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  • 1.
    Boalt, Elin
    Södertörn University, School of Life Sciences.
    Ecology and evolution of tolerance in two cruciferous species2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Tolerance to herbivory is the ability of plants to maintain fitness in spite of damage. The goal of this thesis is to investigate the genetic variation and expression of tolerance within species, determine whether and in what conditions tolerance has negative side-effects, and how tolerance is affected by different ecological factors. Tolerance is investigated with special focus on the effects of different damage types, competitive regimes, history of herbivory, and polyploidization in plants. Studies are conducted as a literature review and three experiments on two cruciferous species Raphanus raphanistrum and Cardamine pratensis.

    In the tolerance experiments, plants are subjected to artificial damage solely, or in a combination with natural damage. A literature review was conducted in order to investigate the effects of damage method. We found that traits related to tolerance, such as growth and fitness were not as sensitive in regard to damage method as measures of induced chemical traits, or measures of secondary herbivory.

    Genetic variation of tolerance was demonstrated within populations of R. raphanistrum and between subspecies of C. pratensis. In R. raphanistrum, traits involved in floral display and male fitness were positively associated with plant tolerance to herbivore damage. A potential cost of tolerance was demonstrated as a negative correlation between levels of tolerance in high and low competitive regimes. I found no evidence of other proposed costs of tolerance in terms of highly tolerant plants suffering of reduced fitness in the absence of herbivores or trade-offs in terms of a negative association between tolerance to apical and leaf damage, or between tolerance and competitive ability. In C. pratensis, higher ploidy level in plants involved higher levels of tolerance measured as clonal reproduction. Furthermore, populations exposed to higher levels of herbivory had better tolerance than populations exposed to lower levels of herbivory. In this thesis, I demonstrate evidence of different components for the evolution of tolerance in plants: genotypic variation, selective factors in terms of costs and ploidization, and selective agents in terms of changing environment or herbivore pressure.

  • 2.
    Caspillo, Nasim Reyhanian
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Örebro universitet.
    Hitting the mark: Studies of alterations in behaviour and fertility in ethinyl estradiol-exposed zebrafish and search related biomarkers2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, we have analysed the effects of EE2 on non-reproductive behaviours and fertility. We have showed that two doses of EE2 in male adult short-term exposures evokes opposite behaviours in the novel tank test. A lower dose induced increased bottom-dwelling, a sign of increased anxiety and a higher dose increased surface-dwelling, which would likely expose themselves to predation in a natural environment. Increased shoaling was observed in both exposures, possibly affecting feeding and reproduction opportunities. Fertility analysis of these fish demonstrated a complete inhibition of spawning in the highest dose group. To investigate mechanisms behind the spawning failure, we examined expression levels of genes involved in zebrafish sex differentiation and maintenance of gonadal function. We found downregulated transcription levels of male-predominant genes, suggesting a demasculinization of the testes contributing to functional sterility in these fish. We have demonstrated that non-reproductive behaviour in zebrafish is highly sensitive to EE2 exposure during development. After exposing male and female zebrafish to low doses of EE2 followed by remediation in clean water until adulthood, the fish displayed increased anxiety and shoaling behaviour, demonstrating persistent effects of EE2. Furthermore, behavioural effects were transferred to their progeny. Decreased fertilisation success of the developmentally exposed fish was observed in both sexes when mated to untreated animals of the opposite sex. These fertility effects persisted although the fish had a long remediation period, implying likely reduced fitness of fish populations in aquatic environments. Based on our findings on non-reproductive behaviours and fertility, we performed RNAsequencing analysis of the brain and testes in order to investigate possible biological mechanisms behind the persistent effects. There is a need for biomarkers allowing detection of both reversible and irreversible effects in animals exposed to estrogenic substances, hopefully contributing to better risk assessments for EDCs. Results from RNA-sequencing would serve as a basis for continued studies in pursuit of potential biomarkers.

