Factors affecting between-lake variation in the occurrence of epidermal papillomatosis in roach,Rutilus rutilus(L.)

The theory of island biogeography predicts that the probability of a species occupying an island depends on a dynamic equilibrium between extinction and colonization. Epidermal papillomatosis is a disease manifesting as skin tumours on fish. We studied the factors affecting the occurrence of the disease in roach, Rutilus rutilus (L.), in 34 lakes. The results of discrimination analysis suggest that maximum depth, percentage of the drainage area of the lake covered by lakes in the vicinity and altitude best identified diseased lakes. Comparison of diseased and non-diseased lakes revealed that lake area could also be regarded as a variable contributing to the occurrence of the disease. The sa…

Genome-wide divergence patterns support fine-scaled genetic structuring associated with migration tendency in brown trout

Brown trout (Salmo trutta) exhibit highly diverse life histories varying from resident, slow-growing, and early maturing to migratory, fast-growing, and late maturing, even within single watersheds. We sampled 11 locations within the transboundary Finnish–Russian River Koutajoki watershed to evaluate genomic differences among mainstem and headwater sites, of which some are isolated by migration barriers. Restriction site associated sequencing (RADSeq) revealed that the most headwater localities supported unique, isolated populations with generally lower heterozygosity compared with the mainstem populations. The sampled migratory adults in the three main stems showed signals of admixture de…

Factors affecting the intensity of epidermal papillomatosis in populations of roach, Rutilus rutilus (L.), estimated as scale coverage

Studies of epidermal papillomatosis in fish populations have only rarely focused on the intensity of the disease, i.e. the number and size of papillomas. Furthermore, the methods used to evaluate the intensity of papillomatosis have not been standardized. We tested the reliability of a method based on counting of scales covered by papilloma tumours in roach, Rutilus rutilus (L). In addition, we studied the frequency distributions of the number of scales covered by papillomas within populations, evaluated the correlation between the prevalence and mean intensity of the disease among populations and examined the intensity of papillomatosis in roach with respect to sex and size of fish. Reliab…

Comparing RADseq and microsatellites for estimating genetic diversity and relatedness : Implications for brown trout conservation

The conservation and management of endangered species requires information on their genetic diversity, relatedness and population structure. The main genetic markers applied for these questions are microsatellites and single nucleotide polymorphisms (SNPs), the latter of which remain the more resource demanding approach in most cases. Here, we compare the performance of two approaches, SNPs obtained by restriction-site-associated DNA sequencing (RADseq) and 16 DNA microsatellite loci, for estimating genetic diversity, relatedness and genetic differentiation of three, small, geographically close wild brown trout (Salmo trutta) populations and a regionally used hatchery strain. The genetic di…

Sperm quality, secondary sexual characters and parasitism in roach (Rutilus rutilus L.)

According to sperm competition models, a male spawning in a disfavoured role should have spermatozoa with higher velocity but shorter longevity compared with a male spawning in a favoured role. Moreover, immunosuppressive androgens are needed to produce both secondary sexual characters and sperm cells. The ‘sperm protection’ hypothesis suggests that the immunosuppressive action of androgens has evolved to protect haploid spermatozoa, which are antigenic, from autoimmune attacks. Therefore, a male with high sexual ornamentation may be more susceptible to diseases but may possess better quality ejaculate than his less ornamented rival. We studied sexual ornamentation (breeding tubercles), eja…

Epizootic cutaneous papillomatosis in roach Rutilus rutilus: sex and size dependence, seasonal occurrence and between-population differences.

Epidemiology of epidermal papillomatosis in roach Rutilus rutilus was studied in 11 roach populations in Finland in 1999 and 2000 during the spawning period. In addition, the seasonal pattern of the disease was described in 1 population. Papilloma tumours were observed on the skin and fins of roach in 8 populations out of 11. Prevalence of papillomatosis varied from 0 to 62%, being higher in populations subject to industrial or sewage effluents. Males and large fish had higher prevalence of papilloma tumours. The disease outbreak peaked during the spawning period and signs of recovered skin on fish were observed later during the year. The gender dependence in the disease prevalence found in…

Effect of epidermal papillomatosis on survival of the freshwater fish Rutilus rutilus.

Epidermal papillomatosis occurs in several marine and freshwater fish species. Previously, papillomatosis has been shown to induce mortality in juvenile carp. We studied the effect of epidermal papillomatosis on the survival of adult male roach Rutilus rutilus by caging naturally diseased, marked (by us) fish in the field. Within the constraints of the experimental design, there was no difference in survival between healthy, slightly diseased and heavily diseased fish. Therefore, we conclude that the possible effect of epidermal papillomatosis on the mortality of wild roach is relatively minor.

