Doctoral Theses / Doktorsavhandlingar Zoologiska institutionen

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Infidelity in Birds – Causes and Consequences of Extra-pair Paternity
(2012-04-13) Augustin, Jakob
Forty years ago, more than 90% of bird species were classified as monogamous and not very exciting systems for studies of e.g. sexual selection. Since then, the discovery of extra-pair paternity (EPP) in more than 75% of surveyed monogamous bird species has made avian monogamy, and the interaction between social and genetic mating systems in general, a challenging and attractive area of research. Despite three decades of research on EPP in birds, however, many questions and controversies remain unresolved. This thesis contributes to the understanding of mechanisms and adaptive reasons, primarily from the female’s perspective, for the highly diverse frequencies of EPP in birds. First, in a population of the common redshank (Tringa totanus), a wader for which the genetic mating system has not been described previously, a surprising absence of EPP is demonstrated (I). Presumably, some female pre- or postcopulatory resistance to extra-pair fertilisations is present. The potential mechanisms and adaptive significance of this is discussed in relation to redshank ecology and behaviour. In the three following papers (II-IV), assumptions and predictions of hypothesised female benefits from EPP are addressed. In sand martins (Riparia riparia), there were no indications that extra-pair fertilisations resulted in genetic benefits (e.g. heterozygosity or ‘good genes’) (II). Paper III tests an assumption related to the genetic compatibility hypothesis, i.e. that overall heterozygosity leads to increased chick survival; this did not seem to be the case in Kentish plovers (Charadrius alexandrinus). In northern lapwings (Vanellus vanellus), the indirect benefits hypothesis is partly supported by a positive association between EPP and brood sex ratio (IV). As predicted by the differential sex allocation hypothesis, broods with extra-pair offspring contained a higher proportion of sons than broods without extrapair offspring. As for the yet unknown mechanism of sex determination in birds, an unusual case of a fertile, triploid Kentish plover female is presented and discussed with regard to the two present major hypotheses for sexdetermination (VI). Finally, as an alternative or additional interpretation of what appears to be brood sex ratio adjustment by the female, the often neglected effect of differential mortality is discussed (V).
Tales of the flying earth: The effect of host flyways on the phylogeny of shorebird lice (Phthiraptera: Ischnocera)
(2012-04-05) Gustafsson, Daniel
On the wings, bodies, and heads of most birds there are lice. These lice spend their whole lives on their host, with the exception of the few lice that get the opportunity to transfer from one host to another, typically when the hosts come into physical contact with each other. In shorebirds (Charadriiformes), such opportunities are unevenly distributed over the year. The hosts are spread out over vast areas in their Arctic breeding grounds during the Arctic summer, but form dense, multispecies flocks in the tropics and subtropics during the Arctic winter. During autumn and spring, when the hosts migrate between the Arctic to the tropics, they follow more or less well-defined routes, called flyways. In this thesis, the impact of this host migration pattern on the phylogeny of shorebird lice is evaluated. More specifically, two complementary hypotheses of pattern formation in the evolutionary history of shorebird lice, flyway homogenisation and flyway differentiation, are tested by phylogenetic reconstruction of the evolutionary history of two genera of lice (Lunaceps and Carduiceps) that parasitize the same group of sandpiper (Scolopacidae: Calidrinae) hosts. Flyway homogenisation is founded on the assumption that opportunities for lateral spread of lice between hosts of different species are prevalent in flyways, which will facilitate gene flow between louse populations on different host species, and prevent speciation of lice on host species that use the same stop-over points and wintering grounds. Over evolutionary time, this would cause a pattern of host species migrating along the same flyways having genetically similar or identical louse populations. Flyway differentiation is, conversely, the hypothesis that the division of a widely spread host species into discrete populations that each follow different flyways during migration will work as an isolating mechanism on the lice. If the generation time of the lice is significantly shorter than that of their hosts, this would result in a pattern where the same Holarctic-breeding host species is parasitized by genetically different louse populations in different parts of the world. Extrapolating from data published on other groups of lice, flyway homogenisation is expected to be more pronounced in wing lice (Lunaceps) than in body lice (Carduiceps) as these are topologically better placed on the host to take advantage of opportunities of lateral transfer to novel host species. Flyway differentiation is expected to be more pronounced in Carduiceps than in Lunaceps, as wing lice of vagrant hosts migrating along the “wrong” flyway would transfer to novel hosts more easily, and could prevent complete isolation between flyways. While no evidence is found in either genus for flyway differentiation, there is evidence for flyway homogenisation in Lunaceps, with three Lunaceps species occurring on multiple host species using the same flyways. Surprisingly, most Carduiceps collected across the world are genetically almost identical, and thus less isolated on their hosts than are Lunaceps. Both Lunaceps and Carduiceps show some partial evidence of a division between lice on New World hosts and those on Old World hosts. This division in echoed in a larger molecular study on the proposed louse family Rallicolidae, where several species group together according to host biogeography rather than host relationships, thus contradicting the so-called Fahrenholz’ rule that states that parasite phylogeny should come to mirror host phylogeny. In the same phylogeny, evidence is presented that the genus Quadraceps, widely distributed on most groups of shorebirds, is paraphyletic with regards to most other louse genera on shorebirds, and is in need of further study. Finally, the genus Lunaceps is revised morphologically. Six new species and one new subspecies are described, and all old species are re-described and illustrated, several for the first time. Five previously recognised species are placed as synonyms to other species, one species is transferred to the genus Quadraceps, one species is resurrected from synonymy, one species is considered a nomen dubium and three populations are placed as incerta sedis.
