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  • 1
    Keywords: Orbiniidae North Sea Region ; Scoloplos armiger ; Polychaeta North Sea Region ; Dissertation ; Hochschulschrift ; Nordsee ; Vielborster ; Fortpflanzung ; Populationsbiologie ; Genetik ; Scoloplos armiger ; Demökologie ; Genetik
    Type of Medium: Book
    Pages: 95 S. , Ill., graph. Darst.
    Series Statement: Berichte zur Polar- und Meeresforschung 438
    RVK:
    Language: English
    Note: Zsfassung in dt. Spr , Zugl.: Kiel, Univ., Diss., 2002
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  • 2
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (88 Seiten = 4 MB) , Illustrationen, Graphen, Karte
    Edition: 2021
    Language: German
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  • 3
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (92 Seiten = 7 MB) , Illustrationen, Graphen, Karten
    Edition: Online-Ausgabe
    Language: English
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 4
    ISSN: 1573-5117
    Keywords: predation ; Corophium arenarium ; prey escape ; drift ; zonation ; Nereis diversicolor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the European Wadden Sea, the nemertine Tetrastemma melanocephalumoccurs together with its prey, the amphipod Corophium arenarium, in the upper intertidal zone. T. melanocephalumleaves the sediment when the tide has receded and captures C. arenarium in its U-shaped burrow. Highest abundances of T. melanocephalumon the sediment surface were found on summer evenings, 2–4 h after high tide, when just a thin film of water was left on the flats. Laboratory Y-maze experiments indicated that gradients of substances produced by C. arenarium in this film of water play a role in tracking the prey. In the field, T. melanocephalum appeared in significantly higher numbers on experimental high density patches of C. arenarium. The amphipod in turn is able to recognize the nemertine. In aquarium experiments, significantly more amphipods escaped from the sediment into the water column when the predator was present. In the field, both predator and prey showed a high mobility by drifting in tidal waters. Benthic abundance maxima of T. melanocephalum and C. arenariumusually did not coincide spatially. It is assumed that the nemertines avoid tidal flats that dry out quickly leaving too little time for prey capture. T. melanocephalum is not able to dig into the sediment, but lives in burrows of Nereis diversicolor. The abundance of this polychaete was inversely related to C. arenarium, presenting a dilemma for T. melanocephalum: the spatial overlap of food and accommodation was rather small.
    Type of Medium: Electronic Resource
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  • 5
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    Springer
    In:  Marine Biology, 142 . pp. 937-947.
    Publication Date: 2018-06-07
    Description: In marine invertebrates multiple modes of development, or poecilogony, may occur in a single species. However, after close examination, many of such putative cases turned out to be sibling species. A case in point may be the cosmopolitan orbiniid polychaete Scoloplos armiger, which inhabits marine shallow sediments. In addition to the well-known direct, holobenthic development from egg cocoons, pelagic larvae have also been described. Our culture experiments revealed a spatially segregated source of the two developmental modes. All females of an intertidal population produced egg cocoons and no pelagic larvae. All but 2 out of 15 females of an adjacent subtidal population produced pelagic larvae and no egg cocoons. Based on these results we performed a molecular genetic analysis (RAPD-PCR) on three intertidal and four subtidal populations in the North Sea. Selected samples from all sites were analysed also by the AFLP method. We found significantly higher genetic diversity within subtidal than within intertidal populations. This is consistent with a wider dispersal by pelagic larvae and a smaller effective population size when development is holobenthic. Total genetic divergence is not related to distance but to the intertidal/subtidal division. We suggest that S. armiger actually represents two sibling species.
    Type: Article , PeerReviewed
    Format: text
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  • 6
    Publication Date: 2018-06-07
    Description: Two distinct modes of development in the common polychaete Scoloplos armiger (O. F. Müller, 1776) occur in the North Sea region: holobenthic development in egg cocoons and pelagic larvae hatching from suspended eggs. In the northern Wadden Sea near the island of Sylt, we observed that egg cocoons are produced intertidally while pelagic larvae originate from the adjacent subtidal zone. A previous genetic comparison between these subtidal and intertidal populations revealed distinct gene pools, suggesting that reproductive differences are not phenotypic but heritable. In this study, crossbreeding experiments show that intertidal and subtidal populations are reproductively isolated. Couples with males and females from different habitats had no offspring. Production of egg cocoons is determined by female origin from the intertidal zone. Pelagic larvae occurred only in couples with subtidal females and subtidal males. Intertidal males have spermatozoa with heads twice as long as those from subtidal males and a significantly shorter flagellum. We suspect that deviating sperm morphology may cause the reproductive breakdown at the fertilization stage. Juveniles hatching from cocoons have shorter anal cirri compared to juveniles that metamorphosed from pelagic larvae. We conclude there to be two sympatric sibling species in S. armiger: 'type I' in intertidal areas, which have egg cocoons, no pelagic larvae, elongated sperm heads, shortened sperm flagella and anal cirri; and a subtidal 'type S', lacking egg cocoons but with pelagic larvae, short sperm heads, long sperm flagella and anal cirri.
