The embryonic and early postembryonic development of all crayfish occurring open water of the Czech Republic were studied under controlled conditions.

Aluminium is the third most abundant element in the lithosphere and yet no biological function has been elucidated. The ubiquity and pH-dependent chemical speciation of aluminium provides multiple routes of exposure to organisms, inducing neurotoxicity, tissue necrosis and organelle dysfunction. However, many studies of aluminium toxicity lack consideration of the speciation and relevant concentration of aluminium and the route of exposure. The aim of this thesis was to examine the accumulation, distribution, excretion and toxicity of aluminium following a common route of exposure (ingestion) at a concentration likely to be encountered by the model organism (freshwater crayfish, Pacifastacus leniusculus) in the wild. Crayfish are sediment dwelling omnivorous crustaceans distributed worldwide and as such are vulnerable to multiple routes of aluminium exposure. They play a central role in aquatic food webs and are becoming increasingly popular for human consumption, raising concern about food chain transfer. Crayfish were fed aluminium chloride-spiked artificial food pellets for either 20 days, 28 days + 10 day aluminium-free clearance period, or 22 weeks + 4 week aluminium-free clearance period. In addition, systemic administration of aluminium citrate was undertaken to draw comparisons with previous mammalian work and compare the two routes of exposure. Tissue distribution and accumulation was measured in the gills, hepatopancreas, flexor muscle and antennal gland. Stress and tissue damage were analysed using biochemical and histopathological techniques. Behavioural toxicity tests and measurements of the neurophysiological parameters of the crayfish medial giant neuron were used to assess aluminium-induced neurotoxicity. In vitro neurotoxicity tests with aluminium chloride were also carried out on isolated nerve tissue to assess the suitability of in vitro studies. The key site of aluminium accumulation following ingestion was the hepatopancreas. Excretion was observed via the gills, antennal glands (in the urine) and hepatopancreas (for incorporation into the faeces). However, physiological consequences such as tissue damage, inflammation and altered neuronal activity were observed and persisted even after cessation of aluminium ingestion. Consequently there are implication for crayfish fitness and survival, the aquatic food web and human toxicity following ingestion of aluminium.

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I estimated yield, population metrics, production costs, and evaluated consumer acceptability and nutritive content of crayfish (Procambarus clarkii, P. zonangulus) harvested from moist-soil wetlands in the Lower Mississippi Alluvial Valley (MAV) during springs 2009-2011. I also compared nutrient and sediment concentrations and loads exported from moist-soil wetlands and nearest agriculture fields in the MAV during winters 2010-2012. Daily yield of crayfish from moist-soil wetlands was 2.4 kg (wet) ha-1 (SE = 0.50; 95% CI = 1.3-3.4). When graded by size, yield of large crayfish (> 30 g) from wetlands dominated by P. clarkii was four times greater (P < 0.05) than yield of large crayfish from wetlands dominated by P. zonangulus. Crayfish harvesting costs (2013 US dollars [$]) ranged from $405.69 ha-1 to $917.88 ha-1 and breakeven selling prices ranged from $3.74 kg-1 to $8.49 kg-1. Consumer acceptability, proximate composition, and total fatty acid content of P. clarkii did not differ (0.73 > P > 0.11) between crayfish harvested from moist-soil wetlands and rice-crayfish culture fields in Louisiana. Although selling prices likely will not compete with prices for crayfish harvested from Louisiana rice fields ($2.75 kg-1; 2012 US$), harvesting crayfish from moist-soil wetlands may enhance recreational opportunities while increasing awareness of ecosystem benefits of these wetlands. Although concentrations (mg L-1) of soluble reactive phosphorus (SRP) in runoff from moist-soil wetlands and adjoining croplands did not differ (P = 0.95), concentrations of total and particulate phosphorus, nitrate-nitrogen, and total suspended solids were 42, 52, 86, and 89% lower (P < 0.03) in runoff from moist-soil wetlands. However, the load (kg ha-1) of SRP from moist-soil wetlands was six times (P = 0.08) greater than load from croplands. Estimated loading rate of total phosphorus from moistsoil wetlands (2.36 kg ha-1 year-1) was greater than the rate reported by regulatory agencies in Mississippi (1 kg ha-1 year-1), but field replication is needed to verify these results. Nearly 80% of the total loads exported from moist-soil wetlands occurred during < 30% runoff events. Retention of runoff from storm events may reduce phosphorus loss from moist-soil wetlands while not interfering with conservation objectives.

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Crayfish exhibit innate immune responses via hemocytes and their products. There are 3 hemocyte populations: hyaline cells, granular cells, and semigranular cells. Hemocytes from laboratory housed, untreated crayfish (normal crayfish) have been quantified on the basis of cell type, cell size, and cell granularity using Flow Cytometry. These data present the first overall picture of normal hemocytes from Red Swamp Crayfish with regard to cell type, cell size, and cell granularity and will serve as a baseline for all future studies in our lab. Experiments using crayfish injected with Pseudomonas aeruginosa, Staphylococcus aureus, or crayfish saline alone showed significant and consistent changes in cell type in cells from crayfish injected with bacteria with a decrease in hyaline cells and an increase in granular cells. This effect was greater in crayfish injected with Gram - bacteria. In addition, crayfish injected with Pseudomonas aeruginosa showed a significant difference in Granular cell size with a shift to larger cells and a significant decrease in granularity in the Granular cell population. Cells from crayfish treated with Staphylococcus aureus did not show these changes.

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Triphenyltin hydroxide (TPTH) appears to be relatively stable in soil. Only minor partitioning into water occurred because of the insolubility of TPTH in water and its adsorption to soil. Residues in the water were also relatively stable. The concentration. of TPTH in the tissues of crayfish exposed to 1.0 ppm of TPTH in the soil was 0.1 ppm or 10% that of the environment. Crayfish exposed to 0.01 ppm of TPTH in the soil had 0.005 ppm TPTH in their tissues or 50% that of the environment. Greater than 80% of the residue in the muscle tissue appeared to be bound, and the extractable residue was essentially all TPTH. Similar binding was observed in visceral tissues and the extractable residue was 83% TP'IH, 9% diphenyltin dichloride, 4% bis-triphenlytin oxide, and 4% unknown. Following 28 days of exposure, the residue was persistent in the crayfish through a 24-day elimination period.

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