Mastergradsoppgaver i biologi

Parasite communities of two three-spined stickleback (Gasterosteus aculeatus) populations : effects of a local-scale host introduction?

Jakobsen, Jonas — Mon, 31 Oct 2011 23:00:00 GMT

Jakobsen, Jonas
The introduction of new hosts into new habitats can bring along hitchhiking parasites, i.e. parasites being introduced with the host. This in particular can be an important dispersal mechanism for autogenic parasites that are otherwise restricted by the natural movement of their fish hosts. In this study, the effect of a local host introduction on the parasite communities of three-spined sticklebacks in two subarctic lakes, was examined by comparing the parasite communities of the “introduced” (Takvatn), versus that of the “founder” (Sagelvvatn) population. Seasonal variation and inter-lake differences in abundance was also integrated in the study. The study revealed great similarity between the parasite communities du to similar ecosystems, close geographical proximity, and the facts that the only two autogenic stickleback specialists present in the systems had been introduced with its host. The subtle differences in parasite species richness were explained by accidental infections of parasites of sympatric fish species.

Næringsøkologi og ontogenetisk nisjeskift hos ørret og røye

Moe, Are Andreassen — Mon, 31 Oct 2011 23:00:00 GMT

Moe, Are Andreassen
Ressursdeling og ontogenetisk nisjeskift ble undersøkt hos sympatrisk ørret og røye ved å inkludere stabile karbon- og nitrogenisotoper for å få et mer langtidsintegrert bilde av fiskens næringshabitat og diettbruk. I begge innsjøene benyttet ørreten seg primært av littoralsonen, mens røya tok i bruk alle tilgjengelige habitater. Det ble funnet en tydelig ressursdeling i diett mellom ørret og røye i begge innsjøene. Både diettanalysene og δ13C` viste at ørreten primært benyttet seg av littorale næringsemner i begge innsjøene. Ved økende lengde hos ørret, økte både andelen stingsild i dietten og ørretens trofiske posisjon beregnet ut i fra δ15N. Det var primært de minste lengdegruppene av røye som benyttet seg av profundale næringsemner, som støttes av både diettanalyser og stabile isotoper i begge vann. Både δ13C` og δ15N verdier viser at røya i Sagelvvatn beitet på profundale næringsemner, men med økende lengde gikk de over til pelagiske næringsemner. Det samme mønsteret ble funnet i Takvatnet, men δ13C`verdier gir indikasjoner på at profundale næringsemner utgjorde en mindre andel av dietten hos de minste lengdegruppene. Det konkluderes med at forskjellene i ressursdeling i habitat og diett både innen røye og ørret populasjoner og mellom ørret og røye populasjoner i stor grad kan forklares ut i fra interaktiv segregering mellom artene og ørretens konkurransefortrinn i som bunndyrspiser i littoralsonen.

