The Robertsonian polymorphism (numerical change in the chromosome complement by centric fusion or fission) in the dog-whelk (Nucella lapillus, Mollusca: Gastropoda) has been known and studied sporadically for almost 50 years. However, the possible causes, consequences and proposed correlations of this phenomenon remain enigmatic. Nucella lapillus (2n = 26 to 36), has undergone a marked reduction in chromosome number from its ancestral form; most other muricid species have a diploid chromosome number in the range 2n = 60- 70. Correlations have been proposed between chromosome number (or karyotype) and habitat (wave exposure), and also directly or indirectly with allozymes, shell shape and physiology. However, firm conclusions are lacking due to either, insufficient knowledge of the karyotypes in the populations studied, or the fact that any correlations are not consistent throughout the broad geographic range. This study reviews all the past research on the chromosomal polymorphism in N. lapillus, advances the karyology of this species by successfully labelling individual chromosomes through silver-staining of nucleolar organizer regions (NORs) and fluorescence in situ hybridisation (FISH) with rDNA and telomeric probes, and proposes a new system of nomenclature for this polymorphism. Knowledge of the geographic variation in chromosome number and karyotype is advanced by studying around 70 populations throughout the range of N. lapillus (mainly in the UK, but also the USA and northern and southern Europe). Evidence is shown that, (1) the polymorphism is far more widespread geographically than was previously thought; (2) more than five pairs of metacentric chromosomes are involved in the Robertsonian polymorphism; and (3) inversions also occur in some populations. Putative links between chromosomal polymorphism in N. lapillus and Darwinian fitness are reviewed in the light of the new findings and more recent work on other species; data are presented on fecundity, fertility, inter- and intra-individual variation in karyotype, selection within populations (adults v. embryos, homo- v. heterozygotes) and a possible genetic/karyotypic link with phenotype (Dumpton syndrome, a reproductive abnormality). Cytogenetic records for other muricids are also reviewed and karyotypes and chromosome lengths of four other species (Ocenebra erinacea, Thais haemastoma, Murex trunculus, Ocinebrina aciculata) are recorded for the first time. Genome size (DNA content) of 8 species of muricid, including the 2n=26 and 2n=36 forms of N. lapillus, are determined by Feulgen densitometry and compared in the context of evolutionary studies on the family. Although chromosome number and haploid length in N. lapillus has been reduced, its genome size is actually greater than all but one of the other muricids studied, and consequently has a much higher DNA packing ratio (>13000). Whether the chromosomal variation in N. lapillus represents polymorphism, polytypy, or speciation in progress remains unresolved, but substantial advances have been made in this dissertation and the required direction and focus for future work are clarified.

Thesis (Ph. D.)--Georgia Institute of Technology, 2006. / Title from PDF t.p. (viewed on Oct. 28, 2006). Weissburg, Marc, Committee Chair ; Dusenbery, David, Committee Member ; Hay, Mark, Committee Member ; Webster, Donald, Committee Member ; Blanton, Jackson, Committee Member. Includes bibliographical references (p. 108-119).

Aspects of the developmental biology of an intertidal predatory gastropod, Nucella lapillus were investigated for a population located on a mussel dominated shore at ^^ihitsand Bay, Cornwall. A field sampling programme revealed that the centre of abundance of. small Nucella {<3.4mm) occurred at lower shore levels than that of a ll larger individuals and the egg capsules. Laboratory studies danonstrated that hatchlings are both negatively geotactic and phototactic, directing than upshore and into crevices. The relative profitabilities of four different sized mussels to four developmental stages of Nucella v/ere investigated using both ability to promote grov/th and energy gain per unit handling time (E/Tj^) as measures of prey value. The response curves were similar m that proportionately large and small prey were less profitable than medium sized prey with the optimal prey size increasing with predator size. However the most profitable size according to the E/T^^ model was larger than in the grovrtli rate model because large meals appeared to be less efficiently utilized. An ontogenetic- shift in prey size selection was danonstrated in laboratory and field, the results of which were more accurately predicted by the grcwth rate model of prey value. Predatory events in the field were investigated using borehole dimension as an index of predator size. The feeding and growth of Nucella were investigated at differing periods of tidal atiersion. Growth rates were substantially reduced at anersion periods of above 30%, but these could not be wholly attributable to reduced feeding rates. Field growth trials danonstrated that a matiore size could be reached in 19-21 months, that growth does not cease at maturity, and that jxiveniles grow throughout the year. A strong correlation existed between growth rate and environmental temperature. Growth rates in the field were about 75% those in the laboratory, suggesting few constraints on foraging in the field.