  • 3.
    Porseryd, Tove
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Reyhanian Caspillo, Nasim
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Örebro universitet.
    Volkova, Kristina
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Örebro universitet.
    Elabbas, Lubna
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology.
    Källman, Thomas
    Uppsala university.
    Dinnétz, Patrik
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Olsson, Per-Erik
    Örebro universitet.
    Porsch Hällström, Inger
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology.
    Testis transcriptome alterations in zebrafish (Danio rerio) with reduced fertility due to developmental exposure to 17α-ethinyl estradiol2018In: General and Comparative Endocrinology, ISSN 0016-6480, E-ISSN 1095-6840, Vol. 262, p. 44-58Article in journal (Refereed)
    Abstract [en]

    17α-Ethinylestradiol (EE2) is a ubiquitous aquatic contaminant shown to decrease fish fertility at low concentrations, especially in fish exposed during development. The mechanisms of the decreased fertility are not fully understood. In this study, we perform transcriptome analysis by RNA sequencing of testes from zebrafish with previously reported lowered fertility due to exposure to low concentrations of EE2during development. Fish were exposed to 1.2 and 1.6 ng/L (measured concentration; nominal concentrations 3 and 10 ng/L) of EE2 from fertilization to 80 days of age, followed by 82 days of remediation in clean water. RNA sequencing analysis revealed 249 and 16 genes to be differentially expressed after exposure to 1.2 and 1.6 ng/L, respectively; a larger inter-sample variation was noted in the latter. Expression of 11 genes were altered by both exposures and in the same direction. The coding sequences most affected could be categorized to the putative functions cell signalling, proteolysis, protein metabolic transport and lipid metabolic process. Several homeobox transcription factors involved in development and differentiation showed increased expression in response to EE2 and differential expression of genes related to cell death, differentiation and proliferation was observed. In addition, several genes related to steroid synthesis, testis development and function were differentially expressed. A number of genes associated with spermatogenesis in zebrafish and/or mouse were also found to be differentially expressed. Further, differences in non-coding sequences were observed, among them several differentially expressed miRNA that might contribute to testis gene regulation at post-transcriptional level. This study has generated insights of changes in gene expression that accompany fertility alterations in zebrafish males that persist after developmental exposure to environmental relevant concentrations of EE2 that persist followed by clean water to adulthood. Hopefully, this will generate hypotheses to test in search for mechanistic explanations.

  • 4.
    Svensson, Melina
    Södertörn University, Teacher Education.
    Framställningen av sexualitet och kön i biologins läroböcker och hur det speglar skolans värdegrund: En läromedelsanalys ur ett queer- och genusperspektiv2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The portrayal of sexuality and gender in biology textbooks and how it reflects the school’s fundamental values.

    The purpose with this thesis is to see how gender and sexuality are portrayed in middle school biology textbooks. This empirical work attempts to answer three questions:

    • How is sexuality portrayed in middle school biology textbooks?

    • How is gender portrayed in middle school biology textbooks?

    • How does the portrayal reflect the fundamental values of the school?

    To answer these questions, a qualitative text analysis, based on close reading of the texts was applied to four different Swedish middle school textbooks in biology. Based on the type of texts, specific questions will be asked during this text analysis. The theoretical framework used in this work is queer and gender theory. Queer theory is the theoretical framework used to analyze gender and sexuality and includes concepts like heteronormativity and performativity. Gender theory is used to analyze context based on an interest in gender. Based on this analysis, three out of four books presented a heteronormative theme. These three books assume that most people are heterosexual, that everyone identifies with the gender they were assigned at birth and are stereotypical in their sex roles. Sometimes the books include other sexualities besides heterosexuality. But only one of the four books analyzed uses a neutral approach by not excluding different sexualities and problematizing gender roles. Two of the books deviate considerably from the school’s fundamental values by discriminating against other sexualities besides heterosexuality. In general, it was found that the books reflect the fundamental values of the school to at least some extent, although it can always be improved.

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