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  • 1
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Tetracycline was used as a chemical tag in a mark-recapture study to examine the pattern of increment formation in the otoliths of Tropheus moorii, a rock-dwelling cichlid from Lake Tanganyika. A total of 256 fish were captured by divers and injected with tetracycline. Of these, nine were recaptured after either 1 or 2 years at liberty and eight retained tags within their otoliths. Comparison of the number of growth increments formed after the tag and the time at liberty demonstrated that increments were deposited on an annual basis in the otoliths of this species. Furthermore, there was a strong relationship between otolith mass and age suggesting that otoliths grew at a predictable rate throughout the life of the fish. Validation of an annual pattern of increment deposition allowed age and growth information to be derived from otoliths. This showed that T. moorii grew rapidly to attain adult size by 3 years of age. Males grew faster than females and also attained a larger size than females (8·74 v. 7·91 cm LS respectively). The longevity of some of these small freshwater fish was surprising; the oldest individual had an age of 10 years, while the average age of adults was 4 years.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 45 (1994), S. 180-184 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Microbial deterioration of materials - case histories and countermeasures for plastics and natural materials: Paper and additivesDuring the production of paper and cardboard several aspects of microbiological attack may be observed. Paper raw materials, additives and the end product paper itself are attacked by microorganisms. The results are deterioriation and an alteration of the properties of valuable raw materials and a reduction of the paper quality. The greatest important economic loss arises from slime formation in the fiber preparation systems and in the paper machine itself. Biofilms are the reason for break-downs in production and affect the quality of the product.This article describes the sites where trouble during production occurs, the effects and value of the loss based on microbiological growth. Chemical and technical arrangements to reduce the origin of damages are discussed.
    Notes: Bei der Papier- und Kartonherstellung können verschiedene Bereiche mit mikrobiell bedingten Schädigungsvorgängen unterschieden werden. Papierroh- und Hilfsstoffe unterliegen dem mikrobiologischen Befall ebenso wie das Endprodukt Papier. Die Folgen sind Abbau und Eigenschaftsveränderung der wertvollen Rohstoffe und die Qualitätsminderung des Endproduktes. Der weitaus größte wirtschaftliche Schaden entsteht durch die Schleimbildung in den Stoffaufbereitungsanlagen sowie in den Papiermaschinen selbst. Die Biofilmbildung ist die Ursache für Produktionsstörungen und Qualitätseinbußen.Der Artikel beschreibt die mikrobiologisch bedingten Störungsursachen und Auswirkungen sowie die Höhe der daraus resultierenden Schäden. Es werden sowohl chemische als auch technische Maßnahmen zur Reduzierung der Schadensursachen diskutiert.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2021-05-19
    Description: Lake Kanyaboli (Kenya), a satellite lake of Lake Victoria, has been suggested as a potential refugium for haplochromine cichlids that have gone extinct in Lake Victoria. We employed mitochondrial DNA and microsatellite DNA molecular markers as well as feeding ecology studies to re- evaluate the evolutionary and ecological significance of Lake Kanyaboli haplochromines. The mitochondrial DNA and microsatellite markers revealed high genetic diversity in the endangered Xystichromis phytophagus and also the presence of mtDNA haplotypes that may have either gone extinct in Lake Victoria or have arisen in situ. Lake Kanyaboli thus acts as a ‘genetic reservoir’ for the Lake Victoria species flock. Gut content analysis revealed six trophic groups among the six haplochromine species. The haplochromine community in Lake Kanyaboli therefore exhibits trophic specializations. The relatively high trophic diversity in this cichlid community contrasts with the currently simplified trophic relationships of Lake Victoria. This high trophic diversity contributes to high energy flow and overall ecological efficiency of the lake. Lake Kanyaboli and similar satellite lakes therefore provide an opportunity for conservation of both genetic and trophic diversity threatened by introduction of exotics in the Lake Victoria basin. Lake Kanyaboli should thus be recognized as an important Evolutionary Signficant Unit (ESU) for Lake Victoria region haplochromine species. Basin wide molecular genetic characterization of the other tilapiine cichlid species as a basis of identifying genetically robust stocks that can be used in aquaculture or to restock Lake Victoria should be undertaken.
