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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

Growth of a sea urchin, Allocentrotus fragilis, at different depths off the Oregon coast

Sumich, James L. 19 August 1970 (has links)
Allocentrotus fragilis (Jackson) was obtained from six stations at depths of 100 to 1260 m on the continental shelf and upper slope off Newport, Oregon. Ages and growth rates of A. fragilis were determined by two methods: 1) A procedure was developed to make growth zones of the skeletal test plates visible. Alternating light and dark growth zones were found to be formed semi-annually. The total number of growth zones was used to indicate the urchin's age. 2) Age and growth rate values were also determined from analyses of size-frequency distributions of trawl collections from 200 m. Collections from other depths were not adequate for size-frequency analyses. Gonad indices of A. fragilis from 200 m were used to determine spawning periodicity and frequency. A semi-annual frequency was found, with spawning occurring in early spring and early autumn. No A. fragilis specimens collected below 400 m were reproductively mature. The growth curve of A. fragilis from 200 m, which was plotted from the mean test diameter of age groups defined by test plate growth zones, shows a good least-squares fit with von Bertalanffy's growth equation. Growth rates were similar for A. fragilis from 100-600 m, but decreased for specimens from 800 and 1260 m. The maximum test diameter decreased with increasing depth below 200 m. Variation of magnesium content of the calcareous skeletal plates was due largely to variation with age. Little skeletal Mg variation was found at different depths for specimens of the same age. Greater Mg content differences occurred between young and old specimens from the same depth, and between young and old test plates of the same individual. The effects of several environmental factors on the growth rate and maximum size of A. fragi1is are discussed. Of these factors, food availability, water temperature, and oxygen tension form gradients with depth or distance offshore; and were considered to be important in affecting the growth of A. fragilis. / Graduation date: 1971
2

Studies on sea urchins

Smith, Daniel Beetham. January 1900 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
3

Salinity sensitivity of embryos of the Antarctic sea urchin, Sterechinus neumayeri

Cowart, Dominique Alexandria. January 2008 (has links)
Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Adam G. Marsh, College of Marine and Earth Studies. Includes bibliographical references.
4

Thyroid hormone-like function in echinoids a modular signaling system coopted for larval development and critical for life history evolution /

Heyland, Andreas. January 2004 (has links)
Thesis (Ph. D.)--University of Florida, 2004. / Title from PDF title page (viewed on July 3, 2005). Includes vita. Includes bibliographical references (p. 161-178).
5

Aspects of the ecology of Anthocidaris crassispina (echinodermata: echinoidea) in Hong Kong /

Chiu, Sein-tuck. January 1987 (has links)
Thesis (Ph. D.)--University of Hong Kong, 1987.
6

Axial organ : its potential role in echnoid immunity

Larson, Maureen Kupke 04 March 1993 (has links)
The echinoderm axial organ is located centrally, at the meeting point of the animals' "circulatory" systems. This, and its unusual histology, have prompted the implication of a number of different functions for the organ, including circulation, excretion and host defense. None of these have been definitively proven. Claims that starfish axial organ cells respond to antigen in an adaptive manner, resembling the vertebrate antibody response, also remain unconfirmed. The purpose of the work on Strongylocentrotus purpuratus presented in this thesis was to independently test the hypothesis that the cells of the axial organ respond to antigenic challenge. To determine if the cells are modified quantitatively following antigen encounter, the cell types of the organ were first classified according to morphological characteristics. Cell subpopulations were then monitored quantitatively after in vivo exposure to several types of antigens. Axial organ cells were also analyzed for qualitative changes; cells from antigen exposed urchins were assayed for immunocytoadherence to antigen-coated sheep erythrocytes. The coelomic fluids from the same animals were tested for antigen-specific binding molecules using ELISA assays. Immunocytoadherence and ELISA assays were validated with cells and sera from trout similarly exposed to antigen and control treatments. Eight subpopulations of axial organ cells were identified. Four of the cells types resemble cells found in the coelomic fluid. A possible precursor cell to the red spherule cell was found to be a member of the axial organ cell population. Changes in the axial organ cell subpopulations after antigen exposure were not significant, regardless of the type of antigen, exposure method or sample time. Cells of the axial organs from TNP-exposed urchins did not bind TNP-SRBC's, and the hemagglutination observed was neither TNP-inhibitable, nor dependent on previous expoure to the TNP antigen. Coelomic fluids from several urchins bound TNP to a greater extent than BSA, but the frequency of binding among urchins was not dependent on their prior treatment. Titrational analysis of one set of urchin coelomic fluids against the hapten, TNP, the carrier, LPS, or an unrelated protein, BSA, revealed identical binding curves with each molecule. This, in addition to a higher titer of binding molecules in the control animals compared to antigen-injected animals, led to the conclusion that the response was nonspecific. The work presented in this thesis does not support the hypotheses that the urchin axial organ cells respond to antigenic challenge either by a modification in cell types present in the organ, or by the production of cell surface or secreted antigen-specific binding molecules. / Graduation date: 1993
7

