The development of shoaling behaviour in the European minnow, Phoxinus phoxinus

The effects of development and disturbance on schooling and shoaling were observed in laboratory-raised minnows. Both behaviours were present at the onset of free swimming. Shoaling increased to become the most important behaviour by 3 weeks after emergence from gravel, while the main increase in schooling behaviour occurred at 4 weeks. These changes were accompanied by rises in elective group size and in the number of following responses, and by a decrease in nearest neighbour distance. The increases in social behaviour were observed at an earlier stage in the same minnows threatened by a standard net chase. The main increase in schooling in disturbed minnows took place between 3 and 4 weeks after emergence; after this time schooling became the dominant behaviour. Disturbed fish were also more likely to follow another minnow during an encounter.     

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 parasitic communities of the minnow (Phoxinus phoxinus L>)

Phoxinus phoxinus being a widely distributed through Palaearctic and ecologically specialised species is a good model to study parasite communities. 72 specimens of P. phoxinus from 5 localities of the Siberia and Mongolia has been studied by the author and 651 specimens--from 5 localities in Kola Peninsula by the other researches. 595 specimens were studied by B. S. Shulman (1983) year around. To describe infra- and component parasite communities the Brillouin, Shannon, Berger-Parker indexes were used. Communities within individual fish were compared within, and between localities with quantitative percentage similarity index (Esch e. a., 1988). The Brillouin, Shannon and Berger-Parker indexes can be calculated based on abundance or total number of parasites of each species for component or compound communities. Intensity cannot be used. Significant negative correlation was observed between the Brillouin and Berger-Parker dominance indexes (r = -0.984, p < 0.01, n = 66) in infracommunities. The Brillouin index was significant positive correlated with the number of parasites in infracommunity (r = 0.407, p < 0.01, n = 66) and with the number of species in infracommunity (r = 0.92, p < 0.01, n = 66). Berger-Parker dominance index was significant negative correlated with the number of parasite in infacommunity (r = -0.815, p < 0.01, n = 66) and with the number of species in infracommunity (r = -0.268, p < 0.05). Total number of parasites and the number of species in infracommunity was positive correlated significantly (r = 0.565, p < 0.01, n = 66). These correlations remain the same at the component community level for the Shannon/Berger-Parker indexes (r = -0.965, p < 0.01, n = 10) and total number of parasites/number of species (r = 0.789, p < 0.01, n = 10) only. Similarity index was not correlate with any other indexes and parameters. No significant correlation was found between the Brillouin, Berger-Parker indexes and geographical characters of localities (longitude, latitude, altitude above sea-level). Weak correlation (r = 0.551, p < 0.098, n = 10) was observed only between the Berger-Parker dominance index and the latitude. 37 metazoan parasites have been found in all localities (specialists--40%, allogenic species--22%, rare species--40%). Allogenic generalist species of the genus Diplostomum (D. phoxini in most cases) were dominant in 60% of the component communities and 36% of infracommunities on average. 20% of the component communities were dominant by autogenic specialists Gyrodactylus magnificus and only 12% of the infracommunities were dominated by this species. Trematode and nematode larvae were core species in most localities. Frequency distribution of infracommunity richness varied from locality to locality being overdispersed in combine sample. Parasite communities at least on the infracommunity level demonstrate high variability of all parameters. Some tendency to decrease the diversity seems to be present depending on remoteness from prospective centre of origin of the genus Phoxinus.     

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 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 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 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.     

Transitory colour changes in the new melanophores formed by quantitative colour change in the minnow Phoxinus phoxinus

Minnows (TeJeosiei: Phoxinus phoxinus (L.)) were exposed on a black background for varying periods to allow melanophore formation. The ages and times of appearance of melanophores were photographically determined. The background responses of the newly-formed melanophores were assessed microscopically in fixed preparations of animals killed in liquid nitrogen at different time-intervals. The results were interpreted according to the generally accepted belief that rapid and slow colour changes indicate nervous and hormonal mediation respectively. The age of the newly-formed melanophores appeared to influence their background responses, the older melanophores being more responsive. It is suggested that the sensitivity to hormonal control develops first in the life of a pigment cell, to be followed later by sensitivity to nervous control. Nervous control, however, does not appear simultaneously for W/B and B/W adaptations but develops first for the latter. This differential development is considered to provide evidence for double innervation of melanophores.     

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.     

