Ergasilid copepods as parasites of perch Perca fluviatilis and roach Rutilus rutilus in Central Finland: seasonality, maturity and environmental influence

A total of 1255 roach Rutilus rutilus (L.) and 866 perch Perca fluviatilis (L.) from four interconnected lakes in Central Finland differing in trophic status and pollution level were studied for parasitic ergasilid copepods between August 1985 and December 1988. In addition, 109 whitefish ( Coregonus sp.) were studied from one of the lakes.
Four ergasilid species were found: (the prevalence and intensity/fish, respectively, for the whole material are given in parentheses) Ergasilus briani (16·9%, 0·5), Neoergasilus japonicus (15·6%, 0·4) and Paraergasilus longidigitus (2·1%, 0·02) on the roach and Ergasilus sieboldi (9·9%, 0·1) and P. longidigitus (4·9%, 0·05) on the perch. Logit analysis was used to assess the significance of the year, the lake and the season for the prevalence of infection. Generally, the prevalence of E. briani on roach depended on the season only, with higher prevalences in summer. That of E. sieboldi on perch was mainly dependent on the lake, being most frequent in the oligotrophic lake. Both lake, year and season affected the prevalence of N. japonicus in roach. The more complicated system for N. japonicus was explained by the long duration of its free-living stage, its loose attachment and different location on the host, being found on the fins whereas E. briani and E. sieboldi were on the gills.
All species were found throughout the year, and age had no clear influence on infection. The occurrence of egg-sacs and length distributions of the copepods suggest that there are two generations a year, e.g. an overwintering E. briani generation which produces offspring in June to attack the fish in July, and a second generation which attacks the fish from August onwards. Whitefish were not infected by these parasites, only one fish being found which carried a single individual of E. sieboldi.     

Metechinorhynchus salmonis infection and diet in the river-spawning whitefish of the Bothnian Bay

A total of 206 river-spawning whitefish Coregonus lavaretus (L.) from the Bothnian Bay was investigated for food objects and acanthocephalans in the years 1975–78. The only acanthocephalan species found was Metechinorhynchus salmonis (Müller 1780), the total number of which was 1295.
The whitefish is shown to be highly susceptible to infection by M. salmonis , with as many as 88·9% of specimens infected in a sample in June 1978, although the mean intensity was only 8·9 parasites per host. The river-spawning whitefish does not favour the intermediate host, Pontoporeia affinis , in its summer diet in the Bothnian Bay preferring to feed on eggs and molluscs, so that the incidence of M. salmonis infection decreases to 33·3% by the middle of summer. This is further reduced in the late summer by the fast associated with the migration to their upriver spawning grounds. The fact that the other acanthocephalan inhabiting the river-spawning whitefish in the southern Gulf of Bothnia, Echinorhynchus gadi Müller, 1776 is not to be found in the Bothnian Bay population suggests that the fish captured in spring have remained in the Bothnian Bay throughout the winter.     

Copepod ectoparasites of Merlangius merlangus and Platichthys flesus

Seasonal changes in the levels of copepod ectoparasitic infections from Merlangius merlangus and Platichthys flesus were examined and related to the annual migrations of young fish into an estuary. Lernaeocera branchialis (L.) was the only parasite common to both fish species; its life-cycle stages infected the branchial chambers of 96·7% flounders ( P. flesus ) and 40·4% whiting ( M. merlangus ). Infection in the two fish species exhibited similar seasonal fluctuations and a temporal relationship between the parasite's occurrence on its two hosts was apparent. Whiting were also parasitized by Clavella uncinata (Milller); 26·9 % fish were affected. The copepods' distribution was highly localized with the majority restricted to the long gill rakers of the first gill arch. Infection was related to size of whiting up to 12·5 cm; there was little increase beyond this length. In addition to L. branchialis , flounder was also host to Acanthochondria depressa (T. Scott) and Lepeophtheirus pectoralis (Müller). A. depressa showed a preference for the ocular side of the body with its developing stages attached mainly to the second gill arch and the adults located in the posterior pocket of the branchial chamber. L. pectoralis was associated with the paired fins. Factors which could result in such localized distributions are discussed.     

