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Comportement d’évitement des congénères parasités chez le crapet-soleil (Lepomis gibbosus)Côté, Ariane 02 1900 (has links)
Les animaux infectés ont une odeur, une apparence, un comportement et/ou un son
différent de leurs congénères non infectés. Ces différences peuvent servir d'indices pour
reconnaître et éviter les individus infectés. Des études récentes montrent que les hôtes
potentiels peuvent utiliser les indices visuels et/ou chimiques pour éviter les individus
infectés et minimiser les risques d'infection. Par ailleurs, la prévalence d’un parasite dans
l’environnement peut influencer l’apprentissage ainsi que la force de sélection pour la
reconnaissance et l’évitement de ce parasite. Bien qu'il existe des preuves que les poissons
utilisent des comportements d’évitement pour réduire le risque d'infection, les mécanismes
sous-jacents restent peu connus. Nous avons examiné la capacité de deux populations (naïves
et expérimentées aux parasites) de crapets-soleil (Lepomis gibbosus) à distinguer les
congénères infectés par des vers parasites et les congénères non infectés (c.-à-d. expériences
de choix binaires) en utilisant séparément les indices visuels et chimiques. En présence
d’indices visuels, les crapets ont montré une forte préférence pour leurs congénères, quel que
soit le niveau d'infection, plutôt que d'être seuls. À l’inverse, les crapets évitaient leurs
congénères et restaient seuls en présence d’indices chimiques. Nous suggérons que les
indices visuels et chimiques ne sont pas redondants et que les crapets utilisent les deux pour
prendre des décisions sociales adéquates. Les poissons des deux populations n'ont montré
aucune préférence en présence d’indices visuels de congénères infectés et non infectés.
Cependant, en présence d’indices chimiques, il existait une grande variation en termes de
préférence : certains préférant les congénères non infectés et d'autres préférant les congénères
infectés. En moyenne, notre population naïve a évité les congénères infectés alors que notre
population expérimentée n'a montré aucune préférence, ce qui suggère une habituation aux
signaux d'infection dans la population expérimentée. Nous proposons que les crapets utilisent
des indices chimiques plutôt que visuels pour discriminer leurs congénères infectés et non
infectés. Notre étude souligne l'importance de prendre en compte différents indices sensoriels
ainsi que la charge parasitaire lors de l'étude des comportements d'évitement et de formation
de bancs. Ceci est particulièrement important sachant que l'environnement chimique et visuel
ainsi que l'abondance des parasites sont modifiés par les changements globaux tel que les
pluies acides, le brunissement et l’eutrophisation des écosystèmes d’eau douce. / Infected animals smell, look, behave and/or sound different from uninfected conspecifics.
These differences can serve as cues used to recognize and avoid infected individuals. Recent studies
show that visual and/or chemical cues of infected individuals can be used by potential hosts to
modify their movement behaviours and minimize risks of infection. Furthermore, the prevalence
of a parasite in the environment can influence learning and the strength of selection for parasite
recognition and avoidance. Although there is some evidence that fishes use prophylactic behaviours
to reduce infection risk, the underlying mechanisms remain unknown. We investigated the ability
of two populations (naive and experienced to parasites) of wild caught pumpkinseed sunfish
(Lepomis gibbosus) in distinguishing between conspecifics infected with parasitic worms versus
uninfected individuals (i.e. binary choice experiments) using visual and chemical cues separately.
Pumpkinseeds showed a strong preference for conspecifics, regardless of their infection level, over
being alone when given visual cues but avoided conspecifics and remained alone when given
chemical cues. We suggest that visual and chemical cues are not redundant, and that pumpkinseeds
use both to make relevant social decisions. Fish of both populations did not show any preferences
when given visual cues of infected and uninfected conspecifics. However, in the presence of
chemical cues, there was a great variation in terms of preference: some preferring uninfected
conspecifics while others preferring the infected ones. On average, our naive population avoided
infected conspecifics whereas our experienced one did not show any preferences, suggesting
habituation to infection cues in the experienced population. We propose that pumpkinseeds use
chemical rather than visual cues to discriminate between infected and uninfected conspecifics and
make a shoaling decision. Our study highlights the importance of considering different sensory
cues as well as parasite load when studying avoidance and shoaling behaviours. This is particularly
important in a time of modifying chemical and visual environment as well as parasites abundance
through global change such as acid rain, browning and eutrophication of freshwater ecosystems.
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A critical review of the South African freshwater angling legislative framework / Morné Viljoen.Viljoen, Morné January 2010 (has links)
Prior to 1993, freshwater angling in South Africa had been governed by the
respective nature conservation legislation of the four South African provinces, the
four “independent homelands" and the six so-called Bantustans. In 1993 a South
Africa with nine provinces was created, of which only Limpopo and Mpumalanga
promulgated its own laws governing freshwater angling.
