The occurrence and life history of Asymphylodora kubanicum (Platyhelminthes: Digenea: Monorchidae) in the Worcester-Birmingham canal, with special reference to the feeding habits of the definitive host, Rutilus rutilus

Two hundred roach and over 400 molluscs were examined over a one year period to investigate the occurrence and life history of Asymphylodora kubanicum in the Worcester-Birmingham canal. Larval stages, infective to the fish definitive host, were present in molluscs throughout the year but did not show a seasonal fluctuation in numbers. Parasites in the intestine of the roach showed a marked annual cycle of occurrence and maturation: low winter infection levels preceded a dramatic increase in infection during the spring and summer. Maturation of the parasite population was rapid during the spring and summer and in late summer and early autumn the parasites laid their eggs and subsequently died. The death of parasites after egg-laying resulted in the low winter infection level during which time little recruitment occurred.
Roach became infected mainly in their third year when molluscs become a dominant component of their diet. Thereafter the older fishes (<2+) are all equally susceptible to infection, but the larger (older) fishes become more heavily infected because of the greater consumption of molluscs per fish. The sex of the fish made no difference to infection with the parasite.     

Gill anomalies of perch and roach from four lakes differing in water quality

This study examined gill anomalies of two common freshwater fish species, roach Rutilus rutilus and perch Perca fluviatilis , collected over five seasons in 1989–1990 from four lakes in central Finland. The lakes differed both in water quality and in fish parasite species composition. Particular attention was paid to the differences in chloride cell proliferation. Gill anomalies were generally more common and abundant in roach than in perch. Chloride cell proliferation was the most frequent histological change in roach but was that least often found in perch. Most of the changes were systemic and light in severity. In perch an unidentified lesion of noncellular eosinophilic inclusions in an enlarged epithelium was also recorded. There was a marked pattern in the severity of histological changes in perch when comparing those from the natural Lake Peurunka to those from three 'altered' lakes. Gills of perch from Lake Peurunka possessed more alterations in all the recorded parameters. In roach, a significant differences were detected in chloride cell and epithelial proliferation: these were greater in Lake Peurunka and 'polluted' Lake Vatia. In perch, all histological changes were significantly more frequent at the end of autumn 1989 when compared to other seasons. In roach, increased frequencies of all gill changes were noted in winter and spring samples. Tissue reactions to parasites were either only localized or absent. The systemic gill alterations in freshwater fish may reflect the soft nature and low winter temperature of Finnish fresh waters, in which chemical imbalances, such as acid peaks, may induce more dramatic changes in fish tissues than in harder waters.     

Seasonal pattern in age, sex and body condition of Barn Owls Tyto alba killed on motorways

The Barn Owl Tyto alba was the most common owl killed on motorways in northeastern France. The possible causes of this mortality and the age, sex and body condition of the road-killed birds in 1991–1994 have been investigated. The number of birds killed on roads was highest in the period from early autumn to late winter, i.e. during the non-breeding period, and showed a pattern similar to that of the temporal difference between sunset, which varies with day length, and peak of traffic, the occurrence of which is constant throughout the year. An autumnal mortality peak, concomitant with the post-fledging dispersal, was mainly of immature birds, especially females. A second mortality peak in late winter was composed mainly of mature birds, with an equal proportion of males and females. From autumn to winter, there was no significant change in body mass in the different age and sex categories of birds killed on roads, except for mature males which had a significantly lower body mass in winter. From early autumn to late winter, the mean body mass of immature owls killed on motorways did not differ significantly from that of captive immatures fed ad libitum. This suggests that the immature birds were in good body condition. In contrast, the body mass of road-killed mature females was significantly lower than that of captive mature females over the same time periods. In mature males in late winter, a drop in body mass in both road-killed and captive birds suggests an endogenous seasonal phenomenon. Except for mature females, Barn Owls killed on roads in 1991–1994 were in good body condition. This does not support the idea that only birds in poor body condition were killed. We conclude that the mortality of Barn Owls on motorways in autumn and winter was probably related to the concomitance between the peak of traffic and the onset of hunting activity and the large number and dispersal of immature individuals during the same period.     