Functional analysis of microRNA 840 in Arabidopsis

Zhong, Zhijian — Sun, 15 May 2011 22:00:00 GMT

Zhong, Zhijian
Three mechanisms have been implicated for plant microRNAs (miRNAs) to regulate gene expression, i.e. directing target RNA cleavage, transcriptional silencing and translational repression. A great number of target genes of plant miRNAs were predicted using different algorithms and verified through experimental methods. In the present work, one miRNA from Arabidopsis, microRNA 840 (miR840) was initially analyzed through the high-through put sequencing and bioinformatic method (Rajagopalan et al., 2006). MiR840 expresses from the complementary strand of its predicted target gene, AtWhirly3. AtWhirly3 encodes a homolog of the potato transcriptional regulator p24. MiR840 is located between 2 genes, At2g02740 (Whirly 3, Why 3) and At2g02750 (Pentatricopeptide Repeat Protein, PPR). Whirly 3 protein belongs to the Whirly protein family which is one of the main interesting topics in our group. Understanding the potential regulative function of miR840 related to Whirly 3 gene is important to deeply analyze the Whirly 3 protein. Searching the TAIR (http://www.arabidopsis.org) and TIGR (http://plantta.jcvi.org), the two databases give different annotation versions for this AtWhirly3 gene, differing at the length of the 3’ untranslated region. According to the annotation from TAIR, the target of miR840 is only at the 3’ untranslated region (3’ UTR) of Why 3 gene, so this means miR840 only down-regulate the Why 3 gene. But the information from TIGR gives another annotation, Why 3 gene (At2g02740) and its neighbor gene, a PPR gene (At2g02750) overlap with their 3’ UTR where the target site of the miR840 is. This means the miR840 may also be able to down-regulate both the Why 3 and PPR gene, depending on what annotation you take. Therefore experimental analysis is necessary to determine the miR840 target. My master project here is to perform the biological experiments for analyzing the function of miR840. To verify the target genes and study the biological function of miR840. 4 vectors have been firstly constructed and then introduced into Arabidopsis thaliana by Agrobacterium-mediated transformation (1: overexpressed precursors of miR840; 2: overexpressed mutated miR840 target for directing the miR840 lost its normal function; 3: overexpressed Why 3; 4: overexpressed PPR). The mutated miR840 was constructed by the mechanism of target mimicry which through artificial insertion of a mismatch-loop into the cleavage site at the miRNAs target, for making mutated miRNAs targets. The mutated target sites will direct the miRNAs cannot cleave their targets (miRNAs lost their normal function). The expression level of the transgenic plants will be analyzed, the changes of the expression levels observed in the transgenic plant lines could imply the possible role of miR840. The subcellular location of the PPR (At2g02750) protein which is still unknown yet, so the bioinformatic method was used to predicted its subcellular location.

Peripheral heterothermia in reindeer (Rangifer tarandus tarandus)

Olsson, Elin Anita Maria — Sun, 15 May 2011 22:00:00 GMT

Olsson, Elin Anita Maria
Reindeer (Rangifer tarandus tarandus) inhabit the Arctic and have evolved adaptions to meet the climatic challenges in this region. Peripheral heterothermia, which is a heat conserving mechanism in homeotherms during cold exposure, is well documented in the reindeer and manifests itself in tissue temperatures in the extremities well below 10°C. It is, however, unknown whether peripheral heteothermia in reindeer requires efficient vascular counter-current heat exchange, or is simply a result of reduced blood flow to the extremities. Vascular corrosion casts, x-ray pictures, dissections and electron microscopy did not reveal any counter-current rete in the front legs, but the vascular anatomy, with arteria brachialis and vena brachialis running in intimate contact with each other for the full length of the leg, still seems to allow quite efficient counter-current heat exchange. Recordings of brachial blood flow and subcutaneous temperature (Tsc) in the front legs of winter insulated reindeer subjected to ambient temperatures (Ta) of 20°C, -10°C and -30° suggest that the initial drop in Tsc seen in reindeer when exposed to moderate cold (-10°C) is primarily the result of use of a circulatory pattern enabling counter-current heat exchange, while decreasing blood flow appears to be a secondary mechanism when Ta falls further towards -30°C.

Site fidelity of Svalbard polar bears revealed by mark-recapture positions

Lone, Karen — Sat, 30 Apr 2011 22:00:00 GMT

Lone, Karen
The spring season is important to polar bears, since females with young cubs leave the maternity dens, ringed seal pupping creates a peak in prey availability, and it is the mating season. Understanding space- and resource use at this time is a key to understanding polar bear ecology. This study from Svalbard, Norway analyzed 348 measurements of spring-to-spring displacement from 220 polar bears obtained by mark-recapture sampling in the period 1987 – 2010 to assess whether the bears exhibit spring site fidelity. All age and sex classes of polar bears showed site fidelity when their movements were compared to a scenario of random movements between all capture locations. The median observed displacement for all bears was 43.0 km (bootstrapped 95% CI: 34.3 - 51.0 km), significantly smaller than the median potential displacement for random movements of 205.4 km (bootstrapped 95% CI: 205.1 - 205.6 km). Linear model analysis of all displacements showed that displacement length depended on both the age and sex of the individual. Subadult females had the longest displacements, followed by adult males and adult females. Consistent, precise site fidelity over time was only displayed by a subset of females. When only the first movement of each bear was included, the effects of age and sex in the linear model were less pronounced, and the difference between adult males (linear model estimate: 50.0 km) and adult females (40.7 km) was not significant. These findings support previous reports in the literature comparing movement patterns of males and females in other parts of the Arctic. Sufficient data to conclusively evaluate subadult movement patterns is still lacking. Overall similarities in site fidelity of adult males and females indicate that findings based on telemetry of females may be relatively representative of the whole adult Barents Sea population.