The Whelk-O1 chiral stationary phase is widely used in liquid and supercritical chromatography for the separation of enantiomers. The enantioselective mechanism of the Whelk-O1 chiral stationary phase is the main focus of this thesis. Semi-flexible models are developed based on ab initio calculations for the Whelk-O1 selector and a series of chiral analytes. Extensive molecular dynamics simulations are then applied to study the solvation, selectivity and in silico optimization of the chiral stationary phase. The solvation of the Whelk-O1 chiral stationary phase has been explored in a normal phase n-hexane/2-propanol solvent, a reversed phase water/methanol solvent, and a supercritical CO2/methanol solvent. We found that, in all three solvents, the Whelk-O1 selectors are open to the bulk, indicating readiness for docking of analyte. Significant solvent partitioning at the interfaces was noticed, which generates a polarity gradient between the stationary phase and the bulk, and may encourage a high analyte concentration at the interface. Hydrogen bonding activities on the amide hydrogen, amide oxygen, and nitro oxygen of the Whelk selector have also been analyzed. The selectivity of the Whelk selector was studied by molecular dynamics simulations of analyte docking on the chiral stationary phase. The elution orders and the separation factors for a series of analytes were predicted successfully. We found that hydrogen bonding and π-π stacking interactions are essential for the enantioselectivity as they are strong and specific, and they hold analytes to the cleft region of the Whelk selector. Other interactions, both stabilizing interactions such as the CH-π interaction and the edge-to-face π-π interaction, and destabilizing interactions such as steric hindrance and unfavorable conformational changes also contribute to the enantioselectivity. We identified a dominant docking arrangement for the most retained enantiomers. Other docking arrangements were found to be more frequent for the least retained enantiomers and these involve interactions with alternative selector sites. Based on the identified enantioselective mechanism obtained from the study, an optimization of the Whelk-O1 chiral stationary phase was undertaken and in silico evaluation of the modified chiral stationary phases was carried out. It was demonstrated that restriction of the alternative docking arrangements for the least retained enantiomers could possibly improve the enantioselectivity of the chiral stationary phase. / Thesis (Ph.D, Chemistry) -- Queen's University, 2008-10-08 11:54:20.249

The American horseshoe crab (HSC), Limulus polyphemus, is one of four species of horseshoe crabs found throughout the world, and the only one found in North America. It is an economically and ecologically important species throughout its native range from Maine to the Yucatan Peninsula. Harvested for fertilizer and livestock feed in the 19th century, the species is now harvested as bait for whelk and eel fisheries, and for their blood by the biomedical industry. The Atlantic States Marine Fisheries Commission (ASMFC) started to formally manage HSC in 1998 with its Interstate Fisheries Management Plan (IFMP). Unique emphasis and harvest limits have been placed on the Delaware Bay stock, as it is commercially exploited and a critical food source for the threatened red knot, Calidris canutus rufa. Previously, estimates of relative and total abundance of HSC in the Delaware Bay area were based on a design-based approach using a stratified random sampling design. In Chapter 1 of this work, I developed hurdle models for each of the six HSC demographic groups to standardize catch-per-unit-effort (CPUE) and estimate relative abundance using a model-based approach. It was determined that while the two approaches resulted in mostly convergent estimates of relative abundance, external factors such as month, time-of-day, and average depth have major effects on the observed CPUE of all demographic groups. Chapter 2 involved the development of hurdle models for the three species of bycatch frequently caught in our trawls, channeled whelk (Busysotypus canaliculatus), knobbed whelk (Busycon carica), and summer flounder (Paralichthys dentatus). It was found that channeled whelk relative abundance has been at a historical low since 2016, while summer flounder has been at a consistent high. Recent estimates of knobbed whelk relative abundance have been less variable than previously seen, with estimates since 2016 being similar to those seen before 2012. These results provide the first estimates for whelk population trends in the mid-Atlantic region and add to the growing knowledge of summer flounder relative abundance in the area. In Chapter 3, I applied the hurdle models developed in Chapter 1 to estimate the total abundance of HSC in the Delaware Bay area. For this work, I developed two spatio-temporal variograms to estimate bottom temperature and bottom salinity at unmeasured cells per month in the time series. The results showed that night estimates of total abundance were consistently higher than daytime estimates, and estimates from September or November resulted in the highest estimated catch for all demographic groups. The results suggest that when comparing September model-based estimates at night to those of the design-based approach, nearly a third of all previous design-based estimates significantly underestimated the total abundance of HSC in the Delaware Bay area. This result suggests that the ASMFC can recommend increased harvest limits for mature individuals if that action aligns with the goals of their adaptive resource management (ARM) framework. / Master of Science / The American horseshoe crab (HSC), Limulus polyphemus, is one of four species of horseshoe crabs found throughout the world, and the only one found in North America. It is an economically and ecologically important species throughout its native range from Maine to the Yucatan Peninsula. Harvested by the millions in the 19th century, the species is still harvested as bait for whelk and eel fisheries, and for their blood by the biomedical industry, on the order of hundreds of thousands. Formal management of HSC by the Atlantic States Marine Fisheries Commission (ASMFC) began in 1998, and allowable catch and landings have decreased since 1999. A strong focus has been placed on the Delaware Bay population, as it is the center of HSC abundance and provides a critical food source for the threatened red knot, Calidris canutus rufa, while also being commercially exploited. To effectively manage the species, it is important to accurately estimate relative and total abundance so that proper harvest limits can be set. Previously, estimates of relative and total abundance of HSC in the Delaware Bay area were based on a design-based approach using a stratified random sampling design. In Chapter 1 of this work, I developed hurdle models (a generalized linear model that models the probability of observations and the observed positive counts using two separate regression models that are then combined) for each of the six HSC demographic groups to remove the effect of external factors (year, latitude, longitude, depth [inshore/offshore], topography, average trawl depth, time-of-day, month, bottom temperature, bottom salinity, and distance from shore) on our observed catch-per-unit-effort (CPUE) and estimate relative abundance using a model-based approach. It was determined that while the two approaches resulted in mostly convergent estimates of relative abundance, factors like month, time-of-day, and average depth had major effects on the observed CPUE of all demographic groups. Chapter 2 involved developing similar hurdle models for three species of bycatch frequently caught in our trawls, i.e., channeled whelk (Busysotypus canaliculatus), knobbed whelk (Busycon carica), and summer flounder (Paralichthys dentatus). It was found that channeled whelk relative abundance has been at a historical low since 2016, while summer flounder has been at a consistent high. Recent estimates of knobbed whelk relative abundance have been less variable than previously seen, with estimates since 2016 being similar to those seen before 2012. These results provide the first estimates for whelk population trends in the mid-Atlantic region and add to the growing knowledge of summer flounder relative abundance in the area. In Chapter 3, I applied the hurdle models developed in Chapter 1 to estimate the total abundance of HSC in the Delaware Bay area. To do this, the bottom temperature and salinity had to be estimated for each geographic cell. This was accomplished by developing two spatio-temporal variograms which allowed me to estimate either variable at an unmeasured point and time based on its spatial and temporal distance from a measured value in a process known as spatio-temporal kriging. The results showed that night estimates of total abundance were consistently higher than daytime estimates and that estimates from September or November resulted in the highest estimated total abundance for all demographic groups. The results suggest that when using September model-based estimates at night to compare against the design-based approach, nearly a third of all previous design-based estimates significantly underestimated the total abundance of HSC in the Delaware Bay area. This outcome could justify ASMFC increasing recommended harvest limits for mature individuals if that action aligns with the goals of their adaptive resource management (ARM) framework.