From 2008 angling for listed threatened and protected freshwater fish species has
been regulated by the National Environmental Management: Biodiversity Act,
supplemented by the Threatened or Protected Species Regulations. In addition, it is
anticipated that the Alien and Invasive Species Regulations, which will regulate
angling for listed alien and invasive freshwater fish, will be promulgated in the near
future. The result is that freshwater angling is currently being governed by a plethora
of pre-1993 provincial, homeland and Bantustan legislation, two post-1993 provincial
acts, as well as post-1993 national legislation.
In this dissertation the South African freshwater angling legislative framework was
critically analysed. It was found that the multitude of fragmented and complex laws,
created 15 “angling provinces” which leads to confusion amongst anglers and
government officials alike. In the process legal certainty and reasonableness,
cornerstones of a sound legal system, are being compromised, indigenous
freshwater fish are not adequately protected and alien or invasive freshwater fish are
not properly managed.
In the light of the above, and after taking comments by anglers and enforcement
officials into account, recommendations are made for an improved legislative
framework for freshwater in South Africa. It is recommended that all freshwater fish
species be managed and/or protected on a catchment basis, as opposed to the
current provincial basis. This will ensure legal certainty and reasonableness and that
all indigenous freshwater fish which are subject to the similar threats are protected
adequately and uniformly. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2010.
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A critical review of the South African freshwater angling legislative framework / Morné Viljoen.Viljoen, Morné January 2010 (has links)
Prior to 1993, freshwater angling in South Africa had been governed by the
respective nature conservation legislation of the four South African provinces, the
four “independent homelands" and the six so-called Bantustans. In 1993 a South
Africa with nine provinces was created, of which only Limpopo and Mpumalanga
promulgated its own laws governing freshwater angling.
From 2008 angling for listed threatened and protected freshwater fish species has
been regulated by the National Environmental Management: Biodiversity Act,
supplemented by the Threatened or Protected Species Regulations. In addition, it is
anticipated that the Alien and Invasive Species Regulations, which will regulate
angling for listed alien and invasive freshwater fish, will be promulgated in the near
future. The result is that freshwater angling is currently being governed by a plethora
of pre-1993 provincial, homeland and Bantustan legislation, two post-1993 provincial
acts, as well as post-1993 national legislation.
In this dissertation the South African freshwater angling legislative framework was
critically analysed. It was found that the multitude of fragmented and complex laws,
created 15 “angling provinces” which leads to confusion amongst anglers and
government officials alike. In the process legal certainty and reasonableness,
cornerstones of a sound legal system, are being compromised, indigenous
freshwater fish are not adequately protected and alien or invasive freshwater fish are
not properly managed.
In the light of the above, and after taking comments by anglers and enforcement
officials into account, recommendations are made for an improved legislative
framework for freshwater in South Africa. It is recommended that all freshwater fish
species be managed and/or protected on a catchment basis, as opposed to the
current provincial basis. This will ensure legal certainty and reasonableness and that
all indigenous freshwater fish which are subject to the similar threats are protected
adequately and uniformly. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2010.
