Genetic variability in the European minnow,Phoxinus phoxinus (L.)

An electrophoretic study of genetic variation at 11 loci was performedfor a population of European minnows, Phoxinus phoxinus (L.). Ten loci, EST-1 ^*, EST-2 ^* EST-3 ^*,GPD-1 ^*,GPD-2 ^*,GPI-1 ^*,GPI-2 ^*,MPI ^*,6PGD ^* and PGM ^* were polymorphic. IDH ^*wasmonomorphic. The mean number of heterozygotic loci over all 176 fish was 3.05 ± 0.104(SE). Observed mean heterozygosity was 0.28±0.058(SE) and expected mean heterozygosity was 0.27±0.054(SE). EST-2 ^*, EST-3 ^* andPGM ^* were not in Hardy-Weinberg equilibrium. Length,condition, parasite numbers or male breeding characters, i.e. red colorationand tubercles, were not influenced by single enzyme loci.     

The problem of sexual inversion in the minnow, Phoxinus phoxinus (L.)

The incidence of sexual inversion in Phoxinus phoxinus has been studied by examining histologically (a) the gonads of 406 adult specimens caught from the wild during a period of 16 months, (b) the gonads of 168 adults kept in captivity in groups with an experimentally altered sex-ratio, and (c) the differentiation of the gonads in the fry.
All the adults had either testes or ovaries and no case of intersexuality was observed. For both testis and ovary, we recognized two phases, depending on the seasonal cycle: an active spring-summer phase, corresponding with the period of reproduction, and a quiescent autumn-winter phase. The ovaries showed an asynchrony in oocyte development, which is typical of species that spawn many times during the breeding season.
In P. phoxinus the ovaries are easily recognizable just one month after hatching and testes are well differentiated in 2-month-old fingerlings. Differentiation is, therefore, precocious and follows a pattern typical of gonochoristic species in which hermaphroditism never occurs.     

The life history of the minnow Phoxinus phoxinus (L.) in a productive stream

SUMMARY. 1. In the River Frome, Dorset, this small cyprinid spawned from mid-April to early August and consequently some 0 group minnows did not develop scales until the following spring.
2. Most I group fish formed a summer hyaline band on their otoliths in a edition to the normal winter band.
3. Life-span was short with a winter age-structure of 67% 0 group, 32% I group and 1% II group fish with mean fork lengths of 29, 55 and 73 mm respectively.
4. In June, substantial numbers of I group fish reached reproductive size (50mm) and thereafter progressively replaced II group fish in the spawning shoals. Few II group males survived beyond June, few females beyond August.
5. Only half of I group minnows reached matutity. These were usually fish which had reached 30mm by the previous winter. Very few of these large I group fish survived to spawn the following year.
6. This differential mortality, together with the loss of condition and disappearance of II group fish during spawning, may indicate the cost of an extended high level of reproductive effort.
7. In this productive environment the life history of the minnow more closely resembles that of the small sympatric species Cottus gobio and Noemacheilus harhatulus than it does that of sympatric cyprinids.     

The effects of spinal nerve section on responses of melanophores in the minnow, Phoxinus phoxinus(L.)

A continuous observation apparatus was used to study the responses of Phoxinus phoxinus melanophores to illuminated black/white backgrounds and their reversal. The fish. Although confined, showed maximum melanosome dispersion (MI 5) and maximum melanosome aggregation (MI 1) when exposed to illuminated black and white backgrounds respectively. Melanophores affected by spinal nerve section showed full melanosome dispersion and the affected area appeared as a black band. The affected melanophores marginally and gradually aggregated their melanosomes if the fish was exposed to an illuminated white background for about a week. The responses of these melanophores to illuminated black and white backgrounds and their reversal indicates that the dispersal of their melanosomes in response to a black background is much faster than their aggregation in response to a white background. It is concluded that an active mechanism is involved and possible factors controlling it are discussed.     

