample from the Adriatic Sea differed in sequence by approximately 10% from the Atlantic P. minutus and is thought to belong to a cryptic species of the genus Pomatoschistus. Limited genetic differentiation with a weak pattern of isolation-by-distance was recorded throughout the distributional range of the typical P. minutus. Phylogeographical analysis suggested a contiguous range expansion in the Atlantic and Baltic basins during the Eemian and evidence for a glacial refugium in the southern North Sea during the Weichselian. In P. minutus from the western Mediterranean Sea a high number of endemic haplotypes as well as the most common Atlantic haplotype were recorded in appreciable frequencies. This might be explained by secondary contact between different mitochondrial lineages, which evolved in allopatry
Comparative visual and DNA-based diet assessment extends the prey spectrum of polar cod Boreogadus saida
No full textsponsorship: Research was funded by Research Foundation Flanders (FWO) through a fellowship for strategic basic research (FWO-SB, grant no. 1S04418N) and by a Brilliant Marine Research Idea Philanthropy Award 2019 granted by the Flanders Marine Institute (VLIZ), Belgium, to S.M.M. and was carried out with infrastructure support from European Marine Biological Resource Centre (EMBRC) Belgium-FWO project I001621N. H.C. was supported by a fellowship from the former Flemish Agency for Innovation by Science and Technology, now Flanders Innovation & Entrepreneurship (VLAIO, grant no. 141328). Fieldwork was supported by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), under expedition grant no. AWI_PS106/1_2-00 and the Netherlands Ministry of Agriculture, Nature and Food Quality (LNV) under its Statutory Research Task Nature & Environment WOT-04-009-047.04. We thank Captain Thomas Wunderlich and the crew of RV 'Polarstern' expedition PS106/2 for their support. We are very grateful to everyone who collected samples, that is Nils Koschnick, Jennifer Steffen, Erik Sulanke, Kim Vane and Susanne Fuchs with the assistance of Elisa Bravo Rebolledo, Giulia Castellani and Julia Ehrlich. We sincerely thank Birte Matthiessen, Paul E. Renaud and 2 anonymous reviewers for their constructive comments that helped improve the paper. Polar cod were sampled and processed according to and within the laws, guidelines and policies of the German Animal Welfare Organisation; no specific permissions were required. The fish collected are neither endangered nor protected in the coastal waters of the Svalbard Archipelago. Polar cod were sacrificed immediately after sampling. (Research Foundation Flanders (FWO) through a fellowship for strategic basic research (FWO-SB)|1S04418N, Flanders Marine Institute (VLIZ), Belgium, European Marine Biological Resource Centre (EMBRC) Belgium-FWO|I001621N, Flanders Innovation & Entrepreneurship (VLAIO)|141328, Helmholtz Centre for Polar and Marine Research (AWI)|AWI_PS106/1_2-00, Netherlands Ministry of Agriculture, Nature and Food Quality (LNV) under its Statutory Research Task Nature Environment|WOT-04-009-047.04, Captain Thomas Wunderlich, Alfred Wegener Institute, Academy of Finland (AKA)|141328)status: Published onlin
Reconstructing colonization dynamics of the human parasite Schistosoma mansoni following anthropogenic environmental changes in northwest Senegal
No full textSchistosoma parasites successfully colonize new regions following the construction of water schemes for power production or agricultural purposes. Here we investigated the colonization history of the human parasite Schistosoma mansoni in Northwest Senegal following the construction of two dams in the `80s. Parasites were collected at several time points following the disease outbreak and their genetic profile was characterized using molecular markers. Our results showed that many genetically different parasites must have been introduced at the onset of the epidemic, which complies with the extensive immigration of infected seasonal agricultural workers from neighboring regions in Senegal, Mauritania and Mali. Furthermore, we showed that parasite transmission occurred over a large geographic distance, which implies that new alleles, like resistance alleles, could spread rapidly in this system. These new insights demonstrate how colonization following anthropogenic environmental changes may lead to genetically diverse parasite populations within a short time span. High genetic diversity is often linked with a stronger potential to cope with selective pressures such as drug treatment, which may complicate efforts to control the disease
Weak population structure and expansive demographic history of the monogenean parasite Kapentagyrus spp. infecting clupeid fishes of Lake Tanganyika
No full textLake Tanganyika, East Africa, is the oldest and deepest African Great Lake and harbours one of the most diverse fish assemblages on earth. Two clupeid fishes, Limnothrissa miodon and Stolothrissa tanganicae, constitute a major part of the total fish catch, making them indispensable for local food security. Parasites have been proposed as indicators of stock structure in highly mobile pelagic hosts. We examined the monogeneans Kapentagyrus limnotrissae and Kapentagyrus tanganicanus (Dactylogyridae) infecting these clupeids to explore the parasites' lake-wide population structure and patterns of demographic history. Samples were collected at seven sites distributed across three sub-basins of the lake. Intraspecific morphological variation of the monogeneans (n = 380) was analysed using morphometrics and geomorphometrics of sclerotised structures. Genetic population structure of both parasite species (n = 246) was assessed based on a 415 bp fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Overall, we observed a lack of clear geographical morphological differentiation in both parasites along a north-south axis. This lack of geographical population structure was also reflected by a large proportion of