RESUMEN
In a process called silvering, European eels prepare for their long-distance migration from European freshwater systems to the Sargasso Sea for reproduction. During this journey, eels perform extended diel vertical migrations, and the concomitant changes in hydrostatic pressure significantly affect the swimbladder, functioning as a buoyancy organ. As the swimbladder is primarily filled with oxygen, the tissue has to cope with extreme hyperoxic conditions, which typically are accompanied by the generation of reactive oxygen species (ROS) and oxidative stress. In addition, since the introduction of the parasitic nematode Anguillicola crassus in the early 1980s, swimbladder function of most of the European eels is impaired by the infection with this parasite. However, the exact pathways to detoxify ROS and how these pathways are affected by silvering or the infection are still unknown. In swimbladder and muscle tissue from uninfected and infected yellow, and from uninfected and infected silver eels, we measured the level of lipid peroxidation, which increases with ROS stress. To assess the capacity of the ROS defense systems, we analyzed the activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and glutathione reductase (GR), and determined the concentration of the antioxidant glutathione (GSH + GSSG). In swimbladder tissue, we found increased concentrations of GSH + GSSG as well as higher activities of SOD, GPx and GR, suggesting that SOD and the glutathione cycle are important for ROS detoxification. Comparing swimbladder tissue of uninfected yellow with uninfected silver eels, the concentration of GSH + GSSG and the activity of SOD were higher after silvering, corresponding with lower levels of lipid peroxidation. Whereas in yellow eels the infection with A. crassus had no effect, in silver eels the capacity to cope with ROS was significantly impaired. In muscle tissue, silvering or the infection only affected the activity of SOD but in exactly the same way as in swimbladder tissue.
Asunto(s)
Sacos Aéreos/metabolismo , Anguilla/parasitología , Dracunculoidea/patogenicidad , Enfermedades de los Peces/parasitología , Especies Reactivas de Oxígeno/metabolismo , Animales , Antioxidantes/metabolismo , Catalasa/metabolismo , Enfermedades de los Peces/metabolismo , Glutatión/metabolismo , Glutatión Peroxidasa/metabolismo , Glutatión Reductasa/metabolismo , Músculo Esquelético/metabolismo , Músculo Esquelético/parasitología , Estrés Oxidativo , Infecciones por Spirurida/metabolismo , Infecciones por Spirurida/veterinaria , Superóxido Dismutasa/metabolismoRESUMEN
Two closely related parasites, Anguillicola crassus and Anguillicola novaezelandiae, originally parasitizing swim bladders of the Japanese eel (Anguilla japonica and the Short-finned eel (Anguilla australis), respectively, were used for analyzing the infection success of each parasite species on either long-known, recently acquired or new definitive host species and the associated effects on the eels' swim bladders. On that account, European eels (Anguilla anguilla) and Japanese eels were experimentally infected with both Anguillicola species in the laboratory. Susceptibility of the two eel species to both parasite species was determined by analyses of infection data. Subsequently, histopathological effects of the nematodes on the hosts' swim bladders were characterized according to already established indices.The present study revealed significant differences between the four different host-parasite systems regarding recovery rates, infrapopulations, and damage levels. Both nematode species achieved significantly lower recovery rates in Japanese eels than in European eels, since the examined swim bladders of Japanese eels contained a high amount of dead encapsulated larvae, whereas those of European eels contained only living nematodes. Encapsulation of larvae in Japanese eels was associated with a distinct thickening of the swim bladder walls. The swim bladders of uninfected Japanese eels turned out to be generally thicker than those of European eels. Infection with both Anguillicola species resulted in a further thickening process of the swim bladder walls in Japanese eels, whereas those of European eels showed only minor changes. The two established classification systems turned out to be inapplicable, since the measurements and the macroscopic evaluations of the swim bladders of the two infected eel species did not entirely correspond to the underlying criteria.