Component parasite communities in the minnow Phoxinus phoxinus (L.) from ecologically safe and polluted reservoirs

A comparative analysis of the structure of component parasite communities in the minnow from ecologically safe or polluted to variable extent reservoirs was made. The analysis showed that the increase of the reservoir pollution by everyday drains, washings of fertilizers from the fields around and the dacha sections causes the change of dominant parasite species in the minnow, alteration of the sum of errors in the regression equation characterizing the spread of values of biomasses of the species forming the parasite community, and change of the "graphic" structure of the community. It is proved, that the high concentration of biogens has a destructive effect on natural systems, and at the same time causes the process of self-organizing, leading to the alteration of the community structure. As soon as even a small part of biogens is stopped to come into the reservoir, and the quality of environment is restored, the community restores its structure.     

Seasonal dynamics of the component community structure of parasites of the minnow Phoxinus phoxinus (L.)

The material represented by 75 specimens of minnow of the age 2-2(+) was collected according to the standard technique in the Chovju River (tributary of the Vychegda River, a region of the settlement Nizniy Chov, district of Syktyvkar town) during the period June-September 2000. The quantitative estimation of the structure of the component parasite communities was performed by calculating errors of the equation of regression for each species group separately, with subsequent summarizing of means of errors by all parasite groups comprising the community (Dorovskikh, 2001 6; 2002 B). In order to have a possibility to get data complementing each other, the calculation of variety indexes and other indexes have been made for metazoan parasites only and for the whole community, including the protozoan parasites. In both cases, i.e. considering only metazoan parasites and the whole composition of parasite species, three states of the component parasite community have been recognised: the formed community (June), the community in destroying (July and August), the community in the process of formation (September). In the course of working on the total species composition we recorded the beginning of community destroying on 30th of June, and the beginning of community formation in August. Considering only the metazoan parasites, the community is defined (after: Pugachev, 1999) as the mature (balanced) one in June, while in July, August and September, it was unmature (off-balance) by its characteristics. Regarding the protozoan parasites, the community in June, August and September was characterized as the mature one based on indices of parasite biomass, and as unripe one based on the number of parasite individuals; however in July, both groups of indices allowed to refer it to the unripe state. However, these unripe states are essentially different. In July, it is the result of dieing out the parasites of the past generation; in August and September, it is the result of the appearances of new generations. Therefore we recognise three states of parasite community named above. Considering the whole species composition of parasites we noted the greater difference of index values based on the parasite specimen numbers and their conventional biomass, that was in the case of the metazoan parasites only. It is particularly noticeable in the middle of the June, in the period of the formed community. This fact, together with high errors of the equations of regression and the presence of the high number of Apiosoma, points to the disturbance in the structure of component parasite community in the minnow from the Chovju River. This is easily explicable, because the Chovju River is the polluted reservoir, and pollution comes from agricultural fields, Verhny-Chov settlement, pigsties and cow-sheds. The pollution is a seasonal factor here. The most powerful pollution was noted at May-June, and then it decreased along the beginning of rains in the end of August; in September it increased again. It is important to point out that the monitoring of the metazoan parasites only allows to reveal the general dynamics of the community during the period of observation, but does not allow to catch the beginning of its destroying and developing and to notice possible disturbances in the community structure caused by pollution of reservoirs, particularly, if this pollution is a seasonal factor as in the Chovju River. Three named states of the component community of the fish parasites take place in other periods of year than this observed in the intestional parasite communities of fish helminths of the temperate climate zone. The developing of parasite communities of the intestinal helminths of the Anguilla anguilla in England (Kennedy, 1997) and of Leuciscus idus from the Rybinsk reservoir (Zhohov, 2003) starts in the beginning of summer. In May, their species diversity is minimal and in August is maximal. In conditions of the middle stream of the Vychegda River, the species diversity of parasite community associated with the minnow is maximal in June and minimal in August, when it only begins developing.     

Host age and structure of the component communities of parasites in river minnow Phoxinus phoxinus (L.)

