Im Rahmen eines selbst-konsistenten Outer-Gap-Modells der Pulsar-Magnetosphäre wurde die elektromagnetische sehr hochenergetische Strahlung des Crab-Pulsars simuliert. Dies wurde parallel anhand zweier verschiedener Fälle getan, die sich in den angenommenen Gleichungen für die elektrische Feldstärke und für den Krümmungsradius der magnetischen Feldlinien unterscheiden. Die Kinetik der geladenen Teilchen bei ihrer Propagation durch die Outer Gap wurde unter Einbeziehung von Krümmungsstrahlung, inverser Compton-Streuung und Triple Paarbildung betrachtet. Das theoretisch simulierte Spektrum wird mit von Fermi-LAT und von den MAGIC Teleskopen gemessenen Daten verglichen. / In a self-consistent model of outer vacuum gaps of pulsar magnetospheres, the gamma-ray output of the Crab pulsar is determined and compared to observational data by the Fermi Large Area Telescope and the Major Atmospheric Gamma-ray Imaging Cherenkov telescopes. Incorporating curvature radiation, inverse-Compton scattering and triplet pair production, the kinetics of the accelerated electrons are considered, energy losses are compared and the emerging spectra are computed. It is found that losses are dominated by curvature radiation emission. Triplet pair production may be relevant concerning particle multiplication and inverse-Compton up-scattering of the curvature photons is forming the spectral energy distribution at very high energies.

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Traditional views of food web dynamics have characterized species interactions as linear and direct. However, modern food web theory suggests that interactions can also be nonlinear and indirect, so that disturbance at one trophic level is transmitted throughout the community. Many previous studies have demonstrated that the removal of top predators from terrestrial ecosystems can have broad-scale impacts on community ecology. I examined the direct and indirect effects of raccoon removal from sea turtle nesting beaches in east-central Florida during the summers of 2003 and 2004. Raccoon and ghost crab predation are among the highest causes of egg mortality for sea turtles in Florida and raccoons are intraguild predators of ghost crabs. Because of the damage done to sea turtle nests, raccoons have been removed from some beaches during the sea turtle nesting season. I compared the diet and demography of a raccoon population that had experienced two decades of raccoon removal to a population that had previously been unmanipulated. I found that long-term raccoon removal had created a significantly male-biased sex ratio in that population. I also examined the indirect effects of raccoon removal by comparing the abundances of raccoons and ghost crabs at four study sites using passive tracking plots. My data suggest intraguild predation by raccoons limits ghost crab abundance and that reduced raccoon abundance allowed ghost crab abundance to increase, resulting in a net increase in sea turtle egg predation. These results support my hypothesis that intraguild predation of ghost crabs by raccoons is an influential interaction on sea turtle nesting beach community dynamics.

The process wastewater from three blue crab processing plants in Virginia was characterized. Most of these effluent streams were highly concentrated. For example, the retort water from the cookers exhibited the following concentrations: BOD₅ = 14,000-29,000 mg/L, TSS = 650-6,200 mg/L, TKN-N = 2,500-4,000 mg/L, NH3-N = 70-160 mg/L and Total Phosphorus= 100-185 mg/L. One process effluent contained chloride concentrations exceeding 100,000 mg/L. Analysis of production and effluent characterization data from two mechanized plants revealed that wastewater volumes and concentrations varied significantly between the two plants. Both plants exhibited highly variable daily and seasonal production. Treatability studies were completed on the process wastewater because discharge limits exist for TSS, Oil and Grease and in some cases BODs and ammonia. Settling and filtration studies were performed on these effluents. The organics and nutrients in the wastes were highly soluble and limited reduction of COD (18-65% reduction), BOD₅ (9-49% reduction), TKN-N (9-62% reduction), and TP (10-66%) was achieved by filtration. Acidification of the concentrated effluents caused some coagulation of the contents. Coagulation by pH adjustment was most effective between pH 3.0-4.0. TSS removals of 76- 93%, and BOD5 removals of 6-30% were achieved by pH adjustment, thereby showing promise as a pretreatment method. Anaerobic biological treatment systems appear promising for the treatment of wastewater from blue crab processing plants (effluent BOD₅s ranged from 150-420 mg/L), especially for cooker effluent. However, there is concern that salt from the Harris Claw operation will decrease anaerobic treatment performance and that effluent NH3 and TSS levels will need to be further reduced to meet permit limits. Pretreatment of process wastewater by means of pH adjustment did not improve anaerobic treatability. / Master of Science