The diet of polar bears (Ursus maritimus)from Svalbard, Norway, inferred from scat analysis

Iversen, Marianne — Tue, 31 May 2011 22:00:00 GMT

Iversen, Marianne
The diet of polar bears in the Svalbard area was assessed based analyses of scats (n=119) collected in the Archipelago between 2003 and 2010. Most of the samples were collected in spring. Morphological analysis of the prey remains together with genetic analyses of tissue fragments found in the scats showed that ringed seals (Pusa hispida) were the most important prey group present; this seal species occurred in 58% (CI 48.6%-67.0%) of the scats. Ringed seal pups were particularly abundant (45.4%, CI 36.2%-54.8%). Bearded seal (Erignathus barbatus) and birds seemed to be minor components in the diet, while Svalbard reindeer (Rangifer tarandus platyrhynchus), considering its size and the frequency with which it occurred in the scats (9.2 %), likely plays a more important role in the diet than previously reported. Whether reindeer are hunted actively by the polar bears or occur in the diet via scavenging is uncertain. Terrestrial plants and marine algae occurred more frequently in the polar bear diet than would be expected from accidental ingestion, with 32.8 % (CI 24.4%-42.0%) and 21.8 % (CI 14.8%-30.4%) of scats containing these food items, respectively. It appears that they are eaten deliberately; perhaps to meet nutritional requirements for mineral nutrients or vitamins. This study has shown that scat analysis is a useful method for assessing the diet of this large carnivore, despite the advanced state of digestion of food items in most polar bear scats.

Local variation in mountain birch spring phenology along an altitudinal gradient in northern coastal Fennoscandia

Sjöskog, Maja Sofia — Thu, 09 Jun 2011 22:00:00 GMT

Sjöskog, Maja Sofia
Currently there is a lack of spring phenology studies covering small-scale altitudinal gradients of mountain birch in coastal northern Fennoscandia, a region characterized by exceptionally high precipitation of snow, which gives reason to investigate the influence of snow cover on birch budburst in this area. Furthermore, ground phenology studies are today increasingly replaced by satellite data studies, but only too rarely is the latter approach properly validated. In order to provide a better basis for studies of local variation in spring phenology of birch in coastal altitudinal gradients, this study aimed at exploring how well (1) thermal sum models could predict budburst in individual birch trees with the inclusion of local conditions such as snow depth, soil temperature and altitude as predictors, and (2) NDVI values from high-resolution satellite images reflect leaf phenology in birch. The result for (1) showed that a simple thermal time model with spring air temperatures provided the best explanation for budburst, and that snow depth, soil temperature and altitude did not improve the predictions. The results for (2) showed that the correspondence between NDVI values and leaf phenology was generally high, but there were still some variation between in situ measurements and the satellite-derived NDVI, probably reflecting the limited capacity of satellite imagery to capture the phenology of merely one species.

Næringsøkologi til fiskespisende ørret og gjedde i Pasvikvassdraget (Vaggatem)