Species composition and structure of the communities of fish parasites in river minnow Phoxinus phoxinus (L.) from the Pechora river were investigated in two of the Pechora-Ilychsky Biosphere Nature Reserve, Komi Republic. The component communities of the parasites in river minnow are shown to have a one-year cycle including the states of development, completion, and destruction. Communities in the state of development are characterized by a low variety of species, low values of Shannon index, often high values of domination index, presence of only two groups of parasites in the structure described by variational curved of the conditional biomasses of species, deviation of the conditional biomasses of species from the linear regression, and sum of errors of the regression equations lower a threshold value. The communities consist of young individual parasites and their larval stages. Completed community is characterized by the following properties. There are three groups of parasites, differing in allometric index, in the structure, discerned by the ratio of conditional biomasses of the species included. Conditional biomasses of species in ecologically safe reservoirs lie on the segments of straight lines. Species variety reaches its maximum. Species are presented mainly by mature specimens and larval stages of the parasites using fish as intermediate host. Community in the state of destruction shows low values of domination index and relatively small variety pf species. Such community is consist of one or two groups of species, which are represented by mature, oviparous, and dying individuals. There are larval stages of parasites using fish as intermediate hosts. Dominant species or species groups, as well as values of indexes describing the component communities of parasites, can be different in mature river minnow from different geographical regions. However, the number of groups of parasites, formed by the ratio of conditional biomasses, remains constant, and sum of errors of the regression equations characterizing the communities is always below 0.25. Component communities of parasites in young river minnows differ from the communities in mature fishes by lower variety of species. Lower biomass, and lower number of individual parasites. The communities of parasites in 0+ old fishes are often characterized by lesser number of groups of parasites, classified by the ratio of their biomasses, and presence of two dominate species. It is often impossible to count the sum of errors of the regression equations describing spread in values of biomasses of the species forming the community.     

The history of the minnow Phoxinus phoxinus (L.) in Norway: from harmless species to pest

The causes, effects and extent of minnow Phoxinus phoxinus introductions in Norway are reviewed to assess why the introductions have had severe effects, especially where brown trout Salmo trutta is the only fish species present. The natural distribution of minnow in Norway was mainly restricted to low altitude localities in the south-eastern part of the country and in some northern areas. The distribution area expanded considerably throughout the 1900s, especially in mountain areas, due in part to the use of minnows as live bait for angling. Although minnow densities do not seem unusually high in the relatively complex fish communities of its native range, the species can achieve very high population densities when introduced to communities with few fish species, such as in the numerous recently invaded lakes where brown trout was the only fish species present. The dense minnow populations in these lakes appear to have led to reduced recruitment and growth rates in the brown trout, with abundances on average 35% lower in lakes where minnow has been introduced. The success of minnow in harsh habitats demonstrates their phenotypic and ecological plasticity, but also implies that their original distribution in Norway was restricted by early immigration history and not by environmental limitations. This suggests that human-assisted spread of the species could have strong adverse effects in Scandinavia lakes of low fish species richness.     

The effect of extreme northerly climatic conditions on the life history of the minnow, Phoxinus phoxinus (L.)

Over its exceptionally wide geographical range the minnow displays a remarkable variability in its life history. In southern England many fish mature after one year and few fish survive to their third birthday. Very few fish spawned for more than one season but a 65-mm female is estimated to spawn up to 3172 eggs over the extended spawning season. In the River Utsjoki in Finnish Lapland maturity was strongly size-dependent and delayed until the fish reached 5, 6 or even 7 years of age, with a maximum age of 13 years at a length of only 75 mm. Unlike some other small-sized species in unproductive environments, individual females continued to spawn successive clutches of eggs though over a much shorter spawning season. The maximum estimated egg production was 824 for a 65-mm fish. Temperature had a strong direct or indirect effect on growth, with significantly lower growth increments in cold summers. At a second Arctic site in eastern Lapland growth rates were higher and maturity earlier, yet clutch size was greatly reduced with a seasonal fecundity estimate of only 314. There were only small differences in size of eggs or larvae between the populations. Evidence from other species indicates that most of the observed changes over the range of the minnow are phenotypic responses to the contrasting environments. However, the different strategies displayed at the two Arctic sites could represent the results of selection for differences in pre- and post-reproductive survival.     