Asunto(s)
Sacos Aéreos/parasitología , Anguilla/parasitología , Dracunculoidea/patogenicidad , Enfermedades de los Peces/parasitología , Infecciones por Spirurida/veterinaria , Sacos Aéreos/patología , Animales , Copépodos , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades , Dracunculoidea/crecimiento & desarrollo , Femenino , Enfermedades de los Peces/patología , Interacciones Huésped-Parásitos , Larva , Masculino , Infecciones por Spirurida/parasitología , Infecciones por Spirurida/patología , VirulenciaRESUMEN
BACKGROUND: Anguillicola crassus, a swim bladder nematode naturally parasitizing the Japanese eel, was introduced about 30 years ago from East Asia into Europe where it colonized almost all populations of the European eel. We conducted a common garden experiment under a reciprocal transfer design infecting both European and Japanese eels with populations of A. crassus from Germany, Poland and Taiwan. We tested, whether differences in infectivity, developmental dynamics and reproductive output between the European and Asian parasite populations occur while harboured in the specimens of native and colonized eel host, and if these differences are genetically based or are plastic responses to the new environment. RESULTS: Under common garden conditions an evolutionary change in the both European parasite populations of A. crassus compared with their Taiwanese conspecifics was observed for infectivity and developmental dynamics, but not for reproductive output. When infecting the European eel, current European populations of the parasite were less infective and developed faster than their Taiwanese conspecifics. In the reciprocally infected Japanese eel the genetically induced differences between the parasite strains were less apparent than in the European eel but higher infectivity, faster development and higher larval mortality of the European parasite populations could be inferred. CONCLUSIONS: The differences in infectivity and developmental dynamics between European and Taiwanese populations of A. crassus found in our study suggest rapid genetic divergence of this parasite after a successful host switch in Europe.
Asunto(s)
Sacos Aéreos/parasitología , Anguilla , Evolución Biológica , Dracunculoidea/genética , Enfermedades de los Peces/parasitología , Animales , Dracunculoidea/patogenicidad , Dracunculoidea/fisiología , Aptitud Genética , Especificidad del Huésped , ReproducciónRESUMEN
Non-invasive diagnoses for most of the extraintestinal helminth infections among vertebrates are rare. In the present study, we developed and tested a non-invasive visual diagnosis method to detect the infection of the nematode Philometra ovata, which is parasitising in the body cavity of the common minnow Phoxinus phoxinus. By observing the surface of minnow's abdomen, we diagnosed infected minnows with irregular or vermiform-shaped uplifts as a consequence of the presence of P. ovata in the body cavity. We conducted the diagnosis in minnows with or without anaesthetisation, and our results showed the non-invasive method is highly reliable (correct rate of diagnoses > 95 %) in both anaesthetised and non-anaesthetised groups. The correct rate of diagnoses in truly uninfected fish (i.e. specificity) was nearly 100 % in both groups, while the correct rate of diagnoses in truly infected fish (i.e. sensitivity) was 71 and 65 % in anaesthetised and non-anaesthetised fish, respectively. The correct rate in fish diagnosed as infected or uninfected (i.e. positive or negative predictive power) of non-invasive diagnosis was nearly 100 % among the anaesthetised fish, and over 95 % in non-anaesthetised group. The diagnosis also yielded prevalence of P. ovata infection similar to the real prevalence in anaesthetised fish. Diagnoses conducted by an inexperienced observer indicated that the method is repeatable. Taken together, the present non-invasive method seems to be a promising new tool for non-invasive detection of P. ovata infections in minnows and probably can be applied for the detection of other body cavity dwelling metazoan parasites in various host taxa.
