Search

Kirjoittajat osallistuivat syksyllä 2022 Oslossa kahteen tilaisuuteen, joissa kuultiin hedelmien ja marjojen kasvinsuojeluun ja laatuun liittyvää uutta tietoa. Pohjoismainen omenan laatuverkosto piti työpajan 7.-8.11.2022. Suomesta mukana oli seitsemän henkeä. Työpajasta siirryttiin suoraan hedelmän- ja marjanviljelyn neuvojien järjestämään seminaariin (Frukt- og bærseminaret, Norsk Landbruksrådgiving). Tapahtumissa esityksien pääpaino oli erityisesti omenan laatumittauksissa, fungisidiresistenssissä sekä hyönteistuhoojissa.

Increasing antimicrobial resistance (AMR) poses a challenge for treatment of bacterial diseases. In real life, bacterial infections are typically embedded within complex multispecies communities and influenced by the environment, which can shape costs and benefits of AMR. However, knowledge of such interactions and their implications for AMR in vivo is limited. To address this knowledge gap, we investigated fitness-related traits of a pathogenic bacterium (Flavobacterium columnare) in its fish host, capturing the effects of bacterial antibiotic resistance, coinfections between bacterial strains and metazoan parasites (fluke Diplostomum pseudospathaceum) and antibiotic exposure. We quantified real-time replication and virulence of sensitive and resistant bacteria and demonstrate that both bacteria can benefit from coinfection in terms of persistence and replication, depending on the coinfecting partner and antibiotic presence. We also show that antibiotics can benefit resistant bacteria by increasing bacterial replication under coinfection with flukes. These results emphasize the importance of diverse, inter-kingdom coinfection interactions and antibiotic exposure in shaping costs and benefits of AMR, supporting their role as significant contributors to spread and long-term persistence of resistance. peerReviewed

Genetic variation in resistance against parasite infections is a predominant feature in host–parasite systems. However, mechanisms maintaining genetic polymorphism in resistance in natural host populations are generally poorly known. We explored whether differences in natural infection pressure between resource‐based morphs of Arctic charr (Salvelinus alpinus) have resulted in differentiation in resistance profiles. We experimentally exposed offspring of two morphs from Lake Þingvallavatn (Iceland), the pelagic planktivorous charr (“murta”) and the large benthivorous charr (“kuðungableikja”), to their common parasite, eye fluke Diplostomum baeri, infecting the eye humor. We found that there were no differences in resistance between the morphs, but clear differences among families within each morph. Moreover, we found suggestive evidence of resistance of offspring within families being positively correlated with the parasite load of the father, but not with that of the mother. Our results suggest that the inherited basis of parasite resistance in this system is likely to be related to variation among host individuals within each morph rather than ecological factors driving divergent resistance profiles at morph level. Overall, this may have implications for evolution of resistance through processes such as sexual selection., Mechanisms maintaining genetic polymorphism in resistance in natural host populations are generally poorly known. Here, we show no differences in resistance between sympatric morphs of Arctic charr, but clear differences among families within each morph. Our results suggest that the inherited basis of parasite resistance in this system is related to variation among host individuals within each morph rather than ecological factors driving divergent resistance profiles at morph level.

Co-infections are common in host-parasite interactions, but studies about their impact on the virulence of parasites/diseases are still scarce. The present study compared mortality induced by a fatal bacterial pathogen, Flavobacterium columnare between brown trout infected with glochidia from the endangered freshwater pearl mussel, Margaritifera margaritifera, and uninfected control fish during the parasitic period and after the parasitic period (i.e. glochidia detached) in a laboratory experiment. We hypothesised that glochidial infection would increase host susceptibility to and/or pathogenicity of the bacterial infection. We found that the highly virulent strain of F. columnare caused an intense disease outbreak, with mortality reaching 100% within 29 h. Opposite to the study hypothesis, both fresh ongoing and past infection (14 months post-infection) with glochidia prolonged the fish host’s survival statistically significantly by 1 h compared to the control fish (two-way ANOVA: fresh-infection, F1, 82 = 7.144, p = 0.009 and post-infection, F1, 51 = 4.227, p = 0.044). Furthermore, fish survival time increased with glochidia abundance (MLR: post-infection, t = 2.103, p = 0.045). The mechanism could be connected to an enhanced non-specific immunity or changed gill structure of the fish, as F. columnare enters the fish body mainly via the gills, which is also the glochidia’s attachment site. The results increase current knowledge about the interactions between freshwater mussels and their (commercially important) fish hosts and fish pathogens and also emphasise the importance of (unknown) ecosystem services (e.g., protection against pathogens) potentially associated with imperilled freshwater mussels.