Environmental, nutritional and endocrine regulation of metabolic processes in fish
(2011-11-18) Kullgren, Andreas
Due to seasonal variations in temperature and food availability, fish in temperate regions should be able to make metabolic adjustments to ensure that enough energy is available for the maintenance of basal processes. The major aim of this thesis was to elucidate how the physiology and lipid metabolism of salmonid fish is affected by temperature and food availability, and to clarify aspects of the endocrine control of lipid metabolism. In this thesis, the effects of increased temperature or reduced food availability were studied in salmonids by employing a non-prejudiced metabolomics approach to assess the physiological responses. Detailed information on the abundance of specific amino acids, lipid classes, fatty acids and other metabolites in tissue extracts and plasma was obtained by nuclear magnetic resonance (NMR) based metabolomics. NMR-based metabolomics were successfully employed and proved to be applicable to studying metabolic fluxes in fish, providing data on novel and integrated responses. The results show similar changes in lipid metabolism during food deprivation and elevated temperature. The observed responses included increased plasma very-low-density lipoprotein (VLDL) and unsaturated fatty acids (FAs) concurrent with decreased high-density lipoprotein (HDL) and choline. The changes during starvation also involved changes in amino acids and glycogen that indicate that amino acids are used for gluconeogenesis in the liver to preserve glycogen stores. Growth hormone (GH) has both lipolytic and lipogenic effects. To further elucidate the mechanisms of GH action on salmonid lipid metabolism, the effects of GH in vivo on the transcription of several key lipid metabolism enzymes in various tissues were investigated. GH inhibited the hepatic expression of lipoprotein lipase (LPL) thereby decreasing hepatic lipid uptake. Hormone-sensitive lipase (HSL) mRNA expression was not increased by GH in any of the studied tissues, suggesting that the well-known GHinduced lipolysis is regulated on posttranslational levels in rainbow trout. The regulation lipid metabolism in salmonids was further investigated by studying direct effects of FAs and ghrelin on freshly isolated cells from mesenteric adipose tissue and liver. FAs elicited acute negative effects on lipid storage by decreasing lipid uptake via LPL activity in adipose cells as well as by stimulating lipolysis of stored triglycerides (TG) in liver cells. Together the results presented in this thesis shows that elevated, suboptimal temperature and nutritional may have propound effects on important processes as growth, food intake and the metabolome of salmonid fish, and may lead to a negative energy balance. Metabolic changes may be mediated by hormonal and nutrient factors acting at gene expression or enzyme activity level. The results may contribute to better understand lipid deposition patterns in farmed fish and potential effects of climate change on salmonids in the wild and in aquaculture.
From Proteomic Analysis to Biomarker Application - Studies of Carbonyl Reductase in Fish
(2011-09-22) Albertsson, Eva
Many anthropogenic substances are present in the aquatic environment, but there is limited information on how this combination of chemicals affects exposed wildlife. To assess the impact of chemicals, a biomarker approach is frequently applied in environmental biomonitoring programmes. In this thesis, proteomic analysis was used as a hypothesis generator for biomarker development in fish. Two-dimensional gel electrophoresis was performed on a liver fraction from rainbow trout (Oncorhynchus mykiss) that were caged downstream of a sewage treatment plant, and it was found that a protein identified as carbonyl reductase was induced. This was confirmed with qPCR, indicating that carbonyl reductase mRNA expression levels were markedly induced by the same effluent and also by a second investigated sewage treatment plant effluent of a similar character. More advanced sewage treatment technologies reduced carbonyl reductase mRNA expression, indicating that fish that were exposed to effluents of conventionally treated sewage have induced hepatic carbonyl reductase expression. To obtain more information regarding the possible inducers of carbonyl reductase, several different single-substance exposure studies were performed with rainbow trout in controlled aquaria systems. The results demonstrated that hepatic carbonyl reductase expression was not induced by the steroids that were tested but by an aryl hydrocarbon agonist and a pro-oxidant. Others have observed substances with the same mode of action in the effluents of Swedish sewage treatment plants. To promote the use of carbonyl reductase as a biomarker, a method for measuring enzymatic activity was developed in the sentinel coastal fish species eelpout (Zoarces viviparus), which is included in the Swedish national integrated fish-monitoring program. The protocol for carbonyl reductase enzymatic activity combined with qPCR analyses in eelpout were applied on a comprehensive field material, including sites with different grades of pollution among the Swedish, Danish and German coasts. Carbonyl reductase activity and mRNA did not show any site-specific differences between the polluted and reference sites. Therefore, it can be concluded that the induction of carbonyl reductase appears to be a promising biomarker for assessing exposure and the possible impact of sewage treatment plant effluents in caged fish. However, more research is required before and if carbonyl reductase can be used in biomonitoring programmes as a biomarker to assess the impact of toxic chemicals in wild fish populations.
