C. Szekely - Academia.edu (original) (raw)
Papers by C. Szekely
Journal of Experimental Marine Biology and Ecology, 2007
Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principa... more Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activitiesrelated to parasite weightreduce swimming endurance, while mechanical damage of the swimbladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (b0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (b 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds.
In this study, we subjected eels from Lake Balaton (Hungary) to a swimming period of 1 week and 2... more In this study, we subjected eels from Lake Balaton (Hungary) to a swimming period of 1 week and 2 or 6 weeks. Most eels were silver and were 13–21 years old. Time dependent changes in morphometrical parameters and developmental characteristics of the oocytes were determined. Already after 1 week of swimming, the gonadal mass increased and oocytes became larger, filled with large numbers of lipid droplets. After 2 and 6 weeks of swimming we found in addition a significant enlargement of the eyes, which is a sign of sexual maturation. In contrast to the resting eels, that had oocytes in the primary growth phase (stage 1–2); the swimming eels had oocytes in stage 3; the cortical alveolus or lipid droplet stage. The results indicate that lipid mobilisation induced by swimming is a requirement for the natural incorporation of lipid droplets in the oocytes, a crucial step in oocyte maturation. As the Balaton eels responded stronger to swimming than young farmed eels, it is suggested that older eels are more sensitive for maturation triggers.
Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principa... more Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activities – related to parasite weight – reduce swimming endurance, while mechanical damage of the swim-bladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (b0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (b 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds.
In this study, we subjected eels from Lake Balaton (Hungary) to a swimming period of 1 week and 2... more In this study, we subjected eels from Lake Balaton (Hungary) to a swimming period of 1 week and 2 or 6 weeks. Most eels were silver and were 13–21 years old. Time dependent changes in morphometrical parameters and developmental characteristics of the oocytes were determined. Already after 1 week of swimming, the gonadal mass increased and oocytes became larger, filled with large numbers of lipid droplets. After 2 and 6 weeks of swimming we found in addition a significant enlargement of the eyes, which is a sign of sexual maturation. In contrast to the resting eels, that had oocytes in the primary growth phase (stage 1–2); the swimming eels had oocytes in stage 3; the cortical alveolus or lipid droplet stage. The results indicate that lipid mobilisation induced by swimming is a requirement for the natural incorporation of lipid droplets in the oocytes, a crucial step in oocyte maturation. As the Balaton eels responded stronger to swimming than young farmed eels, it is suggested that older eels are more sensitive for maturation triggers.
Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principa... more Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activities – related to parasite weight – reduce swimming endurance, while mechanical damage of the swim-bladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (b0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (b 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds.
Systematic parasitology, 2004
Seventy-seven specimens of seven freshwater fish species harvested in four sites from rivers and ... more Seventy-seven specimens of seven freshwater fish species harvested in four sites from rivers and ponds of the Gauteng, North West and Limpopo Provinces (South Africa) were surveyed for coccidian infections. Two fish species were infected with apicomplexans belonging to Goussia Labbé, 1896. In banded tilapia Tilapia sparrmanii Smith unsporulated oöcysts of G. vanasi were found which became sporulated in tapwater within 24 hours. Another species in the gut of chubbyhead barb Barbus anoplus Weber harboured sporulated oöcysts in the faeces and in the intestinal epithelium. The latter species has been described as G. anopli n. sp.
ABSTRACT: Actinospore infection of oligochaetes collected from the mud of 2 freshwater biotopes i... more ABSTRACT: Actinospore infection of oligochaetes collected from the mud of 2 freshwater biotopes in
South Africa was studied. Using the ‘cell-well plate method’, a new aurantiactinomyxon type was
found in 1.1% of the examined Branchiura sowerbyi oligochaete specimens from the Rietvlei River,
north of Johannesburg, Gauteng, South Africa. In 1.5% of B. sowerbyi collected in a pond (Padda
Dam), near the Rand Afrikaans University, Johannesburg, the same aurantiactinomyxon type was
found. Infected oligochaetes were found only after collection and no actinosporean release was
recorded in Branchiura specimens kept alive for several weeks. Actinospore infection showed a high
intensity in oligochaetes in both positive cases. Until now, no actinosporean stages of myxosporeans
have been described from South Africa. The aurantiactinospore type presented in this communication
differs from the known types already described in the literature.