shared haplotypes, and a pattern of seemingly unrestricted gene flow between populations. Significant morphological and genetic differentiation between some populations might reflect temporal differentiation rather than geographical isolation. Overall, the shallow population structure of both species of Kapentagyrus reflects the near-panmictic population structure of both host species as previously reported. Morphological differences related to host species identity of K. tanganicanus were consistent with incipient speciation at the genetic level. Both parasite species experienced a recent demographic expansion, which might be linked to paleohydrological events. Finally, interspecific hybridisation was found in Kapentagyrus, representing the first case in dactylogyrid monogeneans.sponsorship: The authors would like to thank L. Raisingerova, C. Rahmouni, H. Zimmermann, A. P. H. Bose and W. Salzburger for help with collecting host samples. M. Jorissen is gratefully acknowledged for fruitful discussions about monogenean morphological variability and help in the laboratory. Special thanks to the staff of the parasitological group at Masaryk University, Brno (Czech Republic), the Research Group Zoology at Hasselt University (Belgium), Research Centre of Hydrobiology in Uvira (DR Congo) and Fisheries Research Unit in Mpulungu (Zambia) for their hospitality. Research was supported by the Czech Science Foundation (P505/12/G112 (ECIP) and GA19-13573S), EMBRC Belgium - FWO project GOH3817N as well as by a joint program between the Austrian Agency for International Cooperation in Education and Research (OEAD; project number CZ 08/2018; to SK) and the Ministry of Education, Youth and Sports (project number 8J18AT007). MPMV was co-financed by institutional funding of the Finnish Museum of Natural History and the Belgian Directorate-General for Development Cooperation and Humanitarian Aid (CEBioS program). ELRDK was supported by the Belgian Development Cooperation through VLIR-UOS (VLADOC scholarship NDOC2016PR006 to ELRDK and South Initiative project CD2018SIN218A101). Fieldwork was carried out with the approval of the competent local authorities under mission statement 031/MINRST/CRH-U/2016 and the permission of the Fisheries Department of Zambia and under a study permit issued by the government of Zambia (SP 008732). (Czech Science Foundation|P505/12/G112, Czech Science Foundation|GA19-13573S, EMBRC Belgium - FWO project|GOH3817N, Austrian Agency for International Cooperation in Education and Research (OEAD)|CZ 08/2018, Ministry of Education, Youth and Sports|8J18AT007, Finnish Museum of Natural History, Belgian Directorate-General for Development Cooperation and Humanitarian Aid (CEBioS program), Belgian Development Cooperation through VLIR-UOS (VLADOC scholarship)|NDOC2016PR006, Belgian Development Cooperation through VLIR-UOS (South Initiative project)|CD2018SIN218A101)status: Publishe
Unravelling the evolution of Africa’s drainage basins through a widespread freshwater fish, the African sharptooth catfish Clarias gariepinus
No full textAIM: The formation history of Africa's current river basins remains largely unknown. In order to date changes in landscape and climate, we studied the biogeography of the African freshwater fish with the largest natural distribution. We also validated biogeographical units. LOCATION: Continental Africa. TAXON: Clarias gariepinus sl. METHODS: We investigated mitochondrial cytb sequences of 443 individuals from 97 localities, using a haplotype network and a genetic landscape analysis. We inferred a dated phylogeny using maximum likelihood and Bayesian inference approaches and reconstructed ancestral areas with S‐DEC and S‐DIVA models. Microsatellite genotyping complemented the mitochondrial approach in the Congo basin, where the latter revealed complex patterns. RESULTS: Limited differentiation is found in northern and south‐western Africa, and sharp genetic differentiation in the continent's east and centre. Populations with affinities to neighbouring basins occur at the edges of the Congo province. High diversity exists in the south of the Congo basin. The Zambezi province is partitioned into eastern, central and western sectors. In the east, specimens were related to those from the Congo. In the west, they were similar to Southern representatives. Phylogenetic inference placed the origin of C. gariepinus in the East Coast, with intraspecific diversification starting around the Great Lakes. These events occurred ca. 4.8–1.65 and 2.3–0.8 MYA respectively. MAIN CONCLUSIONS: Clades of C. gariepinus sl. show a clear geographical signature. The origin of C. gariepinus in the East Coast and diversification around the Great Lakes coincided with the periods of increased aridity. Low genetic differentiation in northern and southern Africa may result from connectivity during recent periods of higher rainfall. In contrast to other widespread African freshwater fish, colonization rather than extinction seemed to mediate distribution patterns. This can be explained by a high ecological tolerance. We highlight the species’ suitability to study landscape and climate evolution at various scales.sponsorship: Fonds Wetenschappelijk Onderzoek; Belgisch Ontwikkelingsagentschap (Fonds Wetenschappelijk Onderzoek, Belgisch Ontwikkelingsagentschap)status: Publishe
Evaluating genetic traceability methods for captive-bred marine fish and their applications in fisheries management and wildlife forensics