The role of the rock cod Notothenia coriiceps Richardson, 1844 in the life-cycle of Antarctic parasites

Fifty specimens of Notothenia coriiceps caught in Potter Cove, King George Island, were examined for ecto- and endoparasites. Of the 22 parasite species found, 18 were helminths, 2 were hirudineans and 2 were crustaceans. The isopod Aega antarctica and an unidentified hirudinean are reported for the first time from this fish host. Dominant parasites were the adults of Aspersentis megarhynchus, the invasive stage of Corynosoma spp. (cystacanth) and the adults of Macvicaria pennelli, with respective prevalences of infestation of 94, 76 and 74%. The preferred sites of infestation were the pylorus and intestine, where five different larval (nematodes and cestodes) and eight adult (digeneans and acanthocephalans) parasite species were found. No adult nematodes and cestodes were found and no parasites could be isolated from the musculature. The results of the present study are related to previous findings on the parasite fauna of N. coriiceps. The comparison implies a high parasite diversity in this benthic Antarctic fish species. Most parasites found appear to have a wide range of distribution within Antarctic waters together with a low host specificity. Besides its role as final host for several species of trematodes and acanthocephalans, N. coriiceps serves as transmitter of parasite larvae to piscivorous birds and seals. It is concluded that the parasite fauna in Antarctic fish species provides important insights into the different habitat use and trophic relationship of their fish hosts. Received: 11 September 1997 / Accepted: 12 January 1998     

Some differences in the parasitic fauna of three samples of plaice (Pleuronectesplatessa L.) from the southern North Sea

Plaice ( Pleuronectesplatessa L.) from three spawning areas in the southern North Sea were examined for six species of metazoan parasite. Differences of both incidence and level of infestation with particular parasite species were found in fish from the three areas. Neither the incidence nor the level of infestation was associated with the length of fish in the samples except in the case of the larger male fish from Flamborough, which tended to contain more larval nematodes (Anisakidae). All fish contained the intestinal nematode Cucullanus heterochrous , although fewer were found in fish from Flamborough. Southern Bight fish were more likely to contain Capillaria wickinsi than were fish from Flamborough or the German Bight. Flamborough fish were more likely to contain Anisakidae larvae than were fish from the other two areas. Fish from the three areas were similarly infested with Zoogonoides viviparus. Male fish from Flamborough were less likely to be infested with Lepeophtheirus pectoralis than male fish from the German Bight.     

Effects of pollution and parasites on biomarkers of fish health in spottail shiners Notropis hudsonius (Clinton)

Seven biomarkers in 204 spottail shiners Notropis hudsonius were examined for effects of pollution and parasites on fish health at localities along the St Lawrence River, Canada. The number of pigmented macrophage centres and pigmented macrophages in the spleen was significantly higher at polluted localities receiving urban and industrial effluents than at reference localities, indicating that they were good indicators of exposure to pollution in spottail shiners. Seven of the nine species of parasites found in 1+ year fish showed significant correlations with biomarkers. More parasites (18 species) but fewer correlations with biomarkers were observed in 2+ year fish, indicating that parasite effects were more pronounced in young spottail shiners. A significant negative relationship was observed between condition factor and Neoechinorhynchus rutili in 1+ year fish, suggesting its potential pathological significance in young spottail shiners. High abundance of Plagioporus sinitsini was associated with higher spleen macrophage counts and lower indices of condition at polluted localities. Furthermore, infection by P. sinitsini in polluted conditions appeared to have a greater negative effect on fish health than either stressor alone, providing further evidence that parasites should be considered when examining effects of pollution on fish health.     

