966 resultados para Maine crabs


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Mode of access: Internet.

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Description based on: Fiscal year 1981.

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Cover title.

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Description based on: 1993.

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Mode of access: Internet.

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Factors influencing the rate of cannibalism in juvenile blue-swimmer crabs Portunus pelagicus were investigated under controlled conditions using time-lapse video recordings. This study was undertaken to improve blue-swimmer crab culture and experimentally addressed (1) prey vulnerability (2) cannibal-victim interactions, and (3) activity patterns of juveniles in varying degrees of refuge. Crabs used in the study were aged 15 weeks and sorted into two size classes; small (less than or equal to 60 mm carapace width (CW)) and large (greater than or equal to65 mm CW) of a similar sex ratio. Vulnerability and thus survival was influenced by body size variation, moult stage and refuge availability. Crabs with carapace width less than or equal to 60 mm were more vulnerable than larger individuals, as indicated by significant differences in survival rates. As predicted, juveniles in transition stages associated with ecdysis were especially vulnerable. Premoult (redliner) crabs appeared to be in a high state of agitation as evidenced by the frequency of agonistic encounters and this may be a contributing factor to the high mortality observed at this critical premoult stag. increases in refuge density increased survival of juveniles proportionally, indicating that the quantity of shelter is important for reducing cannibalism in this species. Cannibal-victim interactions were frequently asymmetrical in terms of size and moult stage. Cannibals were significantly heavier than victims, and were predominantly at intermoult stage. Sexual biases among cannibals and victims were not found in this study. Activity patterns of juveniles were influenced by the experimental conditions. Crabs provided with high refuge showed reduced aggressive activity and increased time spent resting, but unchanged locomotion or feeding activity. Regular grading as well as the presence of suitable shelter for newly moulted crabs is recommended for improving culture of P. pelagicus. Research into inducing synchronous moulting may also yield promising results. (C) 2004 Elsevier B.V. All rights reserved.

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This thesis is concerned with Maine de Biran’s and Samuel Taylor Coleridge’s conceptions of will, and the way in which both thinkers’ posterities have been affected by the central role of these very conceptions in their respective bodies of thought. The research question that animates this work can therefore be divided into two main parts, one of which deals with will, while the other deals with its effects on posterity. In the first pages of the Introduction, I make the case for a comparison between two philosophers, and show how this comparison can bring one closer to truth, understood not in objective, but in subjective terms. I then justify my choice by underlining that, in spite of their many differences, Maine de Biran and Samuel Taylor Coleridge followed comparable paths, intellectually and spiritually, and came to similar conclusions concerning the essential activity of the human mind. Finally, I ask whether it is possible that this very focus on the human will may have contributed to the state of both thinkers’ works and of the reception of those works. This prologue is followed by five parts. In the first part, the similarities and differences between the two thinkers are explored further. In the second part, the connections between philosophy and singularity are examined, in order to show the ambivalence of the will as a foundation for truth. The third part is dedicated to the traditional division between subject and object in psychology, and its relevance in history and in moral philosophy. The fourth part tackles the complexity of the question of influence, with respect to both Maine de Biran’s and Coleridge’s cases, both thinkers being indebted to many philosophers of all times and places, and having to rely heavily on others for the publication, or the interpretation of their own works. The fifth part is concerned with the different aspects of the faculty of will, and primarily its relationship with interiority, as incommensurability, and actual, conditioned existence in a certain historical and spatial context. It ends with a return to the question of will and posterity and an announcement of what will be covered in the main body of the thesis. The main body is divided into three parts:‘L’émancipation’, ‘L’affirmation, and ‘La projection’. The first part is devoted to the way Maine de Biran and Samuel Taylor Coleridge extricated themselves from one epistemological paradigm to contribute to the foundation of another. It is divided in four chapters. The first chapter deals with the aforementioned change of paradigm, as corresponding to the emergence of two separate but associated movements, Romanticism and what the French philosopher refers to as ‘The Age of History’. The second chapter concerns the movement that preceded them, i.e. the Enlightenment, its main features according to both of our thinkers, and the two epistemological models that prevailed under it and influenced them heavily in their early years: Sensationism (Maine de Biran) and Associationism (Coleridge). The third chapter is about the probable influence of Immanuel Kant and his followers on Maine de Biran and Coleridge, and the various facts that allow us to claim originality for both thinkers’ works. In the fourth chapter, I contrast Maine de Biran and Coleridge with other movements and thinkers of their time, showing that, contrary to their respective thoughts, Maine de Biran and Coleridge could not but break free from the then prevailing systematic approach to truth. The second part of the thesis is concerned with the first part of its research question, namely, Maine de Biran’s and Coleridge’s conceptions of the will. It is divided into four chapters. The first chapter is a reflection on the will as a paradox: on the one hand, the will cannot be caused by any other phenomenon, or it is no longer a will; but it cannot be left purely undetermined, as if it is, it is then not different from chance. It thus needs, in order to be, to be contradictorily already moral. The second chapter is a comparison between Maine de Biran’s and Coleridge’s accounts of the origin of the will, where it is found that the French philosopher only observes that he has a will, whereas the English philosopher postulates the existence of this will. The comparison between Maine de Biran’s and Coleridge’s conceptions of the will is pursued in the third chapter, which tackles the question of the coincidence between the will and the self, in both thinkers’ works. It ends with the fourth chapter, which deals with the question of the relationship between the will and what is other to it, i.e. bodily sensations, passions and desires. The third part of the thesis focuses on the second part of its research question, namely the posterity of Maine de Biran’s and Coleridge’s works. It is divided into four chapters. The first chapter constitutes a continuation of the last chapter of the preceding part, in that that it deals with Maine de Biran’s and Coleridge’s relations to the ‘other’, and particularly their potential and actual audience, and with the way these relations may have affected their writing and publishing practices. The second chapter is a survey of both thinkers’ general reception, where it is found that, while Maine de Biran has been claimed by two important movements of thoughts as their initiator, Coleridge has been neglected by the only real movement he could have, or may indeed have pioneered. The third chapter is more directly concerned with the posterities of Maine de Biran’s and Coleridge’s conceptions of will, and attempts to show that the approach to, and the meaning of the will have evolved throughout the nineteenth century, and in the French Spiritualist and the British Idealist movements, from an essentially personal one to a more impersonal one. The fourth chapter is a partial conclusion, whose aim is to give a precise idea of where Maine de Biran and Coleridge stand, in relation to their century and to the philosophical movements and matters we are concerned with. The conclusion is a recapitulation of what has been found, with a particular emphasis on the dialogue initiated between Maine de Biran and Coleridge on the will, and the relation between will and posterity. It suggests that both thinkers have to pay the price of a problematic reception for the individuality that pervades their respective works, and goes further in suggesting that s/he who chooses to found his individuality on the will is bound to feel this incompleteness in his/her own personal life more acutely than s/he who does not. It ends with a reflection on fixedness and movement, as the two antagonistic states that the theoretician of the will paradoxically aspires to.