    Description: Published
    Description: Xystichromis phytophagus
    Keywords: Genetics ; Swamps ; Lakes ; Swamps ; Inland waters ; Water reservoirs ; Species extinction ; Resource conservation ; Resource management ; Tropical fish ; Genetics ; Swamps ; Lakes ; Resource conservation ; Environment management ; Rare resources ; Resource management ; Trophic relationships ; Genetic diversity ; Swamps ; Inland waters ; Water reservoirs ; Freshwater lakes ; Species extinction ; Ecological efficiency
    Repository Name: AquaDocs
    Type: Proceedings Paper
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  • 4
    Publication Date: 2021-02-22
    Description: The Neogene and Quaternary are characterized by enormous changes in global climate and environments, including global cooling and the establishment of northern high-latitude glaciers. These changes reshaped global ecosystems, including the emergence of tropical dry forests and savannahs that are found in Africa today, which in turn may have influenced the evolution of humans and their ancestors. However, despite decades of research we lack long, continuous, well-resolved records of tropical climate, ecosystem changes, and surface processes necessary to understand their interactions and influences on evolutionary processes. Lake Tanganyika, Africa, contains the most continuous, long continental climate record from the mid-Miocene (∼10 Ma) to the present anywhere in the tropics and has long been recognized as a top-priority site for scientific drilling. The lake is surrounded by the Miombo woodlands, part of the largest dry tropical biome on Earth. Lake Tanganyika also harbors incredibly diverse endemic biota and an entirely unexplored deep microbial biosphere, and it provides textbook examples of rift segmentation, fault behavior, and associated surface processes. To evaluate the interdisciplinary scientific opportunities that an ICDP drilling program at Lake Tanganyika could offer, more than 70 scientists representing 12 countries and a variety of scientific disciplines met in Dar es Salaam, Tanzania, in June 2019. The team developed key research objectives in basin evolution, source-to-sink sedimentology, organismal evolution, geomicrobiology, paleoclimatology, paleolimnology, terrestrial paleoecology, paleoanthropology, and geochronology to be addressed through scientific drilling on Lake Tanganyika. They also identified drilling targets and strategies, logistical challenges, and education and capacity building programs to be carried out through the project. Participants concluded that a drilling program at Lake Tanganyika would produce the first continuous Miocene–present record from the tropics, transforming our understanding of global environmental change, the environmental context of human origins in Africa, and providing a detailed window into the dynamics, tempo and mode of biological diversification and adaptive radiations.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 5
    Publication Date: 2005-05-03
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 6
    Publication Date: 2015-11-20
    Description: Assessing an opponent’s strength is an important component of attack strategies in territorial combats between males. Body size is often considered to directly influence an individual’s strength, but other honest visual signals may also affect the assessment of opponents. Among such visual signals are the so-called egg-spots, a conspicuous ovoid marking on the anal fin of male haplochromine cichlid fishes, made up of carotenoid-containing and other pigment cells. It has long been assumed that egg-spots are mainly relevant in courtship and spawning behavior, and previous work has focused primarily on their function in intersexual selection. Recently, however, both body size and egg-spots have been suggested to play a role in male–male interactions. To test whether egg-spots function in female choice or whether egg-spots and/or body size function as a predictor of strength and the subsequent attack strategy in male–male interactions, we performed a series of behavioral experiments in the haplochromine cichlid Astatotilapia calliptera . The trials revealed a limited involvement of egg-spots in female choice, yet a much stronger influence in male interactions. Territorial males combined information from the strength assessment based on body size and egg-spots to adopt their attack strategies. They launched more attacks against the larger intruder with many egg-spots compared with the smaller intruder without or with fewer egg-spots. Our study provides evidence that egg-spots serve as honest visual signal and that the level of asymmetries in egg-spot pattern and body size determines the relative impact of each trait in strength assessment.
