Inaug.-diss.--Zürich. / "Literaturverzeichnis": p. 105-108.

Thesis (M.S.) in Marine Biology--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 74-81).

No description available.

This thesis presents ultrastructural and biochemical information on meiotic reinitiation during oocyte maturation in the polychaetes, Arenicola marina, A. defodiens and Nereis virens. The ultrastructural changes during meiotic maturation was characterised in the oocytes of Arenicola marina and Nereis virens using transmission electron microscopy in addition to germinal vesicle breakdown, release of the prophase I block was signified by major cortical changes in both species. The ultrastructure of fertilization in A. marina was independent of whether the oocytes were matured in vivo and spawned or matured in vitro by CMF. Oocyte maturation in Arenicola marina is controlled by a hormonal cascade that is initiated by the prostomial maturation hormone, PMH, and followed by the coelomic maturation factor, CMF (Watson and Bentley, 1997). Results presented here demonstrated that PMH has a molecular mass greater than 10 kDa, yet how this molecule triggers CMF activity remains unknown. M-phase promoting factor (MPF) consists of two subunits, cdkl and cyclin B, and is responsible for the control of mitosis and meiosis. The cytoplasmic "second messenger" that transduces the hormone signal to the activation of MPF in the oocyte cytoplasm was investigated in the two Arenicola species and is discussed. MPF regulation was investigated in Arenicola marina and Nereis virens oocytes. MPF activation was driven by the dephosphorylation of cdkl and phosphorylation of cyclin B. The results indicate that as with all other higher eukaryotes, the precursor of MPF in A. marina oocytes was maintained inactive by the phosphorylation of threonine 14 and tyrosine 15 (or equivalent residues) on the cdkl subunit. In contrast to other organisms, however, only a fraction of the cdkl present was complexed to cyclin B and utilised during meiotic reinitiation. All the cdkl in N. virens oocytes was joined with cyclin B but results suggest that the inactive complex contained tyrosine-only phosphorylated cdk1.

Previous studies on Arenicola marina suggest that oocyte maturation is induced by a hormone, from the prostomium, acting directly on the oocyte (Meijer and Durchon, 1977). Results presented here, from studies on British populations of Arenicola marina, show that in this species, oocyte maturation is controlled by two hormonal steps; a prostomial maturation hormone followed by a maturation inducing substance in the coelomic fluid, the Coelomic Maturation Factor (CMF). A reliable in vitro assay for oocyte maturation in A. marina has been adopted distinguishing immature from mature oocytes enabling CMF to be investigated; CMF has a molecular mass greater than 10 kDa, is thermolabile and inactivated by trypsin suggesting a proteinaceous nature. Production of CMF was also investigated; peak production occurs at approximately 2 hours after the injection of homogenised female prostomia. Oocytes require, on average, a minimum time of 20 minutes incubation in CMF to mature and preliminary results suggest calcium may not be necessary for maturation. Immunocytochemical techniques were used to characterise microtubule structures during oocyte maturation and post-fertilization development in Arenicola marina. Different regimes capable of bringing about maturation do not affect the morphology of the meiotic spindle. However, post-fertilization development is slower in oocytes matured in vitro when compared to mature oocytes obtained from naturally spawning females and females injected with homogenised prostomia which then spawn. Changes in microtubule structures in A. defodiens and Nereis virens during post-fertilization have also been partially characterised and these are compared and contrasted with A. marina. The development of a microinjection system will enable intracellular calcium and its role in maturation and fertilization within oocytes to be examined in these polychaetes.

The spermatozoa of Arenicola marina are unlike those of most marine invertebrates, in that they become motile in the body cavity prior to spawning. This occurs in response to a Sperm Maturation Factor (SMF) which is released from the prostomium. Prior to activation, spermatozoa are held as morulae with several hundred spermatozoa connected by a common mass of cytoplasm called the cytophore. Sperm activation by SMF is characterised in vitro, in terms of the ultrastructural changes which occur as the sperm become motile, and an active role for the cytophore during sperm activation is suggested. The morphology of these spermatozoa is 'primitive', and ultrastructural observations show that they possess a discoid swelling at the distal end of the flagellum. It is suggested that this may aid in swimming efficiency. The chemical nature of SMF has been putatively identified as 8,11,14-eicosatrienoic acid from both in vitro and in vivo studies. Biochemical investigations demonstrate that sperm activation is linked to an increase in sperm respiration rate, and an elevation of intracellular pH in the order of 0.2 pH units. Levels of ATP in spermatozoa are higher than those reported in other species, and it is considered that quiescence of sperm is not mediated by the deprivation of ATP to the axoneme. It is reported that sperm activated in vitro display a motile life of less than one hour, sperm which has been spawned in vivo, however, can have a motile life of up to 48 hours. It is suggested that this extension in sperm motile life may result from capacitation-like events which occur during activation and release in vivo. A hypothesis for the synthesis of 8,11,14-eicosatrienoic acid, its release from the prostomium, its transportation and mode of action at the level of the spermatozoa is also developed.