Hosts can defend themselves against parasites either by preventing or limiting infections (resistance) or by limiting parasite-induced damage (tolerance). However, it remains underexplored how these defense types vary over host development with shifting patterns of resource allocation priorities. Here, we studied the role played by developmental stage in resistance and tolerance in Atlantic salmon (Salmo salar). This anadromous fish has distinct life stages related to living in freshwater and seawater. We experimentally exposed 1-year-old salmon, either at the freshwater stage or at the stage transitioning to the marine phase, to the trematode Diplostomum pseudospathaceum. Using 56 pedigreed families and multivariate animal models, we show that developmental transition is associated with reduced resistance but does not affect tolerance. Furthermore, by comparing tolerance slopes (host fitness against parasite load) based on additive genetic effects among infected and unexposed control relatives, we observed that the slopes can be largely independent of the infection, that is, they may not reflect tolerance. Together, our results suggest that the relative importance of different defense types may vary with host development and emphasize the importance of including control treatments for more confident interpretations of tolerance estimates. peerReviewed

Parasitic salmon lice (Lepeophtheirus salmonis) threaten the economic and ecological sustainability of salmon farming, and their evolved resistance to treatment with emamectin benzoate (EMB) has been a major problem for salmon farming in the Atlantic Ocean. In contrast, the Pacific Ocean, where wild salmon are far more abundant, has not seen widespread evolution of EMB-resistant lice. Here, we use EMB bioassays and counts of lice on farms from the Broughton Archipelago, Canada—a core region of salmon farming in the Pacific—to show that EMB sensitivity has dramatically decreased since 2010, concurrent with marked decrease in the field efficacy of EMB treatments. Notably, these bioassay data were not made available through public reporting by industry or by the federal regulator, but rather through Indigenous-led agreements that created a legal obligation for salmon-farming companies to provide data to First Nations. Our results suggest that salmon lice in the Pacific Ocean have recently evolved substantial resistance to EMB, and that salmon-louse outbreaks on Pacific farms will therefore be more difficult to control in the coming years.

Although insect herbivores are known to evolve resistance to insecticides through multiple genetic mechanisms, resistance in individual species has been assumed to follow the same mechanism. While both mutations in the target site insensitivity and increased amplification are known to contribute to insecticide resistance, little is known about the degree to which geographic populations of the same species differ at the target site in a response to insecticides. We tested structural (e.g., mutation profiles) and regulatory (e.g., the gene expression of Ldace1 and Ldace2, AChE activity) differences between two populations (Vermont, USA and Belchow, Poland) of the Colorado potato beetle, Leptinotarsa decemlineata in their resistance to two commonly used groups of insecticides, organophosphates, and carbamates. We established that Vermont beetles were more resistant to azinphos‐methyl and carbaryl insecticides than Belchow beetles, despite a similar frequency of resistance‐associated alleles (i.e., S291G) in the Ldace2 gene. However, the Vermont population had two additional amino acid replacements (G192S and F402Y) in the Ldace1 gene, which were absent in the Belchow population. Moreover, the Vermont population showed higher expression of Ldace1 and was less sensitive to AChE inhibition by azinphos‐methyl oxon than the Belchow population. Therefore, the two populations have evolved different genetic mechanisms to adapt to organophosphate and carbamate insecticides., We tested structural and regulatory differences between two populations of the Colorado potato beetle in their resistance to two commonly used groups of insecticides. We show that despite the similar frequency of resistance‐associated mutations in the target site gene, the more resistant populations had additional mutations in another target site gene, higher expression of the target site genes and had less sensitive to enzyme to insecticide inhibition. Therefore, the two populations have evolved different genetic mechanisms to adapt to organophosphate and carbamate insecticides.