The parasite fauna of the fish of the Shropshire Union Canal, Cheshire

A survey was made of the parasites of 603 roach Rutilus rutilus (L.), 15 bream Abramis brama (L.), 201 perch Perca fluviatilis L., 30 pike Esox lucius L. and four eels Anguilla anguilla (L.) caught in the Shropshire Union Canal at Backford, Cheshire from December 1964 to August 1966. Twenty-seven species of parasites were found, 17 in roach, seven in bream, ten in perch, ten in pike and two in the eel. Two species of Protozoa, seven species of Monogenea, five species of Digenea, six species of Cestoda, two species of Nematoda, one species of Acanthocephala, two species of Hirudinea, one species of Crustacea and mollusc glochidia were recorded. The following parasites are believed to be new records for the British Isles: Henneguya oviperda (Cohn, 1895), Dactylogyrus suecicus Nybelin, 1936, D. wunderi Bykhovskii, 1931, Asymphylodora kubanicum (Isaichikov, 1923), and Philometra rischta Skryabin, 1917.
One table shows the species of parasites found, together with data on the site of occurrence in the host, and the percentage and intensity of infection of the fish. A second table compares the occurrence of the parasites in four other localities in the British Isles, Loch Lomond Scotland, Llyn Tegid (Bala Lake), Merionethshire, Rostherne Mere, Cheshire and the River Lugg, Herefordshire. A further column gives the normal hosts in the U.S.S.R.
A limited comparison is made of the numerical occurrence of six species of parasites in the canal, Llyn Tegid and Druzno Lake, Poland. It is concluded that unless relatively large samples of fish of all length groups are collected on a regular basis throughout the year such comparisons will have little meaning.
The concept of the characterization of parasite faunas is briefly noted. It is suggested that the high degree of host specificity shown by many of the species of parasites is evidence in support of the concept.     

Impact of season and sex on calcium and phosphorus content in the meat of roach (Rutilus rutilus L.) from the Brda River (Poland, Bydgoszcz)

The aim of this work was to compare the concentrations of calcium and phosphorus and Ca/P ratio in the meat of females and males of the roach (Rutilus rutilus L.) caught from the Brda River. The study involved 40 roach individuals caught in fall and spring (10 females and 10 males from each season). The muscle samples for analyses were taken from the large side muscle of the fish body above the lateral line. Ca concentrations were determined by atomic absorption spectrophotometry; P content was analyzed by the colorimetric method. Calcium concentration in the meat of analysed roach was higher in samples collected from fish caught in spring and equaled 1.82 g kg(-1) in females and 1.93 g kg(-1) in males. Values for individuals from autumn amounted to 0.83 and 1.10 g kg(-1), respectively. Statistically significant differences in calcium content were detected between individuals caught in different seasons, but samples taken from females and males caught within one season did not differ substantially. The mean value of P in the meat of analysed roach caught in spring was higher than in fish from autumn, and it was respectively 2.24 g kg(-1) in females and 2.30 g kg(-1) in males from spring, and 1.89 g kg(-1) in the tissue of females and 2.01 g kg(-1) in males in fish from autumn. The ratio of calcium to phosphorus in the meat of analysed wild roach ranged from 0.43:1 to 0.82:1. A negative and statistically significant correlation between Ca and P concentrations was found in the meat and the body length of analysed roach from the Brda River.     

The effects of a change in the growth rate of roach, Rutilus rutilus (L.), on the biology of the fish tapeworm Ligula intestinalis (L.)