Systematics of Marionina (Annelida: Clitellata: Enchytraeidae)
(2011-04-25) Matamoros, Lisa
This thesis is about species of segmented worms that previously were placed in the genus Marionina Michaelsen, 1890, within the family Enchytraeidae, class Clitellata and phylum Annelida. These species are closely related to earthworms, but are much smaller and many of them are found between the sand grains in marine beaches. Species within Marionina have long been suspected to be a non-monophyletic assemblage of only distantly related species, since they lack unique and consistent morphological characters that unify them as a group and distinguish them from other enchytraeids. The main aim of this thesis has been to revise the systematics of Marionina, to obtain a classification that is congruent with the phylogenetic relationships of this assemblage. To clarify the complex taxonomical history of Marionina, a nomenclatural review is conducted, and the type species Pachydrilus georgianus Michaelsen, 1888 is re-described. Based on morphological characters it is concluded that a majority of the species bearing the generic name Marionina are only distantly related to this type species. Within my thesis, DNA sequences from three mitochondrial (12S, 16S, COI) and tree nuclear genes (16S, 18S, ITS) were studied, from different specimens. Molecular analyses confirmed that Marionina is a non-monophyletic taxon, and revealed, e.g., a monophyletic sub-group of almost 50 species that have a pharyngeal bifurcation of the dorsal blood vessel. This feature is shared with the type species of Michaelsena Ude, 1896 and is likely to be an autapomorphy (a derived, unique character) for this group. Michaelsena, which was earlier synonymised with Marionina, was thereby restored as a genus, and proposed to include these nearly 50 species. Seven other former Marionina species form a monophyletic group together with the type species of another genus, Enchytronia parva Nielsen & Christensen, 1959, and they are thus relocated into Enchytronia Nielsen & Christensen, 1959, which is the sister group to Michaelsena. The majority of species within Michaelsena are marine, while Enchytronia species are exclusively terrestrial. Two additional nominal species of Marionina appear to be closely related to, respectively, Bryodrilus and Oconnorella, which are only distantly related to Michaelsena and Enchytronia. The remaining species of Marionina not dealt with in this thesis, may form a non-monophyletic group and their correct phylogenetic position and taxonomy are not yet solved. In several cases within Michaelsena, the molecular variation is large within groups of taxa that are difficult or impossible to separate morphologically. One example is studied in detail: the Marionina achaeta complex, which comprises at least nine separate species that all lack chaetae. Some of these species are impossible to distinguish morphologically and are therefore referred to as cryptic species. A new species, Michaelsena triplex (Matamoros et al., 2007) from the Black Sea has been formally described within this thesis.
Paleolimnological reconstructions of fish population changes in acidified lakes
(2011-03-04) Palm, Fredrik
This thesis deals with the potential of using subfossil Chaoborus spp. and Daphnia spp. remains preserved in lake sediments to reveal past fish community alterations related to progressive acidification. Sediment cores were collected from acidified lakes with known present fish population status and well-documented fish community developments in southwest Sweden. Sediment analyses were conducted on comparatively large sediment samples from sediment cores that were sectioned for a high temporal resolution (5-mm intervals). Subfossil Chaoborus assemblages were related to fish population developments in the study lakes. Mandibles of Chaoborus flavicans were common in most sediment samples, and this species is known to co-exist with fish. However, C. obscuripes mandibles were exclusively recovered and identified in more recent sediments from fish-free lake periods, as judged from known historical fish population changes in the study lakes. These findings suggest that past fish extirpations can be revealed by the appearance and successive presence of C. obscuripes mandibles in sediment records. Progressive acidification was additionally confirmed by the loss of acid-sensitive daphnid zooplankton, as indicated by developments in sedimentary assemblages of Daphnia ephippia (resting eggs). In this thesis I describe and test the first ever paleo-method for revealing periods of cyprinid presence in lake histories, without including fish fossils in the analyses. Cyprinid fish species are characterized by pharyngeal teeth that are used to crush and fragment food items. Cyprinid fish, in this thesis represented by roach (Rutilus rutilus L.), were shown to evacuate significantly higher proportions of fragmented Chaoborus mandibles than non-cyprinid perch individuals (Perca fluviatilis L.), when fed live Chaoborus larvae in the laboratory. Similar and significant differences in proportions of fragmented subfossil Chaoborus mandibles were also shown for three independent paleolimnological approaches; (1) a comparative study of surface sediments from lakes with and without cyprinid fish, (2) a stratigraphical analysis of a dated sediment core from a lake with a known period of roach presence, and (3) a comparison between two dated sediment cores from lakes that differed in historical presence of roach. These findings have important implications for future freshwater management by providing tools for assessing past fish population changes in acidified lakes with uncertain developmental histories.
New Insights into the Evolution of Bryozoa- An Integrative Approach
(2011-02-17) Fuchs, Judith
Bryozoa is a group of aquatic, sessile invertebrates with circumglobal distribution and includes about 6000 recent species. Bryozoans have an indirect life cycle with a larval stage that settles and metamorphoses into the adult. Although a bryozoan individual is barely visible with the naked eye, all bryozoans form colonies, which are often macroscopic in size and display a variety of beautiful shapes and forms. Ever since their first scientific description in the 16th century, bryozoan relationships to other animal groups have been enigmatic. Bryozoan morphology and life history show various differences to other invertebrates, so that their closest relatives could not be identified with certainty. Also, a reliable hypothesis about the evolution of the variety of bryozoan larval and adult body forms is greatly in dispute. In this thesis, questions concerning bryozoan evolution are addressed from diverse angles by exploring different life cycle stages and methodological tools. A new phylogeny of Bryozoa based on molecular data is presented. A similar approach is used to investigate the phylogeny of another animal taxon, Entoprocta, which was long thought to be the sister group of Bryozoa. The results reveal that Bryozoa is a natural group with a single origin (monophyletic clade) and that Bryozoa and Entoprocta are not sister groups. Further, gene expression in the larval stage of the bryozoan Bugula neritina was studied and indicates the importance of molecularly pre-patterned blastemic tissues for adult body plan formation. In addition, a new bryozoan species from the West Coast of Sweden is described and a genetic barcode is provided for the new species, which will help to identify this species in the future. The thesis demonstrates that molecular data combined with high taxon sampling are essential to reveal bryozoan phylogenetic relationships and that gene expression studies of the enigmatic taxon Bryozoa are valuable to get insights into the evolution of their life cycle and to contribute to our general understanding of metazoan body plan evolution.