Genetic variation in defence against parasite infections is fundamental for host–parasite evolution. The overall level of defence of a host individual or population includes mechanisms that reduce parasite exposure (avoidance), establishment (resistance) or pathogenicity (tolerance). However, how these traits operate and evolve in concert is not well understood. Here, we investigated genetic variation in and associations between avoidance, resistance and tolerance in a natural host–parasite system. Replicated populations of Atlantic salmon ( Salmo salar ) and sea trout (an anadromous form of brown trout, Salmo trutta ) were raised under common garden conditions and infected with the eye fluke Diplostomum pseudospathaceum . We demonstrate significant genetic variation in the defence traits across host populations and negative associations between the traits, with the most resistant populations showing the weakest avoidance and the lowest infection tolerance. These results are suggestive of trade-offs between different components of defence and possibly underlie the genetic variation in defence traits observed in the wild. Because the three defence mechanisms affect host–parasite evolution in profoundly different ways, we emphasize the importance of studying these traits in concert.

Platinum‐based chemotherapy persists to be the only effective therapeutic option against a wide variety of tumours. Nevertheless, the acquisition of platinum resistance is utterly common, ultimately cornering conventional platinum drugs to only palliative in many patients. Thus, encountering alternatives that are both effective and non‐cross‐resistant is urgent. In this work, we report the synthesis, reduction studies and luminescent properties of a series of cyclometallated (C,N,N’) PtIV compounds derived from amine‐imine ligands, and their remarkable efficacy at the high nanomolar range and complete lack of cross‐resistance, as an intrinsic property of the platinacycle, against multiplatinum‐resistant colorectal cancer (CRC) and castration‐resistant prostate cancer (CRPC) metastatic cell lines generated for this work. We have also determined that the compounds are effective and selective for a broader cancer panel, including breast and lung cancer. Additionally, selected compounds have been further evaluated, finding a shift in their antiproliferative mechanism towards more cytotoxic and less cytostatic than cisplatin against cancer cells, being also able to oxidize cysteine residues and inhibit topoisomerase II, thereby holding great promise as future improved alternatives to conventional platinum drugs. peerReviewed

Background Elevated levels of environmental ionizing radiation can be a selective pressure for wildlife by producing reactive oxygen species and DNA damage. However, the underlying molecular mechanisms that are affected are not known. Results We isolated skin fibroblasts from bank voles (Myodes glareolus) inhabiting the Chernobyl nuclear power plant accident site where background radiation levels are about 100 times greater than in uncontaminated areas. After a 10 Gy dose of gamma radiation fibroblasts from Chernobyl animals recovered faster than fibroblasts isolated from bank voles living in uncontaminated control area. The Chernobyl fibroblasts were able to sustain significantly higher doses of an oxidant and they had, on average, a higher total antioxidant capacity than the control fibroblasts. Furthermore, the Chernobyl fibroblasts were also significantly more resistant than the control fibroblasts to continuous exposure to three DNA damaging drugs. After drug treatment transcription of p53-target gene pro-apoptotic Bax was higher in the control than in the Chernobyl fibroblasts. Conclusion Fibroblasts isolated from bank voles inhabiting Chernobyl nuclear power plant accident site show elevated antioxidant levels, lower sensitivity to apoptosis, and increased resistance against oxidative and DNA stresses. These cellular qualities may help bank voles inhabiting Chernobyl to cope with environmental radioactivity. Electronic supplementary material The online version of this article (10.1186/s12860-018-0169-9) contains supplementary material, which is available to authorized users.

Stress tolerance and adaptation to stress are known to facilitate species invasions. Many invasive species are also pests and insecticides are used to control them, which could shape their overall tolerance to stress. It is well-known that heavy insecticide usage leads to selection of resistant genotypes but less is known about potential effects of mild sublethal insecticide usage. We studied whether stressful, sublethal pyrethroid insecticide exposure has within-generational and/or maternal transgenerational effects on fitness-related traits in the Colorado potato beetle (Leptinotarsa decemlineata) and whether maternal insecticide exposure affects insecticide tolerance of offspring. Sublethal insecticide stress exposure had positive within-and transgenerational effects. Insecticide-stressed larvae had higher adult survival and higher adult body mass than those not exposed to stress. Furthermore, offspring whose mothers were exposed to insecticide stress had higher larval and pupal survival and were heavier as adults (only females) than those descending from control mothers. Maternal insecticide stress did not explain differences in lipid content of the offspring. To conclude, stressful insecticide exposure has positive transgenerational fitness effects in the offspring. Therefore, unsuccessful insecticide control of invasive pest species may lead to undesired side effects since survival and higher body mass are known to facilitate population growth and invasion success.