Accumulation and effects of aluminium in the minnow (Phoxinus phoxinus L.) at different pH levels

The accumulation and effects of 150 pg All^-1 on minnows ( Phoxinus phoxinus L.) were studied in soft water at pH 7, 6 and 5. The fish were kept in a flow-through water system for up to 48 days. Addition of aluminium to the water resulted in poor appetite, passivity and a tendency for the fish to gather as far as possible from the aluminium inlet. The mortality was high at pH 5 and also after addition of aluminium at pH 6. Severe lesions were noted in the gills and olfactory organs after exposure to aluminium. The concentration of aluminium in the gills, liver and kidney was increased at low pH. A large proportion of the aluminium was located on the surface of the gill epithelium. The recovery capacity was pronounced when the aluminium exposure was terminated and the pH was increased from 5 to 7. No further mortality occurred and gill and olfactory organ structure returned to near normality in about 36 days.     

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.     

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 colour change of the minnow, Phoxinus phoxinus with particular reference to the effect of spinal lesions

An account is given of the anatomy of the spinal cord of the minnow, Phoxinus phoxinus L., and comparisons are made with the spinal cords of other teleosts. The effects on the rapid, neurally controlled colour responses of complete transection of the spinal cord at different levels indicated that, in the particular fish used for this work, the sympathetic pigmento-motor fibres had a localized outflow from the spinal cord around vertebra 13. Partial lesions of the spinal cord at vertebrae 3, 4, 10 and 11 and their effects on the colour responses indicated that, at these spinal levels, the pigmento-motor fibres were dorsomedially located within the dorsal horns. Complete and partial transection of the spinal cord at any single level between vertebrae 12 and 14 and partial transection of the dorsomedial spinal tissues at vertebrae 3, 4, 10 and 11 resulted in differential paling of the entire dorsolateral skin of the fish in response to a change of background from black to white. It would appear that in both cases this differential response of the melanophores was the result of transecting a proportion of the spinal pigmento-motor fibres.     

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.     

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.     

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.     

Identification of extraretinal photoreceptors in the teleost Phoxinus phoxinus

The existence of cells capable of detecting changes of the photoperiod within the deep brain, the so-called deep brain photoreceptors, was proposed in the early years of the twentieth century. By using immunocytochemistry with antisera against phototransductory proteins on paraffin and vibratome sections, we have localized several positive areas in the brain of the teleost Phoxinus phoxinus. These areas were restricted to two encephalic regions: the epithalamus and the hypothalamus. Immunopositive (rod-opsin- and a-transducin-like) pinealocytes and parapinealocytes, as well as some sparse neurons in the habenula, were seen in the epithalamus. The immunoreaction of the hypothalamus was represented by a-transducin-like positive (magnocellular and parvicellular) neurons of the Nucleus Preopticus, as well as by a-transducin- and arrestin-like positive fibers corresponding to the hypothalamic-hypophyseal tract and a few fibers running towards the basal telencephalon. These findings corroborate the data published on other teleost fish and fully support the hypothesis of the presence of photosensitive cells in the encephalon of lower vertebrates. The labelling with antisera against different components of the phototransductory cascade also strengthens the idea that such cells employ a biochemical mechanism similar to that in the retinal visual photoreceptor cells, rods and cones. Although the function is still unclear, the detection of the photoperiod seems to be the most likely role for these extraretinal photoreceptors.     

Appetite and growth compensation in the European minnow,Phoxinus phoxinus (Cyprinidae), following short periods of food restriction

Synopsis Changes in the daily appetite and weekly growth rates of individual adult minnows,Phoxinus phoxinus, on ad libitum rations were recorded before and after they had experienced 4 or 16 days of food restriction. Feeding levels during the restriction periods were either starvation or a maintenance ration. The latter was estimated from a previously determined regression model. Water temperature was 15°C and the photoperiod 9L15D in all experiments. The mean weight of fish used ranged from 1.06 to 2.15 g. The 4 day restriction had no detectable effects on appetite or growth. After the 16 day restriction, the minnows showed hyperphagia and had increased specific growth rates and growth efficiencies compared with control fish. The compensatory increases in appetite and growth were not sustained and within three weeks had declined to levels not significantly different from those of the control fish. At the end of the experiments, there were no significant differences between the mean weights or cumulative food consumption of the restricted and control groups. The results suggest that adult minnows regulate their appetite and growth rate in relation to their previous nutritional history.