Populations of Arenicola marina from different localities have been reported to show variation in certain characteristics. There are morphological differences such as colour, size and annulation patterns, and there is also variation in the duration and timing of the spawning seasons on different beaches. An extensive study of gametogenesis in individuals from three selected study sites was carried out by regular sampling throughout the year. Each site shows a different spawning pattern, either epidemic such as at the East Sands, St. Andrews, or an extended season, such as at the Eden Estuary, St. Andrews. These two sites are less than three kilometres apart and yet there are significant differences in the size of the gravid adults. The third site, Fairlie Sands on the west coast of Scotland shows a very unusual type of spawning season in that a small percentage of the population are gravid throughout most of the year. Genetic variation was assessed using the technique of starch gel electrophoresis of allozymes. There is a degree of genetic differentiation between the three sites. Allele frequencies at the GOT locus are different between east and west coast sites and a third rare allele is present at Fairlie Sands. It is suggested that gene flow mediated by larval transport may be limited and this would cause inbreeding in some subpopulations. The hormones involved in spawning have been investigated with particular reference to a putative female oocyte maturation hormone. Comparative work between Arenicola marina and A. defodiens has demonstrated the presence of an oocyte maturation factor in the prostomia of both species. While this factor acts directly on A. defodiens oocytes in vitro, the presence of a cofactor or secondary product produced in vivo is required in order to reinitiate meiosis in A. marina oocytes. Preliminary studies on the nature of reproductive endocrine substances present in the prostomia of female A. marina have been carried out.

A tidal channel habitat dominated numerically by the tube-building polychaete Lanice conchilega is described from Tentsmuir Beach in N.E. Fife, Scotland. This habitat was named the Lanice tidal channel sub-environment and was characterized by sedimentological features and macrofauna associated with aggregations of Lanice. These aggregations formed a habitat structurally and faunistically more heterogeneous than surrounding mobile sand habitats. The aggregations occurred in discrete areas protected by a linear sand bar from onshore swell but were subjected to relatively strong tidal currents. Eight divisions of the sub-environment were described from surface features and used to compare sediment and macrofauna distribution in relation to environmental features. The dense tube beds provided a stable substratum for settlement and growth of algal species. Mounds and stable flats were produced during the spring by sediment deposition combined with rapid growth of algal thalli and tube extension. The structures were quickly eroded after the death of the algae although some areas maintained high tube densities. The average sediment of Tentsmuir was a fine sand with a moderately well-sorted, negative-skewed, mesokurtic grain size distribution. This average distribution included a coarse tail, primarily composed of carbonate fragments. This coarse tail was concentrated in the areas numerically dominated by Lanice conchilega. Two faunal assemblages were recognized: a shallow-sand association not strongly associated with Lanice density (Nephtys caeca, Tellina tenuis, Ophelia limacina and Donax vittatus), and a Lanice conchilega association (Lanice conchilega, Eumida sanguinea, Anaitides maculata, Harmothoe lunulata). The effect of the projecting tubes of Lanice on particle flux in the benthic boundary layer was studied in laboratory flume experiments. Experiments were performed with dye and denatured egg albumen particles to determine flow patterns and net particle movement in individual tube wakes. Projecting tubes produced characteristic vortex patterns which may increase resuspension of sediment particles. The characteristic vortex patterns were not strongly dependent on obstacle shape or flow regime and resulted in pronounced upward motion of fluid from the bed. Particle velocities within the wake were found to be lower than ambient channel flow velocity. It is suggested that Lanice can utilize this flow disturbance to feed on resuspended food particles.

The trochophore larva of Harmothoe imbricata was examined by both light and electron microscopy. Light microscopy of living trochophores was limited to a study of the action of cilia and muscles, and observations on trochophores at various stages from the egg to the fully formed trochophore. The observations on the developing trochophore revealed the presence of apparently uniquely acting cilia. Fixed, sectioned trochophores were examined under the light microscope as an adjunct to electron microscopy to give the gross anatomy. Scanning electron microscopy was used to determine the arrangement of cilia and glands on the surface of the trochophore. This demonstrated that previous views, at least on the apical array of cilia, were erroneous, and that there is considerable asymmetry in the positions of both cilia and gland pores. Transmission electron microscopy of the fully formed trochophore afforded the first information at an ultrastructural level on all the organ systems of a trochophore, and revealed the presence of previously unknown structures such as modified cilia and a probable photoreceptor which is additional to the pigmented eyespot. Certain general issues of contention in electron-microscopical work were able to be resolved in the course of this work. This included the finding of neuro-ciliary synapses, and certain significant features in the development of trochophores from the egg to the fully formed trochophore. The suitability of this animal for experimental investigation became clear as the fine structural analysis proceeded. Accordingly, preliminary studies were made on pepsin digestion of thin sections and the testing of drugs on whole- animals before fixation.

