Desert environments are characterised by harsh conditions and possess low biodiversity largely caused by abiotic factors such as; low precipitation, soil organic matter, high temperatures, high levels of evapo-transpiration, pH and salinity. These factors significantly reduce primary production, which influences the availability of food resources for deserts organisms. The diversity and the drivers of diversity for below ground invertebrates including Collembola (springtails) are relatively unknown in the Namib Desert. Previous morphological studies have found only five species on the basis of traditional taxonomy. This study assesses the diversity of Namib Desert Collembola and determines the effect of environmental parameters on this diversity, The diversity of Namib Desert Collembola was assessed using DNA Barcoding. The sequence information of the 178 Collembola specimens, taken from mitochondrial barcoding using the Cytochrome-c oxidase subunit I (COI) gene, was analyzed and Molecular Operational Taxonomic Units (MOTUs) were defined. Collembola community responses to soil physicochemical properties were investigated by using Redundancy Analysis (RDA). MOTUs were successfully indentified to family level (Isotomidae, Neanuridae and Sminthuridae). The researcher found a total of 30 MOTUs, most of which showed limited geographical localisation. The mtDNA COI (barcode) locus revealed high levels of previously unreported genetic diversity of Collembola in the Namib Desert. The RDA indicated that none of the soil physicochemical properties significantly drove variation in Collembola community composition. However, total soil nitrogen was shown to be a strong but not significant driver of variation in community composition (p<0,054). The taxonomic identification of the Collembola specimens was also attempted using traditional morphological analysis. A total of 23 individuals, collected from pitfall traps or extracted from soil samples, were selected for identification. Available European keys were used for identification to genus level where possible. A total eight of specimens were identified to genus level (Folsomides sp), 14 to family level (Entomobryidae) and one to order level (Symphypleona). Both Symphypleona and Entomobryidae were previously unreported from the Namib Desert. The Folsomides genus and the family Entomobryidae were the most abundant groups. This research suggests that soil dwelling Collembola in the Namib Desert have a much higher level of diversity than previously known. However, the study also highlighted the need for a more comprehensive database for Namib Collembola that includes COI sequence data as well as the morphological identification of species. / Dissertation (MSc)--University of Pretoria, 2018. / National Research Foundation (NRF) / Genetics / MSc / Unrestricted

Made available in DSpace on 2016-02-26T14:53:08Z (GMT). No. of bitstreams: 1 RosimeireFernandesSilva.pdf: 688815 bytes, checksum: 6b18d7ad71aa6ebd83033fab77a6288e (MD5) Previous issue date: 2007-08-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this study was to verify the composition and the dynamics of the populations of Collembola Class's organisms as bioindicators of environmental impacts, through the comparison of soil samples in natural systems and agroecosystems, and to infer on its roles about the operation and the sustentability of the cultivation systems. The material of this study was removed from five different treatments located at Experimental Farm of Universidade Federal da grande Dourados (UFGD) and at Mata do Azulão (Fazenda Coqueiro): irrigated notillage, non irrigated no-till, irrigated conventional tillage, non irrigated conventional tillage, and natural forests, in five depths of the soil profile for each sampled local. 108 individuals divided in 6 families were obtained. The natural forests registered a decreasing effect in number of individuals from the first to the last sampled layer. In irrigated no-tillage area and natural forests it was obtained the largest mean number of organisms, followed by the non irrigated no-till area. The representatives of the Isotomidae and Entomobryidae families were the most counted in these systems. The Isotomidae familie had an increased number of found individuals from the first to the last sampled time. / O objetivo deste trabalho foi estudar a composição e a dinâmica das populações dos organismos da Classe Collembola como bioindicadores de impactos ambientais, através da comparação de amostras do solo em ambientes naturais e em agroecossistemas e inferir sobre o seu papel no funcionamento e na sustentabilidade dos sistemas de plantio. O material do estudo foi retirado em cinco ambientes distintos localizados na Fazenda Experimental da Universidade Federal da Grande Dourados (UFGD) e Mata do Azulão (Fazenda Coqueiro): plantio direto irrigado (PDI), plantio direto de sequeiro (PDS), plantio convencional irrigado (PCI) plantio convencional de sequeiro (PCS), e ambiente natural (mata), em cinco profundidades do perfil do solo para cada local amostrado no município de Dourados-MS, no período de agosto à dezembro de 2006. Foram obtidos 108 indivíduos divididos em 6 famílias. O ambiente natural registrou um efeito decrescente em número de indivíduos da primeira para a última camada amostrada. Em PDI e ambiente natural ocorreu a maior média de organismos, seguidos por PDS. Os representantes das famílias Isotomidae e Entomobryidae foram encontrados em maior quantidade nestes sistemas. A Família Isotomidae teve um aumento no número de indivíduos encontrados da primeira para a última época amostrada

Springtails (Collembola) are wingless arthropods that are impressively adapted to cutaneous respiration in temporarily rain-flooded habitats by non-wetting skin morphology. Recapitulating the robust and effectively liquid-repellent surface characteristics of springtail skin in engineered materials may offer exciting opportunities for demanding applications. Herein, we present a strategy for mimicking morphological surface features of springtail skin in polymer membranes produced by reverse imprint lithography. We report the fabrication of multi-level silicon masters that, in turn, serve as templates for the replication of flexible polymer membranes. We examined the robust wetting characteristics of polymer membranes by in situ plastron collapse tests and condensation tests. The mechanical stability of the polymer membranes was tested using a tribometer set-up and compared with needle-shaped pillar structures made from similar material. The fabricated membranes are flexible, free-standing, and adaptable to various substrate materials and shapes that allow for emerging applications.