Diseases of Aquatic Organisms, 1992
Goussia trichogasteri n. sp. is described from the gut of the aquarium fish Trichogaster tn'chopt... more Goussia trichogasteri n. sp. is described from the gut of the aquarium fish Trichogaster tn'chopterus trichopterus. Gamogonic stages develop epicellularly in the gut epithelium. Oocysts are shed in early stage of sporulation. Sporulated oocysts are characterised by having centrally locating oocyst residua. The whole development of the species takes place in the aquarium.
Diseases of Aquatic Organisms, 1992
Systematic Parasitology, 1998
The extrapiscine development of Myxobolus portucalensis, a myxosporean parasite of the subcutaneo... more The extrapiscine development of Myxobolus portucalensis, a myxosporean parasite of the subcutaneous connective tissue of eel Anguilla anguilla L. was studied in the experimentally infected oligochaete Tubifex tubifex. After infecting parasite-free tubificids with mature spores of M. portucalensis, development of actinosporean stages was first observed with a light microscope 26 days after infection. Triactinospores of M. portucalensis emerged from the worms after 160 days of intra-oligochaete development. It was observed in histological sections that early pansporocysts were located in the gut epithelium of the experimental oligochaetes. Mature pansporocysts, each containing eight triactinospores, appeared 149 days after infection. After the rupture of pansporocysts, free actinospores were found in the lumen of the oligochaete gut. Released actinospores were floating in the water and showed a typical triactinomyxon form. Each triactinospore had three pyriform polar capsules, a sporoplasm with 32 secondary cells, a moderately long style and three slightly curved, sharply pointed caudal processes. The prevalence of infection in T. tubifex proved to be 52.5% (n = 40). No infection was found in Limnodrilus hoffmeisteri or in control Tubifex specimens.
The Journal of Parasitology, 1999
Journal of Fish Diseases, 2011
This study compares two alternative indices for quantifying the gross pathology of the swimbladde... more This study compares two alternative indices for quantifying the gross pathology of the swimbladder of eels, Anguilla anguilla (L.), infected with the nematode Anguillicoloides crassus. Two observers recorded twice the scores obtained by the two indices on the same set of 71 wild caught eels (from elver to silver eels, French Mediterranean lagoons). The Length Ratio Index (LRI), performed better than the Swimbladder Degenerative Index (SDI), in three of four predefined criteria of decision. First, the LRI better correlated with an estimate of the swimbladder volume reduction, a functional consequence of the infection (representativeness). Also, the LRI was less prone to subjectivity (inter-observer variability) and more precise (intra-observer variability), although less easy to generate (time needed for measurement/ assessment). Using a sub-sample of 32 unaffected eels (showing minor if any swimbladder damage and no living worms at autopsy), we ascertained a linear relationship between the swimbladder length and the total body length, a prerequisite of isometric growth, to definitively accept the new ratio index as a valid alternative to the SDI. Also, because the LRI can be recorded on live specimens with radio-imagery (non-invasive method), we recommend its use, and provide a graph of correspondence between the SDI scores, the LRI scores and the estimated proportion of gas loss in the swimbladder.
Diseases of Aquatic Organisms, 2005
Swimbladder changes resulting from Anguillicola crassus infection of the European eel Anguilla an... more Swimbladder changes resulting from Anguillicola crassus infection of the European eel Anguilla anguilla have been the subject of several studies reported in the literature. These investigations, however, studied exclusively the status of infection at a given point in time and did not deal with changes in swimbladder infection in eels suffering from anguillicolosis over a period of time. In this study, A. crassus-induced pathological changes were monitored in 78 eels naturally infected in Lake Balaton and subsequently kept in the laboratory, thus excluding the possibility of further infection. During the 3 mo study, the status of the swimbladder was checked by radiographic examination on 4 occasions. At the end of the study the eels were dissected and the gross pathological changes in the swimbladders were compared with the radiographic findings. As compared to their starting condition, by the end of the study the pathological status of the swimbladder had deteriorated in 55% and remained the same in 37% of the cases. Tendency to improvement (1%) and variable findings (7%) were recorded in a low percentage of cases only. With the help of the radiographs presented, the dynamics of A. crassus infection and of changes in the swimbladder of individual eel specimens can be monitored easily.