Effects of ultraviolet radiation on developing variegated sea urchins, lytechinus variegatus

Tauchman, Eric Gary. January 2008 (has links)
Thesis (M.S.)--University of West Florida, 2008. / Title from title page of source document. Document formatted into pages; contains 63 pages. Includes bibliographical references.
8

Interspecific interactions of the sea urchin Parechinus angulosus and the effect of variations in microhabitat availability

Farquhar, Michael Robert January 1995 (has links)
Intertidal populations of the sea urchin Parechinus angulosus were examined at seven sites along the south and east coasts of South Africa. At the five southerly sites, P. angulosus occurred in allopatry, while, at the two northerly sites, it occurred in sympatry with several species of Indopacific sea urchins. At the five southerly sites, there was a significant correlation of number of sea urchins per pool with the surface area of the overhang in that pool. This relationship broke down for P. angulosus at the two northerly sites, where there was a significant correlation between these two factors for Stomopneustes variolaris. The density of populations of P. angulosus at the two northerly sites, although not significantly different from all five southerly sites, were considerably lower. There was a significant difference between the mean size of populations at the seven sites. Although no direct evidence is available, a competitive interaction between these two species is proposed to explain the observed patterns of microhabitat utilization and densities. Two series of manipulative experiments were conducted at Kowie Point, where P. angulosus occurs in sympatry, The first, involved urchin removals from three experimental sites. The percentage cover of four functional algal groups was monitored in three experimental and three unaltered control sites over a three month period in spring (Sept. - Dec.) 1993. Two 100 point 0,25m² random point quadrats were thrown at each of the six sites at approximately monthly intervals over the experimental period. Since initial cover of algae varied at the six sites, ANOVA's of the change in percentage cover of four functional algal groups were used to determine treatment effects. No treatment effects were identified for any of the four functional algal groups. There was a strong negative correlation between the percentage cover of foliose algae and encrusting coralline algae, suggesting the possibility of a competitive relationship between them. The second, involved the experimental manipulation of microhabitat availability. The blocking of overhangs, by means of cement filled bags, resulted in an approximate 50% decrease in the total number of urchins in the two experimental pools, and the two control pools without overhangs. However, in the control pool with overhangs there was a slight increase in the number of urchins over the same period. Clearly, the presence of suitable shelters, is a prerequisite for the maintenance of dense intertidal population of P. angulosus. It is proposed that, due to the exposed nature of the South African coast, intertidal populations of P.angulosus are restricted to inhabiting suitable shelters from which they emerge to feed on passing drift algae. The implications of these findings are discussed in terms of current ecological literature.
9

The digestive mechanisms of an intertidal grazer, the sea urchin Parechinus angulosus