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Stomach contents analysis (SCA) provides a snap-shot observation of a consumer's diet. Interpretation of SCA data can be complicated by many factors, including variation in gastric residence times and digestion rates among prey taxa. Although some SCA methods are reported to efficiently remove all stomach contents, the effectiveness of these techniques has rarely been tested for large irregular shaped prey with hard exoskeletons. We used a controlled feeding trial to estimate gastric residency time and decomposition rate of a large crustacean prey item, the Blue Crab (Callinectes sapidus), which is consumed by American Alligators (Alligator mississippiensis), an abundant apex predator in coastal habitats of the southeastern United States. The decomposition rate of C. sapidus in the stomachs of A. mississippiensis followed a predictable pattern, and some crab pieces remained in stomachs for at least 14 days. We also found that certain portions of C. sapidus were prone to becoming caught within the stomach or esophagus, meaning not all crab parts are consistently recovered using gastric lavage techniques. However, because the state of decomposition of crabs was predictable, it is possible to estimate time since consumption for crabs recovered from wild alligators. This information, coupled with a detailed understanding of crab distributions and alligator movement tactics could help elucidate patterns of cross-ecosystem foraging by the American Alligator in coastal habitats.

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5. Acknowledgements This research was supported by grants from the National Natural Science Foundation of China (Nos. 31172438 and U1205123), the Natural Science Foundation of Fujian Province (No. 2012J06008 and 201311180002) and the projects-sponsored by SRF. TW received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.

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Animal pain is defined by a series of expectations or criteria, one of which is that there should be a physiological stress response associated with noxious stimuli. While crustacean stress responses have been demonstrated they are typically preceded by escape behaviour and thus the physiological change might be attributed to the behaviour rather than a pain experience. We found higher levels of stress as measured by lactate in shore crabs exposed to brief electric shock than non-shocked controls. However, shocked crabs showed more vigorous behaviour than controls. We then matched crabs with the same level of behaviour and still found that shocked crabs had stronger stress response compared with controls. The finding of the stress response, coupled with previous findings of long-Term motivational change and avoidance learning, fulfils the criteria expected of a pain experience.

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Insights into the potential for pain may be obtained from examination of behavioural responses to noxious stimuli. In particular, prolonged responses coupled with long-term motivational change and avoidance learning cannot be explained by nociceptive reflex but are consistent with the idea of pain. Here, we placed shore crabs alternately in two halves of a test area divided by an opaque partition. Each area had a dark shelter and in one repeated small electric shocks were delivered in an experimental but not in a control group. Crabs showed no specific avoidance of the shock shelter either during these trials or in a subsequent test in which both were offered simultaneously; however they often emerged from the shock shelter during a trial and thus avoided further shock. More crabs emerged in later trials and took less time to emerge than in early trials. Thus, despite the lack of discrimination learning between the two shelters they used other tactics to markedly reduce the amount of shock received. We note that a previous experiment using simultaneous presentation of two shelters demonstrated rapid discrimination and avoidance learning but the paradigm of sequential presentation appears to prevent this. Nevertheless, the data show clearly that the shock is aversive and tactics, other than discrimination learning, are used to avoid it. Thus, the behaviour is only partially consistent with the idea of pain.