Asunto(s)
Cyprinidae/parasitología , Dracunculoidea/patogenicidad , Enfermedades de los Peces/diagnóstico , Enfermedades de los Peces/parasitología , Parasitología/métodos , Infecciones por Spirurida/veterinaria , Medicina Veterinaria/métodos , Animales , Enfermedades de los Peces/patología , Sensibilidad y Especificidad , Infecciones por Spirurida/diagnóstico , Infecciones por Spirurida/parasitología , Infecciones por Spirurida/patologíaRESUMEN
Three-spined sticklebacks Gasterosteus aculeatus are frequent paratenic hosts of the nematode parasites Anguillicola crassus and Camallanus lacustris. As paratenic hosts, sticklebacks could spread infection by carrying high numbers of infective stages. In contrast, low infective ability of either parasite for the paratenic host could hinder the spread of infection. In the present study, G. aculeatus was, for the first time, infected under controlled laboratory conditions with defined doses of the parasites. Sticklebacks were exposed to 6, 12, 18 and 24 parasite larvae to determine the infective ability of the 2 nematode species. There were significantly higher infection rates for C. lacustris (18 to 49%) than for A. crassus (4 to 14%) at each exposure dose. In C. lacustris-infected sticklebacks, infection rates tended to be highest after exposure to 12 C. lacustris larvae and lowest after exposure to 24 parasites. In A. crassus-infected sticklebacks, no effect of parasite exposure dose on infection rates was observed. Immunity parameters such as respiratory burst activity and lymphocyte proliferation of head kidney leukocytes recorded 18 wk post exposure were not significantly affected by either parasite or exposure dose. Granulocyte:lymphocyte ratios were elevated only within the stickleback group showing the highest infection intensity of C. lacustris, i.e. to those exposed 18 parasites.
Asunto(s)
Enfermedades de los Peces/parasitología , Nematodos/patogenicidad , Infecciones por Nematodos/veterinaria , Smegmamorpha/parasitología , Animales , Copépodos/parasitología , Dracunculoidea/patogenicidad , Granulocitos , Linfocitos/sangre , Nematodos/aislamiento & purificación , Infecciones por Nematodos/parasitología , Estallido Respiratorio/inmunología , Espirúridos/patogenicidad , Infecciones por Spirurida/parasitología , Infecciones por Spirurida/veterinariaRESUMEN
During a survey of parasites of Percichthys trucha (Cuvier et Valenciennes) (Perciformes: Percichthyidae) in northwestern Patagonian lakes, a new dracunculoid of the family Guyanemidae was found parasitizing as adults the heart of the fish. This species belongs to the genus Pseudodelphis Adamson et Roth, 1990 by having deirids, glandular multinucleate oesophagus and anterior branch of the uterus, and by lacking caudal alae and a gubernaculum. Pseudodelphis limnicola sp. n. differs from Pseudodelphis oligocotti Adamson et Roth, 1990 by the number and distribution of the cephalic papillae, a muscular oesophagus submerged into the glandular portion and by lacking a peribuccal ring. This is the first record of a guyanemid inhabiting the heart of a Neotropical perciform fish.
Asunto(s)
Dracunculoidea/clasificación , Enfermedades de los Peces/parasitología , Corazón/parasitología , Perciformes/parasitología , Animales , Argentina , Dracunculoidea/anatomía & histología , Dracunculoidea/patogenicidadRESUMEN
The pathogenicity of female Philometra obturans (Prenant, 1886) was investigated. Fish samples were taken in May and June 2001 from Lake Littoistenjärvi, in southwest Finland. The intensity of infection varied between 1 and 4 worms, these being found in the afferent artery of the 2 outermost gill arches. The prevalence was 33.9% (n = 59). Host condition and tissue reactions were investigated through dissection and analysis of histopathology. The parasites obstructed the gill arteries, and the arterial wall was stretched around intact worms. Hypertrophy of the arterial wall was observed, especially when only disintegrating remains of the parasites were present. Infected pike were in a poorer condition after catch, transportation, and holding in aquaria and thus less tolerant to stress than uninfected pike. This was correlated with the number of infected gill arteries (P < 0.05). The results show that infection with this nematode has a detrimental effect on the host when combined with environmental or physiological stress and may result in host mortality.
