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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.
21

Gametogenesis and gamete morphology of anodonta imbecilis, elliptio icterina, and villosa villosa (Bivalvia: Unionidae)

Unknown Date (has links)
Light and electron microscopic studies of gametogenesis and gamete morphology of fresh-water, larviparous bivalves, Anodonta imbecilis Say, Elliptio icterina (Conrad), and Villosa villosa (Wright) were conducted. There were no qualitative interspecific differences in cellular morphology or histochemistry at any stage of spermatogenesis or oogenesis. All three species exhibited two forms of spermatogenesis. Typical spermatogenesis, involving the production of spermatocytes and the differentiation of spermatids, was similar to that of other invertebrate species. Atypical spermatogenesis involved the differentiation of spermatozoa from spermatogenic cysts produced in follicle cells. Typical spermatogenesis proceeded throughout the year in A. imbecilis and E. icterina and occurred simultaneously with atypical spermatogenesis in summer and winter, respectively. In V. villosa, atypical spermatogenesis replaced typical spermatogenesis in the summer. There was no significant intraspecific variation in spermatozoan morphology, but the spermatozoa of V. villosa differed significantly in shape from those of A. imbecilis and E. icterina. This interspecific variation might be a useful character in assessing phylogenetic relationships among unionid sub-families. The spermatozoa of all three species conformed to the atypical primitive morphology, which is characteristic of organisms that broadcast spermatozoa but retain oocytes for internal fertilization. / Oogenesis occurred throughout the year in all three species, but the seasonal peaks in the presence of mature oocytes varied interspecifically. During the previtellogenic stage of oogenesis, oocyte activity was directed toward synthesis and/or replication of cellular organelles. Vitellogenesis was entirely autosynthetic, and yolk bodies consisted of neutral mucopolysaccharides. Mature oocytes were at the germinal vesicle stage and were surrounded by a thin vitelline layer. No micropyle was observed. The diameters of mature oocytes differed interspecifically, but this variation was not correlated to interspecific differences in the duration of the incubatory period. Rather, it is suggested that unionid oocyte size is a function of the rate of larval development. / Source: Dissertation Abstracts International, Volume: 49-06, Section: B, page: 2082. / Major Professor: William H. Heard. / Thesis (Ph.D.)--The Florida State University, 1988.
22

The biology of shell use by the hermit crab Pagurus longicarpus

Unknown Date (has links)
Many studies have associated hermit crab reproduction with various gastropod shell characteristics. Only limited inferences can be drawn from some of these studies due to lack of controls for the relationship between reproduction and female crab body size. Among Pagurus longicarpus from the northeastern Gulf of Mexico, reproduction correlates with several shell characteristics after variation attributable to body size has been statistically removed. Females are less likely to be reproductive if they occupy shells that are severely damaged or fouled or if the shell is more than 1.5 standard deviations larger or smaller than the predicted shell size. Relative shell size also correlates with clutch size, although the relationship between these parameters differed between populations. / Shell selection experiments that concomitantly examine preferences of several shell characteristics show that relative shell size is more important to Pagurus longicarpus than either shell species or damage. Hermit crabs rarely selected relatively large shells but often selected relatively small shells over damaged shells. Preferences for a particular shell species were easily offset by varying the relative shell size or condition of the preferred shell species. These results suggest that shell choice does not optimize the avoidance of predation and desiccation, the two environmental stresses often linked to relatively small shells and particular shell species. Finally, P. longicarpus appears to judge shell size by shell volume (or some factor that strongly correlates with shell volume) because preferred shell volumes did not vary between shell species. / The cheliped morphology of male Pagurus longicarpus correlates with the species of shell that the crab occupies. Several hypotheses posed to account for this correlation are examined. The likely explanation appears to be that male crab morphology and shell species use changes ontogenetically leading to a coincident correlation between morphology and the species of the occupied shell. / Source: Dissertation Abstracts International, Volume: 49-06, Section: B, page: 2084. / Major Professor: William F. Herrnkind. / Thesis (Ph.D.)--The Florida State University, 1988.
23

Amphibian Head Start Programs| Comparisons of Dermal Microbiomes of Oregon Spotted Frogs (Rana pretiosa) Reared under Traditional and "Mesocosm" Conditions