Interactive effects of low pH and high ammonium levels responsible for the decline of Cirsium dissectum (L.) Hill

The decline of Cirsium dissectum in dessicatingwetlands is attributed to acidification and eutrophication. Experimentalevidence was obtained for the first time on ammonium toxicity under low pH. Inahydroculture experiment, interactive effects of nitrogen forms (250mol NH₄ ⁺ or 250molNO₃ ^–) and pH (4, 5 or 6) were studied with regardtothe vitality of C. dissectum seedlings. The results showthat 250 mol l^–1 ammonium as sole nitrogensource only had negative effects on C. dissectum incombination with a low pH. Ammonium uptake at a rhizosphere pH of 4, resultedinlower nitrogen contents of both roots and shoots, lower internal pH of rootsandshoots and increased contents of basic amino-acids, resulting indecreased survival rate and biomass development. At higher pH, or when nitratewas the nitrogen source, these processes do not take place. This phenomenonstresses the importance of periodic influence of base rich groundwater duringthe winter in wet species-rich heathlands and grasslands, necessary torestore the acid neutralising capacity of the soil. Anthropogenic lowering ofthe groundwater table will lead to acidification enabling ammonium to becometoxic to herbaceous plant species such as C. dissectum.     

Population biology of the helminth parasites of Phoxinus phoxinus (L.), the minnow, in a Cardiganshire lake

Specimens of Phoxinus phoxinus (L.) were collected over a period of a year from September 1967 to September 1968 from Frongoch Lake, Cardiganshire, Wales. Of a total of 650 fish examined for helminth parasites, 32 % were definitive hosts for Macrolecithus papilliger , and 16·5% for Neoechinorhynchus rutili (Müller), both parasites of the alimentary canal. All the fish examined were second intermediate host for Diplostomum phoxini (Faust) in the brain and 1·67% for Ligula intestinalis (L.) in the coelom. An increase in incidence of infestation with M. papilliger in spring and autumn and with N. rutili in summer were evident. The sex of the fish had no apparent effect on worm burden whereas size was more significant. There was a decrease in incidence of infestation with M. papilliger and an increase with N. rutili together with an increase in intensity of infestation with D. phoxini as the fish became larger. The latter species accumulated in the brain as the host increased in age.     

Component communities of parasites in the grayling Thymallus thymallus (L.) (Salmoniformes, Thymallidae) and the minnow Phoxinus phoxinus (L.) (Cypriniformes, Cyprinidae) from the Pechora River

Component communities of parasites of Thymallus thymallus and Phoxinus phoxinus are described. The communities differ in the number of species and in the number of dominate species, which is one in P. phoxinus and usually two in T. thymallus. In the first case the dominate species is allogenic, while in the second case dominate species are autogenic. Values of the species diversity indexes are also different for these communities. The differences between parasite communities of T. thymallus and P. phoxinus underline positions of these hosts in hydrobiocenose. Species specialists take first place in the parasite communities both of the hosts, that is characteristic for the parasite communities of the fishes from the boreal submountain faunistic complex. Parasite communities in both of the hosts consist of three groups of species discriminated by the ratio of their biomasses, that suggests forming of the groups by a coordination of the species biomasses.     

Quantitative analysis of seasonal dynamics of the species structure in a component parasite community of the minnow Phoxinus phoxinus (L.) of the Pechora River

Earlier analysis of a seasonal succession of fish parasites assemblage was, as a rule, performed in May-October. At the same time, winter season can be important in seasonal dynamics of the assemblage. In the present work, quantitative analysis of complete seasonal dynamics of species structure of fish assemblage parasites with an example of the adult minnow of the river Pechora was performed. The new stable state of parasites assemblage of the minnow, corresponding to winter season of its existence, is revealed. Irrespective of population density or a biomass of parasitic assemblages of the minnow, obtained dynamic phase portraits well reflect their seasonal succession.     