Glyphosate is the globally most used herbicide against a wide range of weeds. Glyphosate has been considered safe to animals as it mainly targets physiological pathways in plants. However, recent toxicological studies have revealed that glyphosate can cause various toxic effects also on animals. In this study, we investigated the direct toxic effects of a glyphosate-based herbicide (GBH, Roundup® Bio) on 1) survival and 2) oxidative status of a non-target herbivore by using Colorado potato beetles (Leptinotarsa decemlineata), originating from Poland and USA, as model species. Larvae were randomly divided into three groups: 1) high concentration (100% Roundup Bio, 360 g/l), 2) low concentration (1.5% Roundup Bio) and 3) control group (water). Larvae were exposed to Roundup for different time periods: 2 h, 24 h, 48 h, 72 h and 96 h. Larval survival decreased in the group treated with high concentration of GBH compared to controls, whereas the low concentration group did not differ from the control group. GBH treatment had no association with oxidative status biomarkers (i.e. catalase, superoxide dismutase, glutathione-S-transferase, glutathione and glutathione related enzymes), but increased lipid hydroperoxide levels after 2 h exposure, suggesting increased oxidative damage soon after the exposure. Larvae of different origin also differed in their oxidative status, indicating population-dependent differences in antioxidant defence system. Environmentally relevant concentrations of GBH are not likely to affect larval survival, but high concentrations can reduce survival and increase oxidative damage of non-target herbivores. Also, populations of different origin and pesticide usage history can differ in their tolerance to GBH. peerReviewed

Diet is one of the major factors directly and indirectly influencing insect’s life history traits and risk of getting infected. Additionally the insect’s fitness is severely affected by the broad diversity of parasites they are exposed to. As a consequence insects have developed well-evolved defences. Behavioural responses include self-medication, the ability of insects to change dietary intake in response to an infection. When studying this ability it is of major importance to consider the insects natural diet range. In this thesis I investigated the effect of different host plants on fitness and immunocompetence of polyphagous Arctia plantaginis larvae and whether the larvae can therapeutically and prophylactically self-medicate by optimising their diet intake. Additionally I examined the long-term effect of prophylactic treatment on lab-reared larvae from the same species. Feeding experiments reveal that the host plants plantain (high in biologically active compounds) and dandelion (high nutritional value) have different effect on the larval development and survival. Results show that a monotonous plantain diet provides lowest protection against an infection, whereas a diet switch from plantain to dandelion increases survival. Immunocompetence seems to be not differently affected by the two host plants. When given the choice, all larvae choose to ingest a mixture of both plants. The ratio of both plants differed depending on the infection status or infection risk in their environment compared to control larvae. This highlights the importance of a mixed diet for some polyphagous species and that dietary variety should be considered when studying insects’ ability to therapeutically and prophylactically medicate. A prophylactic medication applied to laboratory- reared insects showed negative effects on life-history traits and reproductive success, and thus should be carefully considered. In conclusion these findings provide insights in the crucial importance of diet mixing for polyphagous larvae and show evidence for the larvae ability to therapeutically and prophylactically medicate by mixing their diet.

Antagonistic coevolution of parasite infectivity and host resistance may alter the biological functionality of species, yet these dynamics in nature are still poorly understood. Here we show the molecular details of a long-term phage–bacterium arms race in the environment. Bacteria (Flavobacterium columnare) are generally resistant to phages from the past and susceptible to phages isolated in years after bacterial isolation. Bacterial resistance selects for increased phage infectivity and host range, which is also associated with expansion of phage genome size. We identified two CRISPR loci in the bacterial host: a type II-C locus and a type VI-B locus. While maintaining a core set of conserved spacers, phage-matching spacers appear in the variable ends of both loci over time. The spacers mostly target the terminal end of the phage genomes, which also exhibit the most variation across time, resulting in arms-race-like changes in the protospacers of the coevolving phage population., Arms races between phage and bacteria are well known from lab experiments, but insight from field systems is limited. Here, the authors show changes in the resistance and CRISPR loci of bacteria and the infectivity, host range and genome size of phage over multiple years in an aquaculture environment.