Springtails (Collembola) are wingless arthropods that are impressively adapted to cutaneous respiration in temporarily rain-flooded habitats by non-wetting skin morphology. Recapitulating the robust and effectively liquid-repellent surface characteristics of springtail skin in engineered materials may offer exciting opportunities for demanding applications. Herein, we present a strategy for mimicking morphological surface features of springtail skin in polymer membranes produced by reverse imprint lithography. We report the fabrication of multi-level silicon masters that, in turn, serve as templates for the replication of flexible polymer membranes. We examined the robust wetting characteristics of polymer membranes by in situ plastron collapse tests and condensation tests. The mechanical stability of the polymer membranes was tested using a tribometer set-up and compared with needle-shaped pillar structures made from similar material. The fabricated membranes are flexible, free-standing, and adaptable to various substrate materials and shapes that allow for emerging applications.

Historically, terrestrial food web research has focused on describing the structure of aboveground grazing webs, and determining how interactions among plants, herbivores and higher trophic levels influence primary productivity. Detrital food webs however, play a significant role in regulation of ecosystem dynamics through direct impacts on decomposition. Unraveling the complex nature of detrital food web structure is critical to developing a better understanding of ecosystem function. Therefore the primary objective of this research was to describe the structure of the leaf-litter food web in a temperate deciduous forest, with emphasis on interactions between a community of generalist predators, the forest-floor spiders, and arthropod prey. Elucidating occurrence of trophic interactions in the forest-floor food web was a formidable task due to the high diversity, small body sizes and cryptic habits of many litter-dwelling arthropods. Analysis of natural variation in consumer stable isotope ratios (δ13C and δ15N) formed the crux of this research because it simultaneously permitted quantification of the trophic positions of litterdwelling arthropods and identification of spider resources, including prey subsidies from the grazing web. A monoclonal antibody-based ELISA was employed to analyze the gut contents of spiders to quantify predation on a major arthropod taxon, the forest-floor flies. Surveys of spider distributions and prey availability in the litter layer also provided fundamental knowledge of community structure. Stable isotope analyses suggested that most spiders exhibited strong trophic connections to the detrital web, but weak links to herbivorous prey. Several lines of evidence supported a strong trophic link between large, litterdwelling collembolans (Tomoceridae) and cursorial spiders, including correlation between spider and tomocerid densities on the forest-floor, similarities in spider and tomocerid carbon signatures, and nitrogen enrichment of tomocerids relative to other prey types. Conversely, this research provided conflicting evidence regarding spider consumption of flies. Gut content assays indicated consistent predation on flies by cursorial spiders, while stable isotope models suggested that flies are likely of little importance in the spiders’ diets. This project yielded valuable insights into the role of spiders in the forest-floor food web and the potential importance of species-specific variation in prey consumption for detrital food web dynamics.