Biodiversity and genetic patterns in marine invertebrates
(2010-09-17) Vodoti, Emma
Abstract: Systematics based on genetic data has both confirmed and contradicted earlier, morphologically defined species and their relatedness. Morphology does not always correspond to genetic lineages, and this will inevitably affect both traditional systematics as well as biodiversity assessments. My thesis aims to investigate genetic biodiversity in some marine invertebrates, dealing with both species and population (intraspecific) relationships. I discuss gene lineage relatedness in correlation to species morphs and geographical species distribution, which has bearing upon the species recognition problem, the barcoding approach and the meaning of phylogeographic patterns. Results show that morphology does not generally reflect gene lineage relationships in the considered species and that cryptic species are common, mainly in the nemertean groups studied (Oerstedia dorsalis; Cerebratulus spp). Despite having a relatively established status as a species, the horse mussel (Modiolus modiolus) is also found to hold cryptic lineages. Further, the difficulties in species delimitation become apparent, as an almost continuous range of genetic divergence prevails between most of the found clades. The Antarctic krill (Euphausia superba) is the only study species lacking cryptisism, at least in the samples and geographical region studied. The intraspecific genealogies were in this case used to estimate population parameters by means of the coalescent. Despite being an abundant species of modest size, results suggest a low effective population size and a population with common ancestry, most likely capable of migrating over relatively great distances. This stresses that factors such as demography and genetics can provide a preliminary, general base for management issues. I conclude that cryptic species are common, and therefore taxonomic work cannot be isolated from the barcoding quest of summoning genetic data for species identification. Since genetic relationships and morphological traits do not always go hand in hand, a barcoding approach could in some cases be misleading. Further, it is probably impossible to find a universal way of defining, identifying and delimiting species. This thesis illustrates some practical examples of these problems, and suggests that a case-to-case evaluation is likely needed in future taxonomic and phylogenetic efforts.
Egg size evolution and paternal care in pipefishes.
(2010-08-30) Braga Gonçalves, Inês
In this thesis I explore how sexual selection, sexual conflicts, coevolution with parental care and an environmental selective agent (hypoxia) affect the evolution of different egg characteristics and embryo survival and size in pipefishes (Syngnathidae). In the broad-nosed pipefish, Syngnathus typhle Linnaeus, both sexes prefer to mate with large partners; large females produce more and larger eggs and large males can care for more young, and, as shown in this thesis, invest more per embryo and provide better oxygenation during brooding. However, if given time to assess their partners prior to mating, females deposit significantly more proteins into eggs when they mate with non-preferred (smaller) males. This result suggests that females are able to improve offspring fitness by compensating for small males’ lower paternal care quality, thus reducing effects of differences in care between small and large males. The spherical shape common to fish eggs minimizes the ratio between surface area and volume. As embryo respiration is assumed to be proportional to egg volume and oxygen availability to be restricted by the surface of the egg, this shape may be unfavourable for larger eggs. In S. typhle, both small eggs and hypoxia (low ambient oxygen levels) during brooding resulted in smaller embryos, but the negative effect of hypoxia on embryo size was similar for small and large eggs. In brooding males, within-pouch oxygen levels were found to be consistently lower than those of the surrounding environment, both in high and low ambient oxygen conditions indicating a limited paternal ability to maintain high levels of oxygenation to the embryos. When comparing pipefish species with and without brood pouches, the species with pouches were found to suffer, on average, greater embryo mortalities during brooding. However, under hypoxia embryo survival and size were negatively affected both in species with and without brood pouches. Between species, large egg size resulted in significantly larger offspring, but had a negative effect on embryo survival, compared to species that produce small eggs. This thesis contributes to the understanding of egg size evolution in relation to hypoxia and paternal care in syngnathids. The studies presented here suggest that the evolution of brood pouches carries costs in terms of embryo oxygenation. Furthermore, the evolution of more complex types of brooding has potentially enabled phenotypic variation to arise in the quality of male care, in turn selecting for flexible female reproductive investment with stronger selection on egg size evolution in species with brood pouches, and greater female control of egg quality.
On the regulation of Postprandial Gastrointestinal Blood Flow in Teleost Fish
(2010-05-20T11:28:46Z) Seth, Henrik
Henrik Seth (2010) On the Regulation of Postprandial Gastrointestinal Blood Flow in Teleost Fish Department of Zoology/Zoophysiology, University of Gothenburg, Box 463, 405 30 Göteborg. The regulation of the cardiovascular changes, in particular the increase in gastrointestinal blood flow that follows after feeding has received little attention in teleost fish. Therefore, the aim of the research that led to this thesis was to discern some of the mechanisms behind the postprandial cardiovascular response. Several methods, described within this thesis, were used in order to study, in vivo, the influence of both mechanical as well as chemical stimuli in triggering the increase in gastrointestinal blood flow that occurs after feeding in fish. Furthermore, additional methods, combining in vivo and in situ pharmacology were used to study the regulatory mechanisms in more detail. The results indicate that both mechanical as well as chemical stimuli are important during the postprandial response. Mechanical stimuli within the stomach evoke an increased adrenergic tone and chemical stimuli induce a subsequent hyperemia that is localized within the gastrointestinal tract. The response to chemical stimuli is also influenced by the composition of the diet. Furthermore, even though the extrinsic innervation (sympathetic and parasympathetic) of the gastrointestinal tract is important in controlling the routine tone of the gastrointestinal vasculature, it is of little importance during the postprandial hyperemia. In contrast, the intrinsic innervation (enteric) within the gastrointestinal tract is of fundamental importance to this hyperemia. In addition, the response is most likely modulated, in response to the diet composition, by endocrine and paracrine factors, such as the gastrointestinal hormone cholecystokinin. In conclusion, the regulation of the gastrointestinal vasculature after feeding is very complex and several mechanisms contribute to the cardiovascular response that will depend on the composition of the diet as well as surrounding environmental factors such as temperature, oxygen levels and stress.