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Effekte von abwasserinduzierten Ionenimbalanzen auf die Reproduktion von Fischen am Beispiel von Danio rerioWagler, Marit 04 August 2020 (has links)
Die salzhaltigen Abwässer des Kalibergbaues führen in natürlichen Süßwassersystemen zu Ionenimbalanzen und einer sekundären Versalzung der Werra in Deutschland. Die Auswirkungen dieser Ionenungleichgewichte auf die Reproduktion von Süßwasserfischen wurden unter Verwendung der Modellfischart Danio rerio untersucht. Angepasst an die aktuellen Grenzwerte für die Einleitung der Abwässer aus dem Kalibergbau wurden fünf verschiedene Kombinationen erhöhter Ionenkonzentrationen getestet. Während eines partiellen Lebenszyklustests wurden adulte Fische 35 Tage lang in den Salzkombinationen exponiert. Anschließend wurden die Nachkommen dieser Fische bis zum 8. Tag nach der Befruchtung den gleichen Salzkonzentrationen ausgesetzt. Zusätzlich wurden Early-Life-Stage-Tests (ELST) mit den Nachkommen von nicht exponierten Eltern durchgeführt. Im Vergleich zu natürlich vorkommenden Ionenkonzentrationen und -verhältnissen in Süßwassersystemen war die Befruchtungsrate der Eier für alle Ionenkombinationen signifikant niedriger, die Koagulations- und Deformationsrate jedoch signifikant höher. Die ELST ergaben bei den Embryonen und Larven u.a. vorzeitige und verlängerte Schlupfzeiten, verringerte Überlebensraten, erhöhte Deformationsraten und Herzschlagfrequenzen sowie Unregelmäßigkeiten des Ganzkörpergehalts von K, Mg, Na und Ca und des Ganzkörper-Ionenverhältnisses von Ca:Mg bei erhöhten Ionenkonzentrationen und Ionenimbalanzen. Im Vergleich zu den Effekten auf die Fortpflanzung und Entwicklung der Nachkommen waren die Effekte auf die adulten Tiere moderat. Die Ergebnisse dieser Dissertation zeigen, dass Teillebenszyklus-Tests besser als Fischeitests oder ELST geeignet sind, die Effekte von durch Abwasser verursachten Ionenimbalanzen, auf die Fortpflanzung und frühe Entwicklung von Süßwasserfischen, zu untersuchen. Weder die momentan gültigen noch die zukünftig herabgesetzten Grenzwerte bis 2027 sind danach als unschädlich, für die Reproduktion von Süßwasserfischen, zu betrachten. / The potash mining industry discharges saline effluents which generate ion imbalances in natural freshwater systems and cause severe secondary salinization in the river Werra in Germany. The effects of these ion imbalances on reproduction of freshwater fish were investigated using the fish model species Danio rerio. Five different combinations of elevated ion concentrations adjusted to the current threshold values for the discharge of potash mining effluents in Germany were tested. During a partial life cycle test, adult fish were exposed to the salt combinations for 35 days. Subsequently, the offspring were exposed to the same concentrations until hatch, and the larvae were further reared at the exposure concentrations from hatch until the 8th day post fertilization. Additionally, a standard early life stage test with offspring from unexposed parents was performed. Compared to naturally occurring ion concentrations and ratios in freshwater systems, the fertilization rate of the eggs was significantly lower for all ion combinations, while coagulation and deformation rates were significantly higher. Early life stage tests on embryos and larvae revealed premature and prolonged hatching times, reduced survival rates, increased deformation and heart rates and irregularities in whole body content of K, Mg, Na and Ca and whole body Ca:Mg ratios at elevated ion concentrations and imbalances of ion ratios. Compared to effects on reproduction and development of the offspring, effects on the parental generation were moderate. The results of this dissertation indicate that partial life cycle tests instead of fish egg tests or ELST are needed to examine most sensitively the effects of ion imbalances caused by potash mining effluents on reproduction and early development of freshwater fish. Neither the recent German threshold values nor the future reduced values until 2027 are safe for the reproduction of freshwater fish.
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Effets d'une infection parasitaire sur la condition corporelle et les traits de comportement du crapet-soleil (Lepomis gibbosus)Gradito, Maryane 08 1900 (has links)
Le parasitisme est de plus en plus considéré comme un facteur écologique pouvant créer des variations dans le comportement des individus. Toutefois, la direction de causalité entre le comportement et le parasitisme reste incertaine. Les infections expérimentales sont le plus souvent réalisées en laboratoire, limitant les inférences écologiques. À l’aide d’une infection expérimentale semi-naturelle, nous avons infecté avec succès des crapets-soleils (Lepomis gibbosus) dans un lac où ils ont été exposés à une variété de vers parasites (trématodes, cestodes), permettant d’examiner les effets de la co-infection naturelle chez les hôtes. Nous avons mesuré la témérité, l’exploration et l’activité avant et après l’infection expérimentale. En utilisant une approche bayésienne, nous avons trouvé que les traits de comportement initiaux exercent une forte influence sur la susceptibilité à l’infection : les poissons les plus téméraires et/ou les moins actifs au départ ont acquis une plus grande densité de points noirs (c.