Mikrobilääkkeille yhä vastustuskykyisemmistä patogeeneista kuuluu hälyttäviä uutisia nopealla tahdilla. Kiihtyvä antibioottiresistenssi muodostaakin yhden aikamme monimutkaisimmista lääketieteellisistä ja bioeettisistä ongelmista, jonka ratkaisujen on oltava poikkitieteellisiä, koko yhteiskunnan läpäiseviä ja kansainvälisiä. YK:n viimesyksyisen yleiskokouksen myötä koordinaation toivotaan tehostuvan ja kriisinhallinnan vähitellen helpottuvan, mutta haasteita riittää yhä kaikilla yhteiskunnan tasoilla eikä aikailuun ole varaa, mikäli tehokas ja oikeudenmukainen lääketiede halutaan pitää maailmanlaajuisena ihanteena ja tavoitteena.

The purpose of the present study was to examine the immediate and prolonged immune response in circulating cytokine and adipocytokine concentrations after two different resistance exercise bouts: hypertrophic (HYP1, 5 × 10, 80% of 1RM) and maximal explosive (POW1, 10 × 5, 60% of 1RM) resistance exercise bouts and how 12 weeks of resistance training (RT) modifies these responses (HYP2, POW2). Eight men completed the study. RE-induced interleukin-6 (IL-6), interleukin-1β (IL-1β), interleukin-1 receptor antagonist (IL-1ra), monocyte-chemoattractant protein-1 (MCP-1), leptin, resistin, and adiponectin were measured before (PRE) and immediately (POST0), 24 (POST24) and 48 (POST48) hours after RE bouts before and after RT. In the untrained state, IL-6 increased immediately after RE in HYP1 (p = 0.002) and in POW1 (p = 0.003) whereas no changes were observed after RT. Similar results were observed in IL-1β, whereas conversely, IL-1ra increased only after RT in HYP2 and POW2 (p < 0.05). Resistin increased before RT in HYP1 and in POW1 (p = 0.011 and p = 0.003, respectively), but after RT, significant responses were not observed. Interestingly, in HYP2, MCP-1 increased significantly at POST24 (p = 0.009) and at POST48 (p = 0.032) only following RT. The present study shows that RT modifies RE-induced cytokine responses towards an anti-inflammatory direction. peerReviewed