Individual variation in behaviour: personality and performance of brown trout in the wild
(2010-05-07T11:15:43Z) Adriaenssens, Bart
Individuals from the same population often show very different behaviour. These differences, when consistent across time, are referred to as animal personality or behavioural syndromes. Explaining the occurrence of animal personality from an evolutionary perspective has however proven a difficult issue to tackle. This thesis studies aspects of individual behavioural variation and personality in brown trout (Salmo trutta). More specifically, I investigate (1) to what extent variation in behaviour is consistent within and across contexts, (2) environmental and genetic effects on behaviour, (3) how this affects performance in the wild, and (4) whether this understanding can be used to improve rearing methods of supplementary hatcheries. I found brown trout to express a wide variation of behaviours and provide evidence that much of this behavioural variation is associated in bigger behavioural syndromes. As a result, separate behaviours of brown trout cannot be considered as isolated units, but combine into clusters that sometimes are associated with non-behavioural measures such as body size or growth rate. Variation was further influenced by both inherited and environmental effects. First, individuals from different maternal and paternal origin differed in size, aggressiveness and response to novel prey or novel food. These results suggest that maternal and/or genetic effects influence behaviour and growth in brown trout (I). Second, reduced rearing densities in a hatchery increased the response to novel prey, food search ability in a maze and predator response (II). And third, hatchery trout were more successful foragers than wild conspecifics, yet showed less repeatable explorative behaviour across time (III). Personality traits were generally poor predictors of growth and survival upon release, suggesting that several behavioural strategies can be successful in nature. Nevertheless, in paper IV, slow exploring individuals grew faster than more bold trout. Furthermore, parr reared at reduced densities were twice as likely to survive in the stream as trout reared at high densities. In conclusion, my results contradict simple associations between risk taking behaviour and growth-mortality tradeoffs under natural conditions. This challenges the recent view that individual differences in growth strategies can explain variation in behaviour and suggests more heterogeneous links between personality and life-history in nature (V). In addition, I show that reduced rearing hatchery densities facilitate the development of adaptive behaviour in brown trout, a finding that may have implications for current rearing methods in supplementary hatcheries.
Age-class interactions in Atlantic salmon and brown trout: Effects on habitat use and performance
(2010-05-06T12:42:48Z) Kaspersson, Rasmus
This thesis investigates the underlying mechanisms and the density-regulatory effects of age-class interactions, using juvenile Atlantic salmon (Salmo salar L.) and brown trout (Salmo trutta L.) as study species. Field experiments were performed in streams along the western coast of Sweden, in which densities of older age-classes were reduced and the response on young-of-the-year habitat use and performance (growth, movement and survival) was observed (Papers I and II). Observational data from 159 trout populations was extracted from the Swedish Electro-fishing Register to test the generality of age-class competition (Paper III) and observations in controlled artificial stream environments were used to establish the underlying mechanisms with regard to habitat use and behavioural interactions (Papers IV and V). The combined findings of these studies show that age-classes of stream-living salmonids compete for limited resources in the stream habitat. This competition favours old individuals, although the behavioural observations of Paper V suggest that their competitive benefit may decrease at increasing densities of young-of-the-year fish. Density-reductions of older cohorts in field increased the growth of young-of-the-year trout, an effect that was observed at the later part of the growth season (Papers I and II). The observational data-set (Paper III), provided further evidence of the prevalence of inter-cohort competition, reflected as a negative association between density of older cohorts and young-of-the-year body-size, in the same magnitude as on an intra-cohort level. In accordance with previous studies, juvenile salmon and trout were segregated in the stream habitat, with young-of-the-year individuals using shallow, low-velocity, habitats close to the spawning area while older cohorts were positioned in deep, high-velocity, areas (Papers II and IV). However, when experimentally reducing the density of older cohorts in field and lab (Papers II and IV), this spatial pattern was shown to be an effect of habitat exclusion rather than size-dependent habitat preference, as suggested in previous studies, with subsequent negative effects on young-of-the-year foraging activity (Paper IV). Thus, this finding provides a potential underlying mechanism to the negative effect on young-of-the-year performance presented in Papers I, II and III. From an applied point of view, the findings of this thesis highlight the importance of taking age-class interactions into account when investigating density-dependence and habitat use among stream-living salmonids. The findings also suggest that marginal stream habitats may be essential during the first months after emergence by acting as refuges from inter-cohort competition, thus emphasizing the importance of maintaining and restoring these habitats in the wild.
Taxonomy and phylogeny of polychaetes
(2010-05-03T12:26:18Z) Eklöf, Jenny
Polychaetes are a large group of segmented worms that display an enormous morphological diversity. Molecular data has shown in recent years that groups previously thought to be separate from polychaetes are actually part of the group. The relationships within polychaete groups have been difficult to discern, and molecular data only partly corroborate classifications done on morphological grounds. The main focus of this thesis is on Phyllodocidae, a family of polychaetes, and its phylogenetic relationships. Our results show that none of the phyllodocid subfamilies, as previously delineated by morphology, find support from molecular data. Instead groups previously not recognized receive high support. A number of polychaete families are holopelagic, and most of these have been regarded as closely related to phyllodocids. We have found that one of these holopelagic families, Alciopidae, is well nested within the phyllodocids, with its closest sister being Eumida arctica, making the genus Eumida, as delineated today, paraphyletic. Part of this thesis also deals with cryptic species, which means that two or more species are virtually impossible to separate morphologically, but still represent separately evolving lineages, reproductively isolated from each other. We have found that Arctic and boreal populations of Paranaitis wahlbergi belong to two separate species, and the boreal populations are referred to a new species, P. katoi sp. n. We have also found that sympatric populations of Notophyllum foliosum, found in deep and shallow waters are two separate species, morphologically distinguished only by subtle details in their colouration, and the deep form is described as N. crypticum sp. n. A description is also provided for Axiokebuita, previously not found in European waters. Due to delineation problems with the two described species in the genus it was not possible to refer these new specimens to either of them or to a new species. A phylogenetic analysis of molecular data confirms the position of Axiokebuita among scalibregmatids. Part of this thesis also deals with cryptic species, which means that two or more species are virtually impossible to separate morphologically, but still represent separately evolving lineages, reproductively isolated from each other. We have found that Arctic and boreal populations of Paranaitis wahlbergi belong to two separate species, and the boreal populations are referred to a new species, P. katoi sp. n. We have also found that sympatric populations of Notophyllum foliosum, found in deep and shallow waters are two separate species, morphologically distinguished only by subtle details in their colouration, and the deep form is described as N. crypticum sp. n. A description is also provided for Axiokebuita, previously not found in European waters. Due to delineation problems with the two described species in the genus it was not possible to refer these new specimens to either of them or to a new species. A phylogenetic analysis of molecular data confirms the position of Axiokebuita among scalibregmatids.
