Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 15

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  Gymnocephalus cernuus
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
EN
Background. Ruffe, Gymnocephalus cernuus is a small fish inhabiting vast areas of Europe, Asia, and also North America. Its substantial geographical dispersal range in different climatic zones, in waters of different parameters indicates that this is a particularly plastic species. Recent implementation of new fish-processing machinery has increased dramatically the economical importance of ruffe, which is now treated as a gourmet food. In the wake of the increased interest in this fish we decided to study aspects of its developmental biology. Methods. Fertilised eggs and the developing embryos of ruffe were incubated under five different temperature regimes. They were monitored in two planes, horizontal and vertical, using a light microscope fitted with a digital camera and connected to a computer with a monitor and a VCR. The data collected were processed using MultiScan software. Results. Perivitelline space in ruffe constitutes as much 65% of the egg volume. This facilitates movements of an embryo and enhances processes of gas exchange through mixing of perivitelline fluid. It finally contributes to the distribution of the hatching enzyme on the inner surface of the egg shell. Similarly as in the other percid fish, the lack of integration between the "lipid raft" and the embryonic disc, causes the fall of the disc on the lateral side of the vitelline sphere. This lateral position persists throughout all sequential stages of the embryogenesis. The diversified thermal regimes of the development affect the timing of the embryogenesis, as well as the condition, weight, and the size of newly-hatched ruffe larvae. The highest rate of specimens hatched in good condition-marked by the highest weight and body length-was observed at the optimal temperature range of 16-18oC. Newly-hatched larva is small (5 mm body length, 0.10 mm3 of yolk sac volume), active, and fully prepared for independent life in the water. Under the optimal temperature range, determined in the present study, the duration of embryonic development of ruffe (from fertilisation to hatching) was 2122 dh (accumulated degree-hours). Conclusion. The present study constitutes a contribution to the knowledge of the embryonic development of ruffe and its biological sense, emphasizing the morpho-physiological differences between this species-living under, specific, diversified ecological conditions-and other fish.
EN
Anguillicola crassus is an Asian nematode accidentally introduced to Europe and parasitising the swimbladder of European eels. Planktonic copepods are the major intermediate hosts but the success of this parasites depends on small fishes, acting as paratenic hosts and transmitting the nematode to eels. The role played by cyprinids and percids in the life cycle of A. crassus in the Vistula Lagoon was analysed. A total of 2398 fish specimens (1091 percids and 1307 cyprinids) were examined within December 1994-March 1997. The presence of the nematode was recorded in zander (Sander lucioperca), European perch (Perca fluviatilis), ruffe (Gymnocephalus cernuus), carp bream (Abramis brama), ziege (Pelecus cultratus), and roach (Rutilus rutilus), the ruffe being the most heavily infected fish species. The present findings advance our knowledge on the biology A. crassus and will help to predict its spread to other bodies of water.
EN
From May 1993 to April 1995 a comparative study on the seasonal dynamics of Phyllodistomum folium (von Olfers, 1816) infection was carried out on 633 blue bream, Abramis ballerus (L.) and 266 ruffe, Gymnocephalus cernuus (L.) from the Oder River (Germany/Poland). In blue bream, the monthly prevalences and mean intensities of infection varied irregularly throughout the year: prevalence values attained up to 50% and mean intensities reached 7.6 (range: 1-34) trematodes per infected fish. Conversely, in ruffe a temperature dependent occurrence of P. folium was observed: both the prevalence and mean intensity of infection were significantly higher at a water temperature beneath 10°C than above, with a highest monthly prevalence of 60.8% and a mean intensity of 2.9 (range: 1-7) P. folium. Juvenile and gravid trematodes were found in blue bream and ruffe at all seasons. Based on this study, it is concluded that (a) infection of fish is possible throughout the year, and that (b) modifications in course of infection are determined by the host species rather than on water temperature.
EN
The food composition of small common bream, roach, pikeperch and ruffe was studied in the shore area of the Włocławek Reservoir between July and October 1999. Zoobenthos and pelagic Chironomidae pupae dominated. Rotifers, copepods and cladoceran pelagic zooplankton were almost not consumed at all. Common bream fed mainly on benthic cladoceran Chydoridae and Chironomidae larvae. Roach consumed vegetation, Chironomidae larvae and small molluscs Sphaeriidae. Ruffe ate Chironomidae larvae, and pikeperch ate fish and various developmental stages of Chironomidae. Pelophilous chironomid forms, mainly from the genus Chironomus, dominated among the consumed larvae. Due to its exceptional abundance, the benthic fauna in the Włocławek Reservoir is an attractive food source for fish, and it plays an important role in their diet from the earliest life stages onwards. The benthic fauna also provides good developmental conditions, especially for typical benthic feeders.
PL
Zbadano skład pokarmu 61 małych leszczy i 53 płoci oraz 48 małych sandaczy i 44 jazgarzy pozyskanych ze Zbiornika Włocławskiego 21 lipca, 24 sierpnia i 3 października 1999 roku. Ryby odławiano późnym popołudniem lub wieczorem, w płytkim (0,5-2 m głębokości) pasie przybrzeżnym (40-50 m szerokości) w rozlewiskowej części zbiornika, przy prawym brzegu na wysokości około 640-641 km biegu Wisły. W pokarmie badanych ryb dominował zoobentos i pelagiczne poczwarki Chironomidae. Wrotkowo-widłonogowo-wioślarkowy zooplankton pelagiczny nie był prawie wcale zjadany. Leszcz spożywał głównie naddenne wioślarki Chydoridae oraz larwy Chironomidae (łącznie w poszczególnych miesiącach stanowiły one od 83 do 92% udziału wagowego - tab. 1), płoć - pokarm roślinny, larwy Chironomidae oraz drobne małże Sphaeriidae (od 98 do 100% - tab. 2), jazgarz - larwy Chironomidae (od 99 do 100% - tab. 3), a sandacz - ryby i różne stadia rozwojowe Chironomidae (od 99 do 100% - tab. 3). Wśród zjadanych larw ochotkowatych dominowały pelofilne formy z rodzaju Chironomus. Zbiornik Włocławski jest typowo rzecznym, silnie przepływowym (czas retencji wynosi 4-5 dni), płytkim i wysoce eutroficznym zbiornikiem zaporowym. Obfitość fauny dennej jest w nim wyjątkowo duża, a zooplanktonu pelagicznego jest znacznie mniej. W takich warunkach zoobentos jest atrakcyjnym źródłem pokarmu dla różnych gatunków ryb (zróżnicowanych pod względem możliwości pobierania pokarmu dennego) i już od wczesnych etapów ich życia odgrywa ważną rolę w odżywianiu się. Stwarza to dogodne warunki do rozwoju zwłaszcza dla typowych bentosożerców.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.