Longterm climate changes are an inseparable part of the evolution of Earth. In the last few milions of years the changing of glacials and interglacials was as ordinary and regular phenomenon as changing from day to night or from spring to summer. These cycles also have similar influance on evolution of nature on Earth. Eventhough the state of nature appears to us stable for the few last human generations, the reality from the long term point of view is differnt. During these cycles, the location of climatic zones, size of glaciers, deserts, savannahs, steppes or rainforests have changed. Organisms changed locations of their areas of distribution, many nowadays widespread species were pushed into isolated local populations. This Master's thesis reveals the impact of glacial cycles on a freshwater crustacean aquatic Isopod (Asellus aquaticus). Very variable mitochondrial COI gene was sequenced within 139 individuals of this species from 62 different localities in Europe. This data were included into an extensive scope of an already known phylogeographic structure of the continent. An Aquatic Sowbug shows a quite high rate of a genetic heterogenity (maximum Nucleotide Divergence discovered is 0,132 and average is 0,016) in the area of the Czech Republic. Where there are found representatives of two...

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That ecological and evolutionary processes can take place on the same time scale is a recent insight. Today we also know that they are directly linked to each other. In the lake Tåkern, in year 2000, there was a structural change when phytoplankton declined and submerged vegetation, mainly stoneworts began to spread. This led to evolutionary changes in the aquatic sowbug, Asellus aquaticus which had previously been limited to the reed, most likely feeding on detritus. But then, sowbugs could exploit the new habitat in stoneworts and a new food resource in terms of periphyton. The aim of this study was to investigate whether the differentiation of the populations has led to specialization in the ecological roles of sowbugs as shredder of coarse detritus and grazer of periphyton. The study was a laboratory experiment in which groups of sowbugs were feeding on decomposing alder (Alnus glutinosa) leaves or periphyton growing on tiles. The results showed that there was no specialization in the habitat-specific food. However, reed animals had a greater (31 %) grazing effect than the stonewort animal on periphyton. There was also a non-significant tendency for reed animals to consume more leaves than the stonewort animals. The conclusion is that the different populations are not different in their functional roles, but the reed animals consume approximate 25 % more food than the stonewort animals, possibly because of higher activity.

The purpose of this study was to investigate how elevated levels of heavy metals affect the faunal species composition, abundance and species-diversity. The bentic macroinvertebrate fauna in the highly polluted lake Tisken was compared with the bentic macroinvertebrate fauna in the unpolluted lake Varpan. Mine wastes account for most of the metal that is discharged into Tisken. The hypotheses was that the heavy metal pollutions in lake Tisken influenced the species composition, abundance and diversity of the macroinvertebrates. Twenty samples were taken in both sites. The invertebrates were collected with a bag net and a plastic cylinder one meter from the shoreline. The invertebrates in the forty samples were classified and statistical analyses were made.Some taxa, common at undisturbed sites, were missing at metal polluted sites. Mayfly larvae, Ephemeroptera, were only found in Varpan. Surprisingly, more taxa were found in the polluted lake Tisken (23 taxa) compared to the unpolluted Varpan (19 taxa). However, the abundance of macroinvertebrates in Varpan (291 individuals) was higher than in Tisken (242 individuals).

Dispersal influences several ecological and evolutionary processes, such as intraspecific competition, genetic drift and inbreeding. It can lead to phenotypic mismatch with the habitat when a locally adapted individual winds up in an environment with a divergent selection regime compared to the source habitat. The aim of this project was to compare dispersive traits in the freshwater isopod Asellus aquaticus from a cave habitat, with surface dwelling isopods collected upstream and downstream from the cave system. The subterranean stream (cave) represents a rare, geographically limited habitat which has a divergent selective pressure compared to the surrounding habitats. Experiments on dispersal were performed in the laboratory, in darkness with IR-equipment for visualization. Displacement was measured using one-dimensional test arenas. Compared to the surface phenotype, the cave phenotype was expected to have reduced fitness outside of the cave and unlikely to successfully disperse to new areas of similar suitable conditions. The results did not follow my main hypothesis that isopods from the cave would be less dispersive than individuals from the surface. The inconclusive results might derive from large variation in the data and divergent adaptations which yield similar expression of dispersal.