Commercial shrimpers in the Mississippi Sound frequently encounter marine debris in their nets, which results in loss of time, loss of catch, and added repair costs. Yet, the spatial and temporal distribution of this marine debris and the economic impact faced by shrimpers in the Mississippi Sound is not well known. This study measured the quantity and economic impact of marine debris by surveying 20 commercial shrimpers. Participants logged marine debris encounters, fishing data, and damage to fishing gear during the July 2020 through December 2020 shrimping season. It was found that shrimpers encounter marine debris 19% of all tows, and the majority of all marine debris encountered by shrimpers (79%) was derelict crab traps. Additionally, 10% of all tows reported direct impacts.

This study examined the effects of blood extraction on the survival of horseshoe crabs and performed a preliminary investigation into amebocyte maintenance in vitro. Hemolymph volume of L. polyphemus was estimated over a representative size range of adults. Hemolymph volume expressed as a percentage of wet body weight was 25 ± 2.2% (mean ± S.D.) for males and 25 ± 5.1% for females. Mortality associated with blood extraction was evaluated for horseshoe crabs bled 0, 10, 20, 30, and 40% of their estimated hemolymph volume (unstressed group, N = 200). Mortality associated with the same bleeding levels was evaluated in horseshoe crabs that underwent simulated transport and handling procedures of the biomedical industry's bleeding process (stressed group, N = 195). Mortality rates of the unbled crabs were not significantly different between the stressed group and unstressed group. Of the bled animals, there was a higher (8.3%) mortality rate in the stressed group, than that (0%) in the unstressed group (P < 0.0001). Within the stressed group, mortality was significantly associated with bleeding (P = 0.0088). Horseshoe crab serum and a variety of standard insect cell culture media were evaluated for their effects on amebocyte morphology and viability after 7 days of maintenance in vitro. Horseshoe crab serum-supplemented cultures had significantly higher cell viability than serum-free cultures (N = 6; P = 0.0147). Significant differences in amebocyte viability were identified among the six insect cell culture media tested (N = 36; P < 0.0001), with the highest amebocyte viability of 77.2 ± 5.1% (mean ± S.D.) in Grace's Insect Medium without serum. Information gained from this study provides guidance on altering biomedical bleeding protocols to decrease horseshoe crab stress and mortality, and advances information on amebocyte culture medium selection, both of which contribute to decreasing the biomedical industry's impact on the horseshoe crab population. / Master of Science

Crab meat is important to the economy of coastal Virginia. The objectives of this study were to complete a shelf-life study on two different packaging styles of fresh crab meat and to test the inhibition capabilities of Carnobacterium piscicola against the pathogen, Listeria monocytogenes. In a shelf-life study, a 12 ounce food grade polyethylene traditional snap-lid container of fresh crab meat was compared to an 8 ounce SimpleStep® trays with Cryovac™ film of equally fresh crab meat sealed with 10,000 cc/m2/24hr oxygen transmission rate (OTR) film. Eleven g samples were used for the microbial shelf-life study conducted at 4°C for 12 days. Aerobic plate counts of crab meat indicated microbial growth from the SimpleStep® trays with Cryovac™ film in 10,000 cc/m2/24hr OTR versus the polyethylene snap-lid was not significant (P>0.05). In objective two, 25 g samples of fresh and pasteurized blue crab (Callinectes sapidus) meat were inoculated with 0.1ml of each, C. piscicola and L. monocytogenes. Three different concentrations of the inoculation levels were studied on select days at both 4°C and 10°C. Microbial spoilage was defined as 107 CFU/g. In fresh crab meat, at both 4°C and 10°C, crab meat spoilage occurred at 7 days or less. In the pasteurized crab meat, at 4°C and 10°C, spoilage did not occur prior to 26 days, and studies were terminated at 28 days of storage. The growth of the two organisms in fresh crab meat was found to be significant for the differing concentration levels and sampling days (P<0.05). The growth of the two organisms in pasteurized crab meat was significant for different concentration levels, sampling days and temperature (P<0.05). In both fresh and pasteurized crab meat, regardless of the inoculation ratios, the L. monocytogenes and C.piscicola followed similar growth trends, but L. monocytogenes was higher in the 2:2 CFU/g concentration and lower at the 6:2 CFU/g concentration level. Although C. piscicola did not completely inhibit L. monocytogenes growth at any concentration ratio, some inhibition was observed. / Master of Science