Studies of fish responses to the antifoulant medetomidine
(2010-03-31T11:02:12Z) Lennquist, Anna
ABSTRACT Growth of marine organisms, fouling, on man-made constructions submerged in the water is regarded as a major problem. For vessels, fouling increases drag and thereby fuel consumption, wherefore antifouling paints are used. Traditionally, they contain toxic compounds, and several of these have unwanted effects in the environment. Today the search for environmentally acceptable and efficient alternatives is intense. Medetomidine, originally used as a veterinary sedative, inhibits barnacle settling at nanomolar concentrations. It is presently under evaluation for use as an antifouling agent. The studies within this thesis were performed to investigate medetomidine responses in fish. The focus was to identify early effects, occurring from low concentrations. Studies have been performed in the species rainbow trout, Atlantic cod, turbot, Atlantic salmon and three spined stickleback. Exposure time vary from 1 up to 54 days, and a set of parameters have been investigated including biochemical biomarkers, growth and related parameters, behaviour and large scale gene expression. Paleness is the most obvious effect of medetomidine in fish and appears from 0.5 to 50 nM, depending on species. Colour was observed and quantified, and the function of melanophores (pigment cells) after long term exposure to medetomidine was investigated. It is suggested that melanophores are functional after treatment, and thus the colour change may be reversible. Although not lethal per-see, paleness may have consequences for fish predator-prey interactions (camouflage), social signalling and UV protection. Medetomidine also showed to affect the activity of the hepatic enzyme Cytochrome P4501A (CYP1A), measured as EROD activity. A minor increase in activity was observed in vivo in several of the investigated species. In vitro, medetomidine showed instead to be a potent inhibitor of EROD activity with median inhibition values (IC50) in the nanomolar range. An inhibited CYP1A activity may interfere with fish detoxification of toxicants abundant in the aquatic environment. No significant effects were found on growth rate, but the results indicate lowered blood glucose levels and decreased liver size after medetomidine treatment and thus a shift in carbohydrate metabolism. The large scale gene expression study revealed no significant differences among treatments. We found no effects on glutathione or glutathione dependent enzymes in any of the studies. In the behavioural studies, fish were less active and had less appetite in medetomidine treatments compared to control. Medetomidine had no effects on investigated antioxidant enzymes and showed no cytotoxicity. Among the responses studied within this thesis, paleness and inhibition of EROD activity are perhaps the most important. These effects appear early and are clear and consistent among several species.
Phylogeny and Signal Diversity in Widowbirds and Bishops (Euplectes spp.)
(2010-02-19T08:56:11Z) Prager, Maria
Although sexual selection for elaborate signals is well documented in numerous species, the extreme diversity in signal design and expression in many taxa is largely unexplained. This thesis explores phylogenetic, mechanistic and ontogenetic explanations for divergence in two classic condition-dependent signal traits in the African widowbirds and bishops (Euplectes spp.); elongated black tails (in widowbirds) and patches of bright yellow or red carotenoid coloration (most prominent in bishops). A molecular phylogeny of 33 Euplectes subspecies (representing all 17 species) was derived using parsimony and Bayesian analyses of mitochondrial and nuclear DNA sequences. A consensus tree, or a sample of the most probable Bayesian trees, was then used in parsimony, likelihood and Bayesian reconstructions of ancestral signal states. Specifically, the discrete presence of a nuptial tail (i.e. prenuptial tail moult), continuous tail length, and discrete as well as continuous reflectance-based measures of carotenoid colour hue were analysed. The proximate basis of interspecific colour variation was investigated using High Performance Liquid Chromatography (HPLC) analyses of feather and plasma pigments in five Euplectes species. Finally, the relative importance of nutritional and metabolic constraints behind differential occurrence of C4-keto-carotenoids, and thus red plumage color, in Euplectes, was tested by diet manipulation in a yellow and a red bishop species. Results show monophyly of the genus Euplectes, but not of ‘widowbirds’ or ‘bishops’. Most notably, the red-collared widowbird E. ardens belongs to a clade of short-tailed bishops and not to the ‘true’ widowbirds. Extant Euplectes furthermore derive from ancestors in which breeding males had short (not prenuptially moulted) tails and yellow colour signals. Nuptial tail elongation and red coloration have since evolved at least twice in distinct lineages, possibly as convergent responses to early established and directional sexual selection for increasingly exaggerated quality advertisements. This provides an interesting contrast to several recent findings of labile ornament evolution in birds and other animals. Three different pigment profiles were identified in Euplectes feathers. Yellow colours primarily depend on dietary yellow carotenoids, while red hues result either from addition of metabolically derived red C4-keto-carotenoids, or from high concentrations of dietary and derived yellow pigments. A possible genetic constraint on colour evolution was also identified, as the southern red bishop E. orix, but not the yellow-crowned bishop E. afer, can manufacture red C4-keto-carotenoids (α-doradexanthin and canthaxanthin) from yellow dietary precursors (lutein and β-carotene). Combined with previous work on adaptive signal functions in Euplectes, the phylogenetic and proximate analyses in this thesis provide an unusually complete picture of avian plumage diversification, and a useful framework for further exploration of both genetics and ecology of avian colour signalling.
