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Research Assessment Exercise 2007 University of Oulu

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3a.3 Year 2003

Sirkka Heinimaa (2003) Juvenile years of Atlantic salmon in the wild and in the hatchery: ecophysiological differences. Acta Universitatis Ouluensis A 407. University of Oulu, Department of Biology.
This study investigated the ecophysiology of one of the world's northernmost Atlantic salmon (Salmo salar L.) stocks in the River Teno. The juvenile years of salmon of same genetic background were studied in the wild and in the hatchery conditions. In addition, the maternal size effect on reproduction was studied in wild females.
Benefit of body size was not only quantitative but also qualitative in reproduction success of the wild female salmon in the River Teno. Total number of eggs and energy content of eggs were higher in big females than in smaller ones.
In the hatchery, under natural day length and water temperature conditions, the growth rate, liver glycogen content and condition factor of the parr was higher than in the wild. The liver glycogen content of the hatchery-reared parr increased throughout the growing season and decreased during winter, whereas that of the wild parr was the lowest in summer, and stayed relative stable from September to May. The observed differences in annual fluctuation in liver glycogen content may reflect the differences in carbohydrate content of feed and in behaviour between the hatchery and wild.
Overall, the hatchery-reared juveniles maturated and smoltificated 1–2 years earlier than the wild fish. The mean age of wild precocious males was 3 years and that of wild smolts 4 years. However, there was considerable variation in the age of precocious males (1–6 yr) and smolts (2–8 yr) in the wild. The maturing and smolting juvenile age groups were restricted to two (1–2 yr and 2–3 yr, respectively) in the hatchery.
In June, the hypo-osmoregulatory ability of hatchery smolts was developed parallel to the wild smolts. Some differences in physiological parameters between different smolt groups could be observed in the wild and between hatchery-reared and wild smolts indicating that completing of smolting process varies to some extent under different conditions. However, the hatchery-reared smolts showed higher levels of fin damage and body energy stores than the wild smolts.
As the hatchery practices should aim at controlling the quantity and quality of the juvenile salmon in production, the environmental conditions governing the physiological development of the juvenile fish should be taken into account. Hatchery practices should be planned so that the seasonal timing of smolting would follow the wild fish as close as possible.
Keywords: ecophysiology, life-history, maternal reproduction, parr, Salmo salar, smolt
Susanna Huttunen (2003) Genetic basis of male courtship song traits in Drosophila virilis. Acta Universitatis Ouluensis A 397. University of Oulu, Department of Biology.
The pattern and the genetic basis of variation in courtship song of D. virilis were studied using three different approaches: a candidate gene, a biometrical and a quantitative trait locus (QTL) method. Nucleotide variation in a candidate song gene, no-on-transientA, was analysed both within the species (D. virilis and D. littoralis) and between the species of the D. virilis group. Nucleotide variation showed no signs of selection and there was no association between the nucleotide or repeat length variation in nonA gene region and the song characters of the D. virilis group species.
Molecular markers (microsatellites) were isolated for D. virilis and their cross-species amplification was tested in all members of the D. virilis group. Intraspecific variation in D. virilis was studied at the phenotypic level in male song characters and at the genetic level in microsatellites. Significant geographic variation was detected in both levels, grouping the strains according to the main continents of the species' distribution range: America, Asia, Europe and Japan. The strains with most extreme song phenotypes were chosen for further analysis. The inheritance of two courtship song characters, the number of pulses in a pulse train (PN) and the length of a pulse train (PTL) was studied by analysing the means and variances of these characters between parental and reciprocal F1, F2 and backcross males. This biometrical analysis showed the genetic basis of these song characters to be polygenic with significant dominance, epistatic and Y-chromosomal effects on both characters. A subset of these data (F2 generation males) were used to conduct a QTL study with the aid of a recombination linkage map constructed for the microsatellites. Composite interval mapping (CIM) revealed significant QTLs, which were shared in both characters. Altogether, significant QTLs, located on the X, 2nd, 3rd and 4th chromosome, were found to affect PN, whereas only QTLs on the 3rd chromsome was found to affect PTL. The effect of the same QTL on the 3rd chromosome on both characters accounted for 31.8% and 49.1% of the mean difference between the parental strains in PN and PTL, respectively. These results suggest the genetic basis for these song characters is caused mainly by autosomal QTLs with a relatively large effect.
Keywords: courtship song, DNA sequence variation, Drosophila virilis, microsatellite, QTL mapping
Laura Jaakola (2003) Flavonoid biosynthesis in bilberry (Vaccinium myrtillus L.). Acta Universitatis Ouluensis A 404. University of Oulu, Department of Biology.
Flavonoids are a class of secondary metabolites in plants that are involved in many important functions. Various flavonoid compounds have also been reported to be beneficial for human health. Bilberry (Vaccinium myrtillus L.) is the characteristic field layer species in boreal forests and the fruits of bilberry are rich in anthocyanin pigments, a subclass of flavonoids. In the present work, flavonoid biosynthesis was examined in different tissues of bilberry. The focus was on the developing fruits of wild type and natural color mutants of bilberry, and on effect of solar radiation on flavonoid biosynthesis in bilberry leaves.
For the isolation of RNA for gene expression analysis, a method was optimized for different tissues of bilberry. The cDNA fragments of five genes from the flavonoid pathway, coding phenylalanine ammonia-lyase, chalcone synthase, flavanone 3-hydroxylase, dihydroflavanol 4-reductase and anthocyanidin synthase, were isolated from bilberry using polymerase chain reaction technique, sequenced, and labelled with dioxigenin-dUTP label. These homologous, bilberry-specific probes were used for determining the expression of the flavonoid pathway genes in bilberry fruits, flowers and leaves with a modified non-radioactive method developed in the course of the study. The anthocyanins, catechins, proanthocyanidins, flavonols and hydroxycinnamic acids in fruits, leaves and different fractions of bilberry were identified and quantified with high-performance liquid chromatography combined with a diode array detector and mass spectrometer.
