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ASCR > Inst. Vertebrate Biology > Dept. Fish Ecology > Martin Reichard – Research Interests |
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Bitterling-mussels coevolution /Reichard, Polačik, Ondračková, Bryja, Vrtílek/
Bitterlings (subfamily Acheilognathinae) are freshwater cyprinid fishes that evolved an unusual spawning symbiosis with living freshwater mussels. Female bitterling possess long ovipositors that they use to place their eggs onto the gills of a mussel and males fertilise the eggs by releasing sperm into the inhalant siphon of the mussel. The embryos develop inside the mussel gill cavity and actively leave the mussel after about one month. Unionid mussels that bitterling use for oviposition have parasitic larvae known as glochidia. They are released into the water column and snap shut on contact with a fish, typically attaching to the gills or fins. Once attached, the glochidia are encysted by host tissue and obtain nourishment from the fish. The relationship between bitterling and mussel has long been considered mutualistic (beneficial for both partners) on the premise that bitterling use mussels as spawning sites while the mussel benefits by using bitterling to disperse their glochidia. Our current research investigates the situation in Europe, We compare the use of mussels and mussel responses to bitterling oviposition between ancient bitterling populations from Turkey (coevolving with mussels for millions of years) and recently established populations of the bitterling in Central and Western Europe (that may be in contact for few centuries) (refs 25, 36). Collaboration with teams of Carl Smith, Serhan Tarkan, Mirek Przybylski, Tedi Trichkova, Liu Huanzhang & Jyun-ichi Kitamura Bitterling mating tactics /Reichard, Polačik, Bryja, Řežucha/
Male bitterling are territorial and court females passing near their territories. Female may spawn several times each day, laying a clutch of about 3 eggs on each occasion. Bitterling are promiscuous and do not form stable pairs. An introduction to bitterling biology is presented in ref.14. Males compete for fertilizations through aggressive interactions (ref. 17) and sperm competition (ref.10) that may lead to an effective sperm depletion (ref. 37). Sneaking fertilizations, when one male releases sperm into a mussel guarded by another male, are common and the success of sneaking increases with male density (ref. 18). Females appear to actively incite sperm competition (ref. 29) and benefit from it through the increased fertility (ref. 20). It is likely that their behaviour effectively overcomes reduction of their mate choice (ref. 30) imposed by dominant males' harassment (ref. 19). This inevitably results in intersexual conflict (ref. 36). Outcome of the conflict varies across season (ref. 32) and depends on the spatial distribution of mussels (ref. 31), with clear microevolutionary consequences (ref. 39). Collaboration with teams of Carl Smith, Bill Jordan & Mirek Przybylski. Evolutionary biology of African annual fishes (Nothobranchius) /Reichard, Polačik/
The genus Nothobranchius (Cyprinodontiformes) contains small (3-15 cm), short-living (3-12 months) fish inhabiting isolated savannah pools throughout eastern Africa. My current research involves mainly a group of Nothobranchius fishes from southern and central Mozambique, including N. furzeri - a species with the shortest lifespan among all vertebrates. Throughout its small range, N. furzeri populations vary considerably in their intrinsic longevity (from a minimum of 12 weeks !), which is likely linked to patterns of rainfall. We combine fieldwork and experimental approaches to investigate demography of wild populations and its long-term variability across N. furzeri range. At interspecific level, we investigate comparative phylogeography of three Nothobranchius species complexes (N. furzeri, N. orthonotus and N. rachovii) that differ in their habitat preference (ref. 38). We are also interested in mechanisms of species coexistence and evolution of barriers that maintain the species isolated in nature (despite their frequent hybridization in the lab). Collaboration with teams of Alessandro Cellerino, Matthias Platzer, Bettina Reichenbacher & Karel Janko Fish ecology in Niokolo-Koba National Park in Senegal, West Africa /Reichard, Ondračková, White, Petrášová, Bímová, Blažek/We have recently completed fish biology part of a long-term project (2004-2008) on species diversity and ecology of selected vertebrates in West Africa. We worked in the floodplain of the River Gambia in the National Park Niokolo-Koba in southeastern Senegal, at the southern limit of West African savannah. We have compiled database of fish species occurring within diverse habitats of the park and studied their ecology. We compared fish communities in five main habitat types (main river channel, permanent tributaries, large permanent oxbow lakes, small temporary streams and pools and spring areas and adjacent forested streams). We currently work on our extensive database from this project to understand the patterns of fish habitat use at landscape scale; a very small part was published so far (ref. 34). A large part of our work was devoted to cooperation with fish parasitologists.
Downstream drift of larval and juvenile European cyprinids /Reichard, Jurajda/
Downstream movement of early developmental stages of fishes is widespread among European cyprinids (ref. 7). During my PhD. project I demonstrated that most YOY fishes drifted along the river bank (ref. 16) and that drifting was age-dependent and seasonal (ref. 28) This is driven by presence of particular life-history stages in nursery areas (ref. 7,16). The nocturnal pattern of drift was apparent, with light levels being the key factor controlling drift behaviour (ref. 9,15). Species differed in their utilisation of the drift and at the developmental stage at which they drifted (ref. 28). Water turbidity promoted daytime drift during elevated river discharges (ref. 5,15). Most patterns of drifting were consistent among localities and populations. Drift in cyprinid fishes appeared to be an active decision to enter the current. |
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However, we found that in Europe bitterling are parasites of mussels. The presence of bitterling embryos in mussel gills decreases mussel growth, while adult bitterling actively avoid infection by glochidia (ref. 
This is combined with basic ecological studies, since data on Nothobranchius ecology are highly deficient. We further use population genetics tools to study effective population size, within-population structuring as a consequence of colour polymorphism and migration rates between individual pools, demes and metapopulations.
It may shape YOY fish assemblage structure, promote dispersal and, in some species, is part of a complex migratory behaviour.