Diseases of Aquatic Organisms, 2003
Actinospore infection of oligochaetes living in the mud of 3 freshwater biotopes in Japan was stu... more Actinospore infection of oligochaetes living in the mud of 3 freshwater biotopes in Japan was studied. Using the cell-well plate method, a new aurantiactinomyxon type was found in 0.77% of the examined Tubifex tubifex oligochaete specimens from a brook near Yamanashi Prefectural Fisheries Experimental Station on Fuji Mountain. In 0.14% of Lumbriculus variagetus collected from Chitose River, near Chitose Salmon Hatchery, a new siedleckiella type was found, while at the same time 8.1% of the Lumbriculus spp. oligochaetes released triactinomyxons of Myxobolus arcticus. Of the examined Rhyacodrilus komarovi oligochaetes collected from the Mena River system, Hokkaido, 0.2, 0.6, 0.5 and 0.8% were infected with echinactinomyxon, neoactinomyxum and 2 types of triactinomyxon spores, respectively, and described in our previous paper. The oligochaetes released actinospores for several weeks. Actinospore infection showed high intensity in positive oligochaetes in the case of all the actinosporean types. Two of the actinospore types (aurantiactinomyxon and siedleckiella) presented here have not been previously described.
Diseases of Aquatic Organisms, 2002
Actinospore infection of oligochaetes living in the mud and on the roots of vegetation in an infl... more Actinospore infection of oligochaetes living in the mud and on the roots of vegetation in an inflow brook of a Hokkaido salmon hatchery was studied within the framework of a Japanese-Hungarian research program. Two triactinomyxon types, 1 echinactinomyxon, and 1 neoactinomyxum type were isolated from the oligochaete Rhyacodrilus komarovi Timm, 1990 collected during the survey. The aurantiactinomyxons were recorded over a period of 3 mo starting from the day after oligochaete collection. The oligochaetes released actinospores for several weeks from the first day of the study. Spore excretion of individual oligochaetes was not synchronous. Of the oligochaetes examined, 0.7, 7, 3 and 3%, were infected with the echinactinomyxon, neoactinomyxum and the 2 types of triactinomyxon spores, respectively. Actinospore infection was intense in the positive oligochaetes in all 4 types. Of the 4 actinospore types presented here, 3 are described for the first time.
Diseases of Aquatic Organisms, 2004
Aquaculture, 2009
The European eel, Anguilla anguilla, is a major warm water fish species cultured in North and Sou... more The European eel, Anguilla anguilla, is a major warm water fish species cultured in North and South Europe. A total of 140 eels measuring 28-92 cm in total length (70.9 ± 14.7, mean ± SD cm), collected on 10 separate occasions during October 2005 to May 2006 from the Comacchio lagoons, were examined. Ninety-six (69%) harbored parasitic helminths. Of infected eels, 55% contained 3 digenean species, 2% a single cestode species, and 5% 2 nematode species. Intestinal pathology associated with digenean and cestode infection was minimal. The main damage caused by digeneans was destruction of the mucosal epithelium of the villi. Necrosis and degeneration of epithelial cells were also evident. At the site of digenean infection, a high number of rodlet cells (RCs) and mucous cells were observed in the epithelium, with both types of cells exhibiting discharge activity. The number of RCs per area (30,000 µm 2 ) in parasitized A. anguilla (10.83 ± 7.08, mean ± SD, n = 40) was significantly greater than in uninfected (2.18 ± 2.15, mean ± SD, n = 40, t-test, P b 0.01). The majority of RCs in both infected and uninfected intestine were mature cells and presented the typical cell cortex. The number of mucous cells per area (30,000 µm 2 ) was significantly higher in intestine of parasitized eels (70.58 ± 17.95, mean ± SD, n = 40) than in uninfected (27.18 ± 5.58, mean ± SD, n = 40, t-test, P b 0.01). Severe intestinal damage was caused by Contracaecum rudolphii A larvae encysted within the tunica propria and over the external surface of the stomach and intestine. At these sites, conspicuous granulomas showing chronic inflammatory responses characterized by infiltration of mast cells and fibroblasts were observed.
Journal of Experimental Marine Biology and Ecology, 2007
Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principa... more Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activitiesrelated to parasite weightreduce swimming endurance, while mechanical damage of the swimbladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (b0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (b 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds.