Systematics of Grania (Clitellata: Enchytraeidae), an interstitial annelid taxon
(2010-02-12T09:55:47Z) De Wit, Pierre
In between the grains of sand on the ocean floor, there exists a world which few people are aware of. Representatives of almost all animal phyla can be found here. The clitellate family Enchytraeidae is in the marine interstitial environment represented in large part by species of a genus called Grania, which are long slender worms found in marine sands throughout the world. This thesis is a study on the systematics of these worms. The body wall of Grania is searched for phylogenetically informative morphological characters. It is found that the cuticular morphological variation seen in naidids is absent, but the collagen fiber thickness varies between Grania species. Also, the circular and outer, triangular longitudinal musculature is reduced compared to that of closely related taxa while the inner, ribbon-shaped longitudinal muscle fibers are well-developed, possibly an adaptation to interstitial life. The Grania-fauna of the Great Barrier Reef is investigated, with four new species described and Grania trichaeta re-described. The phylogenetic position of Grania within the family Enchytraeidae is elucidated by molecular means, where Lumbricillus arenarius is shown to be a close relative of a monophyletic Grania. Within the genus, a molecular phylogeny is inferred of a sample of 19 species, showing considerable morphological homoplasy, while geographical distribution is concordant with the phylogeny. Thus, we combine morphology with geography, while using the DNA-based tree as a backbone constraint, to estimate a phylogeny of all 71 currently described species within the genus. Finally, the genetic variation within Scandinavian species of Grania is studied with the resulting find of a cryptic species, and the realization that although intraspecific variation generally is low, deviant individuals exist. Within this study, we also infer a phylogeny of the Scandinavian species of Grania, which seems to be a monophyletic group, and discuss their morphological character evolution.
Environmental influences on the behavioural ecology of juvenile salmonids – the importance of rearing density
(2010-01-10T13:41:41Z) Brockmark, Sofia
Background and aims: Early environmental conditions are known to influence the phenotypic development of animals, including behavioural alterations. The overall aim of this thesis is to investigate the effects of density, social stability and structural complexity on growth, behaviour, and survival in the wild, using juvenile brown trout (Salmo trutta) and Atlantic salmon (Salmo salar) as model species. The result can add to the basic knowledge in this research area and can also be used to enhance the welfare and fitness of released hatchery-reared fish. Methods: In papers II-IV sea-ranched trout and salmon were reared from early life stage in conventional hatchery tanks with modified physical structure and/or density. Hatchery fish were measured for growth, studied for individual and social behaviours, and analysed for fin-erosions and smolt-status. In paper I wild-caught juvenile trout were used for behavioural studies. In papers II-IV fish from different treatment groups were also released in natural streams to investigate treatment effects on survival and growth in the wild. Results and conclusions: My results collectively show clear positive effects of reduced rearing density, whereas the effects of structure were unclear and harder to interpret. In papers II-IV reduction of conventional hatchery densities generally increased growth rate in the hatchery and post-release survival. Salmonids reared at reduced densities were more dominant in competition for food, consumed more novel prey, escaped faster to refuges after a predator attack and located more food in a maze, compared to fish from higher densities. At time of parr-smolt transformation, salmon reared at reduced densities had less fin erosions and were more fully smolted than salmon reared at higher densities. Taken together, the results presented in this thesis clearly show that reduced rearing densities facilitate the development of adaptive individual and social behaviour in salmonids, resulting in increased growth and survival after release in nature. In paper I wild trout in familiar groups were more vigilant, responded faster to a simulated predator attack and consumed more food compared to trout in unfamiliar groups. These novel results suggest that social stability confer immediate fitness benefits, i.e. higher probability of survival under conditions of high predation risk. In summary, my results show that conventional rearing methods in supplementary hatcheries do not prepare fish adequately for life in the wild and could be improved considerably, with density reduction as one key factor. Incorporating behavioural aspects in supplementary rearing methods is also important from an ethical point of view. However, there is a limit to what can be accomplished with improving supplementary hatchery rearing methods. Hatchery rearing should therefore be viewed as a complement rather than an alternative to habitat restoration.
Morphological antipredator adaptations in water fleas
(2009-10-19T10:31:43Z) Lord, Hans
Some Bosmina and Daphnia species have the ability to develop extreme morphological antipredator defences, such as long antennules, high carapaces and helmets. The relative sizes of these plastic traits may differ substantially between populations, and also between individuals within a population, between sexes and during ontogeny. In this thesis I examine how abiotic factors (trophic levels and temperature) and biotic factors (fish and invertebrate predators) affect the size and shape of these traits. In the first two studies, calculations based on experimental results using physical morphological models sinking in glycerine, were used to estimate body drag and energy consumption in Bosmina. Eubosmina longispina, with a low carapace and short antennules, and Eubosmina coregoni gibbera, with a very high carapace and long antennules, were examined. At 5○C, E. c. gibbera had 32-45 % higher body drag than E. longispina. At 20○C the difference was 20-45 %. A model of swimming predicted that, all else being equal, this difference should result in 18-20 % (at 5○C) or 14-16 % (at 20○C) lower swimming speed for E. c. gibbera than for E. longispina. This indicates substantial hydrodynamic costs of the morphological antipredator defences, particularly in low temperatures. The morphological antipredator defences in E. c. gibbera are larger and more variable in females than in males. Male models had lower body drag than models of asexual and sexual females, suggesting that males can swim 14-28 % faster with the same energy consumption. High speed video documentation of swimming E. c. gibbera showed that males advanced 55-73 % further than females in each swimming stroke. Hydrodynamic body drag may therefore have significant implications for swimming and evolution of sexual dimorphism in water fleas. Males may lack the defensive, but hydrodynamically expensive, high carapace of female E. c. gibbera probably because competition over mates favours low body drag. The morphology and size of heads and trunks in Daphnia cristata individuals were studied in twenty lakes in the same drainage basin. The lakes showed a variation in lake total phosphorus and in densities of invertebrate predators and fish. In the end of the summer D. cristata had varying shape and size of their heads. Our results indicate that D. cristata, in nutrient rich lakes, show adaptive morphological defences against both visually hunting and size limited predators. Female D. cristata head shape, in the examined lakes, varied from small and rounded to large and curved. A significant positive correlation between lake total phosphorus and the allometric head coefficients was found, suggesting that the most extremely shaped heads are found in nutrient-rich lakes.