Accumulation of plerocercoids of Triaenophorus crassus in the second intermediate host Coregonus lavaretus and their effect on growth of the host

Patterns of accumulation of Triaenophorus crassus in its second intermediate host whitefish Coregonus lavaretus s.l. were studied between 1991 and 1996 from two host populations in two separate areas of Lake Saimaa, Finland. Whitefish were infected commonly with several T. crassus plerocercoids and the parasites were aggregated into the oldest hosts. In one host population the annual parasite accumulation was 0·9 parasites in all host age groups between 3 and 8 years. In the other host population the annual accumulation was 1·6 parasites in 3–5-year-old fish, but increased up to 3 to 4 parasites per year in fish over 5 years old. The increase did not coincide with the period of maturation or any increase in whitefish growth, both of which could alter the food intake of the fish. The sharp increase in the annual accumulation suggests a threshold intensity above which the probability of acquiring further parasites increases. In spite of a heavy aggregation of parasites there was no evidence of parasite-induced host mortality. The annual increase in mean abundance was not correlated with the mean annual weight increase in 2–4-year-old fish within cohorts. However, evidence of a negative effect of parasites on whitefish growth was revealed by back-calculation of lengths of uninfected and infected whitefish and correlations between length or weight of fish and intensity of infection with fish age. Both analyses suggested that larger young fish harboured more parasites than the smaller ones while in older fish the reverse was true, a pattern that has not been shown earlier for parasitized fish.     

Salinity tolerance of the mosquito fish, Gambusia affinis (Baird and Girard)

Experiments were conducted to determine the adaptability of mosquito fish to various salt concentrations. Mosquito fish, Gambusia affinis , (total length (T.L.) 27–37 mm) were subjected to abrupt and gradual changes from fresh water to various salinities (S). Low mortality (10%) occurred when the fish were transferred from fresh water (S = 0·5‰) to 50% sea water (S = 19·5‰ Through gradual adaptation 65·0% of the fish were able to tolerate 100% sea water for 7 days. After a 7 -day stay in sea water, fish were readapted to fresh water during a 3-h period. The results indicate that they were well able to tolerate the abrupt change. Through a gradual adaptation fish were also able to tolerate salinities ranging from 39·0‰ (100% sea water) to 58·8‰     

Mantle displays of freshwater mussels elicit attacks from fish

1. Gravid females of some North American freshwater mussel species (Bivalvia: Unionidae) display highly modified mantle margins and other reproductive structures which mimic small fish, terrestrial insects, or aquatic macro-invertebrates. We report the responses of fish to these lures, based on the results of laboratory encounters between the following pairs of displaying mussels and fishes: Lampsilis cardium and Micropterus coosae; L . perovalis and M . coosae; and Villosa nebulosa and Percina nigrofasciata . In all three encounters, the lures elicited attacks from fish.
2. Encounters between Lampsilis spp. and M. coosae resulted in gill infestations of the fish by larval mussels, which are obligate parasites on fish. An encounter between V . nebulosa and P . nigrofasciata did not result in infestation.
3. The use of these lures to attract fish may greatly increase the chances of parasite/host encounters and may also reduce the chances of infestation of unsuitable hosts.     

Seasonal occurrence of sea lice Lepeophtheirus salmonis on sea trout in two north Norwegian fjords

Seasonal occurrence of the parasitic copepod Lepeophtheirus salmonis (sea lice) was studied from March to December 2001 in two large north Norwegian sill fjords without fish farming activity, the Ranafjord and the Balsfjord. Anadromous brown trout Salmo trutta (sea trout) in both fjords had a low infestation rate during all sampling periods, but followed a seasonal pattern. During early and late winter (November to December and March to April) and spring (May to June), the prevalence varied from 0 to 25% and the abundance was <0·5 sea lice. Adults dominated (92%) during this period, particularly gravid females. In both fjords, the highest prevalence was during September (80–81%, all stages represented). In Ranafjord, the abundance and mean intensity during this month was 6·8 and 8·6 sea lice, respectively, while in Balsfjord it was 3·6 and 4·5 sea lice, respectively. Fish were captured at temperatures down to 1° C and at full strength sea water which is supposed to cause osmoregulatory problems for the fish. This observation has implications for the understanding of high‐latitude sea trout behaviour and can also make the fish more vulnerable to heavy sea lice infestation during this period. It is suggested that winter running sea trout help to maintain a self replicating local population of sea lice within such fjord systems where other possible hosts ( e.g . farmed Atlantic salmon Salmo salar ) are not present during a whole year cycle.     

