pH is a fundamental parameter controlling physicochemical processes in environmental systems. Cloud droplet pH controls the dissolution of important micronutrients (iron, phosphorus) which in turn affects the biological carbon pump and ultimately global climate. Using bulk cloud/fog water pH measurements to represent the whole pH spectrum can potentially lead to large errors in climate models. Optochemical sensors (optodes and nanosensors) have been developed for numerous analytes and applications. Optodes for pH however, are typically limited to biomedical applications due to their small pH sensing range (2 – 4 pH units). In this work, pH sensing optodes were developed ultimately combined into a single pH sensing optode with an extended range of pH 1-11. The optode material properties were re-designed to allow for the collection, storage and analysis of individual droplets on the sensor surface. Core-shell pH nanosensors were also developed and used to map the pH distribution within the model organism Daphnia magna, the pH along the gut was found to range from pH 5.8 – 7.2. Finally, a device (electrostatic precipitator) for collecting individual cloud/fog droplets was designed and constructed. The electrostatic precipitator was used in conjunction with the optodes to deposit and measure pH in standard (artificial) cloud/fog droplets under laboratory conditions.

After a survey of the occurrence of Asellus aguaticus in South Lancashire rivers, one site on the polluted river Calder and another on the unpolluted Woodplumpton Brook were selected for further investigation. Calder Asellus were shown to be more tolerant to lead than Woodplumpton Asellus but there was no difference between the populations in their tolerance to copper, zinc, cadmium or arsenic. Calder Asellus took up more lead from solution than Woodplumpton Asellus at concentrations from 1-300 mg/I, but less at concentrations from 300 to 500 mg/I. Neither population took up lead from food (decaying sycamore or lettuce leaves). Comparison.of lead lost from the medium with lead gained by Asellus showed that lead was accumulated on the sides of the containers only in the presence of Asellus. This was found to be due to micro-organisms. Antibiotic treatment decreased lead uptake on the containers and in the Asellus. Two 6pecies of lead-accumulating bacteria, Aeromonas punctata and Citrobacter freundii, were isolated from Asellus and their environment. Experiments using an anti-microbial agent 'Steralize' showed that lead tolerance in both populations was increased in a medium of distilled water, but decreased in 0.025 M CaCl2. Steralize' also increased lead uptake from a freshwater medium. Dissection. experiments showed that lead was accumulated mainly in the cuticle or its underlying tissues: Lead inhibited oxygen uptake in both populations. Calder Asellus took up more oxygen than Woodplumpton animals in distilled water and in 0.025 M CaCl2, but there was no difference between the populations in river water or in freshwater medium. Pre-treatment of Asellus with 0.1 mg/l Pb caused the tolerance of large and medium-sized Woodplumpton Asellus to increase to the level of untreated Calder animals. Large Calder Asellus were made less tolerant by pre-treatment, but there was no significant effect on medium sized animals. It was concluded that lead tolerance in A. aguaticus is mainly due to acclimation.

A general account is given of the development of Daphnia magna from the egg to the mature adult. A review of previous work reveals that authors have concentrated on the early development, neglecting the later development. An adequate technique has been developed. An account of the development based on living material gives a detailed series of stages. A summary of the present state of knowledge of the physiological aspects of development is included. The development of the parthenogenetic egg is described. The early development includes a superficial cleavage and gastrulation by immigration. The mesenteron develops from a solid rod of cells in the ventral part of the egg, and acquires a central cavity which never contains yolk. The yolk cells develop from the blastoderm. The mesoderm develops a single small pair of coelomic cavities, and the heart develops from a compact group of cells. The history of the dorsal organ is described. The development of the ephippial egg resembles that of the parthenogenetic egg except in some features related to the smaller and more even sized nature of the yolk globules. Daphnia magna hatches from the brood pouch of the mother as an immature adult. The account of the anatomy of the adult is a confirmation and extension of previous work, including histology and indicating function. The muscles of the mesenteron are striated, and the heart wall contains anincomplete longitudinal, as well as a circular, layer of muscles. A suggestion is made for a new interpretation of the cells of the branchial sacs. The results obtained and the importance of a large quantity of yolk are discussed.