Borek, Alyssa 19 April 2019 (has links)
<p> Woodland Park Zoo (WPZ) participated with Washington Department of Fish and Wildlife (WDFW) and other partners in the Oregon Spotted Frog (<i> Rana pretiosa</i>; OSF herein) species recovery program from 2008&ndash;2015. This species, listed as federally Threatened in 2014, and Endangered in Washington in 1997, is declining throughout its range. For this study, dermal microbiomes were compared between frogs reared in traditional &ldquo;zoo sterile&rdquo; environments, more naturalistic mesocosm environments, frogs reared at a correctional facility, as well as wild caught frogs. Additional comparisons were made before and after Itraconazole treatments when one cohort of frogs was treated for an infection of amphibian chytridiomycosis. Over 10 million sequences of DNA data were analyzed in collaboration with the University of Colorado. Not surprisingly, there were differences in microbiomes between each group tested. More surprising, were the actual differences- all WPZ samples were more similar to wild samples, and samples from the correctional facility were less similar to WPZ and the wild samples. Of the comparisons between wild and captive samples, and the comparisons between pre and post-Itraconazole samples, both captive and post- Itraconazole samples exhibited higher species richness, higher alpha diversity, and higher OTU evenness. Unplanted (planted vs. unplanted treatments) showed higher species richness but no significant differences in alpha diversity or OTU evenness, possibly due to contamination between stock tanks.</p><p>
24

Evaluating Potential Age Structures for Three Alaska Crustacean Species

Rebert, April L. 02 May 2019 (has links)
<p> Banding patterns are observed in calcified structures of red king crab (<i>Paralithodes camtschaticus</i>), snow crab (<i>Chionoecetes opilio</i>), and spot shrimp (<i>Pandalus platyceros</i>). Recent research supports an age determination method based on these banding patterns; however, processing methodologies for these structures have not been established. Further, species-specific evidence is needed to determine whether these patterns indicate actual age or growth. The objectives of this thesis are to: (1) describe optimal species-specific methods for producing and evaluating band counts for red king crab, snow crab, and spot shrimp; and (2) use differences in shell condition to test whether band counts indicate age for snow crab. For each species, we comprehensively thin-sectioned structures, evaluated each section for banding pattern presence (readability), and developed band count criteria. To address objective 1, we used generalized additive models to describe readability across structures to find the location that optimizes the production of readable sections. For objective 2, we used a one-way ANOVA to compare band count and endocuticle measurements among shell conditions in snow crab. Results indicated preferred structures, locations, section orientation, and thickness. Results also indicated that there is no relationship between band count and shell condition for terminally molted snow crab. These results describe optimal methods for processing crustacean structures and suggest that the potential age structures may not continue to produce bands after terminal molt in the case of snow crab. Further evaluation is needed to validate potential age relationships and the use of this technique for age estimation.</p><p>
25

MOVEMENTS, ORIENTATION AND RELATED SENSORY CAPABILITIES OF LITTORINA IRRORATA SAY (GASTROPODA: PROSOBRANCHIA)

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 37-10, Section: B, page: 4926. / Thesis (Ph.D.)--The Florida State University, 1976.
26

THE ORIGIN AND SEASONALITY OF THE FISH FAUNA ON A NEW JETTY IN THE NORTHEASTERN GULF OF MEXICO

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 33-07, Section: B, page: 3384. / Thesis (Ph.D.)--The Florida State University, 1972.
27

MONOGENETIC TREMATODES OF SOME GULF OF MEXICO FISHES

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 14-07, page: 1115. / Thesis (Ph.D.)--The Florida State University, 1954.
28

STIMULATION OF SCHISTOSOMATIUM DOUTHITTI CERCARIAE TO PENETRATE THEIR HOST

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 20-08, page: 3449. / Thesis (Ph.D.)--The Florida State University, 1959.
29

HOST HIBERNATION AND ITS EFFECTS ON SCHISTOSOMATIUM DOUTHITTI AND SCHISTOSOMA MANSONI (TREMATODA: SCHISTOSOMATIDAE)

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 21-08, page: 2409. / Thesis (Ph.D.)--The Florida State University, 1960.
30

ELECTRON MICROSCOPIC STUDIES OF DICYEMID MESOZOA

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 28-03, Section: B, page: 1284. / Thesis (Ph.D.)--The Florida State University, 1967.

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