Mechanisms of honest sexual signalling and life history trade-offs in three cyprinid fishes

Anssi Vainikka on väitöskirjassaan selvittänyt vaikuttavatko särjen ja suutarin ornamenttien tuottoon kytketyt hormonit niiden immuunipuolustuskykyyn. Vastoin ennakko-oletuksia, testosteronin tai estradiolin ei havaittu alentavan immuunipuolustuskykyä. Myöskään ornamenttien ja immuunipuolustuskyvyn mittareiden väliltä ei löytynyt seksuaalivalinnan teorioiden ennustamia positiivisia yhteyksiä. Korkea testosteronipitoisuus oli kuitenkin yhteydessä koirassuutarin hyvään kuntoon ja ornamentit kertovatkin koiraan hyvästä elinkyvystä. Testosterone is known to enhance reproductive success, but has also been proposed to suppress immune defence. Prior to spawning, male roach (Rutilus rutilus L.) pro…

Do pheromones reveal male immunocompetence?

Pheromones function not only as mate attractors, but they may also relay important information to prospective mates. It has been shown that vertebrates can distinguish, via olfactory mechanisms, major histocompatibility complex types in their prospective mates. However, whether pheromones can transmit information about immunocompetence is unknown. Here, we show that female mealworm beetles (Tenebrio molitor) prefer pheromones from males with better immunocompetence, indicated by a faster encapsulation rate against a novel antigen, and higher levels of phenoloxidase in haemolymph. Thus, the present study indicates that pheromones could transmit information about males' parasite resistance ab…

Predation risk allocation or direct vigilance response in the predator interaction between perch (Perca fluviatilis L.) and pike (Esox lucius L.)?

Predation risk allocation hypothesis predicts that a prey's response to predator depends on prey's previous experience on predator. Here we tested whether the group of three perch respond differentially to pike, predator of perch, depending on the timing of high constant (HC) and high unpredictable (HU) risk periods within low constant risk periods in short-term (10 h) experiments, and whether the response is stronger during a HU risk period than during a HC risk period. Perch clearly erected the dorsal fin in response to predation risk treatments (pike odour only, odour and visible pike). Decrease in activity and increase in shoaling behaviour were observed mainly during high risk periods.…

In vitro embryo survival and early viability of larvae in relation to male sexual ornaments and parasite resistance in roach, Rutilus rutilus L.

According to the ‘good genes’ hypothesis, sexual ornaments provide an indication of the ‘quality’ of the bearer. In roach, Rutilus rutilus, breeding tubercles (BTs) may signal resistance against the digenean parasite, Rhipidocotyle campanula. Life history theory predicts that there should be a trade-off between parasite resistance and other life history traits. In roach, this could imply a trade-off between parasite resistance in mature fish and some larval feature. We studied embryo survival and the early viability of larvae of male roach in relation to expression of BTs and parasite resistance in maternal half-sibling families. Highly ornamented males had higher resistance against R. camp…

Association Mapping Based on a Common-Garden Migration Experiment Reveals Candidate Genes for Migration Tendency in Brown Trout

A better understanding of the environmental and genetic contribution to migratory behavior and the evolution of traits linked to migration is crucial for fish conservation and fisheries management. Up to date, a few genes with unequivocal influence on the adoption of alternative migration strategies have been identified in salmonids. Here, we used a common garden set-up to measure individual migration distances of generally highly polymorphic brown trout Salmo trutta from two populations. Fish from the assumedly resident population showed clearly shorter migration distances than the fish from the assumed migratory population at the ages of 2 and 3 years. By using two alternative analytical …

It takes time to see the menu from the body: an experiment on stable isotope composition in freshwater crayfishes

For many applications and ecological studies in which wild individuals are brought to laboratory it would be essential to know accurately how fast novel diet is reflected in composition of different tissues. To study the effects of two different diets on the stable isotope composition of freshwater crayfish muscle and hemolymph, we conducted a three month experiment on noble crayfish (Astacus astacus) and signal crayfish (Pacifastacus leniusculus) by feeding them sweet corn (Zea mays) or Baltic herring (Clupea harengus membras) as novel food. During the experiment, the crayfish were given 0.4 g of selected food daily and the amount consumed was recorded. The samples for the stable isotope a…