In this study, we subjected eels from Lake Balaton (Hungary) to a swimming period of 1 week and 2... more In this study, we subjected eels from Lake Balaton (Hungary) to a swimming period of 1 week and 2 or 6 weeks. Most eels were silver and were 13–21 years old. Time dependent changes in morphometrical parameters and developmental characteristics of the oocytes were determined. Already after 1 week of swimming, the gonadal mass increased and oocytes became larger, filled with large numbers of lipid droplets. After 2 and 6 weeks of swimming we found in addition a significant enlargement of the eyes, which is a sign of sexual maturation. In contrast to the resting eels, that had oocytes in the primary growth phase (stage 1–2); the swimming eels had oocytes in stage 3; the cortical alveolus or lipid droplet stage. The results indicate that lipid mobilisation induced by swimming is a requirement for the natural incorporation of lipid droplets in the oocytes, a crucial step in oocyte maturation. As the Balaton eels responded stronger to swimming than young farmed eels, it is suggested that older eels are more sensitive for maturation triggers.
Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principa... more Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activities – related to parasite weight – reduce swimming endurance, while mechanical damage of the swim-bladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (b0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (b 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds.
In this study, we subjected eels from Lake Balaton (Hungary) to a swimming period of 1 week and 2... more In this study, we subjected eels from Lake Balaton (Hungary) to a swimming period of 1 week and 2 or 6 weeks. Most eels were silver and were 13–21 years old. Time dependent changes in morphometrical parameters and developmental characteristics of the oocytes were determined. Already after 1 week of swimming, the gonadal mass increased and oocytes became larger, filled with large numbers of lipid droplets. After 2 and 6 weeks of swimming we found in addition a significant enlargement of the eyes, which is a sign of sexual maturation. In contrast to the resting eels, that had oocytes in the primary growth phase (stage 1–2); the swimming eels had oocytes in stage 3; the cortical alveolus or lipid droplet stage. The results indicate that lipid mobilisation induced by swimming is a requirement for the natural incorporation of lipid droplets in the oocytes, a crucial step in oocyte maturation. As the Balaton eels responded stronger to swimming than young farmed eels, it is suggested that older eels are more sensitive for maturation triggers.
Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principa... more Infection with the swim-bladder parasite Anguillicola crassus is suggested as one of the principal causes of the collapse of the European eel population. This nematode has been introduced in Europe from Asia in the 80s and parasitized in a short time Anguilla eel species in different geographical regions across the globe. The parasites drain energy due to their sanguivorous feeding and they cause mechanical damage on the swim-bladder wall. These two effects are hypothesized to impair the spawning migration of the European eel. In this study, we have investigated both effects on swimming performance. We hypothesized that parasitic sanguivorous activities – related to parasite weight – reduce swimming endurance, while mechanical damage of the swim-bladder impairs buoyancy control. Eighty eels suffering various degrees of infection were introduced in swim-tunnels and subjected to a swimming fitness test. The relation between A. crassus infection and swimming efficiency was measured for large female silver eels swimming at various speeds. Infected eels had lower cruising speeds and a higher cost of transport. Eels without parasites, but with a damaged swim-bladder showed similar effects. Almost half of the eels that contained damaged swim-bladders (43%) stopped swimming at low aerobic swimming speeds (b0.7 m/s). Simulated migration trials in a recent related study have confirmed that eels with a high parasite level or with damaged swim-bladder show early migration failure (b 1000-km). Reduced swimming performance appears to be associated with swim-bladder dysfunction. As we found that especially silver eels have much higher infection levels than yellow eels, it is concluded that migrating silver eels with severely infected or damaged swim-bladders are unable to reach the spawning grounds.
Systematic parasitology, 2004
Seventy-seven specimens of seven freshwater fish species harvested in four sites from rivers and ... more Seventy-seven specimens of seven freshwater fish species harvested in four sites from rivers and ponds of the Gauteng, North West and Limpopo Provinces (South Africa) were surveyed for coccidian infections. Two fish species were infected with apicomplexans belonging to Goussia Labbé, 1896. In banded tilapia Tilapia sparrmanii Smith unsporulated oöcysts of G. vanasi were found which became sporulated in tapwater within 24 hours. Another species in the gut of chubbyhead barb Barbus anoplus Weber harboured sporulated oöcysts in the faeces and in the intestinal epithelium. The latter species has been described as G. anopli n. sp.