Chronic stress and intestinal barrier function: Implications for infection and inflammation in intensive salmon aquaculture
(2009-10-09T13:52:59Z) Sundh, Henrik
Aquaculture is a fast growing food-producing sector worldwide. This has increased the awareness among the public as well as governments of the need to secure the welfare and health of farmed fish. Atlantic salmon is, in non-Asian countries, one of the most successful aquacultured species. Despite continuous improvement of husbandry practices and development of new vaccines, both bacterial and viral diseases are main threats to the health of farmed Atlantic salmon. Chronic stress, created by sub- optimal husbandry conditions is believed to be an important factor behind disease outbreaks. The intestinal epithelium of Atlantic salmon is an important organ. Not just in nutrient absorption, but also as a barrier, preventing antigens and pathogens within the intestinal lumen to gain entrance to the host and thereby start an infection. Chronic stress is known to have a negative impact on the intestinal barrier in mammals, a situation that can cause a leaky epithelium and increased bacterial translocation. Stressful husbandry conditions could have a similar effect on the intestine of Atlantic salmon and would thus be a major threat to the welfare of farmed fish. This thesis aimed at elucidating the importance of the intestinal physical and immunological barrier function in disease susceptibility of farmed Atlantic salmon. It further aimed to reveal the impact of key husbandry conditions in Atlantic salmon aquaculture hypothesized to be potential threats to health and welfare of the fish. All husbandry conditions examined, i.e. hyperoxygenation combined with low water flow, low levels of dissolved oxygen and high temperature as well as high fish density in combination with poor water quality was concluded stressful to the fish. These common husbandry practises all generated primary and secondary stress responses such as increased plasma cortisol levels, increased cortisol release rate into the water and a decreased function of all intestinal barriers. Decreased physical barrier was evident in the form of increased paracellular permeability. This was accompanied by increased translocation rates of the pathogen bacteria Aeromonas salmonicida, suggesting an increased risk for bacterial infections in fish under chronic stress. Dysfunction of the intestinal immunological barrier was manifested as impaired expression of the pro-inflammatory cytokine IFN-γ. This down regulation could be the result of an immuno suppressive effect of cortisol but could also be an effect of the decreased physical intestinal barrier resulting in increased leakage of luminal antigens. The decreased expression of IFN-γ could be a sign of decreased cellular immunity which would render an intestinal barrier with reduced ability to cope with virus infections like the IPNV. Chronic stress also resulted in increased homing of neutrophils and signs of sever local inflammation. These findings suggest that stressed fish may experience increased disease susceptibility towards viral pathogens like IPNV as well as an increased risk of developing chronic intestinal inflammation. Intestinal barrier function was further evaluated as a new scientific tool for assessment of potential threats to welfare in aquaculture. The intestine was demonstrated to be a sensitive indicator of stress at times when no or only minor differences in primary stress responses was observed In conclusion, common husbandry may constitute a threat to health and welfare of farmed fish and intestinal barrier function can serve as a valuable tool for assessing potential stressful husbandry conditions in the future.
Melanosome transfer, photoreception and toxicity assays in melanophores
(2009-10-02T09:24:19Z) Hedberg, Daniel
Many animals such as fish and frogs have developed the ability to change colour of their skin to adapt to the environment or to signal to other individuals. This ability is due to specialised skin cells called melanophores. Melanophores contain thousands of melanosomes, small membrane-enclosed organelles containing the black or brown pigment melanin. The melanosomes can aggregate to the cell centre rendering the cells pale or disperse throughout the cell to become dark. The intracellular transport of melanosomes is regulated by neuronal or hormonal external stimuli. Fast colour change is achieved by aggregation/dispersion of melanosomes but long-term colour change can also be achieved by melanosome transfer to surrounding skin cells. An amphibian immortalized melanophore cell line was used from the African claw frog, Xenopus laevis to study transfer of melanosomes to co-cultured fibroblasts. Melanosome transfer was observed and up regulated by the hormone α-MSH . The transfer was quantified using light-, fluorescence and electron microscopy. A new and powerful method for transfer experiments was developed. Fluorescent semiconductor nanocrystals, qdots, were used in combination with flow cytometry. The qdots were taken up by the cultured Xenopus laevis melanophores, localised to the melanosomes and transferred to co-cultured fibroblasts. The method is a step towards enabling large scale analysis of pigment transfer. Xenopus laevis melanophores can be cultivated in 96-well culture plates which allow quantification of aggregation or dispersion in a fast and reproductive way. Glyphosate containing herbicides, i.e. Roundup, are commonly used in the world, but some toxic effects have been found on amphibians in vivo and human and mouse cells in vitro. To learn more about potential effects on intracellular transport and the cytoskeleton in animal Roundup, glyphosate, glyphosateisopropylamine and isopropylamine were tested on the transport of melanosomes to the cell centre by spectrophotmetry and by fluorescence microscopy on microtubules and actin filaments. All tested compounds inhibited the aggregation and affected the morphology of the cytoskeleton. The effect was found to be pH dependent. Amphibian melanophores can be regulated directly by light via a melanopsin receptor. Photoreception was found in cultured early embryos of the zebrafish Danio rerio. Light induced dispersion of the melanophores was contrast to what is found at adults when light causes aggregation of the melanosomes due to signals from the CNS. At least one subclass of melanopsin was detected in the zebrafish retinal pigment epithelial cells.

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