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This PhD studies the ecology and fishery of the veined squid Loligo forbesi in Scottish waters by making use of different spatial and statistics tools, such as Geographic Information System (GIS), Generalised Additive Models (GAMs) and Geostatistics. The PhD thesis is divided in 6 chapters, arranged in a sequential order driven by the hypothesis and question which have arisen throughout the study. Chapter 1 aims to provide a general introduction of the objectives, state of the art and techniques utilised along all this work. Chapter 2 reports the use of Geographical Information Systems (GISs) to study squid resources in the North East Atlantic. Long-term monthly average Landings Per Unit of Effort (LPUE) series are mapped against SST, SBT, SSS, SBS and Depth to reveal plausible spatio-temporal relationships between oceanographic conditions and squid abundance. Hypotheses about the squid distribution and abundance in relation to environment, habitat selection and spatial migration are suggested. Chapter 3 reports a GAM application to describing intra-annual and inter-annual variation in squid abundance in Scottish waters is also reported. Geostatistical tools were applied in chapter 4 to model spatial patterns in squid abundance in Scottish waters to explore spatial heterogeneity and distribution. Spherical and gaussian model variograms and neighbourhood analysis were made. Results provide enough evidence to indicate that there are differences between the east and the west coast of Scotland. Chapter 5 reports a two-stage model to study distribution and abundance by a Binomial and Gamma sequential approach. GAMs and Regression trees on two stages were utilised using all the available environmental variables. These non-parametric modelling was used to forecast probability of presence and abundance of 1994 by a environmental data set. Finally, chapter 6 comprises the conclusions of the work, particularly from a point of view of the ecology of the squid.

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The aim of this investigation was to study molluscan tissue regeneration, as exemplified by wound healing of the mantle edge in Arion hortensis, and to attempt an analysis of blastema formation. As a necessary preliminary the structure of the mantle edge was investigated. It consists of a glandular epithelial fold within which is a zone of connective tissue composed of a dorsal pigmented region, a median vascular region through which ramifies a lattice-work of smooth muscle fibres, and a ventral region containing a mat of muscle fibres. The structural and metabolic changes following wounding by excision were studied and where possible related. Immediately after wounding the undamaged muscle fibres adjacent to the wound contract and the meshes of the lattice close, thus temporarily constricting the blood sinuses and arresting bleeding. Wound closure is achieved initially by blood-cell agglutination and finally by coverage of the injured surface by the epithelial cells. Damaged tissue is removed from the wound by histolysis and phagocytosis. A blastema then forms at the injured surface; its cells grow, divide, and differentiate replacing the excised tissue. Differentiation begins in those regions adjacent to the uninjured tissue and extends into the rest of the blastema. Changes in the distribution of acid and alkaline phosphatase, ribonucleic acid, glycogen, and sulphydryl and disulphide groups were noted. The method of blastema formation was analysed by the following techniques: carmine marking of epithelial cells, tissue culture of isolated blastemata, and colchicine treatment of wounded animals. It was shown that both immigrant and indigenous cells contribute to the blastema, the majority of the blastema cells being immigrant. Epithelial and connective tissue components of the regenerate arise from immigrant cells while muscle tissue develops from indigenous material.

The phagocytic system of the periwinkle and the in vivo and in vitro response towards foreign particles was studied by light and electron microscopy, using carmine, yeast (S, cereviciae), human erythrocytes, bacteria (E. coli) and viruses (lambda bacteriophage) as test-particles. The involvement of humoral factors was studied by haemagglutination/haemagglutination-inhibition experiments. It was found that: 1) Injected markers are cleared by diapedesis through the epithelium covering the head, the mantle cavity and the foot (exluding the sole of the foot). Emboli formed in the circulation are cleared relatively quickly by circulating haemocytes; haemocytes containing the marker may persist for longer periods in adjacent tissues but eventually find their way to diapedesis sites through circulatory routes. Clearance of carmine is not completed during the observation time (64 days), whereas yeast appears to elicit a much quicker response. Intracellular digestion may enhance the removal of injected markers in the case of digestible materials. 2) Periwinkle haemocytes form a homogenous population with respect to morphology (as determined by light and electron microscopy) and function (all haemocytes appear to be capable of migrational and phagocytic responses towards injected markers). The haemocytes are avidly phagocytic when challenged in vivo or in vitro with vertebrate RBC or yeast; around 90% of the haemocytes contain one or more particles in 30 min, and the average content of each phagocyte is 2.2 particles. Additional uptake apparently proceeds at a steady state which is considered to depend upon the rate of intracellular digestion or membrane synthesis. The correlation of in vitro to in vivo results is discussed, and lower values in the latter case are attributed to diapedesis. 3) The connective tissue of the periwinkle is composed of ground substance with fibres resembling collagen, and 5 types of cells, i.e. pore cells, calcium cells, supportive cells, granular cells and tissue-associated haemocytes. Among these, phagocytosis of injected markers, i.e. human RBC, bacteria (E. coli) and virus particles (lambda bacteriophage) is restricted to haemocytes, which by their morphology cannot be classified as a separate subset, and so it appears that the periwinkle does not contain fixed or tissue resident phagocytes. Reports of fixed phagocytes in other invertebrates are discussed, as well as functional aspects of the pore cell.4) The haemolymph of the periwinkle contains a factor which agglutinates several types of vertebrate erythrocyte in addition to bacteria (E. coli) and yeast (S. cerevisiae). The active part of this molecule is a protein, and so it classifies as a lectin (Goldstein et al 1980). Agglutination of H-RBC was inhibited most strongly by L-xylose, but moderate inhibition was obtained with other pentoses (D-ribose, D-xylose, a-L-fucose). The lectin appears to function as a defence molecule, since (1) a moderate increase is found in circulating levels upon antigenic challenge (human erythrocytes), and (2) particles which are agglutinated by the lectin are phagocytosed more avidly than particles which fail to agglutinate. The baseline level of the lectin is quite variable between individuals, and is not affected by age or sex; this polymorphism is believed to be genetically determined, although to some extent it may also be modified by environmental factors (starvation, antigenic challenge).