Investigations into the biology of the roach and the pathogenic tapeworm Ligula intestinalis (L.) populations at Slapton Ley, Devon were carried out between October 1982 and December 1984. Data collected from the lake since 1977 have also been re-analysed to determine how the dramatic improvement in the individual growth rate of the roach over this period may have affected the growth, maturation and life-cycle of Ligula. Only the very young roach at this site become infected, so it was possible to follow cohorts of plerocercoids of similar age through each roach year class. Results for the 1978 and 1983 year classes are presented in detail. The roach grew extremely rapidly from May to August in each year, resulting in a pronounced cyclical pattern of changes in the condition of the roach, with the lowest condition occurring in late winter and spring. The yearly increase in the roach growth rate was accompanied by an increase in plerocercoid growth rate in the 0 + roach, but not in the 1 + roach. The growth rate of the plerocercoids was very high compared to that at other sites. It is usual for the parasite index (PI) of Ligula-infected fish to be high and to increase throughout their first few years of life. At Slapton, however, a lack of multiple infections has prevented high PIs from occurring, and in recent years the growth rate of the roach has been so high that the plerocercoids were unable to maintain a high weight relative to the fish, and the highest PIs occurred in the 0 + roach throughout late winter and spring. In recent year classes, therefore, the maximum PIs and highest pathogenicities coincided with the period of lowest condition in the 0+ roach. Observations of both caged and natural populations of 0+ roach over winter showed that a significant loss of roach containing the larger plerocercoids occurred from the population. In vitro cultivation of Ligula plerocercoids showed that they were capable of maturation at weights of 0.5 g, and only 6 months after having infected the roach. The increase of the growth rate of the plerocercoids in the 0+ roach has therefore resulted in a greater proportion of these plerocercoids being capable of infecting the definitive host. As a result of the increase in individual growth rate of the roach at Slapton, the potential for Ligula transmission, as measured in terms of both their pathogenicity and maturity, has shifted from the 1 + to the 0+ roach.     

Location-dependent infection of fish parasites in Lake Constance

Perch Perca fluviatilis and roach Rutilus rutilus were caught at various locations around Lake Constance (Bodensee). Infection of perch and roach with the eyeflukes Diplostomum spathaceum and Tylodelphis clavata was greatest in the western location (Bottighofen). The varied occurrence of parasite species at different locations indicated that maximum interchange between fish populations was slight. Whitefish Coregonus lavaretus migrating up the River Rhine were less infected with both the tapeworm Proteocephalus exiguus and the copepod Ergasilus sieboldi than whitefish from the middle of the lake. Some of the parasites had already left their hosts. Newly established infections were not found in migrating whitefish.     

Contrasting the seasonal and elevational prevalence of generalist avian haemosporidia in co‐occurring host species

Understanding the ecology and evolution of parasites is contingent on identifying the selection pressures they face across their infection landscape. Such a task is made challenging by the fact that these pressures will likely vary across time and space, as a result of seasonal and geographical differences in host susceptibility or transmission opportunities. Avian haemosporidian blood parasites are capable of infecting multiple co‐occurring hosts within their ranges, yet whether their distribution across time and space varies similarly in their different host species remains unclear. Here, we applied a new PCR method to detect avian haemosporidia (genera Haemoproteus, Leucocytozoon, and Plasmodium) and to determine parasite prevalence in two closely related and co‐occurring host species, blue tits (Cyanistes caeruleus, N = 529) and great tits (Parus major, N = 443). Our samples were collected between autumn and spring, along an elevational gradient in the French Pyrenees and over a three‐year period. Most parasites were found to infect both host species, and while these generalist parasites displayed similar elevational patterns of prevalence in the two host species, this was not always the case for seasonal prevalence patterns. For example, Leucocytozoon group A parasites showed inverse seasonal prevalence when comparing between the two host species, being highest in winter and spring in blue tits but higher in autumn in great tits. While Plasmodium relictum prevalence was overall lower in spring relative to winter or autumn in both species, spring prevalence was also lower in blue tits than in great tits. Together, these results reveal how generalist parasites can exhibit host‐specific epidemiology, which is likely to complicate predictions of host–parasite co‐evolution.     

Effect of stripping on the length, condition and gonadal state of mature male Atlantic salmon, Salmo salar L., parr during autumn and winter

Hatchery-reared mature male Atlantic salmon parr were shorter than immature parr of the same age through the winter period and this difference increased prior to smolting in spring. Stripping had no effect on growth. In autumn mature male parr had a higher condition factor (CF) than immature parr, but from early January no difference was observed between unstripped mature males and immature parr. Stripping reduced the CF of male parr but the difference had disappeared by the time of smolting when the CFs of both mature groups were lower than that of immature fish. The quantity of expressible milt in stripped males decreased from c . 3% body weight in November and December to <0.05% by 2 March, after which no further milt expression was recorded. Milt expression in previously unstripped males was about 1% of body weight on 2 March, similar to that of stripped males 1 month earlier.     