Sweijd, Neville Anthony January 1991 (has links)
Echinoids are important grazers in the near-shore ecosystem and can significantly effect their ecology. The sea urchin Parechinus angulosus occurs inter- and subtidally along the southern African coast. Within this range it consumes an extremely wide variety of algae. Since algal cell walls have an almost species specific chemical composition, the question arises as to how it can digest the algae that it consumes. In order to investigate the digestive mechanisms employed by P. angulosus, an ultrastructural study of the gut was undertaken to characterize the tissue and identify functional regions in the gut. Ten structural and storage polysaccharides commonly found in macroalgae were used as substrates to assay the digestive polysaccharidases of the sea urchin. The enteric bacteria of the sea urchin were isolated and tested separately for polysaccharidase activity using the same substrates. The results shown that the gut of Parechinus angulosus is regionally specialized, with the foregut primarily responsible for the production of hydrolytic enzymes, while the hindgut is primarily absorptive. The occurrence of lamellar bodies, heterolysosomes, cytoplasmic blebs and paddle cilia among other characteristic features of the digestive epithelium are described and discussed. Two levels of enzyme activity are apparent. Generally the urchin could hydrolyze the reserve polysaccharides, but only partially hydrolyze the structural polysaccharides, of red and green algae. P.angulosus was unable to digest alginic acid, the main structural polysaccharide of brown algae. Mixed cultures of bacteria utilized only the reserve polysaccharides of red and green algae. Significantly, the bacteria were able to hydrolyze alginic acid. Enteric bacteria also showed agarolytic activity. Parechinus angulosus has the ability to digest red and green algae. No lysozyme activity was detected. The enteric bacteria can digest the same algal reserve polysaccharides and so may compete for carbon in the gut. However, in the case of brown algae, bacteria have a potentially important endosymbiotic role as agents of digestion. These results correspond with food preference studies which have shown that, although P.angulosus consumes the kelp Ecklonia maxima, in the western Cape, it is amongst its least preferred food species. The reasons for this are its unpalatability and the urchin's inability to digest brown algae. The digestibility of algal material can be an important factor in determining algal-herbivore interactions.
10

Histamine ??? a naturally occurring settlement cue for larvae of the Australian sea urchin Holopneustes purpurascens

Swanson, Rebecca, School of Biological, Earth & Environmental Sciences, UNSW January 2006 (has links)
The importance of chemical cues in triggering the settlement of marine invertebrate larvae has long been recognised but very few such cues have been definitively identified. Larvae of the Australian sea urchin Holopneustes purpurascens, which lives enmeshed in the fronds of macroalgae, are induced to settle by a water-soluble cue produced by the host alga Delisea pulchra. This cue was previously identified as a floridoside-isethionic acid complex. I present evidence in this thesis which supports histamine as the true settlement cue for larval H. purpurascens. The settlement cue was isolated from the polar extract of D. pulchra by bioassay-guided cation-exchange chromatography and identified as histamine using nuclear magnetic resonance spectroscopy. Algal derived and synthetic histamine at ~5 ??M induced rapid settlement in 80???100 % of larval H. purpurascens. In the first study of its kind for any marine invertebrate, variation in the distribution of new recruits was compared with quantitative variation in the distribution of histamine in the habitat. More than 90 % of new recruits were found on either the foliose red alga D. pulchra or on coralline turf algae. These algae induced &gt90 % settlement of larvae in laboratory assays after 24 h. D. pulchra contained far higher levels of histamine than all other algae, however, the coralline algae lacked measurable histamine. Seawater collected in situ adjacent to D. pulchra induced up to 16 % settlement of older larvae and contained the highest concentration of histamine (~5 nM). With the exception of coralline algae, variation in settlement and recruitment was consistent with the variation among species histamine contents. Initial results supported a biofilm derived settlement cue from coralline algae. I also showed that older H. purpurascens larvae settle in response to lower concentrations of histamine than younger larvae and required less exposure to histamine (10 ??M) in order to initiate irreversible metamorphosis. Histamine induced settlement of two other echinoids with non-feeding larvae. Histamine did not induce settlement of feeding larvae of two echinoids or settlement of non-feeding larvae of asteroids. Histamine may be a general settlement cue for echinoids with direct development.

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