The freshwater isopod Asellus aquaticus has been shown to exist in two different ecotypes, stonewort ecotypes and reed ecotypes. The differentiation is likely due to adaptation towards different predator regimes and possibly also other selective forces. It is unknown if the ecotypes have different adaptations when it comes to food preferences and roles in the ecosystems. In the present study, isopods of each ecotype were collected from two lakes where the differentiation of pigmentation was especially pronounced to examine whether this had a connection with other physiological adaptations. Growth rate, competitiveness, exposing behaviour and grazing efficiency were tested in two experiments with periphyton or coarse detritus as food sources. None of the results indicated a specialization towards their regular food. Instead, the stonewort ecotype had significantly faster growth rate for both food sources. Presence of snails caused a slight, but statistically insignificant increase in growth rate when periphyton was the food source. Individuals of the reed ecotype were more exposed on the substrate than the stonewort ecotype, but the difference was not statistically significant. Grazing efficiency of both detritus and periphyton was similar and not significantly different between ecotypes. The results thus show no indication to phenotypical differences between ecotypes in the ability to graze or process different types of food. However, currently known adaptations, e.g. in behaviour and pigmentation may be important for the ecological role of the species. / Sötvattengråsuggan Asellus aquaticus har visats kunna förekomma i två ekotyper, kransalgsekotyper och vassekotyper. Differentieringen beror troligen på en anpassning till olika predatorregimer och möjligen även andra selektiva krafter. Det är okänt om ekotyperna har olika anpassningar till födoval och roller i ekosystemen. I denna studie samlades vattengråsuggor av vardera ekotyp in från två sjöar där differentieringen av pigmentering var speciellt markant för att undersöka om detta hade något samband med anpassningar till lokala födoresurser. Tillväxthastighet, konkurrenskraft, exponerat beteende och beteseffektivitet testades i två experiment med perifyton eller detritus som matkällor. Inga av resultaten visade på en specialisering till den normalt förekommande matkällan. Istället visade sig kransalgsekotypen ha signifikant högre tillväxthastighet för båda matkällorna. Närvaro av snäckor orsakade en liten, men icke signifikant ökning av tillväxthastigheten hos vattengråsuggor med perifyton. Individer av vassekotypen var exponerade på substratet oftare än kransalgsekotypen, men skillnaden var inte statistiskt signifikant. Beteseffektiviteten av både detritus och perifyton var jämbördig och inte signifikant olika mellan ekotyperna. Resultaten visar inga indikationer på fenotypiska skillnader mellan ekotyperna i förmåga att beta eller omsätta olika födotyper. Däremot kan fler ekologiska effekter beroende på de i nuläget kända anpassningarna, exempelvis beteende och pigmentering inte uteslutas, och kan ha betydelse för artens funktion i ekosystemet.

Pharmaceuticals that end up in our aquatic environment continue to increase. In recent years, serotonin re-uptake inhibitors (SSRI) have increased in usage as it is considered safer than other substances to treat depression.  Fluoxetine (Prozac) is a widely used anti-depressant that commonly leak out after human use to aquatic environments. Although widely spread, the impact of fluoxetine on aquatic animals in is poorly investigated. The objective of this study was to see if fluoxetine impacts the behaviour of freshwater isopod Asellus aquaticus. Asellus aquaticus were exposed to an ecologically relevant concentration of fluoxetine for 28 days. Through a series of behavioural assays designed to measure the personality traits boldness, activity, exploration and escape behaviour, Asellus aquaticus responses were investigated. A. aquaticus can differ greatly in phenotype, from non-pigmentation to dark pigmentation. Further objective was therefore to investigate if pigmentation correlated with any of the measured behavioural responses, due to potential across-reaction between serotonergic and melatoneric systems. I found that fluoxetine reduced boldness, but had no effect on activity, exploration or escape behaviour. Furthermore, I observed no correlation between pigmentation and behaviour measured in fluoxetine exposed, or control animals. These results indicate that fluoxetine at low levels  affect boldness of wild A. aquaticus but no other personality traits explored. However, other research contradicts these results and show that fluoxetine can affect a range of behaviours. Taken together fluoxetine can have ecological impact on aquatic environments. Hence, our residual pharmaceuticals can have ranging effects.

Local differentiation may occur during a short period of time and is part of the formation of new species. The isopod Asellus aquaticus is an example of a species in which local adaptation has occurred during a short period of time. An establishment of stonewort (Chara spp.) vegetation in Lake Tåkern (in the 2000) resulted in two different Asellus ecotypes; a lighter pigmented, smaller one that lives among stoneworts grazing periphytic algae, and a darker, larger ecotype that feeds on decaying leaves in reed (Phragmites australis vegetation. The purpose of this study was to examine whether there are differences in growth between ecotypes, depending on whether the food was periphytic algae or leaves, and to study the choice of substrates between the two food types. For the study, animals from both habitats were brought in from Lake Tåkern to the laboratory. I found that both the reed and the stonewort animals grew better when feeding on periphytic algae than on leaves, but that there was no difference in weight gain between the two ecotypes. There was no indication that the animals preferred any of the substrates. Results suggest that despite earlier noted differences in behavior, size and pigmentation (which differentiation had brought), there is no evidence that Asellus aquaticus has adapted to feed on plant matter prevailing in their original habitat. The animals grew better when the food was algae maybe due to that the algae, as previous studies show, are easier assimilated, whereas Asellus has to eat a larger amount of leaves to reach the same energy intake.