No full textGrowing demands for marine fish products is leading to increased pressure on already depleted wild populations and a rise in aquaculture production. Consequently, more captive-bred fish are released into the wild through accidental escape or deliberate releases. The increased mixing of captive-bred and wild fish may affect the ecological and/or genetic integrity of wild fish populations. Unambiguous identification tools for captive-bred fish will be highly valuable to manage risks (fisheries management) and tracing of escapees and seafood products (wildlife forensics). Using single nucleotide polymorphism (SNP) data from captive-bred and wild populations of Atlantic cod Gadus morhua L. and sole Solea solea L., we explored the efficiency of population and parentage assignment techniques for the identification and tracing of captive-bred fish. Simulated and empirical data were used to correct for stochastic genetic effects. Overall, parentage assignment performed well when a large effective population size characterized the broodstock and escapees originated from early generations of captive breeding. Consequently, parentage assignments are particularly useful from a fisheries management perspective to monitor the effects of deliberate releases of captive-bred fish on wild populations. Population assignment proved to be more efficient after several generations of captive breeding, which makes it a useful method in forensic applications for well-established aquaculture species. We suggest the implementation of a case-by-case strategy when choosing the best method
Aerial surveillance of operational oil pollution in Belgium's Maritime Zone of Interest
No full textBelgium's Maritime Zone of Interest (BMZI), including the Belgian Territorial Sea, Belgian Continental Shelf, and Bonn Agreement Zone of Multilateral Responsibility, were regularly surveyed by remote-sensing aircraft for the presence of operational oil spills between 1991 and 1995, Simultaneously wind speed and direction were recorded; wave height was obtained from the literature, In total, 228 spills of various sizes, volumes and origins mere analysed by means of univariate statistical analysis. We documented that the observed oil spills were generally elongate, narrow and thin, that spill dimensions were interrelated, and that wind speed and wave height affected these dimensions. A major fraction of the total variation however could be attributed to slick thickness. Spills found outside the Traffic Separation Scheme (TSS) tended to be smaller in surface area but showed no significant difference in average volume. Thus, the source of the spill more so than the hydrodynamics of the sea determined the characteristics of the spill. Given the impact of oil spills on marine life, continuous attention should be paid to monitoring and pollution control measures in the BMZI, (C) 2000 Elsevier Science Ltd. All rights reserved
Detecting Holocene divergence in the anadromous-freshwater three-spined stickleback (Gasterosteus aculeatus) system
No full textThe anadromous–freshwater three-spined stickleback (Gasterosteus aculeatus) system allows for inferring the role of adaptation in speciation with a high level of accuracy because the freshwater ecotype has evolved multiple times from a uniform anadromous ancestor. A cause for concern is that independent evolution among drainages is not guaranteed in areas with a poorly resolved glacial history. This is the case for the west European great rivers, whose downstream valleys flanked the southern limit of the late Pleistocene ice sheet. We tested for independent and postglacial colonization of these valleys hypothesizing that the relationships among anadromous and freshwater sticklebacks correspond to a raceme structure. We compared the reduction in plate number accompanying this colonization to the genetic differentiation using 13 allozyme and five microsatellite loci in 350 individuals. Overall microsatellite differentiation (FST = 0.147) was twice as large as allozyme differentiation (FST = 0.066). Although habitat-specific gene flow may mask the ancestral relationships among both ecotypes, levels of microsatellite differentiation supported the hypothesis of raceme-like divergence, reflecting independent colonizations rather than the presence of two distinct evolutionary clades. Under an infinite alleles model and in the absence of gene flow, the observed freshwater divergence might be reached after 440 (microsatellites) to 4500 (allozymes) generations. Hence, the anadromous–freshwater stickleback system most likely diverged postglacially. We conclude that the reduction in plate number in two freshwater basins probably occurred independently, and that its considerable variation among populations is not in agreement with the time since divergence
Identification and stage-specific association with the translational apparatus of TbZFP3, a CCCH protein that promotes trypanosome life-cycle development
No full textThe post-transcriptional control of gene expression is becoming increasingly important in the understanding of regulated events in eukaryotic cells. The parasitic kinetoplastids have a unique reliance on such processes, because their genome is organized into polycistronic transcription units in which adjacent genes are not coordinately regulated. Indeed, the number of RNA-binding proteins predicted to be encoded in the genome of kinetoplastids is unusually large, invoking the presence of unique RNA regulators dedicated to gene expression in these evolutionarily ancient organisms. Here, we report that a small CCCH zinc finger protein, TbZFP3, enhances development between life-cycle stages in Trypanosoma brucei. Moreover, we demonstrate that this protein interacts both with the translational machinery and with other small CCCH proteins previously implicated in trypanosome developmental control. Antibodies to this protein also co-immunoprecipitate EP procyclin mRNA and encode the major surface antigen of insect forms of T. brucei. Strikingly, although TbZFP3 is constitutively expressed, it exhibits developmentally regulated association with polyribosomes, and mutational analysis demonstrates that this association is essential for the expression of phenotype. TbZFP3 is therefore a novel regulator of developmental events in kinetoplastids that acts at the level of the post-transcriptional control of gene expression
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