The overall aim of this thesis was to elucidate the relative importance of the bacterial and fungal energy channels within the soil food web and to differentiate and appreciate the differences in niche of the soil fauna when affected by differing land management. Feeding niche of the soil fauna is ambiguous and has been previously determined by observation, inference or biochemical studies. One method that can determine feeding preferences in situ is the use of stable isotopes. Stable isotopes trace the passage of C and N through different trophic levels, both at natural abundance and by the addition of a pulse of enrichment. The work described within this thesis describes the development of methods of culturing and labelling organisms for use in stable isotope studies. Bacteria, protozoa and fungi were cultured with stable isotopes enriched to 99 atom% and their growth and survival monitored. Utilising stable isotope enriched organisms means that empirical testing of the feeding interactions can occur and that differences between the bacterial and fungal energy channels can be explored. Two field sites were chosen to assess how management changes affect the food web, both sites were historically grassland with the same soil type, but one was converted to a willow woodland twenty years ago. The results of these studies have shown, at natural abundance a grassland and woodland habitat with very different stable isotope signatures, reflecting plant and soil composition, as well as differences in trophic niche and C drivers. The introduction of enriched bacteria illustrated that bacterial feeding was more widespread than normally portrayed in food web diagrams. The introduction of enriched protozoa highlighted that protozoan feeding by soil fauna was more prevalent in the grassland habitat; reflecting differences in linkages between trophic levels within the two habitats. Methods were also developed to “grow” enriched fungal hyphae back into soil food webs in a comparable way to the investigation of the bacterial energy channel. Different species of saprotrophic fungi were found to fractionate to differing extents when grown on the same natural abundance media and the fungus Absidia cylindrospora's growth was impacted when grown on a dually enriched medium. We can now infer that the bacterial energy channel is not as divergent from the fungal energy channel as previously hypothesised. The majority of soil fauna were found to be omnivorous through empirical results, consuming bacteria and protozoa, even when they were considered to be fungal feeders by the literature. The different habitats within the study were found to have different C drivers, with roots and soil being the primary driver in the grassland whilst litter was in the woodland, consequently favouring different food webs. This work makes a first step in measuring the contribution of the different feeding channels and feeding interactions occurring within the different trophic levels in the two habitats and shows the effect that one change in management has had over the entire faunal assemblage.

Made available in DSpace on 2015-09-25T12:22:34Z (GMT). No. of bitstreams: 1 PDF - Roniere Andrade de Brito.pdf: 2760263 bytes, checksum: 4171856aa7d072d88e28f06371abbb23 (MD5) Previous issue date: 2013-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The Atlantic Forest bears high biodiversity and is being degraded by human activities for use and occupation of soil. The edaphic fauna is potentially vulnerable, and Collembola respond very quickly to environmental perturbations, considered efficient bioindicators of soil quality. Therefore, this study evaluated the Collembola community in an Atlantic Forest comparing different vegetation types in preserved areas and sugar cane fields, and analyzing how the group influences the decomposition process in these sites. Soil samples were collected and decomposition experiments conducted in the dry and rainy season in three regions of distinct phytophisionomic features, of three fragments of Atlantic Forest called SEMA I, II and III, and surroundings, at Biological Reserve Guaribas. In each region of the three fragments was established one sample point with five sub-samples, distributed linearly and equidistant, amounting 45 sub-samples of soil and decomposition bags by season. It was observed high diversity and homogeneity in the distribution of species of springtails in forest regions. Suga cane fields and savanna tree were more heterogeneous. The &#946;-diversity was highest among the preserved regions of the SEMA I, and lowest in the SEMA III, showing up among the most conserved area. The springtails abundance of Reserve Guaribas was low, possibly due to the organic composition of soil or long periods of drought. The species composition of Collembola and also environmental factors were distinct for each vegetation type, the group may be used as a tool of segregation of environments within forest ecosystems. Collembola was not correlated with decomposition rates in the surface layer of litter in both seasons, being linked to later stages where there is action of microbes specialized. The maximum understanding of the functioning of this group and intrinsic processes that maintain a forest ecosystem, provide more tools for management strategies and conservation for the Atlantic Forest. / O bioma Mata Atlântica abriga uma alta diversidade biológica, e está sendo degradado por atividades antrópicas para uso e ocupação do solo. A fauna edáfica é potencialmente vulnerável e, por responder rapidamente às perturbações ambientais, os Collembola são considerados bioindicadores eficientes das alterações na qualidade do solo. Por isso, este trabalho buscou avaliar a comunidade de Collembola em uma área de Mata Atlântica, comparando diferentes fitofisionomias conservadas e degradadas por monoculturas, e analisando como o grupo influencia o processo de decomposição nessas regiões. Foram realizadas coletas de solo e experimentos de decomposição, no período seco e chuvoso, em três regiões fitofisionômicas de três fragmentos de Mata Atlântica e seu entorno, denominados de SEMA I, II e III, na Reserva Biológica Guaribas. Em cada região dos três fragmentos foi estabelecido um ponto amostral contendo cinco pontos subamostrais, distribuídos de forma linear e equidistantes, totalizando 45 subamostragens, de solo e decomposição, por período sazonal. Observou-se que as regiões de floresta apresentam altos índices de diversidade e maior homogeneidade na distribuição das espécies. Tabuleiro e Canavial tiveram maior heterogeneidade. A -diversidade foi maior entre as regiões preservadas da SEMA I, e menor na SEMA III mostrando-se, dentre as áreas, a mais conservada. A abundância da ReBio Guaribas foi baixa, podendo estar relacionada com a composição orgânica do solo ou períodos longo de estiagens. A composição de espécies de Collembola, e também dos fatores ambientais, foi distinta para cada fitofisionomia, podendo o grupo ser utilizado como ferramenta de segregação de ambientes dentro dos ecossistemas florestais. Collembola não esteve correlacionado com as taxas de decomposição na camada superficial de serrapilheira em ambos os períodos sazonais, estando ligado a estágios posteriores em que há ação de microorganismos especializados. A máxima compreensão do funcionamento deste grupo, em processos intrínsecos que mantêm um ecossistema florestal, fornece mais ferramentas para estratégias de gestão e conservação da Mata Atlântica.