    Type: Article , PeerReviewed
    Format: text
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  • 7
    Publication Date: 2017-07-18
    Description: The model of ecological speciation implies that habitat differences may split a species by strong selection and rapid adaptation even under sympatric conditions. Recent studies on the polychaete Scoloplos armiger in the Wadden Sea, North Sea, indicate sibling species existing in sympatry: the intertidal 'Type I' with holobenthic development out of egg cocoons and the subtidal 'Type S' shedding pelagic larvae into the open water. In the current study, Type I and S are compared in habitat-related traits of reproductive timing and physiological response to hypoxia and sulphide. Spawnings of Type I and Type S recorded over six years overlap in spring and both appear to be triggered by rise in sea temperature above 5°C. Type S exhibits an additional autumn spawning (at water temperatures around 10 °C) which was unknown till now and is absent in Type I. High overall abundances of pelagic larvae in the Wadden Sea are shown. Since the pelagic dispersal mode has been neglected so far, reassessment of S. armiger population dynamics models is suggested. Tolerance against sulphide and hypoxia were both lower in Type S than in Type I. This correlates with a measured 5 to 10-fold lower sulphide concentration in the subtidal compared to the intertidal habitat. Physiological tolerance and divergence in developmental mode appear as traits which may have ultimately led to reproductive isolation between Type I and Type S. Their role in allopatric and sympatric speciation scenarios in S. armiger is discussed.
    Type: Article , PeerReviewed
    Format: text
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  • 8
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    Springer
    In:  Hydrobiologia, 456 (1/3). pp. 21-32.
    Publication Date: 2017-01-30
    Description: The ecology of nemertean predators in marine ecosystems is reviewed. Nemerteans occur in most marine environments although usually in low abundances. Some species, particularly in intertidal habitats, may reach locally high densities. During specific time periods appropriate for hunting, nemerteans roam about in search of prey. Upon receiving a stimulus (usually chemical cues), many nemertean species actively pursue their prey and follow them into their dwellings or in their tracks. Other species (many hoplonemerteans) adopt a sit-and-wait strategy, awaiting prey items in strategic locations. Nemerteans possess potent neurotoxins, killing even highly mobile prey species within a few seconds and within the activity range of its attacker. Most nemertean species prey on live marine invertebrates, but some also gather on recently dead organisms to feed on them. Heteronemerteans preferentially feed on polychaetes, while most hoplonemerteans prey on small crustaceans. The species examined to date show strong preferences for selected prey species, but will attack a variety of alternative prey organisms when deprived of their favourite species. Ontogenetic changes in prey selection appear to occur, but no further information about, e.g. size selection, is available. Feeding rates as revealed from short-term laboratory experiments range on the order of 1–5 prey items d–1. These values apparently are overestimates, since long-term experiments report substantially lower values (0.05–0.3 prey items d–1). Nemerteans have been reported to exert a strong impact on the population size of their prey organisms through their predation activity. Considering low predation rates, these effects may primarily be a result of indirect and additive interactions. We propose future investigations on these interactive effects in combination with other predators. Another main avenue of nemertean ecological research appears to be the examination of their role in highly structured habitats such as intertidal rocky shore and coral reef environments.
    Type: Article , PeerReviewed
    Format: text
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  • 9
    Publication Date: 2017-01-30
    Description: In the European Wadden Sea, the nemertine Tetrastemma melanocephalumoccurs together with its prey, the amphipod Corophium arenarium, in the upper intertidal zone. T. melanocephalumleaves the sediment when the tide has receded and captures C. arenarium in its U-shaped burrow. Highest abundances of T. melanocephalumon the sediment surface were found on summer evenings, 2–4 h after high tide, when just a thin film of water was left on the flats. Laboratory Y-maze experiments indicated that gradients of substances produced by C. arenarium in this film of water play a role in tracking the prey. In the field, T. melanocephalum appeared in significantly higher numbers on experimental high density patches of C. arenarium. The amphipod in turn is able to recognize the nemertine. In aquarium experiments, significantly more amphipods escaped from the sediment into the water column when the predator was present. In the field, both predator and prey showed a high mobility by drifting in tidal waters. Benthic abundance maxima of T. melanocephalum and C. arenariumusually did not coincide spatially. It is assumed that the nemertines avoid tidal flats that dry out quickly leaving too little time for prey capture. T. melanocephalum is not able to dig into the sediment, but lives in burrows of Nereis diversicolor. The abundance of this polychaete was inversely related to C. arenarium, presenting a dilemma for T. melanocephalum: the spatial overlap of food and accommodation was rather small.
    Type: Article , PeerReviewed
    Format: text
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  • 10
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    In:  (Diploma thesis), Christian-Albrechts-Universität, Kiel, Kiel, Germany, 74 pp
    Publication Date: 2021-07-30
    Type: Thesis , NonPeerReviewed
    Format: text
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