Commercial farming of mud crab Scylla serrata is a significant industry throughout South East Asia. The limited scientific knowledge of mud crab nutritional requirements and digestive processes, however, is recognised as a major constraint to the future growth of this industry. To better understand the mechanisms of digestion in the mud crab we have analysed the diversity of digestive enzymes from the hepatopancreas. Significant protease, amylase,cellulase and xylanase activities were detected in soluble extracts from this organ. Temperature profiles for all enzymes were basically similar with optimal activities observed at 500C. Examination of pH tolerance revealed optimal activities for protease and amylase at pH 7.0 while optimal activities for cellulase and xylanase were observed at pH 5.5. Under optimum conditions,protease and amylase activities were approximately two orders of magnitude greater than those seen for either cellulase or xylanase. Interestingly, hepatopancreatic extracts were able to liberate glucose from either starch or carboxymethyl (CM)-cellulose suggesting that a range of carbohydrates may be utilised as energy sources. The effects of dietary carbohydrates on feed digestibility, digestive enzyme levels and growth were also studied by inclusion of additional starch or CM-cellulose at the expense of casein in formulated diets. It was shown that amylase, cellulase and xylanase activities in extracts from the hepatopancreas were highest in mud crabs fed diets containing 47% carbohydrate. Based on the findings, we suggest that the ability of the mud crab to modulate digestive enzyme activities may represent a mechanism to maximise access to essential nutrients when the dietary profile changes.