The effect of Schistocephalus solidus infection on meal size of three‐spined stickleback

The effect of infection with the pseudophyllidean cestode Schistocephalus solidus on the meal size of individually housed three‐spined stickleback Gasterosteus aculeatus was quantified. Infected fish harboured plerocercoid loads that contributed from 1·1 to 33·9% of their total mass. Across this range of infection levels, the presence of S. solidus infection had no significant directional effect on standard length ( L _S) corrected meal size of host three‐spined sticklebacks. Amongst multiply infected fish there was a significant negative relationship between L _S‐corrected meal size and the proportion of host mass contributed by S. solidus parasites. This relationship, however, did not hold for singly‐infected fish. Furthermore, the data suggest that multiply‐infected fish that harbour a combined mass of parasites contributing < c . 15% to host body mass might exhibit meal sizes that exceed those of length‐matched uninfected fish. The results suggest that although heavy infections can significantly reduce the meal size of heavily infected three‐spined sticklebacks, in the early stages of multiple S. solidus infections host food intake may increase. The probable causes of these differential effects on meal size and their consequences for the host‐parasite system are discussed.     

Histopathological and ultrastructural observations of metacercarial infections of Diplostomum phoxini (Digenea) in the brain of minnows Phoxinus phoxinus

The spatial distribution and histopathological changes induced by metacercariae of the digenean trematode Diplostomum phoxini (Faust, 1918) in the brains of European minnows Phoxinus phoxinus (L.) from the River Endrick, Scotland, were studied by light and electron microscopy. Post-mortem examination of a sample of 34 minnows revealed that 50% (n = 17) of the population was infected with 13.7 +/- 2.6 (mean +/- SE; range 1 to 38) metacercariae per infected host. Serial histological sections of the infected minnow brains revealed that the metacercariae were unevenly distributed throughout the brain, with aggregations occurring in the cerebellum, the medulla oblongata and the optic lobes. In fish with highest intensities of infection, over 40% of the cerebellar area and about 30% of the medulla oblongata area were occupied by larvae. Metacercariae disrupt the integrity of brain tissue, with individuals being found in small pockets surrounded by cellular debris. Metacercariae were rarely encountered on the surface of the brain. Electron microscopic examination of infection sites revealed that the granular layer surrounding metacercariae was necrotic, exhibited nuclear degradation and was marked by vacuolation of the cytoplasm. Rodlet cells, the only inflammatory cell types recorded in this study, were found only in parasitized brains and in close proximity to the teguments of metacercariae. It is hypothesised that secretions released from the teguments of metacercariae are a counter response to protect the metacercariae from the fish brain's cellular defence mechanisms.     

The prevalence and intensity of external parasites in domestic pigeons (Columba livia domestica) in Egypt with special reference to the role of deltamethrin as insecticidal agent

This study aimed to investigate the prevalence and intensity of external parasites in domestic pigeons in Giza, Egypt, from January 2020 to December 2020. A total of 300 domestic pigeons (25 pigeons per month) were examined. The birds were divided into groups based on their age. The oxidative stress parameters; serum zinc concentration, serum malondialdehyde (MDA), and serum Nitric oxide were evaluated in single and mixed external parasitic infestations. The prevalence of external parasites in examined pigeons was 80.3%. The detected parasites were Pseudolynchia canariensis (P. canariensis), Hippobosca equina (H. equina), Columbicola columbae (C. columbae), Menopon gallinae (M. gallinae), Knemidocoptes species (spp.) and Dermanyssus gallinae (D. gallinae); their incidences were 41.6, 26, 7, 5,0.33 and 0.33%, respectively. The highest infestation was recorded in both spring and summer. . The incidence of disease was higher in squabs and young birds than in adults. The mixed external parasitic infestation was recorded in this study. The infected birds showed decreased serum zinc concentration and elevated MDA and serum Nitric oxide levels. In conclusion, regular monthly treatment with deltamethrin is recommended as an effective drug in the treatment of the infested birds and succeeded in reducing the incidence of externalparasites in the treated birds; in addition, pigeon management measures must be implemented to reduce the risk of external parasites.     