This thesis consists of a series of reprints of publications in which are reported the results of researches on the systematica of the Notostracan Crustacea. Studies were made on the cytology, the biochemistry end the comparative ecology of the group and were utilised in a systematic study of the Notostrace. This research was initiated after the finding by the candidate of living Notostraca in a rain-pool in southern England, which proved to be the only known locality for the group in the British Isles in recent years, having been found there previously by Professors Hobson and Fox. Success in culturing Triops cancriformis from this pool under laboratory conditions stimulated efforts to obtain cultures of other species, and finally cultures of all four species of Triops and of two species of Lepidurus were maintained at Bedford College. These, together with the collections of preserved material in a number of European, American and Australian museums, formed the basis of the study. The cultures were utilised for investigations of the development of exoskeletal characters during growth, for the investigation of the variability of these characters in a single line of individuals under differing environmental conditions, for cytological studies resulting in some knowledge of the chromosome numbers within the group, and for an investigation of the specificity of blood pigments in different species and in different races of a single species. The study was recorded in five publications, which are bound together to form this thesis; a preliminary report of the discovery that the so-called parthenogenetic forms are in fact hermaphroditic is bound in as E in the thesis. The main paper, B, contains a review of Notostracan literature, the analysis of the validity to systeraatics of the exoskeletal characters used in the past, the chromosome counts, the investigation of biochemical specificity, and the basic systematic revision of the group. The conclusion reached in this paper was that the Hotostraca are composed of a small number of very widely dispersed species, all rather close to each other systematically but characterised by considerable individual variation. The number of species previously described was shown to be much too high. A separate account of the details of the cytology and reproductive qycle which were elucidated incidentally in the investigation of chromosome numbers appears as D and describes in considerably more detail than hitherto the cytology of the gonads during reproduction. An attempt was made in a separate publication. A, to explain the widespread nature of the distribution of llotostracan species and to relate it to the extreme longevity of the group in palaeontological terms, and an explanatory hypothesis is developed, derived from the ecology of the group. Finally, under C, there is an account of the existence of what appears to be a most unusually high proportion of abnormal individuals occurring in populations of Notostraca compared with the proportion in other animal groups, and this again is referred to the palaeontological longevity of the Botostraca. For convenience the constituent papers of the thesis are listed below: A: Evolution in the Notostraca. Evolution.; B: A review of the Notostraca. Bull. Brit. Mus. (N.H.); C: Abnormal variation in the Notostraca. Syst. Zool.; D: Reproduction in the Notostraca. Proc. Zool. Soc. Lond.; E: Reproduction in the Notostraca. Nature, Lond.