Predators can have large effects on prey populations and on the structure and function of communities. In addition to direct consumption of prey, predators often cause prey to alter their foraging behavior, habitat selection, and morphology. These non-lethal effects of predators can propagate to multiple trophic levels and often exert equal or larger effects upon communities than those of direct consumption. For non-lethal predatory effects to occur, prey must detect and respond to predation risk. While the importance of information transfer in this process has been realized, few studies explore how prey responses are influenced by predator characteristics and environmental conditions that influence the transmission of cues indicative of predation risk. In this dissertation I investigate factors that influence how a single prey species evaluates and responds to predation risk. Here, I examined: 1) the type and nature of cues prey use to evaluate predator risk; 2) how predator identity, predator diet, and the relative risk of predators influence prey response to predation risk; 3) how hydrodynamic conditions influence the delivery of predator cues; 4) how biogeographic trends in predator distribution influence prey response to predation risk; and 5) how genetic structure might vary according to prey geographic location and habitat. To address these questions, I used a common intertidal model system consisting of the rocky intertidal whelk Nucella lapillus (Linnaeus, 1758) and a suite of its predators, the native rock crab Cancer irroratus (Say, 1817), Jonah crab Cancer borealis (Stimpson, 1859), and the invasive green crab Carcinus maenas (Linnaeus, 1758). Nucella use chemical cues emanating from their most common predator (Carcinus maenas) and crushed conspecifics to evaluate predation risk. Nucella from different habitats experience different levels of predation risk, and Nucella from habitats with high levels of predation had larger antipredatory responses to predator risk cues than Nucella that experienced less predation. These chemical cues indicative of predation risk are influenced by hydrodynamic conditions, and Nucella have the strongest anti-predatory response in flow velocities of u= ~4- 8 cm s^-1. Furthermore, Nucella from geographic regions where green crabs are historically absent did not elicit anti-predatory responses, while Nucella from regions where green crabs are common frequently responded. Findings from my dissertation research demonstrate that prey detection and response to predation risk is highly dependent upon predator identity, predator diet, environmental forces, and biogeographic patterns in predator and prey distributions.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / The mangrove crab, Ucides cordatus is one of the most shellfish produced in Brazil, but his consumption becomes scarce during closed season. This study aimed development of freezedried products of the mangrove crab stored at ambient temperature and analyze the effect of lyophilization in relation to physicalchemical, microbiological, nutritional and sensory characteristics. Two products were developed: a "freeze-dried crab meat" and "freeze-dried crab cone". The product quality was evaluated through sensory tests, microbiological, TBARS, water activity, water holding capacity, centesimal composition, nutritional value, fatty acids content, and amino acid profile of volatile compounds. The best formulation of the "freeze-dried crab cone", acceptance by the tasters, corresponded to that contained only crab meat and dehydrated condiments. The lyophilized products were stored in two different packages (laminated polyethylene terephthalate) in the period 0 to 120 days of storage at ambient temperature. Both products did not suffer microbiological and sensory changes during this period, occurring only a slight increase in water activity and moisture. As to biochemical characteristics, freeze-dried products showed all essential amino acids in quantities greater than those recommended by FAO. In the freeze-dried products was higher concentration of fatty acids when compared to the fresh beef. The volatile compounds were detected in highest concentrations after rehydration of the product in heated water ( 100  C), mainly in relation to groups of aldehydes (hexanal and pentanal) and alcohol (2-methyl-3- phenyl-propanal and 3,7-dimethyl-1,6-octadien-3-ol). In general, the total volatile compounds were lowered after 240 days of storage at ambient temperature. Therefore, with this research was observed the feasibility of developing lyophilized products ("land crab freeze-dried meat" and "freeze-dried crab cone") the basis of land crab meat can be stored at ambient temperature with sensory attributes, physicalchemical and microbiological characteristics acceptable. / O caranguejo-uÃÃ, Ucides cordatus à um dos crustÃceos mais produzido no Brasil, porÃm o seu consumo torna-se escasso no perÃodo do defeso da espÃcie. Desta forma, o objetivo deste trabalho foi o desenvolvimento de produtos liofilizados do caranguejo-uÃa armazenados à temperatura ambiente e analisar o efeito da liofilizaÃÃo em relaÃÃo Ãs caracterÃsticas fÃsicoquÃmicas, microbiolÃgicas, nutricionais e a sensoriais. Foram desenvolvidos dois produtos: a âcarne de caranguejo liofilizadaâ e âcasquinha de caranguejo liofilizadaâ. A qualidade dos produtos foi avaliada, atravÃs de anÃlises sensoriais, microbiolÃgicas, TBARS, atividade de Ãgua, capacidade de retenÃÃo de Ãgua, composiÃÃo centesimal, valor nutricional, teor de Ãcidos graxos, perfil de aminoÃcidos e dos compostos volÃteis. A formulaÃÃo da âcasquinha de caranguejo liofilizadaâ de melhor aceitaÃÃo pelos degustadores correspondeu Ãquela que continha somente carne de caranguejo e condimentos desidratados. Os produtos liofilizados foram acondicionados em dois tipos de embalagens (laminada e tereftalato de polietileno) no perÃodo de 0 a 120 dias de armazenamento à temperatura ambiente. Ambos os produtos, nÃo sofreram alteraÃÃes microbiolÃgicas e sensoriais, neste perÃodo, ocorrendo apenas um leve aumento da atividade de Ãgua e umidade. Quanto Ãs caracterÃsticas bioquÃmicas, os produtos liofilizados apresentaram todos os aminoÃcidos essenciais em quantidades superiores Ãs recomendadas pela FAO. Nos produtos liofilizados houve maior concentraÃÃo dos Ãcidos graxos quando comparados com a carne in natura. Os compostos volÃteis foram detectados em maiores concentraÃÃes apÃs a reidrataÃÃo dos produtos, em Ãgua aquecida (Â100 ÂC), principalmente, no que se refere aos grupos dos aldeÃdos (hexanal e pentanal) e alcoÃis (2- metil-3-fenil-propanal e 3,7-dimetil-1,6-octadien-3-ol). De modo geral, o total dos compostos volÃteis foi reduzido apÃs 240 dias de armazenagem à temperatura ambiente. Portanto, com essa pesquisa observou-se a viabilidade de desenvolver produtos liofilizados (âcarne de caranguejo-uÃà liofilizadaâ e uma âcasquinha de caranguejo liofilizadaâ) a base de carne de caranguejo-uÃà que podem ser estocados a em temperatura ambiente com caracterÃsticas sensÃrias, fÃsico-quimica e microbiolÃgica aceitÃveis.