Comparison of Lactococcus garvieae strains isolated in northern Italy from dairy products and fishes through molecular typing

Aims:  To investigate the genetic relatedness between Lactococcus garvieae strains isolated from fish and dairy samples collected in northern Italy, using random-amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR), Sau -PCR and amplified fragment length polymorphism (AFLP).
Methods and Results:  Eighty-one isolates from bovine and caprine dairy products ( n  = 53) and from diseased rainbow trouts and other fishes ( n  = 28) were examined. All methods showed a typeability of 100%, repeatability ranging from 84·4% to 97·5% and discriminatory powers from 0·798 to 0·986. Dairy and fish strains revealed a low genetic relatedness as they are often grouped into distinct clusters. RAPD analysis discriminated 52 genotypes when primer M13 was used, whereas with primer P5 only 27 genotypes were identified. When Sau -PCR was performed, 13 genotypes were detected while AFLP analysis allowed the differentiation of 32 genotypes.
Conclusion:  L. garvieae strains isolated from dairy samples are generally not related to those collected from fish lactococcosis outbreaks.
Significance and Impact of the Study:  L. garvieae strains exhibit a genetic diversity related to the specific animal host they colonize. RAPD M13 fingerprinting proved to be a molecular tool for comparing isolates, whereas Sau -PCR and AFLP analyses were useful techniques to investigate the distribution of L. garvieae populations in the environment.     

Occurrence of the caryophyllid cestode Lytocestus parvulus Furtado, 1963 in Clarias batrachus (L.) in a tropical environment, Kedah, Malaysia

Clarias batrachus (L.) and C. macrocephalus Gunther were collected monthly between October 1982 and September 1984 from Pendang, Kedah, Malaysia. The caryophyllid cestode Lytocestus parvulus Furtado, 1963 was found in 37.7% of C. batrachus examined, with a mean intensity of 11.3. Infection of the cestode in C. macrocephalus was minimal, so detailed study was not attempted. In C. batrachus , no seasonal cycles of prevalence, mean intensity or maturation of the cestode were detected. The prevalence and mean intensity of L. parvulus decreased with increasing size of the fish. The first segment of the intestine was the preferred site where larger numbers of the cestodes and the greatest numbers of mature parasites were found. The number and maturation decreased towards the posterior end of the intestine.     

Barbus comizo infestation by Lernaea cyprinacea (Crustacea: Copepoda) in the Guadiana River,southwestern Spain

The purposes of this study were to collect baseline data on parasitology of a native species and to determine if parasite infestations by Lernaea cyprinacea were related to size, month and sex. An infestation of L. cyprinacea was monitored on Barbus comizo (n = 307) from March to October 2004 in the River Guadiana, south‐western Iberian Peninsula; over 55.7% of the examined B. comizo were infested. The number of female parasites per fish ranged from 1 to 8. There were significant differences in prevalence, abundance, and intensity among months. Prevalence was highest in August, while abundance (5.16) and intensity (5.32) were highest in September. Infestation levels were significantly related to fish size (r_s = 0.947, n = 171, P < 0.05) and condition factor (r_s = ?0.199, n = 169, P < 0.05). Haematocrit values were significantly lower in infected fish (Mann–Whitney U = 21, P < 0.05). The level of infestation was independent of sex (χ² = 0.87, P < 0.05). The dorsal and ventral areas of the fish were the most heavily parasitized.     

Ligula infestation of bleak Alburnus alburnus (L.) in the tidal Thames

Heavy infestations of the cestode Ligula are reported in bleak Alburnus alburnus (L.) from the tidal Thames. This parasite has not apparently been recorded previously from this host in the British Isles. The life cycle of the parasite is briefly summarized. Data on this infestation suggest an increase in the incidence of infestation up to a maximum in young bleak, followed by a decrease in older fish. There also appears to be a decrease from summer to autumn. The positive relationship between the weight of the parasite and the length of the host is discussed. Observations are made on the effect of Ligula on its host; it is suggested that many of the young bleak die during the autumn and winter, following their infestation.     