Despite their huge diversity, abundance and ecological importance, very little is still known about sex determining mechanisms within Crustacea. Sex determination in crustaceans is known to be influenced by environmental factors, via parasitic infection and genetically, however, it is possible that all three mechanisms can be involved in a single species. The gonochoristic marine amphipod Echinogammarus marinus (Leach, 1815) is currently being used for the development of biomarkers to measure the influence of environmental contamination on crustacean sex determination and differentiation pathways. To truly understand whether anthropogenic disruption of sex determination is currently an issue, it is critical that all the mechanisms governing the process in E. marinus are fully evaluated. Therefore, the aim of this project was to fill gaps in our knowledge of the general population dynamics of E. marinus, with a particular focus on elucidating the mechanisms of sex determination in this ubiquitous amphipod. Sex determination in E. marinus has been linked with feminising parasites, however, to date, no such studies have linked this species with environmental sex determination (ESD) or genetic sex determination (GSD). This project investigated two E. marinus populations that differed in population structure. The Langstone Harbour E. marinus population (Southern England, UK) revealed no presence of parasitic sex determination (PSD). However, this study has shown that the population has a seasonal breeding pattern, with population growth and decline closely related to environmental parameters (temperature) and parasites (trematodes) respectively. The population data also revealed seasonally altered sex ratios, ranging from 36% to 71% males. ESD was recorded for the first time in an E. marinus population by revealing that photoperiod was the cue for sex determination. This finding was validated by a laboratory study that showed a male bias in broods that developed in long day light regimes (16h light: 8h dark) and a female bias in broods that developed in a short day light regime (8h light: 16h dark). The laboratory data and the seasonally altered sex ratios found in the field showed significant correlation with each other supporting these findings. A new species of trematode parasite belonging to the Microphallidae family has been identified that encysts in the amphipod brain and demonstrates clear capacity for behavioural changes in its host. Individuals infected with the trematode parasite displayed distinct positive phototaxic and negative geotaxic behavioural alterations that could potentially increase susceptilbility to predation. These behavioural alterations have been linked to changes at the level of gene expression suggesting modulation of neuronal genes in the infected individuals. Putative serotonin receptor 1A, inebratied neurotransmitter, tryptophan hydroxylase and amino acid decarboxylase like genes displayed the most dramatic change in their gene expression. This represents the first study to record such changes in the neuronal pathways of parasite infected amphipods. Another E. marinus population investigated from Invertkeithing (Scotland, UK) displayed a high female bias and high levels of intersexuality. The project has strengthened the evidence that PSD is present in this population with 40.4 % of the population being infected by either Paramyxea or microsporidia parasites. From the infected individuals 75% of that infection were female bias and 88.5% of intersexes, also presented an infection. The investigation explored the transmission pathways and efficiency of the parasites involved. Vertical transmission of a Paramyxean sp. was shown for the first time in an amphipod host and alsoshowed the highest transmission efficiency from the mother to the eggs (96.8%). This has lead to the question of whether the microsporidian D. duebenum is a feminiser and has highlighted another parasite candidate for E. marinus sex distortion. Despite the range of genomic techniques employed, the attempt to determine genomic sexual determination in E. marinus did not reveal any sex specific genomic regions. However, considering the preliminary nature of the work, this study has provided insight for future directions. Several key genes involved in sexual differentiation that presented sex exclusive expression were identified. In addition, crucial method development was performed that will allow future investigations of genetic variation in E. marinus. The transcriptome of the E. marinus has now been sequenced and along with population models enabling a greater understanding of the links between genome and population ecology. With such a large investment in E. marinus as an ecological model species, it is crucial that basic biological questions and gaps in the field are addressed. Consequently, the data presented within this thesis will aid in the study of E. marinus and other crustaceans from the level of genetics to population effects.

Crayfish are keystone species and ecosystem engineers that affect the structure and function of aquatic ecosystems. Whilst ecological impacts are caused by crayfish in their native range, non - native crayfish species typically have a greater ef fect on some other aquatic organisms and ecosystem processes (Chapter 2). Crayfish are extremely successful invaders that often cause declines in native cra yfish (Chapter 3). Of the 7 non - native crayfish species in the UK, the signal crayfish ( Pacifastacus leniusculus ) is currently the most widespread (Chapter 3). Field and laboratory data, however, suggest that in parts of the UK signal crayfish are being outcompeted by more recently introduced virile crayfish ( Orconectes cf. virilis ) (Chapter 4). Non - native crayfish also threaten native crayfish through disease, notably crayfish plague ( Aphanomyces astaci ), transmission. Whilst non - native North American crayfish are largely resistant to A. astaci , infection in susceptible native European species is usually lethal. Within this study 23 signal crayfish populations were screened for A. astaci and 13 were infected (Chapter 5). Virile crayf ish from the UK were also infected with A. astaci , and therefore should also be considered as a transmission pathway for this pathogen in the UK (Chapter 6). Whilst the majority of studies on crayfish symbionts are focused on A. astaci , crayfish host a wid e range of micro and macro - parasites. One group of particular interest are branchiobdellidans (Annelida: Clitellata). Two species of these ectosymbionts, Xironogiton victoriensis and Cambarincola aff. okadai , were recently discovered on invasive signal cra yfish in the UK (Chapter 7). Owing to their abilities to survive for extended periods off the host and reproduce rapidly both species have a high invasion potential in the UK (Chapter 8). Laboratory experiments show that signal crayfish infested with X. victoriensis were less aggressive and poorer foragers than uninfested c rayfish , therefore these symbionts may influence signal crayfish invasion dynamics (Chapter 9).