The results demonstrate a correlation between anthocyanin accumulation and expression of the flavonoid pathway genes during the ripening of berries. A correlation between flavonol and anthocyanin biosynthesis was detected in bilberry and also in previous literature collected from flavonol and anthocyanin analyses from other fruits. Accordingly, models for the connection between flavonol and anthocyanin synthesis in fruit species were suggested. Activation of the expression of flavonoid pathway genes and accumulation of flavonoids and hydroxycinnamic acids was detected in leaves growing under direct solar radiation, compared to the shadow leaves of the same plants. Based on the results, it is suggested that cyanidin of anthocyanins and flavonol quercetin play a predominant role in the defence against high solar radiation in Vaccinium leaves.
The results give new information about the biosynthesis of flavonoids in bilberry at the gene level, in addition to the information of the composition and content of flavonoids during fruit development and in different parts of the bilberry plant. Also, new information was obtained of the roles of flavonoids in protecting plants from excess solar radiation.
Keywords: anthocyanins, bilberry, flavonols, gene expression, hydroxycinnamic acids, proanthocyanidins, Vaccinium myrtillus
Mari Katvala (2003) Female reproduction and conspecific utilisation in an egg-carrying bug. -Who carries, who cares? Acta Universitatis Ouluensis A 398. University of Oulu, Department of Biology.
Female ability to exploit conspecifics in reproduction may have unusual expressions. I studied the reproductive behaviour of the golden egg bug (Phyllomorpha laciniata; Heteroptera, Coreidae) experimentally in the field and in the laboratory. Female golden egg bugs lay their eggs mainly on the backs of conspecific males and other females. Non-parental eggs are often carried. Occasionally, the eggs are laid on the food plant (Paronychia spp; Polycarpea, Caryophyllaceae) of the species but typically, those eggs survive poorly due to egg parasitism and predation. I explored the dependence of female reproduction on conspecific presence and encounter rate. I also studied female current reproductive state (which depends on if she has recently oviposited) in relation to her activity as well as male choice of a female.
Female bugs preferred to oviposit on conspecifics when presented with a choice between a bug and a food plant. When alone females often did not lay eggs. Increased encounter rate with others increased female egg laying rate. Survival of carried eggs among bugs did not vary significantly although males received more eggs than females. Females with high current fecundity (mature eggs accumulated to reproductive tract) were more active than females with lower current fecundity (recently oviposited). Females with high current fecundity seemed to search for conspecifics to lay eggs on. Males also preferred to court females with high current fecundity. These females were more likely to oviposit immediately after mating, lowering the risk of female remating before oviposition.
To conclude, conspecifics are important egg-laying substrates for female golden egg bugs. Conspecific availability affects female egg laying and the rate of egg production in short term. In particular, males are necessary for egg-laying females and they typically receive unrelated eggs when they court females. Sexual interactions resulting from female polyandry are crucial factors that maintain female egg laying on the backs of males and other females in the unique reproductive system of the golden egg bug.
Keywords: egg laying, host selection, Phyllomorpha laciniata, polyandry
Anna Liisa Ruotsalainen (2003) Mycorrhizal colonization and plant performance in arcto-alpine conditions. Acta Universitatis Ouluensis A 399. University of Oulu, Department of Biology.
Mycorrhizal symbiosis is generally advantageous for plants in nutrient-poor soils. Arcto-alpine areas are relatively nutrient-poor, but abundantly inhabited by non-mycorrhizal species. Possibly, mycorrhizal symbiosis is not favoured due to the harsh climatic conditions and the short growing season, which constrain the photosynthetic gain and growth of the arcto-alpine plants. This hypothesis was theoretically evaluated by assuming that optimal mycorrhizal colonization maximizes the net carbon gain of the host plant. In addition, the prevalence of arbuscular mycorrhizal (AM) and dark-septate endophytic (DSE) fungi along an altitudinal gradient was studied in the field, and their effects on the plant performance were tested in the laboratory.
In the model, the photosynthetic nutrient use efficiency (PNUE) had a key role in determining whether mycorrhizal strategy would be optimal for the plant net carbon gain. The model generated several colonization patterns depending on possible changes in PNUE and soil nutrient concentrations along altitudinal gradients. Field studies indicated that species-level colonizations do not yield a consistent pattern along the altitude except for fine endophyte, which increased along an altitudinal gradient. In a high-alpine field site root fungal colonizations were rare. Seasonal shifts in colonizations in low-alpine conditions were not found. DSE fungi were common root-associates in the field. In the laboratory, AM had a positive impact on the performance of Gnaphalium norvegicum at 15°C, but not at 8°C. DSE-inoculation did not colonize the roots, but it had a positive impact on seedling performance, which may be due to the saprophytic activity of the fungus in the substrate. Additionally, mycorrhizal inoculum was found to decrease the performance of a non-mycorrhizal plant in a competition experiment.
Species-level mycorrhizal colonization patterns may differ from community-level pattern along altitudinal gradients and the relative abundance of different fungal symbionts may change along with the altitude. The performance of mycorrhizal plants in high-alpine conditions may be decreased due to several factors e.g. low temperature constraints on plant and fungal physiology and allocation, soil disturbances and low availability of inoculum. Climatic constraints for plant photosynthesis may thus affect the mycorrhizal colonization patterns in arcto-alpine conditions, but are not necessarily the primary cause for lower performance of mycorrhizal plants at higher altitudes.
Keywords: alpine ecology, arbuscular mycorrhiza, benefit, cost, dark-septate endophytes

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