-à-d. points noirs visibles sous la peau, les nageoires et dans les muscles du poisson) et de cestodes lors de l’infection. Par ailleurs, nous avons montré que la condition corporelle est réduite par la densité de cestodes, suggérant la débilitation de l’hôte. La condition corporelle était corrélée positivement avec la distance parcourue, quel que soit le statut d’infection individuel. Nous avons également trouvé une relation négative entre la distance parcourue après l’infection et la densité de trématodes, suggérant que l’infection causant la maladie des points noirs diminue le niveau d’activité des hôtes. La témérité et l'exploration n'étaient pas affectées par la densité parasitaire ou la condition corporelle. Nous suggérons que la diminution de l’activité est causée par une réponse adaptative de l’hôte, visant à rediriger son énergie pour combattre l’infection. Sachant que les points noirs ont un cycle de vie complexe et que le crapet-soleil est un hôte intermédiaire, ce changement dans le comportement de l’hôte pourrait aider le parasite à compléter sa transmission aux oiseaux-hôtes piscivores en augmentant la prédation sur les poissons infectés. Bien que nous ne puissions confirmer la direction de causalité, nos résultats montrent qu’il existe un lien étroit entre le comportement et le parasitisme. Nous suggérons que deux mécanismes peuvent simultanément agir : le comportement initial des individus influence le risque d’infection, et l’infection peut créer de la variation au niveau de la plasticité comportementale des individus. / Parasitism is increasingly seen as an ecological factor that can create variations in individual behaviour. However, the direction of causality between behaviour and parasitism remains uncertain. Experimental infections are most often conducted in laboratories, limiting ecological inferences. Using a semi-natural experimental infection, we successfully infected pumpkinseed sunfish (Lepomis gibbosus) in a lake where they were exposed to various parasitic worms (trematodes, cestodes), allowing us to examine the effects of natural co-infection in hosts. We measured boldness, exploration, and activity before and after the experimental infection. Using a Bayesian approach, we found that initial behavioural traits strongly influence infection susceptibility: initially bolder and/or less active fish acquired a higher density of black spots (i.e., visible black spots under the skin, fins, and in the fish's muscles) and cestodes during the infection. Additionally, we found that body condition was reduced by cestode density, suggesting host debilitation. Body condition was positively correlated with distance swam, regardless of individual infection status. We also found a negative relationship between distance swam after infection and trematode density, suggesting that infection causing black spot disease decreases host activity levels. Boldness and exploration were not affected by parasite density or body condition. We suggest that a decrease in activity is caused by an adaptive host response to redirect its energy to combat the infection. However, since trematode parasites have a complex life cycle and pumpkinseed sunfish are intermediate hosts, decreases in activity levels following infection may make infected fish more susceptible to predation by piscivorous birds, which is needed for trematodes to complete their life cycles. While we cannot confirm the direction of causality, our results show a close link between behaviour and parasitism. We propose that two mechanisms may simultaneously operate: the initial behaviour of individuals influences their risk of infection, and infection can create variation in behavioural plasticity of individuals.
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Untersuchungen zum Auftreten von Myxosporidien bei Nutz- und Wildfischarten aus Binnengewässern der DDRSedlaczek, Jürgen 16 February 2016 (has links)
Die Arbeit verfolgt das Ziel, eine Übersicht über die bei verschiedenen Süßwasserfischarten festgestellten Myxosporidien zu geben. Aus Gewässern der DDR-Bezirke Potsdam, Berlin, Frankfurt (Oder), Cottbus und Dresden wurden 1.850 Fische (1.015 Karpfen, 258 Regenbogenforellen, 143 Silberkarpfen, 104 Plötzen sowie weitere 22 Fischarten in geringer Zahl untersucht. Es wurden 40 Myxosporidienarten folgender taxonomischer Gruppen nachgewiesen: Myxidiidae (7), Sphaerosporidae (6), Chloromyxidae (4) und Myxobolidae (23). In der Arbeit sind Maße, Fotos und Zeichnungen der Parasiten enthalten. Es wurden Angaben über die Taxonomie, Organspezifität, Saisondynamik, Epizootiologie und Auswirkungen auf die Fischgesundheit gemacht. Es erfolgte ein Vergleich mit früheren Arbeiten in der DDR auf diesem Gebiet. Der Artenbestand an Myxosporidien konnte um 39 Arten erweitert werden. Anhand faunistischer Arbeiten aus benachbarten Ländern wurden die Bedeutung und Perspektiven zum Auftreten von Myxosporidiosen in der DDR herausgestellt. / This work aims to give an overview about the detected Myxosporeans in different species of freshwater fishes. From inland waters of the GDR districts Potsdam, Berlin, Frankfurt (Oder), Cottbus and Dresden 1.850 fishes (1.015 carps, 258 rainbow trouts, 143 silver carps, 104 roach and more 22 Fish species in small numbers were studied. 40 Myxosporean species of following taxonomic groups were detected: Myxidiidae (7), Sphaerosporidae (6), Chloromyxidae (4) und Myxobolidae (23). In this work are presented dimensions, photos and drawings of the parasites. Details are given on taxonomy, organ specificity, season dynamics, epizootiology and the impact on fish health A comparison with previous work in the GDR on this subject was carried out. The species inventory on Myxosporidia could be extended to 39 species. Based on faunal work from neighboring countries the importance and prospects for occurrence of Myxosporidiosis in the GDR were highlighted.
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