The role of Bithynia tentaculata in the transmission of larval digeneans from a gravel pit in the Lower Thames Valley

The freshwater snail, Bithynia tentaculata (Gastropoda: Prosobranchia), is frequently found in gravel pits and its role in the transmission of larval digeneans was assessed in one of these unstable water bodies from the Lower Thames Valley (UK) from June 1982 to December 1984. Eight species of cercarial and five species of metacercarial infections were reported from B. tentaculata, with up to 7.7% and 4.7% prevalence of infections, respectively, occurring in the snail, making it the most important host at this site. Seasonal peaks in cercarial infections occurred in late autumn/early winter but little seasonality was apparent in the occurrence of metacercarial infections. The life history characteristics of both hosts and parasites, which can affect intramolluscan digenean dynamics, are discussed.     

The establishment and subsequent history of a population of Ligula intestinalis in roach Rutilis rutilis (L.)

The introduction, establishment and subsequent history of a population of Ligula intestinalis in roach, Rutilus rutilus , of a small lake was studied over a period of seven years. The introduction is believed to be a natural, chance colonization achieved by the return of Great Crested Grebes as permanent residents. Within two years the parasite had infected 33% of the roach between 60–120 mm in size. It exhibited a pronounced seasonal cycle in infection. Fish were often infected when only a few months old in autumn, and young fish and parasites over-wintered together. Parasite growth resumed in the following summer, when some further infections occurred. The majority of infected fish died in or before their second winter, possibly as a result of selective predation, but a small proportion survived into a third year. Dispersion of the parasite was close to random for most of the time. Multiple infections and slight over-dispersion occurred only in summer months. Infections were scarcer in large fish, due partly to selective mortality of infected fish and partly to a change in the host diet. The pattern of seasonal infection compared favourably with other localities, but prevalence and intensity of infection were consistently lower, parasite dispersion closer to random and multiple infections much scarcer than elsewhere. Infection levels and parasite growth rates varied from year to year, but these annual fluctuations were irregular and showed no consistent pattern. The Ligula population exhibited both regulatory and destabilizing features and there was no definite evidence that it was stable. It is suggested that Ligula is an opportunist species. It is endemic in some sites but in others, especially small lakes, the populations are unregulated and unstable and so persist for short periods only in a non-equilibrium state.     

Cold tolerance of micro-arthropods from Alaskan taiga

Abstract. Mean supercooling points for a variety of soil and litter arthropods including mites, springtails, a heteropteran and immature spiders from a central Alaskan taiga site ranged from -6.3 to -28.5°C during autumn. Variation in supercooling ability of five species of cryptostigmatid mites occurred throughout the year with increased cold tolerance in autumn and early winter concomitant with the temperature pattern of the habitat. No correlation between the level of supercooling and water content of the mites was evident. Changes in the frequency distribution of individual supercooling points occurred in autumn, winter, spring and summer samples which were species specific. All arthropods tested were susceptible to freezing, and the mites utilize supercooling to avoid freezing.     

Seasonal variation in the prevalence and intensity of canine Gnathostoma spinigerum infection in northeastern Thailand.

Gnathostoma spinigerum was found in gastric nodules in 4.1% of 2940 dogs surveyed in northeastern Thailand. The prevalence and worm burden of G. spinigerum exhibited a seasonal fluctuation. The parasites were more abundant in the rainy season and the early winter (August-December) than in the summer (April-March). Most parasites were sexually mature between August and December while immature worms were observed during March and April. The distribution of gnathostomes within the sampled dogs was highly dispersed and few animals were found to harbour more than five worms.     