Male steroid hormones and female preference for male body odor

It has been suggested that human scent works as a signal in mate selection, but the empirical evidence is scarce. Here, we examined whether women’s olfactory preferences for a man’s scent could be correlated with his testosterone, estradiol, or cortisol concentrations, and whether these preferences change along with the menstrual cycle. In line with previous studies, women in their most fertile period gave the highest attractiveness ratings to all men. However, the intensity ratings by women at different menstrual phases did not significantly differ statistically. Interestingly, we found that cortisol concentration in saliva correlated positively with the attractiveness but not with the int…

Measured immunocompetence relates to the proportion of dead parasites in a wild roach population

Summary 1. Although various methods are used to measure immunocompetence, their relationship with the actual parasite clearance or parasite load is seldom demonstrated in natural systems. 2. We combined nine measures of immune function using principal component analysis (PCA), and examined the relationship of the collective measures with (i) the proportion of parasites killed by the host, (ii) the burden of several parasite species and (iii) a viral disease in a wild population of the roach, Rutilus rutilus. We also studied if these variables were associated with the concentration of steroids (testosterone and oestradiol). 3. Most significant correlations between the loads of ecto- and gill…

Condition dependence of pheromones and immune function in the grain beetleTenebrio molitor

Summary 1. Pheromones are chemical signals that function not only as mate attractors, but may also relay important information to prospective mates. In order for the information to be reliable, the signal must be costly to produce and this is likely to result in condition dependent expression of the signal. 2. We present results from two experiments on the grain beetle Tenebrio molitor examining phenotypic condition dependence of pheromones and patterns of female preference for pheromones. We also analysed condition dependence of two measures of immunocompetence: encapsulation response and phenoloxidase activity. 3. By manipulating the nutritional condition of the males we found that the at…

Comparison of migratory and resident populations of brown trout reveals candidate genes for migration tendency

Candidate genes associated with migration have been identified in multiple taxa: including salmonids, many of whom perform migrations requiring a series of physiological changes associated with the freshwater–saltwater transition. We screened over 5,500 SNPs for signatures of selection related to migratory behavior of brown trout Salmo trutta by focusing on ten differentially migrating freshwater populations from two watersheds (the Koutajoki and the Oulujoki). We found eight outlier SNPs potentially associated with migratory versus resident life history using multiple (≥3) outlier detection approaches. Comparison of three migratory versus resident population pairs in the Koutajoki watershe…

The role of juvenile hormone in immune function and pheromone production trade-offs: a test of the immunocompetence handicap principle

The immunocompetence handicap hypothesis postulates that secondary sexual traits are honest signals of mate quality because the hormones (e.g. testosterone) needed to develop secondary sexual traits have immunosuppressive effects. The best support for predictions arising from the immunocompetence handicap hypothesis so far comes from studies of insects, although they lack male-specific hormones such as testosterone. In our previous studies, we found that female mealworm beetles prefer pheromones of immunocompetent males. Here, we tested how juvenile hormone (JH) affects male investment in secondary sexual characteristics and immune functions in the mealworm beetle, Tenebrio molitor. We inje…

Tutkimus ja seuranta

Kalavarojen käyttö ja hoito pysyvät kestävällä pohjalla, kun päätökset perustetaan mahdollisimman luotettavaan ja ajantasaiseen tietoon. Tietoa tarvitaan toiminnan kaikissa vaiheissa, mutta erityisesti silloin, kun asetetaan tavoitetilaa ja osatavoitteita sekä myöhemmin, kun on aika arvioida toimenpiteiden tuloksellisuutta. Tässä luvussa esitellään alueelliseen käyttöön soveltuvia tiedonhankintamenetelmiä sekä annetaan ohjeita aineistojen keruuseen ja tulosten tulkintaan. nonPeerReviewed

Comparison of Migratory and Resident Populations of Brown Trout Reveals Candidate Genes for Migration Tendency

Abstract Candidate genes associated with migration have been identified in multiple taxa: including salmonids, many of whom perform migrations requiring a series of physiological changes associated with the freshwater–saltwater transition. We screened over 5,500 SNPs for signatures of selection related to migratory behavior of brown trout Salmo trutta by focusing on ten differentially migrating freshwater populations from two watersheds (the Koutajoki and the Oulujoki). We found eight outlier SNPs potentially associated with migratory versus resident life history using multiple (≥3) outlier detection approaches. Comparison of three migratory versus resident population pairs in the Koutajoki…

Predator odor recognition and antipredatory response in fish: does the prey know the predator diel rhythm?