Asunto(s)
Dracunculoidea/patogenicidad , Esocidae/parasitología , Enfermedades de los Peces/parasitología , Branquias/irrigación sanguínea , Infecciones por Spirurida/veterinaria , Animales , Arterias/parasitología , Arterias/patología , Femenino , Finlandia , Enfermedades de los Peces/patología , Agua Dulce , Branquias/parasitología , Branquias/patología , Infecciones por Spirurida/parasitología , Infecciones por Spirurida/patologíaRESUMEN
Gravid females of the nematode Philometra lateolabracis (Yamaguti, 1935), a parasite of gonads of marine perciform fishes, were found in wild and cultured dusky grouper Epinephelus marginatus (Lowe) from waters near the Balear Islands (Spain, Mediterranean Sea) and Sicily (Italy, Thyrrenean Sea), and in the greater amberjack Seriola dumerili (Risso) in Croatia (south-eastern Adriatic Sea). In wild E. marginatus in Spain, the overall prevalence was 21% and the intensity of infection 1 nematode per fish. The nematodes are briefly described and illustrated. The species Sanguinofilaria jordanoi López-Neyra, 1951, described from the ovary of Epinephelus gigas Brünich from Morocco, is synonymized with P. lateolabracis. This is the first documented record of P. lateolabracis from fishes of the Mediterranean region and its finding in S. dumerili represents a new host record. The possible importance of this pathogenic parasite for cultures of marine perciform fishes in the region is stressed.
Asunto(s)
Dracunculoidea/aislamiento & purificación , Enfermedades de los Peces/epidemiología , Perciformes/parasitología , Infecciones por Spirurida/veterinaria , Animales , Dracunculoidea/anatomía & histología , Dracunculoidea/patogenicidad , Femenino , Enfermedades de los Peces/parasitología , Gónadas/parasitología , Región Mediterránea/epidemiología , Mar Mediterráneo , Prevalencia , Infecciones por Spirurida/epidemiología , Infecciones por Spirurida/parasitologíaRESUMEN
The ability of the nematode Anguillicola crassus to infect eel larvae (glass-eel stage) was tested. The results show that glass-eels fed on infected copepods, the natural intermediate host of the nematode, can be infected. Light microscopical examination of the infected developing swimbladder tissue revealed that the infection results in a significant thickening of the connective tissue. The basolateral labyrinth of gas gland cells is very much reduced in infected swimbladders, and the distance of gas gland cells to blood capillaries is enlarged. Critical swimming speed, defined as the speed where the larvae were no longer able to swim against the current, was similar in infected and uninfected animals. At intermediate speeds (about 60-80% of critical swimming speed) infected eels showed a slightly higher swimming activity than control animals. Resting oxygen consumption, measured as an index of metabolic activity, within the first 2 months of infection was higher in control animals, which may be due to a reduced rate of activity in infected glass-eels. By 4-5 months after the infection, however, it was significantly higher in infected animals. This may indicate that at this stage a higher activity of the animals is required to compensate for the increase in body density, but swimming performance of infected and non-infected glass-eels was not significantly different. Oxygen consumption during swimming activity, measured in a swim tunnel at 50% of maximal swimming speed, also was not affected. The results thus show that even glass-eels can be infected with A. crassus, and this probably contributes to the rapid spread of the nematode in Europe. While aerobic metabolism during swimming activity is not affected at this stage of infection, the swimbladder tissue shows severe histological changes, which most likely will impair swimbladder function.