Disease transmission in an extreme environment: nematode parasites infect reindeer during the Arctic winter

Parasitic nematodes are found in almost all wild vertebrate populations but few studies have investigated these host-parasite relationships in the wild. For parasites with free-living stages, the external environment has a major influence on life-history traits, and development and survival is generally low at sub-zero temperatures. For reindeer that inhabit the high Arctic archipelago of Svalbard, parasite transmission is expected to occur in the summer, due to the extreme environmental conditions and the reduced food intake by the host in winter. Here we show experimentally that, contrary to most parasitic nematodes, Marshallagia marshalli of Svalbard reindeer is transmitted during the Arctic winter. Winter transmission was demonstrated by removing parasites in the autumn, using a novel delayed-release anthelmintic bolus, and estimating re-infection rates in reindeer sampled in October, February and April. Larval stages of nematodes were identified using molecular tools, whereas adult stages were identified using microscopy. The abundance of M. marshalli adult worms and L4s increased significantly from October to April, indicating that reindeer were being infected with L3s from the pasture throughout the winter. To our knowledge, this study is the first to experimentally demonstrate over-winter transmission of a gastro-intestinal nematode parasite in a wild animal. Potential mechanisms associated with this unusual transmission strategy are discussed in light of our knowledge of the life-history traits of this parasite.     

Seasonal dynamics of a flea number (Siphonaptera) on the common shrew (Sorex araneus) in the north part of the Novgorod oblast

In the course of 5-year stationary investigations of the common shrew Sorex araneus in the north part of the Novgorod oblast, 12 flea species have been recorded on this host. Among them, Palaeopsylla soricis and Doratopsilla dasycnema are specific parasites of small insectivores, including the common shrew. Hystrichopsylla talpae is a polyxenous species, parasitizing both rodents and insectivores. Other 9 flea species are not common parasites of S. araneus and apparently have come to this host from other mammal species inhabiting the forest biotopes in the area of investigation. P. soricis and D. dasycnema have similar phenology of parasitism. These fleas appear in spring (April), are present during summer and autumn and disappear in winter. During a year, the abundance of these species shows three pikes, which correspond to three generations: spring (April), summer (June-July) and autumn (September-October) generation. The first species dominates in spring (April-May) and in the autumn-winter period, while the second species predominates in summer. These two species comprise over 90% of total number of fleas collected and determine general dynamics of the flea number on the shrews; during the year the flea number has a sinusoidal increasing from spring to autumn and minimum in winter.     

东海普通波水蚤种群特征与环境关系研究

根据1997～2000年东海23°30′～33°N、118°30′～128°E海域4个季节海洋调查资料,对东海浮游桡足类普通波水蚤(Undinula vulgaris)自然种群特征与环境的关系进行研究,并与1979～1980年资料进行比较.结果表明,普通波水蚤优势度、平均丰度、出现频率和占浮游桡足类总丰度的百分比均有显著的季节变化,其中秋季分别为0.09、556 ind·100 m^-3、93.69％和9.90％,夏季为0.03、86 ind·100 m^-3、68.49％和4.08％,冬季为0.02、42 ind·100 m^-3、53.85％和3.80％,春季为0.01、16 ind·100 m^-3、34.35％和2.31％.普通波水蚤在东海的优势性主要表现在秋季.与20年前同海域研究结果相比,近年春、夏和秋3季普通波水蚤在东海浮游桡足类中的重要性有所降低,而冬季有所增加.冬季的增加可能与全球气候变暖相关.底层水环境变化是影响普通波水蚤种群数量分布的主要因子,说明该种数量变化与暖流势力有密切关系.普通波水蚤对沿岸水团和低温环境敏感,其高丰度分布区是暖流位置的良好指示.作为秋季东海重要的桡足类浮游动物,普通波水蚤在东海海洋渔业中有重要意义.     

Determinants of habitat use in large roach

In this study gillnet catches of large roach Rutilus rutilus and their potential predators, large perch Perca fluviatilis , pikeperch Sander lucioperca and pike Esox lucius , in combination with data on food resources and abiotic variables were used to reveal the variables influencing the habitat use of large roach in Lake Großer Vätersee. The occurrence of large roach was negatively coupled with the occurrence of potential predators. Although almost all roach studied were larger than those actually fed on by the predators, high roach catches never coincided with high predator catches. Since the overall habitat-specific distribution of roach and its predators was nevertheless highly similar, this indicated that large roach obviously avoided the immediate vicinity of the predators without being forced to a full habitat shift. The behavioural response to predators of roach in Lake Großer Vätersee was clearly length dependent, since the patterns of diel habitat use differed between large and small roach. For lake-wide estimates of trophic interactions, size groups of prey should be separated, since size-dependent trait changes may impact habitat-specific resources in a contrasting way.     