No description available.

Nephrops norvegicus is a mid-sized benthic decapod lobster found at depths of between 30-300 metres along the eastern Atlantic coast from Norway to Morocco, and within the Mediterranean sea. They inhabit marine muddy sediments in which they excavate burrow systems and from which they make short excursions to feed by predation and scavenging. The females of this species are known to reside within their burrows over the winter period while brooding their eggs, although their feeding behaviour over this period has not been investigated. Two aspects of the nutrition of N. norvegicus, namely nutritional status (the condition of an animal, which is maintained through a balance between energy intake and energy expenditure) and trophic dynamics (the flow of energy from exogenous inputs throughout food webs in an ecosystem) have been studied, to answer questions relating to the influence of season, sex and site on nutrition in this species. Specific questions that have been addressed include: with regard to season, is there a reduction in the nutritional status of N. norvegicus over the winter due to a decrease in primary production? With regard to sex, do females have a reduced nutritional status to males when they emerge from their winter brooding period, indicating that females go through a period of fasting over the winter? Also do females employ a filter feeding strategy over the winter? With regard to site, do N. norvegicus at two different sites on the west coast of Scotland (i.e. the Clyde Sea Area [CSA] and the North Minch [NM]) occupy different trophic levels and have different fatty acid signatures, which would indicate that their diets are made up of different prey species? A range of biochemical markers was tested to describe how N. norvegicus reacts to a period of forced starvation, and thus to determine their nutritional status. There was clear metabolic depression, indicated by an increase in the copper concentration of the hepatopancreas in both males and females. In contrast to the findings of previous studies, lipids in the hepatopancreas did decrease with starvation, however was mitigated by the metabolic depression and only became significantly lower than fed individuals after 12 weeks in males and 20 weeks in females. Lipids and water combined made up 80% of the mass of the hepatopancreas, and when the lipids decreased the proportional mass was replaced by water. However, as indicated by the hepatosomatic index (HSI), the total mass of the hepatopancreas decreased over the period of starvation. A temperature effect was also seen which influenced the amount of reserves required by the animal under these conditions. Using the results from the starvation trials, a predictive tool was developed for determining the nutritional status in N. norvegicus from the wild, and for calculating threshold values which indicate whether animals were in a starved state. These measurements and threshold values were applied to field caught animals, assessing the factors of season, sex and site. The seasonal analysis showed that there was low nutritional status in N. norvegicus during the winter of 2008-2009, whereas the nutritional status of winter 2009-2010 was not as low. The site analysis showed that N. norvegicus in the CSA, where burrow density is 0.85 m-2, were found to have a lower nutritional status than N. norvegicus in the NM, where burrow density was only 0.55 m-2. These results are consistent with the notion that in high density areas N. norvegicus has a lower nutritional status than in low density areas. Females were found to have a larger lipid store within the hepatopancreas than males, presumably to sustain reproduction. Females were also found to be metabolically depressed over the winter and spring months of early 2009. However they were not in an advanced state of starvation over this period. It is therefore concluded that over the winter months females reduce feeding, perhaps in a response to reduced mobility brought about by the brooding stage of reproduction, but do not follow different feeding strategies to males over this time. The differences of trophic level between N. norvegicus in the CSA and the NM were assessed through the use of stable isotope analysis. It was found that although the animals in the CSA had higher 15N values than the animals in the NM, the animals in the NM were actually feeding at 0.6 trophic level units higher than those in the CSA. The high 15N values in the CSA were ascribed to organic enrichment of nitrates in that area. There was no significant difference between males and females at the end of the winter period, indicating that when females are brooding their eggs they do not use different feeding strategies (e.g. filter feeding) as an alternative means of nutrition. The differences between the Fatty Acid (FA) signatures of N. norvegicus in the CSA and the NM were determined by fatty acid analysis. A clear difference was demonstrated between sites, indicative of differences in the dietary composition of the two populations, and suggestive of a greater input from pelagic food sources (either zooplankton or fish) in the NM. However, no significant difference was found in FA signatures between male and female N. norvegicus at either site or at any time of the year. Thus, consistent with the conclusions from the other monitoring methods, the FA signatures indicate that females and males had similar feeding patterns at all times of year, with regard to the type of food consumed. As well as addressing issues directly concerned with the nutrition of N. norvegicus in relation to season, sex and site, the results of these studies have a number of wider applications, including the development of optimal feeding strategies for holding lobsters under impoundment conditions for long periods, and for identifying the procedures required to assess more directly the dietary composition of N. norvegicus populations, and especially the contribution of fish to their diet.