Thesis (Ph. D.)--Georgia Institute of Technology, 2006. / Title from PDF t.p. (viewed on Oct. 28, 2006). Marc Weissburg, Committee Chair ; Mark Hay, Committee Member ; Lin Jiang, Committee Member ; David Dusenbery, Committee Member ; Don Webster, Committee Member. Includes bibliographical references (p. 115-122).

Hard clams, Mercenaria mercenaria, are slow-moving organisms that are heavily preyed upon by both blue crabs and knobbed whelks in coastal Georgia. Hard clams are unable to escape from these predators, and when found, are commonly injured and/or consumed. Thus, their best survival strategy is to avoid their predators. In this study, we compared changes in clam behavior when exposed to blue crab and knobbed whelk predators. Clams reduced their feeding time when exposed to crabs and whelks, exudates from these predators, and to injured conspecifics. In a field experiment, we compared clam survival when caged predators where near clam beds vs. controls with empty cages. Clam survival was significantly higher when caged crabs or whelks were near, suggesting that clams detected these predators, reduced their feeding time, and were less apparent to ambient consumers. In lab behavioral assays, clams were less responsive to blue crabs in turbulent flows, and in the field, turbulence reduced the distance clams reacted to blue crabs. Previous studies have shown that blue crabs turbulence also diminishes blue crab foraging efficiency, and we conducted a field experiment to determine how turbulence affected clam-crab interactions. Our results suggest that predation intensity is greatest at intermediate turbulence levels, and lowest in flows with low and high turbulence levels. We attribute this pattern of predation intensity to differential effects of turbulence on the sensory abilities of crabs and clams. That is, in low turbulent flows, clams have a sensory advantage over crabs, and initiate avoidance behaviors before they are detected. However, as turbulence increases, clam perception diminishes faster than crabs, switching the sensory advantage to crabs, and making clams more vulnerable to consumers. In highly turbulent flows, crab perception declines at a rate faster than clams, and the sensory advantage returns to clams.