<p>Sposobnost insekata da se prilagode različitim ekolo&scaron;kim uslovima je veoma dobro<br />dokumentovana; oni predstavljaju najrasprostranjeniju grupu životinja na planeti, sa vrstama koje naseljavaju različita kopnena i vodena stani&scaron;ta, od tropskih predela do polova. Razumevanje mehanizama koji omogućavaju insektima da prežive ekstremne temperature i zadrže vitalne funkcije tokom dugog perioda dormancije je kao model sistem od interesa za mnoge naučne oblasti. Na osnovu načina na koji preživljavaju temperature ispod 0&ordm;C insekte možemo podeliti u tri grupe:<em> i)</em> insekti koji toleri&scaron;u formiranje leda u ekstraćelijskom prostoru,<em>ii)</em> insekti koji ne toleri&scaron;u zamrzavanje i moraju da ga izbegnu,&nbsp; a to&nbsp; čine superhlađenjem svojih telesnih tečnosti i<em>&nbsp; iii) </em>insekti koji preživljavaju zahvaljujući gubitku vode kroz permeabilnu kutikulu, &scaron;to je nazvano krioprotektivna dehidratacija. Zajednička odlika organizama sa različitim mehanizmima adaptacije na niske temperature je setbiohemijskih jedinjenja&nbsp; čija se fiziolo&scaron;ka funkcija razlikuje u zavisnosti da li organizam pripada grupi koja toleri&scaron;e ili ne toleri&scaron;e zamrzavanje. To su nukleatori kristalizacije leda, krio/anhidroprotektanti i antifriz proteini.<br />Cilj ovih istraživanja je bio ispitivanje molekularne osnove otpornosti na niske temperature dve vrste polarnih kolembola&nbsp;<em> Onychiurus arcticus </em>i <em>Cryptopygus</em> <em>antarcticus </em>kombinujući fiziolo&scaron;ki, biohemijski i molekularno biolo&scaron;ki pristup. Ispitivane vrste izbegavaju zamrzavanje svojih telesnih tečnosti primenjujući različite strategije preživljavanja. Za antarktičku vrstu&nbsp;<em> C. antarcticus </em>karakteristična je brza promena tačke superhlađenja, kao i njena bimodalna distribucija tokom leta, kada neke jedinke mrznu na&nbsp; vi&scaron;im temperaturama (manje otporne na hladnoću), a druga na nižim (otpornije na hladnoću). Ova bimodalna distribucija tačke superhlađenja je dobro dokumentovana, ali slabo razja&scaron;njena na molekularnom nivou. Druga, arktička vrsta<em>&nbsp; O. arcticus&nbsp;</em> koristi strategiju preživljavanja zimskih temperature koje idu i do -25&ordm;C nazvanu krioprotektivna dehidratacija. Na ovaj način, količina slobodne vode u telu se značajno redukuje, a akumulira se trehaloza koja deluje kao&nbsp; krio/anhidroprotektant. Iako je krioprotektivna dehidratacija opisana i kod drugih vrsta<br />insekata, molekularni mehanizmi koji se nalaze u osnovi ovog fenomena su veoma slabo razja&scaron;njeni.<br />Za karakterizaciju genoma generisano je 16379 EST sekvenci za&nbsp;<em> O. arcticus </em>i 1180 za&nbsp; <em>C. antarcticus</em>. To su ujedno i prvi javno dostupni podaci u bazama podataka o genomima ove dve vrste koji predstavljaju značajnu osnovu za komparativne genomske analize. Činjenica da kod obe analizirane vrste, oko 60% EST sekvenci nije pokazalo statistički značajnu sličnost sa proteinima iz baza podataka ukazuje na specifičan patern genske ekspresije kao adaptivni odgovor ispitivanih vrsta na niske temperature.<br />Sa ciljem da se identifikuju geni uključeni u preživljavanje niskih temperatura konstruisani su mikroereji, za&nbsp;<em> O. arcticus</em> &scaron;tampanjem 6912 cDNK u duplikatu, a za&nbsp; <em>C. antarcticus</em> &scaron;tampanjem 672 cDNK u duplikatu.. Analizom sekvenci identifikovanih putem homologije sa dostupnm bazama podataka kod C. antarcticusuočen je jasan trend povećane ekspresije gena koji kodiraju strukturne proteine u grupi koja je otporna na hladnoću. Ove strukturne proteine uglavnom&nbsp; čine kutikularni proteini, &scaron;to je u skladu sa rezultatima nedavnih istraživanja kod kolembola, da je presvlačenje proces tokom kog se snižava tačka superhlađenja, odnosno da varijacije u tački superhlađenja mogu nastati kao posledica endogenih fiziolo&scaron;kih procesa tokom presvlačenja. Kod&nbsp;<em> O. arcticus </em>analizom EST sekvenci i mikroereja identifikovani su<br />potencijalni geni i biohemijski putevi povezani sa krioprotektivnom dehidratacijom, a istakli bi gene uključene u metabolizam ugljenih hidrata, gene za akvaporine, proteine toplotnog stresa, LEA proteine i enzime antioksidativne za&scaron;tite.