Lisääntymissysteemiltään gynodieekkisissa kasvipopulaatioissa on tavallisesti sukupuoleltaan kahdenlaisia yksilöitä, puhtaasti emikukkaisia kasveja sekä kaksineuvoisia kukkia tuottavia kasveja. Nämä eri sukupuolet eroavat toisistaan geneettisten, morfologisten ja fysiologisten piirteiden suhteen. Lisääntymissysteemi vaikuttaa myös yksilöiden resurssiallokointitapaan sekä siihen miten ja missä suhteessa gynodieekkisten populaatioiden yksilöt osallistuvat geenien siirtämiseen jälkeläisilleen. Emikasvit osallistuvat jälkeläistuotantoon siemenaiheita tuottamalla ja kaksineuvoiset kasvit siemenaiheita sekä siitepölyä tuottamalla. Edellä mainitut sukupuolisidonnaisten erojen vaikutukset voivat heijastua myös yksilöiden resistenssiin. Esimerkiksi enemmän lisääntymiseen panostava sukupuoli saattaa olla alttiimpi patogeeneille, sillä on mahdollista ettei kasvi kykene allokoimaan resursseja lisääntymisen ohella samanaikaisesti resistenssin ylläpitämiseen. Mikäli gynodieekkisen populaation emikasvien ja kaksineuvoisten kasvien kyvyssä ylläpitää resistenssiä on sukupuolisidonnaisista ominaisuuksista johtuvia eroja, voi tämä edelleen vaikuttaa kuolleisuuden tai heikentyneen jälkeläistuotannon kautta kasvipopulaation geneettiseen rakenteeseen ja populaation sukupuolijakaumaan. Seuraukset voivat heijastua takaisin lajin lisääntymissysteemin evoluutioon sekä vaikuttaa kasvin ja muun ympäristön välisiin ekologisiin vuorovaikutussuhteisiin. Tässä työssä tutkittiin kasvihuonekokeen avulla sitä, vaihteleeko gynodieekin metsäkurjenpolven (Gerianium sylvaticum) patogeeniresistenssi yksilön sukupuolen mukaan eli eroaako emikasvien, välimuotojen tai kaksineuvoisten kasvien alttius kurjenpolvenhärmälle (Podosphaera fugax). Tutkimuksessa havaittiin, että välimuotojen ja kaksineuvoisten välillä oli kokoeroja, jotka eivät kuitenkaan vaikuttaneet sukupuolten härmäinfektionlaajuuteen. Kvalitatiivisessa tai kvantitatiivisessa resistenssissä ei havaittu sukupuolisidonnaisia eroja. Tutkimuksen perusteella gynodieekkiseen lisääntymissysteemiin kuuluvat sukupuolisidonnaiset erot eivät ainakaan metsäkurjenpolvella vaikuta sukupuolten infektioalttiuteen. Gynodioecious plant populations are usually composed of two kinds of gender morphs, females and hermaphrodites. Between these two genders there are genetic, morphological and physiological differences that may influence plant's resource allocation patterns and how and to what extent each morph contributes to the production of offspring. In a gynodioecious population females allocate resources to ovule production whereas hermaphrodites allocate resources to both ovule and pollen production. Since resources are limited, these differences in resource allocation patterns may influence other life cycle traits through trade-offs. In case of infection, gender morph that allocates more of its resources to reproduction, that is, to the production of certain kinds of flowers, may not be able to allocate enough resources to resistance. If females and hermaphrodites differ in their resource allocation patterns and it affects their resistance in different ways this may eventually lead to changes in population's genetic structure and its sex ratio through increased mortality or decreased production of offspring. These changes may eventually influence the evolution of plant breeding system and ecological interactions between plants and their environment. In this study greenhouse experiment was set up to study whether females, intermediates or hermaphrodites of gynodioecious Geranium sylvaticum differ in their susceptibility to fungal pathogen, Podosphaera fugax. The results showed that gender morphs have size differences that did not, however, have an effect on the extent of plant infection. Qualitative resistance did not differ significantly between genders and neither did quantitative resistance of leaves and reproductive organs. Based on the results it seems that there are no significant differencies between quantitative or qualitative resistance of different genders of Geranium sylvaticum to Podosphaera fugax.

Antibioottiresistenssi luokitellaan ihmisen terveyden suurimmaksi uhaksi. Antibioottiresistenssi lisääntyy bakteeripopulaatiossa konjugatiivisen plasmidin sisältävien bakteerien välityksellä jopa eri bakteerilajien välillä. PRD1-virus infektoi N-, P- ja W-tyypin konjugatiivisia plasmideja kantavia bakteereja. Tämän työn tarkoituksena oli selvittää, voisiko PRD1-viruksen avulla poistaa bakteeripopulaation vastustuskyky antibiooteille. Tätä testattiin kasvattamalla antibiooteille vastustuskykyisiä bakteereja ilman virusta ja viruksen läsnä ollessa. Bakteerien kasvukäyrät mitattiin lisäksi eri kasvuympäristöissä. Tulosten mukaan virus pudottaa populaation antibioottiresistenssin 100 %:sta jopa alle prosenttiin kymmenessä päivässä. Bakteerien kasvattaminen sekä antibiootti- että virusympäristössä muokkaa osasta bakteereja vastustuskykyisiä molemmille. Tulosten perusteella voidaan siis ehdottaa PRD1-virusta avuksi taistelussa antibioottiresistenttejä bakteereja vastaan. Viruksella voi olla potentiaalia tehostaa terveydenhoitoa ensiksi vaikuttavana hoitona, joka tuhoaa vastustuskykyisiä bakteereja, jonka jälkeen antibioottikuurilla taltutettaisiin jäljelle jääneet antibiooteille herkät bakteerit. Mahdollisuutena on myös käyttää viruksia tartuntojen ehkäisyssä.