Skog, Martin — Sun, 14 Aug 2011 22:00:00 GMT

Skog, Martin
Pasvikvassdraget ble tidlig på 1990-tallet utsatt for en invasjon av lagesild fra Enaresjøen i Finland. I 2009 ble det gjennomført et eksperiment med utsetting av 1500 ørret i Ruskebukta i øvre del av vassdraget, for å undersøke ørretens egnethet til biokontroll av den invaderende lagesilda. For at biokontroll med fiskespisende ørret skal være vellykket er det viktig å ha god kjennskap til økosystemet de settes ut i. Gjedda er en potensiell predator på ørret og i Pasvik er den tidligere også observert i pelagialsonen, som er den fiskespisende ørretens hovedhabitat. Både ørret og gjedde var fiskespisere, men de hadde forskjellig næringshabitat. Dietten hos ørret i øvre del av Pasvikvassdraget var dominert av pelagisk lagesild. Gjeddas diett omfattet alle de vanligste fiskeartene i området, men littorale arter som sik, abbor og andre gjedder var viktigst. Gjeddas diett så ut til å være styrt av en kombinasjon av sesongmessig tilgang og en preferanse for arter med et minimum av antipredatortrekk. Både ørret og gjedde inkluderte lagesild i dietten, men diettoverlappet var generelt lavt. Ørreten foretrakk små lagesild, mens gjedda inkluderte et bredt størrelsesspekter av byttefisk i dietten. Gjedda utgjorde en betydelig trussel for nyutsatt ørret, men utover en omfattende predasjon på de nyutsatte fiskene fantes det ingen indikasjon på at gjedda er en viktig predator på ørret. Dette er trolig en effekt av at fiskespisende ørret er pelagiale jegere, mens større gjedde hovedsakelig har en littoral diett.

Fatty acids in the blubber of minke whales (Balaenoptera acutorostrata) -stratification and relation to diets

Gade-Sørensen, Lars Aage — Sun, 15 May 2011 22:00:00 GMT

Gade-Sørensen, Lars Aage
The fatty acid (FA) composition of 37 minke whales (Balaenoptera acutorostrata) from 4 different areas, Spitsbergen, Bjørnøya, Vesterålen and the North Sea was determined. Stratification between inner, middle and outer blubber was present. Most saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) with 20 and 22 carbon atoms had a higher relative amount in the inner blubber while short-chain MUFAs with 14, 16, 17 and 18 carbon atoms had a higher amount in the outer blubber. Whales from the different areas had a different fatty acid composition in inner blubber layer, but a more similar FA composition in outer blubber layer. The inner blubber layer were found different from all potential prey species, even though prey species from expected and observed diets were found with most similar fatty acid composition as the inner blubber layer. Fatty Acid Trophic Markers (FATMs) indicating the copepod Calanus sp. based food-webs, were found in high relative numbers with all whale samples from all areas, FATMS indicating diatoms were found with Spitsbergen/Bjørnøya samples, and FATMs indicating dinoflagellates were found with samples from Vesterålen and the North Sea. FA profiles have the potential in bio monitoring minke whale diet, but more study of the influence of metabolism in FA incorporation of blubber are needed.

Prey selection of the Red King Crab (Paralithodes camtschaticus) preying on lumpfish eggs (Cyclopterus lumpus), sea urchins (Strongylocentrotus droebachiensis) and scallops (Chlamys islandica)

Michelsen, Helena Kling — Sun, 15 May 2011 22:00:00 GMT

Michelsen, Helena Kling
The red king crab, Paralithodes camtchaticus, is a new generalist predator in the Barents Sea and may have negative effects upon the commercially fished lumpfish eggs (Cyclopterus lumpus), sea urchins (Strongylocentrotus droebachiensis) and scallops (Chlamys islandica). Generalist predators consume an array of prey types, but have been shown to select certain prey over others. To obtain knowledge on how the king crab consume, select and actively select these prey, a laboratory experiment was performed. To detect active selection, the experiment was divided in two parts: first the crabs were given one prey item (no selection) and second they were given all three prey items (selection). Prey organisms consumed was evaluated after 22 hours. There was a significant selection for eggs and scallops and a significant active selection for scallops. The consumption, selection and active selection of prey appeared to be dependent on crab size and availability of alternative prey. With increasing crab size the amount of prey consumed increased and diet composition included a wider array of prey types. Due to the juvenile crabs residence in shallow waters for 5 years until maturation and the adult crabs annual migration to these areas during moulting/spawning, the red king crab predation could have a negative effect on all three prey types.