Endoparasites of the blue whiting, Micromesistius poutassou from north-west Spain

The communities of metazoan endoparasites of blue whiting, Micromesistius poutassou, in waters of north-west Spain were analysed and a geographical comparison made with other localities. Four hundred blue whiting collected in July 1999 and September 2000 were examined for parasites, excluding the head and gills. Six species were found: Anisakis simplex s.l. (L3), A. physeteris (L3), Hysterothylacium aduncum (L2 and L3), Stephanostomum lophii (metacercaria), S. pristis (adult), and Prosorhynchus crucibulum (metacercaria). The latter is a new host record, and A. physeteris is reported for the first time in blue whiting from the north-east Atlantic. Host gender was not a significant predictor of abundance of any helminth species, and host length was only weakly and positively related to the abundance of A. simplex. Infracommunities were species-poor, with 56% of fish harbouring only one parasite species, and 92% up to two species. Infracommunities were strongly dominated by A. simplex (389 fish) or S. lophii (6 fish). Fish length or gender, and the year of capture, did not affect species richness nor the degree of dominance. There were no significant pair-wise associations between species. Infracommunities were basically composed of several allogenic parasites with different life histories that converge in the blue whiting through the local food web. The parasite fauna of blue whiting in the study area was poor and distinctive compared with that of other localities in the north-east North Atlantic. These peculiarities might primarily be related to the composition of the local community of definitive hosts, although there might also be some influence of the geographical distribution of parasites.     

The helminth parasites of the bullhead Cottus gobio (L.) and the stone loach Noemacheilus barbatulus (L.) from the River Avon, Hampshire

Specimens of Cottus gobio and Noemacheilus barbatulus from the River Avon, Hampshire, were examined between July 1970 and July 1971. Both fish were found to act as hosts for Nicolla gallica (adult), Pomphorhynchus laevis (adult) and Triaenophorus nodulosus (plerocercoid). The incidence and intensity of infection were lower in N. barbatulus than in C. gobio , and this was related to differences in host diet. A small number of N. barbatulus were also found to harbour Proteocephalus torulosus . Seasonal cycles of incidence and intensity were evident in N. gallica , with a peak occurring in the winter. P. laevis and T. nodulosus showed no such cycles. Increasing host size was associated with a higher infection of both N. gallica and P. laevis , but not T. nodulosus . The diet of the host was considered to be important in influencing this increase. Differences in host reproductive condition affected the population levels of N. gallica only, where an increased parasite burden was evident in gravid female fish. This was considered to influence the observed increase in incidence and intensity of this parasite during the winter. None of the parasites showed any seasonal maturation cycles. There was no evidence of any interactions between the parasite populations. Host diet and the availability of infective larvae were considered to be the most important features influencing the number of parasites which became established, and the rate at which this occurred. Temperature probably acted indirectly on the establishment of N. gallica , by controlling the availability of the larval stages, and also, by influencing the host reproductive condition, on the length of time for which the parasite was retained by the host.     

Helminth and arthropod parasites of fishes in the mountain national parks of Canada

Sixteen parasite species including one monogenean, two digeneans, five cestodes, six nematodes. one acanthocephalan, and one copepod were collected from 257 fish of 13 species examined from 32 lake and nine stream sites in the mountain National Parks of British Columbia and Alberta. The following parasites are reported from Alberta for the first time: Bunodera luciopercae (Müller, 1776), Eubothrium rugosum Batsch 1786, Proteocephalus parallacticus MacLulich, 1943, Rhabdochona cascadilla Wigdor, 1918, Rhabdochona milleri Choquette, 1951, Contracaecum brachyurum (Ward & Magath, 1917), Bulbodacnitis truttae (Fabricius, 1794), Neochinorhynchus rutili (Mueller, 1780), and Ergasilus nerkae Roberts 1963. Tetraonchus variabilis Mizelle & Webb, 1953 and Rhabdochona milleri Choquette, 1951 are reported from British Columbia for the first time.