</p> / <p>The ability of insects to adapt to diverse ecological conditions iswell documented; they &nbsp;are the most diverse fauna on earth, with different species occupying arange of terrestrial and aquatic habitats from the tropics to the poles. Understanding the mechanisms by which insects survive such extreme temperatures and retain viability for longperiods in the dormant state is of great interest to many scientific fields. Insects have evolved three main strategies to survive sub-zero temperatures:&nbsp; i) freeze tolerance,&nbsp; ii) freeze avoidance and&nbsp; iii) cryoprotective dehydration. The main biochemical compounds involved in surviving sub-zero temperatures are same for different strategies but their physiological&nbsp; role is different. They include: ice nucleating agents (INAs), cryo/ anhydroprotectants, and antifreeze proteins (AFPs).&nbsp;</p><p>The aim of this study was to determine molecular adaptations to extreme cold&nbsp; environments, combining physiology, biochemistry and molecular biology&nbsp; pproaches, in thePolar Collembola:&nbsp; Cryptopygus antarcticus and&nbsp; Onychiurus arcticus. Both species are freeze avoiding but employ different strategies for surviving low temperatures. The Antarctic springtail&nbsp; C. antarcticusis capable of rapid cold hardening with a bi-modal distribution of super cooling points (SCP) with high (less cold-hardened) and low (more&nbsp; cold-hardened) groups of animals present even during the growing season in summer. This bimodal distribution has been well documented, but is poorly understood. The Arctic springtail&nbsp; O. arcticusemploys the strategy known as cryoprotective dehydration to survive winter temperatures as low as &nbsp; -25&ordm;C. With this technique, the amount ofavailable water in the body&nbsp; is reduced to almost zero and also there is an accumulation of trehalose, which acts as a cryo/anhydroprotectant. Although cryoprotective dehydration has been described in &nbsp;other&nbsp; insects, the molecular mechanisms behind this phenomenon are poorly understood.</p><p>A total of 16,379 EST clones were generated for O. arcticus and 1180 for C. antarcticus. This represents the first publicly available sequence data for this two species providing useful data for comparative genomic analysis. The fact that around 60% of the clones for both species showed no sequence similarity to annotated genes &nbsp;in the datasets, suggests a specific pattern of gene expression in these species as adaptation to low temperatures.</p><p>Two microarrays were constructed to identify genes involved in&nbsp; surviving low temperatures, one for C. antarcticus by printing 672 clones in duplicate and the other&nbsp; for O. arcticus by&nbsp; printing 6912 clones in duplicate. An analysis of those where putative function could be inferred via database homology, in C. antarcticus there was aclear pattern of up-regulation of structural proteins being associated with the cold tolerant group.&nbsp; These structural proteins mainly comprised cuticle proteins and provide support for the recenttheory that summer SCP variation within Collembola species could be a consequence of moulting, with moulting population having lowered SCPs. In O. arcticus EST and microarrayanalysis revealed clones&nbsp;and biochemical pathways associated with cryoprotective dehydration with a particular&nbsp; reference to genes involved in carbohydrate metabolism, aquaporin&nbsp; genes, heat shock&nbsp; proteins, LEA proteins and antioxidant enzymes.</p>

Lic.-avh. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 2 uppsatser.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.