    Print ISSN: 1045-2249
    Electronic ISSN: 1465-7279
    Topics: Biology
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  • 7
    Publication Date: 2013-09-16
    Description: Sex determination mechanisms are highly variable across teleost fishes and sexual development is often plastic. Nevertheless, downstream factors establishing the two sexes are presumably conserved. Here, we study sequence evolution and gene expression of core genes of sexual development in a prime model system in evolutionary biology, the East African cichlid fishes. Using the available five cichlid genomes, we test for signs of positive selection in 28 genes including duplicates from the teleost whole-genome duplication, and examine the expression of these candidate genes in three cichlid species. We then focus on a particularly striking case, the A- and B-copies of the aromatase cyp19a1 , and detect different evolutionary trajectories: cyp19a1A evolved under strong positive selection, whereas cyp19a1B remained conserved at the protein level, yet is subject to regulatory changes at its transcription start sites. Importantly, we find shifts in gene expression in both copies. Cyp19a1 is considered the most conserved ovary-factor in vertebrates, and in all teleosts investigated so far, cyp19a1A and cyp19a1B are expressed in ovaries and the brain, respectively. This is not the case in cichlids, where we find new expression patterns in two derived lineages: the A-copy gained a novel testis-function in the Ectodine lineage, whereas the B-copy is overexpressed in the testis of the speciest-richest cichlid group, the Haplochromini. This suggests that even key factors of sexual development, including the sex steroid pathway, are not conserved in fish, supporting the idea that flexibility in sexual determination and differentiation may be a driving force of speciation.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
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  • 8
    Publication Date: 2015-02-04
    Description: Single-gene and whole-genome duplications are important evolutionary mechanisms that contribute to biological diversification by launching new genetic raw material. For example, the evolution of animal vision is tightly linked to the expansion of the opsin gene family encoding light-absorbing visual pigments. In teleost fishes, the most species-rich vertebrate group, opsins...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2013-12-11
    Description: Immune-related genes are often characterized by adaptive protein evolution. Selection on immune genes can be particularly strong when hosts encounter novel parasites, for instance, after the colonization of a new habitat or upon the exploitation of vacant ecological niches in an adaptive radiation. We examined a set of new candidate immune genes in East African cichlid fishes. More specifically, we studied the signatures of selection in five paralogs of the human immunodeficiency virus type I enhancer-binding protein ( Hivep ) gene family, tested their involvement in the immune defense, and related our results to explosive speciation and adaptive radiation events in cichlids. We found signatures of long-term positive selection in four Hivep paralogs and lineage-specific positive selection in Hivep3b in two radiating cichlid lineages. Exposure of the cichlid Astatotilapia burtoni to a vaccination with Vibrio anguillarum bacteria resulted in a positive correlation between immune response parameters and expression levels of three Hivep loci. This work provides the first evidence for a role of Hivep paralogs in teleost immune defense and links the signatures of positive selection to host–pathogen interactions within an adaptive radiation.
    Electronic ISSN: 2160-1836
    Topics: Biology
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  • 10
    Publication Date: 2014-10-03
    Description: Males and females of the same species differ largely in gene expression, which accounts for most of the morphological and physiological differences and sex-specific phenotypes. Here, we analyzed sex-specific gene expression in the brain and the gonads of cichlid fishes from Lake Tanganyika belonging to four different lineages, so-called tribes (Eretmodini, Ectodini, Haplochromini, and Lamprologini), using the outgroup Nile tilapia ( Oreochromis niloticus ) as reference. The comparison between male and female brains revealed few differences between the sexes, consistent in all investigated species. The gonads, on the other hand, showed a large fraction of differentially expressed transcripts with the majority of them showing the same direction of expression in all four species. All here-studied cichlids, especially the three investigated mouth-breeding species, showed a trend toward more male- than female-biased transcripts. Transcripts, which were female-biased in expression in all four species, were overrepresented on linkage group (LG)1 in the reference genome and common male-biased transcripts showed accumulation on LG23, the presumable sex chromosomes of the Nile tilapia. Sex-specific transcripts contained candidate genes for sex determination and differentiation in fishes, especially members of the transforming growth factor-β-superfamily and the Wnt-pathway and also prominent members of the sox-, dm-domain-, and high mobility group-box families. We further confirmed our previous finding on species/lineage-specific gene expression shifts in the sex steroid pathway, including synthesizing enzymes as the aromatase cyp19a1 and estrogen and androgen receptors.
    Electronic ISSN: 1759-6653
    Topics: Biology
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