ABSTRACT: Actinospore infection of oligochaetes collected from the mud of 2 freshwater biotopes i... more ABSTRACT: Actinospore infection of oligochaetes collected from the mud of 2 freshwater biotopes in
South Africa was studied. Using the ‘cell-well plate method’, a new aurantiactinomyxon type was
found in 1.1% of the examined Branchiura sowerbyi oligochaete specimens from the Rietvlei River,
north of Johannesburg, Gauteng, South Africa. In 1.5% of B. sowerbyi collected in a pond (Padda
Dam), near the Rand Afrikaans University, Johannesburg, the same aurantiactinomyxon type was
found. Infected oligochaetes were found only after collection and no actinosporean release was
recorded in Branchiura specimens kept alive for several weeks. Actinospore infection showed a high
intensity in oligochaetes in both positive cases. Until now, no actinosporean stages of myxosporeans
have been described from South Africa. The aurantiactinospore type presented in this communication
differs from the known types already described in the literature.
Diseases of Aquatic Organisms, 1992
Goussia trichogasteri n. sp. is described from the gut of the aquarium fish Trichogaster tn'chopt... more Goussia trichogasteri n. sp. is described from the gut of the aquarium fish Trichogaster tn'chopterus trichopterus. Gamogonic stages develop epicellularly in the gut epithelium. Oocysts are shed in early stage of sporulation. Sporulated oocysts are characterised by having centrally locating oocyst residua. The whole development of the species takes place in the aquarium.
Diseases of Aquatic Organisms, 1992
Systematic Parasitology, 1998
The extrapiscine development of Myxobolus portucalensis, a myxosporean parasite of the subcutaneo... more The extrapiscine development of Myxobolus portucalensis, a myxosporean parasite of the subcutaneous connective tissue of eel Anguilla anguilla L. was studied in the experimentally infected oligochaete Tubifex tubifex. After infecting parasite-free tubificids with mature spores of M. portucalensis, development of actinosporean stages was first observed with a light microscope 26 days after infection. Triactinospores of M. portucalensis emerged from the worms after 160 days of intra-oligochaete development. It was observed in histological sections that early pansporocysts were located in the gut epithelium of the experimental oligochaetes. Mature pansporocysts, each containing eight triactinospores, appeared 149 days after infection. After the rupture of pansporocysts, free actinospores were found in the lumen of the oligochaete gut. Released actinospores were floating in the water and showed a typical triactinomyxon form. Each triactinospore had three pyriform polar capsules, a sporoplasm with 32 secondary cells, a moderately long style and three slightly curved, sharply pointed caudal processes. The prevalence of infection in T. tubifex proved to be 52.5% (n = 40). No infection was found in Limnodrilus hoffmeisteri or in control Tubifex specimens.
The Journal of Parasitology, 1999
Journal of Fish Diseases, 2011
This study compares two alternative indices for quantifying the gross pathology of the swimbladde... more This study compares two alternative indices for quantifying the gross pathology of the swimbladder of eels, Anguilla anguilla (L.), infected with the nematode Anguillicoloides crassus. Two observers recorded twice the scores obtained by the two indices on the same set of 71 wild caught eels (from elver to silver eels, French Mediterranean lagoons). The Length Ratio Index (LRI), performed better than the Swimbladder Degenerative Index (SDI), in three of four predefined criteria of decision. First, the LRI better correlated with an estimate of the swimbladder volume reduction, a functional consequence of the infection (representativeness). Also, the LRI was less prone to subjectivity (inter-observer variability) and more precise (intra-observer variability), although less easy to generate (time needed for measurement/ assessment). Using a sub-sample of 32 unaffected eels (showing minor if any swimbladder damage and no living worms at autopsy), we ascertained a linear relationship between the swimbladder length and the total body length, a prerequisite of isometric growth, to definitively accept the new ratio index as a valid alternative to the SDI. Also, because the LRI can be recorded on live specimens with radio-imagery (non-invasive method), we recommend its use, and provide a graph of correspondence between the SDI scores, the LRI scores and the estimated proportion of gas loss in the swimbladder.
Diseases of Aquatic Organisms, 2005
Swimbladder changes resulting from Anguillicola crassus infection of the European eel Anguilla an... more Swimbladder changes resulting from Anguillicola crassus infection of the European eel Anguilla anguilla have been the subject of several studies reported in the literature. These investigations, however, studied exclusively the status of infection at a given point in time and did not deal with changes in swimbladder infection in eels suffering from anguillicolosis over a period of time. In this study, A. crassus-induced pathological changes were monitored in 78 eels naturally infected in Lake Balaton and subsequently kept in the laboratory, thus excluding the possibility of further infection. During the 3 mo study, the status of the swimbladder was checked by radiographic examination on 4 occasions. At the end of the study the eels were dissected and the gross pathological changes in the swimbladders were compared with the radiographic findings. As compared to their starting condition, by the end of the study the pathological status of the swimbladder had deteriorated in 55% and remained the same in 37% of the cases. Tendency to improvement (1%) and variable findings (7%) were recorded in a low percentage of cases only. With the help of the radiographs presented, the dynamics of A. crassus infection and of changes in the swimbladder of individual eel specimens can be monitored easily.