Effects of ration, temperature and body size on the body composition, energy content and condition of the minnow, Phoxinus phoxinus (L.)

The effects of ration and temperature on the body composition, energy content and indices of condition of the minnow. Phoxinus phoxinus (L.) (Cyprinidae). were studied experimentally. Five ration levels over the range starvation to ad libitum and five temperatures over the range 5–15°C were used. The fish weighed 1-5-4 g. At each temperature, the relative dry matter content, lipid content and energy content increased with increased ration. The response of the protein content to ration was temperature-dependent. Temperature had a significant effect on body composition and energy content, but this effect was irregular. The Fulton condition factor was less sensitive to ration than the wet or dry liver-somatic index. Temperature had a significant effect on the condition factor and liver indices. Significant, positive correlations were found between growth rate, lipid content and the indices of condition. The liver indices were better predictors of growth rate than the condition factor or lipid content and may provide useful information on the physiological condition offish in field studies.     

The genetic structure and microdistribution of shoals of Phoxinus phoxinus, the European minnow

Efficient foraging and a reduction in predation risk have been proposed as reasons for shoal formation. Some behaviours in cyprinid shoals are at first sight altruistic (e.g. predator inspection behaviour, reactions to alarm substance), such that kin selection may have been involved in their evolution. If shoaling behaviour does evolve through kin selection, then genetic differentiation is expected to be greater between shoals than within shoals. Such a hypothesis was tested here by examining shoal integrity and the relatedness of individuals within and between shoals in the European minnow, Phoxinus phoxinus , using nuclear and mitochondrial DNA markers. The breeding structure of 13 minnow shoals collected from Dorset and North Wales, U.K., was examined using allozymes. Genetic affinity within and between shoals was tested using mitochondrial DNA and multi-locus DNA fingerprinting. Shoals consisted of a random assortment of allozyme genotypes, shoal members did not share the same maternal mtDNA lineages and DNA fingerprint profiles were as varied within shoals as between them. The data indicate that it is unlikely that kin selection occurs in P. phoxinus and there is no apparent relationship between shoaling behaviour and genotype distribution in this species.     

The adenohypophysis of the flounder,Pleuronectes flesus,and the minnow,Phoxinus phoxinus

Summary The pituitary gland of the flounder, Pleuronectes flesus, showed several unusual cytological features. Between the RPD and the PPD was a zone of cells that stained purple with Alcian blue—PAS—orange G. Many of these cells were apparently degenerating. In the PPD the strands and coils of presumptive STH cells showed a tremendous variation in both size and staining properties. In the PI there were two cell types, the PAS-positive one bordering the neurohypophysis. Around the periphery of the PI was a zone of chromophobic cells, and throughout the PI were numerous intracellular and extracellular acidophil spheres.No well defined ACTH cells were found in the RPD of the minnow (Phoxinus phoxinus). The Alcian blue—PAS—orange G technique distinguishes between blue TSH cells and purple GTH cells in the RPD and PPD. GTH cells from animals collected in the winter were vacuolated. The PI contained two cell types whose staining reactions and ultrastructure were extremely variable. Intra- and extra-cellular acidophil spheres were present.I should like to thank Dr. T. Kerr of the Zoology Department, Leeds University, for his help and encouragement, and Mr. J. Dingley of the Department of Zoology, Aberystwyth, for collecting the flounders.     

Grouping fails to affect the growth and energy budget of a cyprinid, Phoxinus phoxinus (L.)

The effects of grouping on the growth and some components of the energy budget of the minnow, Phoxinus phoxinus (L.), were tested in the laboratory. No effects of grouping were detected on absorption efficiency, the proportion of food energy lost in nitrogenous excretion, maximum rate of food consumption and conversion efficiency. Grouping had no significant effect on either specific growth rate or the dry matter content of individual fish.