We studied in a laboratory experiment using stream tanks if two percid prey fish, the perch (Perca fluviatilis) and the ruffe (Gymnocephalus cernuus), can recognize and respond to increased predation risk using odors of two piscivores, the pike (Esox lucius) and the burbot (Lota lota). Burbot is night-active most of the year but pike hunts predominantly visually whenever there is enough light. Perch is a common day-active prey of pike and dark-active ruffe that of burbot. We predicted that besides recognizing the predator odors, the prey species would respond more strongly to odors of the predator which share the same activity pattern. Both perch and ruffe clearly responded to both predator…

Effects of testosterone and β-glucan on immune functions in tench

A hormone manipulation was performed to examine the effects of testosterone on basal and β-glucan-induced immune functions in wild-caught male and female tench Tinca tinca. Testosterone administration elevated testosterone concentration in plasma, but did not suppress lytic activity of plasma or the chemiluminescence response of blood or head kidney phagocytes in any of the three successive samples or in any of the treatment groups. Both testosterone and β-glucan administrations had a negative effect on the relative mass of the spleen, and testosterone-treated fish lost more mass than control fish. Males had a relatively larger spleen than females, but there were no gender differences in im…

Epizootic cutaneous papillomatosis, cortisol and male ornamentation during and after breeding in the roach Rutilus rutilus.

The prevalence of epidermal papillomatosis in roach is known to peak during the spawning period and to be higher in males than in females. The high occurrence of papillomatosis in polluted waters suggests that stress may contribute to the outbreak of the disease. However, little is known about breeding-induced stress in fish and its relationship with diseases. In this study, plasma cortisol concentration, hematocrit and the relative size of the spleen were determined in healthy and diseased male and female roach Rutilus rutilus during and shortly after spawning in a wild population. In addition, the sexual ornamentation (breeding tubercles on the lateral sides and on the frontal) of male ro…

Kalastuksen ohjaus

Gender- and season-dependent relationships between testosterone, oestradiol and immune functions in wild roach

Plasma testosterone and 17β-oestradiol concentrations, differential leukocyte counts and proportion of dead Rhipidocotyle campanula gill parasites (parasite resistance) were determined five times during a year in two populations of roach Rutilus rutilus and analysed for seasonal and gender differences. In addition to the above immune variables, plasma Immunoglobulin M (IgM) concentration, chemiluminescence and migration differential of head kidney phagocytes, size of the spleen, haematocrit and total leukocyte count were correlated with sex hormones for each population, sampling time and sex separately, using condition factor as a partial correlate. There were no clear gender differences in…

Breeding Tubercles, Papillomatosis and Dominance Behaviour of Male Roach (Rutilus rutilus) During the Spawning Period

We studied the relationship between the breeding tubercle ornamentation (i.e. skin roughness) and male pre-spawning dominance and courtship behaviour in roach (Rutilus rutilus) within an experimental laboratory system. Sexually mature fish were caught during their migration to their spawning pond and their behaviours were studied in an artificial spawning arena. Males behaved naturally both in terms of male–male interactions and attempts to achieve spawnings. Males having many, large breeding tubercles (i.e. rough skin) were significantly more often dominant in our dyadic trials than those with smooth skin. The dominant male in the trial exhibited a more active courtship behaviour than its …

Supplemental Material for Lemopoulos et al., 2019

Beagle file for the ANGSD pipeline. Genotype probabilities of 116 brown trout. 7520 SNPs are identified and mapped to corresponding location in the Atlantic salmon genome.

Management of human-induced contemporary evolution to maintain and restore genetic diversity in brown trout

Maintaining genetic diversity and integrity of animal populations is a key challenge in conservation. While ecological population declines can be reversed, loss of genetic diversity and original trait distribution is often a one-way road. Migratory brown trout is critically endangered in Finland due to extensive modification of river ecosystems and unrestricted fishing on feeding areas. In addition to being too intense in general, fishing creates challenges by being selective for a number of traits in fish. We have shown that recreational angling, for example, is selective for certain personality traits and can cause inherited behavioural changes in the offspring of brown trout. Only a few …

Genetic causes and consequences of Brown trout migratory behaviour

Salmonids are among the most famous and economically important migrating organisms, but unfortunately also often endangered because of multiple human activities. As many other salmonids, brown trout exhibits diverse life history types related to migration strategies. Resident brown trout stay in rivers for their entire life. In contrast, migratory trout undergo a physiological and morphological transformation called smoltification before leaving their natal rivers to enter either sea, lakes or larger river sections. While the phenotypic variation between resident and migratory ecotypes is well documented, little is known about the intraspecific genetic variation associated with these differ…