Made available in DSpace on 2016-08-15T20:31:28Z (GMT). No. of bitstreams: 1 HiagosFFL_DISSERT.pdf: 794630 bytes, checksum: b9112529e3742dd0a6d9fbab5a1a63fa (MD5) Previous issue date: 2016-02-23 / In animal production, where food represents about 70% of the cost of production, the supply of calcium to participate in large numbers in feed formulations, become the use of mineral origin organic important to maximize animal performance and minimize costs. Taking up the importance of integrity and eggshell strength in the conservation of its nutritional and microbiological property that mean the product quality and food safety, these features become essential for the approval of the egg by the consumer market. The objective was to evaluate different sources of calcium in diets on growth performance and eggs quality of laying hens light. The cages are equipped with linear feeder in galvanized sheet and drinker type nipple. The birds were housed in shed screen, in masonry, with clay tile roof equipped with 120 metal cages (0,20m x 0,40m x 0,40m) galvanized wire provided sideboard eggs arranged in four rows with corridor central. We used 120 birds of Bankiva line in the initial laying phase, starting the experiment when animals were in egg production and body weight even, the experimental period was 22-34 weeks old and the birds distributed in a completely randomized design with four treatments. Each treatment had 10 repetitions with 3 birds each unit experimental and consisted of four experimental diets with different sources of calcium: limestone, búzio shell flour (Anomalocardia brasiliana), oyster shell flour (Crassostrea brasiliana) and egg shell flour. Were evaluated: egg production rate, feed intake, feed conversion, absolute and relative weight of yolk, albumen and shell, height and width of the egg, specific gravity, yolk color, eggshell thickness, Haugh unit, albumen and yolk index. Had no significant effect (P> 0.05) between the treatments, for performance variables, egg production rate had a significant effect (P <0.05), its worst result egg shell flour. The egg shell flour was the only treatment showed significantly (P <0.05) for the weight, height and width of the egg, specific gravity, height and width albumen yolk, yolk absolute weight, albumen and shell, relative weight of the albumen and shell thickness, with worse results compared to the other treatments. Therefore, limestone, búzio shell flour and oyster shell flour, can be used as a source of calcium for laying rations / Na produção animal, onde a alimentação representa cerca de 70% do custo de produção, o suprimento de cálcio por participar em grande quantidade nas formulações de rações, torna a utilização de minerais de origem orgânica importante para se maximizar o desempenho animal e minimizar os custos. Levando-se a importância da integridade e resistência da casca do ovo na conservação de sua propriedade nutricional e microbiológica que significam a qualidade do produto e segurança alimentar, estas características tornam-se essenciais para a aprovação do ovo por parte do mercado consumidor. Diante disso, objetivou-se avaliar diferentes fontes de cálcio em rações, no desempenho produtivo e qualidade de ovos de poedeiras de linhagem leves. As aves foram alojadas em galpão telado, em alvenaria, com cobertura de telha de barro equipado com 120 gaiolas metálicas (0,20m x 0,40m x 0,40m) de arame galvanizado providas de aparador de ovos, dispostas em quatro fileiras com corredor central. As gaiolas são equipadas com comedouro linear em chapa galvanizada e bebedouro do tipo nipple. Foram utilizadas 120 aves da linhagem Bankiva em fase inicial de postura, iniciando o experimento quando os animais estavam com produção de ovos e peso corporal uniforme, o período experimental compreendeu de 22 a 34 semanas de idade sendo as aves distribuídas em delineamento inteiramente ao acaso com quatro tratamentos. Cada tratamento composto por 10 repetições com 3 aves por unidade experimental e sendo constituídos por quatro rações experimentais, com diferentes fontes de cálcio: calcário calcítico, farinha de concha búzio (Anomalocardia brasiliana), farinha de concha de ostra (Crassostrea brasiliana) e farinha de casca de ovo. Foram avaliados: taxa de postura, consumo de ração, conversão alimentar, peso absoluto e relativo de gema, albúmen e casca, peso, altura e largura do ovo, gravidade específica, espessura de casca, unidade Haugh, índice de albúmen e de gema. Não foram significativas (P>0,05) entre os tratamentos estudados, as variáveis de desempenho, exceto taxa de postura, a qual obteve efeito significativo (P<0,05), tendo resultado inferior para o tratamento com a farinha de casca de ovo. A farinha de casca de ovo foi o único tratamento que apresentou efeito significativo (P<0,05), para as variáveis de peso, altura e largura do ovo, gravidade específica, altura da gema e largura do albúmen, peso absoluto de gema, albúmen e casca, peso relativo do albúmen e espessura de casca, apresentando resultados inferiores em comparação aos demais tratamentos. Portanto, o calcário calcítico, farinha de concha de búzio e farinha de concha de ostra, por apresentarem uma maior granulometria demonstrou melhores resultados, podendo ser utilizadas como fonte de cálcio em rações de poedeiras de linhagem leves