Asunto(s)
Sacos Aéreos/parasitología , Anguilla/parasitología , Dracunculoidea/patogenicidad , Enfermedades de los Peces/parasitología , Infecciones por Spirurida/veterinaria , Anguilla/fisiología , Animales , Crustáceos/parasitología , Conducta Alimentaria , Consumo de Oxígeno , Infecciones por Spirurida/parasitologíaRESUMEN
The effect of salinity on hatching, larval survival and infectivity of Anguillicola crassus was studied under experimental conditions using eggs obtained from naturally infected eels. Egg hatching rate, second-stage larval survival and larval infectivity were maximal in fresh water and declined with increase in salinity. Larvae survived up to 100 d in fresh water, 70 d in 50 % sea water and 40 d in 100% sea water. Infectivity experiments demonstrated that salinity influenced transmission success throughout the life cycle by decreasing total infectivity of the larval population in utero within female A. crassus and when larvae were free-living in the aquatic environment. Infectivity was age-dependent in relation to salinity. Larvae were infective to intermediate and paratenic hosts for up to 80 d in fresh water, 21 d in 50% sea water and up to 8 d in 100% sea water. The data confirm field observations that infection levels decrease with an increase in salinity. The study contributes to experimental verification of the colonization abilities of A. crassus and supports the hypothesis that A. crassus can be disseminated and transmitted in brackish water. The importance of regular monitoring and stringent hygiene practices in the transportation of eels is emphasized.
Asunto(s)
Anguilla/parasitología , Dracunculoidea/crecimiento & desarrollo , Infecciones por Spirurida/veterinaria , Sacos Aéreos/parasitología , Animales , Crustáceos/parasitología , Cyprinidae/parasitología , Dracunculoidea/patogenicidad , Dracunculoidea/fisiología , Femenino , Peces/parasitología , Agua Dulce , Larva/crecimiento & desarrollo , Larva/patogenicidad , Distribución Aleatoria , Agua de Mar , Cloruro de Sodio , Infecciones por Spirurida/parasitologíaRESUMEN
The content of 5 macroelements and 5 microelements were analyzed using the atomic absorption method in muscle samples of European eels infected and uninfected by Anguillicola crasus. The mean contents of these substances in infected eels were statistically highly significantly lower in Ca, P, Fe, Mn, but only statistically significantly lower in Na, Mg, Zn and Cu as compared to uninfected fishes. These differences are discussed in relation to hematophagus feeding and pathogenity of the parasite.
Asunto(s)
Anguilla/parasitología , Dracunculoidea/patogenicidad , Enfermedades de los Peces/metabolismo , Músculo Esquelético/metabolismo , Infecciones por Spirurida/veterinaria , Animales , Calcio/análisis , Calcio/metabolismo , Cobalto/análisis , Cobalto/metabolismo , Cobre/análisis , Cobre/metabolismo , Enfermedades de los Peces/parasitología , Hierro/análisis , Hierro/metabolismo , Magnesio/análisis , Magnesio/metabolismo , Manganeso/análisis , Manganeso/metabolismo , Músculo Esquelético/química , Músculo Esquelético/parasitología , Fósforo/análisis , Fósforo/metabolismo , Potasio/análisis , Potasio/metabolismo , Sodio/análisis , Sodio/metabolismo , Infecciones por Spirurida/metabolismo , Infecciones por Spirurida/parasitología , Zinc/análisis , Zinc/metabolismoRESUMEN
The swimbladder parasite Anguillicola crassus Kuwahara, Niimi et Itagaki, 1974 (Nematoda: Dracunculoidea) is a well-known pathogenic parasite of the Japanese and European eels. Numerous studies on the life cycle of the parasite have revealed the involvement of a copepod or an ostracod intermediate host and a fish paratenic host, in which the third-stage larvae (L3) infective to the eel develop. The present study comprised infection experiments with the larvae of A. crassus. These experiments can be divided into three groups: (1) experimental reproduction of the parasite's life cycle via copepod intermediate hosts and fish paratenic hosts, (2) infection of another potential paratenic host with third-stage larvae of A: crassus collected from a paratenic host; (3) study of the ability of larvae damaged by paratenic hosts to infect the final host, the eel. Infection experiments have revealed that larvae which are still viable but have become encapsulated as a result of the host reaction mounted against them by cyprinid paratenic hosts (bleak, Alburnus alburnus) have lost their ability to infect the final host, the eel. At the same time, experimental infection of the eel with larvae derived from other paratenic fish hosts (river goby, Neogobius fluviatilis; ruffe, Gymnocephalus cernua) showing no or only weak host reaction proved to be successful.