Runsas altistuminen auringolle on tunnetusti haitallista ihmisten ja eläinten hyvinvoinnille. Eveliina Markkula tutki väitöskirjatyössään, miten ultravioletti B (UVB) -säteilylle altistuminen vaikuttaa kalojen vastustuskykyyn ja tautialttiuteen.- Ilmakehän otsonikerroksen oheneminen viime vuosikymmenten aikana on johtanut UVB-säteilyn lisääntymiseen maan pinnalla. UVB-säteily tunkeutuu myös kirkkaisiin järvi- ja merivesiin ja voi näin aiheuttaa haittaa kaloille, Markkula kertoo.UVB-säteilyn on jo aiemmin todettu lisäävän kalojen varhaisten elinvaiheiden epämuodostumia ja kuolleisuutta. Kertaluonteinenkin altistuminen lampuilla tuotetulle UVB-säteilylle aiheuttaa muutoksia kalan immuunijärjestelmässä. Sama tapahtuu myös ihmisillä ja jyrsijöillä.Pitkä, neljästä kuuteen viikkoon kestävä altistuminen keinotekoiselle UVB- säteilylle aiheuttaa kalojen immuunitoiminnoissa muutoksia, jotka eroavat lyhyissä altistuksissa havaituista. Nämä haittavaikutukset eivät kuitenkaan kasaannu, ja kalat kykenevät ainakin osittain sopeutumaan kohonneisiin säteilyarvoihin.Erilaisista elinympäristöistä peräisin olevien lajien sopeutumista tutkittaessa havaittiin, että karppi oli kirkkaissa vesissä esiintyvää kirjolohta herkempi valkosolujen toimintakyvyn muutoksille. Molemmilla lajeilla altistuminen UVB-säteilylle heikensi kalojen kuntoa.Markkulan tutkimuksessa immunologisten muutosten merkitystä kalan vastustuskykyyn tutkittiin kahden viikon mittaisella altistamisella UVB-säteilylle. Tutkimuksessa havaittiin, että UVB-säteily lisää kirjolohen herkkyyttä lois- ja bakteeri-infektiolle. Säteilyn ja kalojen tautialttiuden välillä on siis yhteys.- Skandinavian leveysasteilla säteilytasot eivät vaaranna ulkona kasvatettuja lohenpoikasia. Luonnollinen auringon säteily tai vähän kohonnut UVB-taso ei 20 viikkoa kestävässä kokeessa aiheuttanut haittaa kaloille, Markkula huomauttaa.Merkittävästi lisääntynyttä UVB-säteilyä voidaan kuitenkin pitää uhkana kalojen terveydelle, sillä lohenpoikasten kasvu ja kunto heikkenivät sekä immunologiset häiriöt lisääntyivät, kun kaloja altistettiin säteilylle, joka vastaa 20 prosentin otsonikatoa.Markkulan väitöstutkimuksen tuloksia voidaan hyödyntää kalanviljelyssä ja immunologian tutkimuksessa. Tutkimus tuo myös uutta tietoa siitä, miten ympäristön muutosten vaikutuksia voidaan arvioida. Solar ultraviolet B (UVB) radiation is an environmental stressor known to have harmful impacts on aquatic organisms. While the immunomodulatory effects of UVB on fish have been demonstrated in short-term exposures, the present work focused on the long-term effects of low-dose UVB on fish species adapted to live at high or low levels of natural solar radiation. In general, the immunomodulatory effects of the long-term exposures with low UVB doses were less profound than those induced by short-term exposures.Suppressed functioning of head kidney phagocytes was detected after different exposure regimes ranging from a single UVB dose to an irradiation of 6 weeks, and was the most sensitive of the studied cellular parameters. Natural cytotoxic cells and lymphocytes were more inconsistently affected by radiation treatments, as were the hematological and humoral parameters of the blood. Cortisol-mediated stress reaction was common after short-term exposures. A comparison of the fish species revealed that benthic carp (Cyprinus carpio) is more sensitive to UVB than rainbow trout (Oncorhynchus mykiss), a representative species of clear water habitats. In outdoor experiments, the exposure simulating 20 % stratospheric ozone loss for 8 weeks negatively affected the growth, condition, and plasma IgM concentration of the juvenile Atlantic salmon (Salmo salar) indicating potentially compromised immune defense.The exposure simulating 8 % ozone loss for 20 weeks, however, caused no detectable change in fish when compared to the natural solar radiation. The relationship between the UVB exposure and disease resistance was demonstrated in rainbow trout irradiated over 1-2 weeks. Resistance of exposed fish to parasite Diplostomum spathaeum was significantly decreased, and clearance of bacteria Yersinia ruckeri from the tissues of infected fish was affected as well. The results suggest that increased UVB radiation levels can potentially harm fish health in long-term exposures, and that there is an association between UVB exposure and disease resistance.