Influence of grazing management on the seasonal change in testicular morphology in Corriedale rams

The present study was conducted: (a) to determine the degree of seasonal variation in testis stereology in Corriedale rams between autumn and winter; (b) to test the hypothesis that testis stereology of Corriedale rams grazing native pastures during autumn and winter would differ from those of Corriedale rams grazing sown pastures and supplemented with grain during the same period; and (c) to determine whether Sertoli cell numbers differ in adult rams between the breeding season (autumn) and the following non-breeding season (winter). Twenty experimental animals were studied. Six rams (autumn control group, C-A) that had been grazing on native pasture (stocking rate=2–3 animals ha⁻¹) were castrated at the beginning of the experiment (March, early autumn). Seven rams (winter control group, C-W) continued to graze on native pasture at the same stocking rate until the end of the experiment (August, late winter). Another seven rams (treated group, T) grazed on improved pasture (stocking rate=1–2 animals ha⁻¹) and were supplemented with 1 kg grain ram⁻¹ day⁻¹ until the end of the experiment. Live weight, scrotal circumference, serum testosterone concentration and selected testicular stereological parameters were measured. The treatment did not impede the winter reduction in testicular activity and reduced its magnitude slightly (group T) compared with controls (group C-W). Sertoli cell numbers were higher in autumn (group C-A) than in winter, both on native (group C-W) and sown pastures (group T). Diminishing Sertoli cell numbers between autumn and the following winter suggest the occurrence of that Sertoli cell death during this period. The results indicate that, although the reproductive activity of Corriedale rams is moderately seasonal, a restricted change in grazing and grain supplementation can only modify it to a limited extent.     

Studies on Ligula intestinalis Some aspects of the pathology in the second intermediate host

A 3 year survey of a lake, in which 120 roach, Rutilus rutilus , were examined revealed the presence of the plerocercoids of Ligula intestinalis in more than 90 % of the fish. The average number of parasites per fish was 4.2 although fish exceeding 32 g were not ligulosed. Gudgeon, Gobio gobio , of all sizes were affected. Implants of the plerocercoids into small roach, gudgeon and goldfish, Carassius auratus , were successful but not in the case of Perca fluviatilis, Esox lucius and Leuciscus cephalus. The pathological effects of the plerocercoids on roach and gudgeon are described.     

Comparative study of reproductive biology in single- and multiple-spawner cyprinid fish. I. Morphological and histological features

To clarify the dynamics and regulation of oogenesis in single- and multiple-spawning cyprinid fish with group-synchronous oocyte development, a multidisciplinary approach to their reproduction was undertaken using three species from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. The gonadosomatic index (GSI) and histomorphometric changes (distribution of oocyte size, relative proportion of the various oocyte stages) in the ovary are compared. Different patterns of GSI and oocyte growth were observed both between the single- and multiple-spawner fish and between the two multiple spawners. Maximum GSIs were higher in roach (21%) than in bleak and white bream (17.7 and 14.5%, respectively), and compared to the rapid decline of GSI in the roach population, the GSI of multiple spawners decreased progressively during the spawning season. In roach, a short gonadal quiescent period and an early onset of vitellogenesis was recorded from late summer onwards whereas, in bleak and white bream, exogenous vitellogenesis was not systematically observed before winter. A protracted spawning season and/or a low water temperature in autumn are hypothesized to explain this long period of gonadal quiescence. In bleak, during the spawning season, the oocytes recruited arose from the stock of endogenous vitellogenesis and attained the final maturation stage very rapidly. This recruitment occurred during the whole spawning season. In white bream, the differentiation of vitellogenic oocytes from smaller oocytes was completed before the onset of the spawning season. During the spawning period, the proportion of vitellogenic oocytes decreased progressively whereas the percentage of oocytes in the final maturation stage remained approximately constant.