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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Invertebrate community structure along a habitat-patch size gradient within a bog pool complex

Towers, Naomi M. January 2004 (has links)
This thesis characterises species richness and community structure over a habitat-patch size gradient of a typical bog-pool complex, investigating the effect of pool size on aquatic invertebrate communities. In this study, twenty-two pools were surveyed ranging in area from 8.6 m2 to 280.9 m2 within a single complex at Forsinard in the north of Scotland. Three different sampling methods were used: baited and unbaited activity traps and a sediment sampler. Univariate and multivariate methods were used to investigate the effects of pool size and pool location within the complex on species richness and community structure. The research expands our knowledge of peatland pool invertebrates by providing a comprehensive survey of the aquatic invertebrate fauna representative of the Flow Country of northern Scotland. Two IUCN British Red Data Book species were recorded: the Northern Damselfly, Coenagrion hastulatum (Charpentier), and the cased caddisfly, Nemotaulius punctatolineatus (Retzius). Three species of aquatic Coleoptera were collected that have Nationally Notable status according to Ball (1986): Dytiscus lapponicus Gyllenhal, Ilybius aenescens Thomson and Gyrinus minutus Fabricius. All these species are typical of, and often restricted to, this habitat type. The three different sampling methods differed in their sampling efficiency and each gave a different species spectrum. A distinct seasonal change in the samples was also observed. The number of taxa caught per standardised sampling unit (taxon density) was investigated over the pool size gradient. Relationships between taxon density and area were weak or non-existent in both unbaited activity traps and sediment samples. However, the number of beetle species caught in baited activity traps increased significantly with pool size, indicating that the total number of beetle species per pool may also increase over the size gradient. Ratios of the number of predator taxa to prey (non-predator) taxa for each pool ranged from 0.34 to 0.78 with a mean of 0.49 and were not affected by pool area or total taxonomic richness. Taxa displayed a positive abundance-occupancy relationship and the possible underlying mechanisms involved in creating this pattern are discussed. Multivariate techniques showed that pool area, depth, and distance from the centre of the pool complex (periferality) all had a small but significant affect on community composition and that between certain taxa there were distinctly different optima along the pool size gradient. These results are discussed in the context of species area theory.
2

Intraspecific variation in trematodes

Lewis, Digby Stuart Cameron January 1969 (has links)
No description available.
3

A study of the activity and function of calciferours glands in selected Lumbricidae (Annelida : Oligochaeta)

Piearce, Trevor George January 1969 (has links)
No description available.
4

Studies on some cestode parasites of British birds

Davies, Thomas Idwal January 1937 (has links)
No description available.
5

Sensory systems in marine invertebrates

Sumner-Rooney, Lauren Héloïse January 2016 (has links)
Sensory systems form the first point of contact between animals and their surroundings. The study of sensory systems is both a rich and diverse anatomical and behavioural field, and a potentially invaluable tool in evolutionary biology. This thesis examines four systems in three molluscan classes and ophiuroid echinoderms, addressing novel or poorly-understood systems and examining evolutionary trends by assessing the anatomy of more familiar structures in a phylogenetic context. The primary study system is a novel discovery reported herein throughout the chiton order Lepidopleurida, named the Schwabe organ. By combining detailed anatomical study, electrophysiology and behavioural experiments, 1 demonstrated that the Schwabe organ mediates light-avoidance behaviour and likely shares developmental origins with the chiton larval eye. A similar integrative approach was applied to a putative ‘visual* system in the ophiuroid Ophiocoma wendtii. Anatomical and behavioural results indicated that animals may use an extensive network of dermal photoreceptors for image formation, however this system differs substantially from the established model. The two final chapters focus on sensory and nervous systems in evolution. A re-description of scaphopod neuroanatomy in Rhabdus rectius demonstrates the potential power of a neurocladistic approach in solving deep phylogenetic questions, highlighting important similarities with cephalopod neural architecture and prompting the re-assignment of the major body axes in adult scaphopods. Finally, a study of eye reduction and eye loss in deep sea solariellid gastropods found surprising morphological diversity and differential progression between independent eye reductions, even within genera. This thesis makes several important contributions to our knowledge of four sensory systems and their evolution across two major invertebrate phyla: the Schwabe organ, extra-ocular photoreception in 0. wendtii, the Steiner organ and gastropod eyes. Overall, it also demonstrates the powerful nature of cross-disciplinary projects as well as the versatile role of sensory biology in broader evolutionary studies.
6

Effects of nutrition and stress on ageing in Caenorhabditis elegans

Keaney, M. January 2004 (has links)
This thesis addresses two topics relating to the biology of ageing in C. elegans. The first is dietary restriction (DR), a treatment that is known increase longevity over a broad evolutionary range, from Protozoa to rodents. The mechanism by which DR works remains obscure, but it has been proposed that DR extends lifespan by lowering insulin/IGF-like (IIF) signalling, or by diverting resources from fertility into somatic maintenance. To test these possibilities requires quantitative application of DR. The first aim of this work was to establish such a DR method in C. elegans. To this end four reported methods were tested: Use of feeding defective mutants, use of agar plates with thinner bacterial lawns, use of bacterial dilution in liquid culture, and use of defined liquid medium. In all four cases, methodological shortcomings were identified. Thus, a good quantitative method of DR for C. elegans remains to be discovered. The second topic of this thesis is the oxidative damage theory of ageing. Despite being the focus of intense investigation, it remains unclear whether or not this theory is true. A range of antioxidants was applied in the expectation that they should retard ageing. In no case was this seen, even in the case of the SOD mimetics EUK-8 and EUK-134, previously reported to increase lifespan dramatically. Further studies were conducted to establish why SOD mimetics do not extend lifespan. Protection by SOD mimetics against pro-oxidants, in wild-type and hormesis-defective mutants implies that if superoxide levels limited lifespan as the oxidative damage theory predicts, then EUK-8 should increase lifespan. In fact even a EUK-8 dose optimised for protection against superoxide generators did not increase lifespan. The results in this thesis imply that oxidative damage due to superoxide is not the cause of ageing.
7

The biology of some freshwater oligochaetes

Kennedy, Clive Russell January 1964 (has links)
No description available.
8

Terrestrial nematodes of the Antarctic region : taxonomy, biogeography and an ecological study

Maslen, Norbert Rolf January 1979 (has links)
No description available.
9

The interrelationship between marine nemertean worms, their symbiotic bacteria and the production of toxins

Patel, Manishadevi V. January 2010 (has links)
No description available.
10

Experimental studies on the common liver fluke Fasciola hepatica L

Robinson, Graham January 1971 (has links)
No description available.

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