SOUSA, Rossana Cristina de Azevedo. Distribuição espacial dos poliquetas (ANNELIDA, POLYCHAETA) dos Recifes de arenito na praia da Pedra Rachada (Paracaru - Ceará). 2005. 70 f. Dissertação (Mestrado em Ciências Marinhas Tropicais) - Instituto de Ciências do Mar, Universidade Federal do Ceará, Fortaleza, 2005. / Submitted by Debora Oliveira (deby_borboletinha@hotmail.com) on 2011-12-22T14:36:28Z No. of bitstreams: 1 2006_dis_rcdasousa.pdf: 1654091 bytes, checksum: ed9b68df546408f9b1d3e4ab3341285d (MD5) / Approved for entry into archive by Nadsa Cid(nadsa@ufc.br) on 2012-01-23T17:05:51Z (GMT) No. of bitstreams: 1 2006_dis_rcdasousa.pdf: 1654091 bytes, checksum: ed9b68df546408f9b1d3e4ab3341285d (MD5) / Made available in DSpace on 2012-01-23T17:05:51Z (GMT). No. of bitstreams: 1 2006_dis_rcdasousa.pdf: 1654091 bytes, checksum: ed9b68df546408f9b1d3e4ab3341285d (MD5) Previous issue date: 2006 / Sandstone rock reefs consist of consolidated substrata with a high fauna and flora diversity, where polychaetes represent a very important group. This study aims to contribute to the knowledge about polychaete annelids biodiversity on the coast of Ceará and their spatial distribution on hard substratum. The sampling took place on the reefs at Pedra Rachada beach (Paracuru-CE) and was carried out during low spring tides in August 2004 (dry season) and May 2005 (rainy season). A transect was placed perpendicularly to the coastline, throughout which samples, 10m apart from each other, were collected using a 25x25cm square. The sampled area was divided in three zones: lower, middle, and higher reefs. Considering the two studied seasons, 1315 specimens were identified and distributed in 60 polychaete species pertaining to 25 families and 42 genera. The most abundant families were Eunicidae, Orbinidae and Neredidae. Most of the found species are either carnivores, herbivores or burrowers. The typical species of the studied areas were Eunice cariboea, Naineris dendritica, Nematonereis hebes and Lysidice ninetta. No significant difference was observed in the absolute abundance of the species between the studied periods. However, a significant difference was observed between the lower and higher zones. During the dry season, the major abundance of individuals was found at the higher reef, whereas during the rainy season it was found at the lower reef. Nereis riisei was the only specie to present significant difference in its average abundance between the studied periods. The sandstone rock reef polychaetes at Pedra Rachada beach presented a distribution strongly related to the substratum features. / Os recifes de arenito constituem um ambiente consolidado com alta de diversidade de fauna e flora, no qual os poliquetas representam um grupo importante. Este estudo teve como objetivo contribuir para o conhecimento da biodiversidade de anelídeos poliquetas da costa cearense e estudar a distribuição espacial desses organismos em substratos consolidados. As coletas, realizadas nos recifes de arenito da praia Pedra Rachada (Paracuru-CE), foram realizadas durante maré baixa de sizígia, em agosto de 2004 (período seco) e maio de 2005 (período chuvoso). Um transecto perpendicular à linha de praia foi demarcado, no qual as amostras foram coletadas utilizando-se um quadrado de 25 cm de lado, dispostos em intervalos de 10 m. A faixa de recife amostrada foi dividida em três zonas, recife inferior, médio e superior. Considerando os dois períodos de estudo, foram identificados 1.315 indivíduos distribuídos em 60 espécies de poliquetas, pertencentes a 25 famílias e 42 gêneros. As famílias mais abundantes foram Eunicidae, Orbiniidae e Nereididae. A maioria das espécies encontradas possui hábito alimentar carnívoro, herbívoro e escavador. As espécies típicas da região estudada foram Eunice cariboea, Naineris dendritica, Nematonereis hebes e Lysidice ninetta. Não foi observada uma diferença significativa, com relação à abundância absoluta das espécies, entre os períodos estudados, entretanto, foi observada diferença significativa entre as zonas do recife inferior e recife superior. No período seco, a maior abundância de indivíduos ocorreu no recife superior, já no chuvoso, ocorreu no recife médio. Nereis riisei foi a única espécie que apresentou diferença significativa quanto a sua abundância média quando comparados os dois períodos estudados. Os poliquetas dos recifes de arenito da praia da Pedra Rachada apresentaram uma distribuição de acordo com as características do substrato