Anlagda våtmarker i avrinningsområden från jordbruksmarker mottar ofta vatten med höga halter av partikelbunden fosfor. Den viktigaste processen för avskiljning av inkommande partikelbunden fosfor är sedimentation. Resuspension är en process som motverkar netto-sedimentationen av partiklar och kan således minska våtmarkers förmåga att hålla kvar fosfor. Syftet med den här studien var att undersöka om A. aquaticus påverkar resuspensionen av partiklar, och om större tätheter av A. aquaticus orsakar större turbiditet i vattenmassan. Två försök genomfördes i plastakvarier med sediment insamlat från våtmarker anlagda på lerjord. Varje försöksuppställning bestod av en behandling och en kontroll utan några djur. I det första försöket innehöll behandlingen A. aquaticus motsvarande en täthet på 2083 individer m-2 och i det andra försöket en täthet på 500 individer m-2. Turbiditeten mättes med en turbidimeter en gång per dag under sju dygn. Aktiviteten hos A. aquaticus orsakade en signifikant högre turbiditet i vattenmassan i behandlingen än i kontrollen. Turbiditeten var i genomsnitt 161 NTU i akvarier med 2083 individer m-2 och 37 NTU i akvarier med 500 individer m-2. Slutsatsen som drogs är att förekomst av A. aquaticus skulle kunna öka resuspensionen av partiklar i våtmarker. Detta kan i sin tur ha en påverkan på våtmarkers förmåga att hålla kvar fosfor som är bundet till lerpartiklar. / Constructed wetlands in agricultural catchments with clay soils often receive water with high concentrations of particle-bound phosphorus. Sedimentation of particle-bound phosphorus is the main retention process. Resuspension is a process that counteracts net sedimentation of the particles and can therefore reduce phosphorus retention in wetlands. The aim of this study was to investigate if A. aquaticus through bioturbation affects the resuspension of particles, and if a larger density of A. aquaticus causes a larger turbidity in the water column. The experimental design included plastic aquariums with sediment collected from wetlands constructed on clay soils. There were two experiments, each with a treatment and a control with no animals. In the first experiment, the treatment contained A. aquaticus at a density of 2083 individuals m-2. In the second experiment the treatment contained A. aquaticus at a density of 500 individuals m-2. Turbidity was measured with a turbidimeter once a day over the course of seven days. The bioturbation activity of the A. aquaticus caused a significantly larger turbidity in the water column in the treatment than in the control. The turbidity was on average 161 NTU in the presence of 2083 individuals m-2 and 37 NTU in the presence of 500 individuals m-2. The conclusion was that the presence of A. aquaticus can increase resuspension of particles in wetlands. This could have a negative impact on the ability of wetlands to retain phosphorus that is bound to particles.

Fosfor (P) är ofta det begränsande ämnet i akvatiska system och kan i höga mängder bidra till övergödning i sjöar och hav. För att minska tillförseln av partikelbunden fosfor som läcker från jordbruksmark kan våtmarker anläggas i avrinningsområdet. För en effektiv avskiljning är det viktigt att partiklar sedimenterar i våtmarken och stannar i sedimentet. Studier har visat att vissa karpfiskar och märlkräftor genom bioturbation kan orsaka resuspension av partiklar, samt att effekten ökar med ökad täthet. Syftet med denna studie var att undersöka om även makroevertebraten Asellus aquaticus (sötvattensgråsugga) kan orsaka resuspension av partiklar. Två hypoteser undersöktes: (i) A. aquaticus orsakar resuspension av sedimenterade partiklar; (ii) ökad täthet av A. aquaticus ger ökad resuspension. Två försök genomfördes och varje försöksuppställning bestod av 15 akvarier, varav finpartikulärt sediment och bäckvatten tillsattes till tio stycken medan fem innehöll endast bäckvatten. I hälften av akvarierna med sediment tillsattes A. aquaticus i olika täthet för försöken. Försöken pågick i sju dygn med dagliga mätningar av vattnets grumlighet. Resultat från försöken bekräftade båda hypoteserna. Genomsnittlig grumlighet efter sju dygn var 161 NTU (143 mg L-1 TSS) vid en täthet på 2083 A. aquaticus m-2 och 37 NTU (26 mg L-1 TSS) vid 500 A. aquaticus m-2. Studiens resultat indikerar att A. aquaticus kan ha en negativ påverkan på retentionen av partikelbunden fosfor i våtmarker. / Phosphorus (P) is often the limiting nutrient in aquatic systems and can in excessive quantities cause eutrophication in lakes and seas. To reduce the input of particle-bound phosphorus leaking from agricultural land, wetlands can be constructed as traps for particles. It is important that particles settle in the wetland and remain in the sediment. Studies have shown that bioturbation by e.g. common carp and amphipods can cause resuspension of settled particles, and that the effect increases with an increasing density of organisms. The purpose of this study was to examine if the macroinvertebrate Asellus aquaticus can also cause resuspension of particles. Two hypotheses were tested: (i) bioturbation by A. aquaticus will cause resuspension of particles; (ii) an increased density of A. aquaticus increases the resuspension of particles. This was tested in two experiments, each of which included 15 aquaria. In ten of these, sediment and stream water were added. To five of the aquaria with sediment, A. aquaticus were added in different densities for the two experiments. Water turbidity was measured daily for seven days. The results confirmed both hypotheses. Average turbidity after seven days was 161 NTU (143 mg L-1 TSS) at a density of 2083 m-2 and 37 NTU (26 mg L-1 TSS) at 500 m-2. The results indicate that the presence of A. aquaticus may have a negative impact on the retention of particle-bound phosphorus in wetlands.