Diseases of Aquatic Organisms, 2003
Actinospore infection of oligochaetes living in the mud of 3 freshwater biotopes in Japan was stu... more Actinospore infection of oligochaetes living in the mud of 3 freshwater biotopes in Japan was studied. Using the cell-well plate method, a new aurantiactinomyxon type was found in 0.77% of the examined Tubifex tubifex oligochaete specimens from a brook near Yamanashi Prefectural Fisheries Experimental Station on Fuji Mountain. In 0.14% of Lumbriculus variagetus collected from Chitose River, near Chitose Salmon Hatchery, a new siedleckiella type was found, while at the same time 8.1% of the Lumbriculus spp. oligochaetes released triactinomyxons of Myxobolus arcticus. Of the examined Rhyacodrilus komarovi oligochaetes collected from the Mena River system, Hokkaido, 0.2, 0.6, 0.5 and 0.8% were infected with echinactinomyxon, neoactinomyxum and 2 types of triactinomyxon spores, respectively, and described in our previous paper. The oligochaetes released actinospores for several weeks. Actinospore infection showed high intensity in positive oligochaetes in the case of all the actinosporean types. Two of the actinospore types (aurantiactinomyxon and siedleckiella) presented here have not been previously described.
Diseases of Aquatic Organisms, 2002
Actinospore infection of oligochaetes living in the mud and on the roots of vegetation in an infl... more Actinospore infection of oligochaetes living in the mud and on the roots of vegetation in an inflow brook of a Hokkaido salmon hatchery was studied within the framework of a Japanese-Hungarian research program. Two triactinomyxon types, 1 echinactinomyxon, and 1 neoactinomyxum type were isolated from the oligochaete Rhyacodrilus komarovi Timm, 1990 collected during the survey. The aurantiactinomyxons were recorded over a period of 3 mo starting from the day after oligochaete collection. The oligochaetes released actinospores for several weeks from the first day of the study. Spore excretion of individual oligochaetes was not synchronous. Of the oligochaetes examined, 0.7, 7, 3 and 3%, were infected with the echinactinomyxon, neoactinomyxum and the 2 types of triactinomyxon spores, respectively. Actinospore infection was intense in the positive oligochaetes in all 4 types. Of the 4 actinospore types presented here, 3 are described for the first time.
Diseases of Aquatic Organisms, 2004
Aquaculture, 2009
The European eel, Anguilla anguilla, is a major warm water fish species cultured in North and Sou... more The European eel, Anguilla anguilla, is a major warm water fish species cultured in North and South Europe. A total of 140 eels measuring 28-92 cm in total length (70.9 ± 14.7, mean ± SD cm), collected on 10 separate occasions during October 2005 to May 2006 from the Comacchio lagoons, were examined. Ninety-six (69%) harbored parasitic helminths. Of infected eels, 55% contained 3 digenean species, 2% a single cestode species, and 5% 2 nematode species. Intestinal pathology associated with digenean and cestode infection was minimal. The main damage caused by digeneans was destruction of the mucosal epithelium of the villi. Necrosis and degeneration of epithelial cells were also evident. At the site of digenean infection, a high number of rodlet cells (RCs) and mucous cells were observed in the epithelium, with both types of cells exhibiting discharge activity. The number of RCs per area (30,000 µm 2 ) in parasitized A. anguilla (10.83 ± 7.08, mean ± SD, n = 40) was significantly greater than in uninfected (2.18 ± 2.15, mean ± SD, n = 40, t-test, P b 0.01). The majority of RCs in both infected and uninfected intestine were mature cells and presented the typical cell cortex. The number of mucous cells per area (30,000 µm 2 ) was significantly higher in intestine of parasitized eels (70.58 ± 17.95, mean ± SD, n = 40) than in uninfected (27.18 ± 5.58, mean ± SD, n = 40, t-test, P b 0.01). Severe intestinal damage was caused by Contracaecum rudolphii A larvae encysted within the tunica propria and over the external surface of the stomach and intestine. At these sites, conspicuous granulomas showing chronic inflammatory responses characterized by infiltration of mast cells and fibroblasts were observed.