Populations of non-native signal crayfish, Pacifastacus leniusculus, are damaging to UK native species and habitats though their populations are expanding with no coherent framework in place for their control. This is partly the result of a literature gap on the effect of trapping on non-native crayfish population structure which this thesis will explore in order to add to the European literature. Population size structure analysis has been facilitated via the creation of novel samplers and an in-depth analysis of the effect of aperture on the size/life stage of crayfish sampled. Smaller trap apertures, the addition of refuge material and novel samplers increased the catch of juvenile crayfish. Sex was indeterminable for up to 50% of juvenile crayfish, with juvenile sex ratios potentially biased towards females. Conditions on the River Lark did not limit populations, though temperature varied significantly between sites whilst substrata, pH and biological oxygen demand did not. Three years of trapping and juvenile sampling enabled population analysis at a site level. The population at Lark Head (professionally trapped), had a consistent size structure from 2010 to 2012, whilst individuals at Barton Mills (community trapped) and the Plough (untrapped), showed size decreases over time. The proportions of adult to juvenile individuals, and males to females, were similar at all three sites in 2011 & 2012. Catch per unit effort, decreased at all three sites with the greatest reductions at trapped sites. There is no evidence that catch sizes, or the proportion of juveniles, increased with trapping in spite of one site being trapped by the community since 2001 and another trapped by professionals since 2005. This refutes inferences that trapping causes an increase in biomass due to a reduction in the number of cannibalistic and dominant large males, with size and sex bias in traps also not corroborated.

The effects of salinity on the physiology and ecology of the mud-dwelling estuarine animal Corophium volutator (Pallas), a crustacean amphipod, have been investigated. A study of the effects ot salinity on the distribution and abundance of C. volutator on the estuary of the River Ythan, Aberdeenshire, indicates that 2‰ is a critical minimum salinity controlling its distribution. In areas with salinities between 2 and 5‰ C. volutator was present, but in reduced numbers. In areas with salinity greater than 5‰ , the distribution and abundance of C. volutator were controlled by the nature of the substrate; however, in areas with suitable substrates, but where the salinity was below 5‰ , the effects of salinity override the effects of the substrate. Experimental studies indicated that, if supplied with mud, it will survive the salinity range of 2 - 50‰, and without mud, the range 7.5 - 47.5‰. Moulting occurred in salinities of 2.6 - 46‰ , but most frequently in tho range 5 - 20‰ . Growth occurred at a maximum rate in 15.4 o/oo and only slightly slower at 4.4 and 30.6‰ ; but below 4.4‰ the growth rate was progressively reduced. The effects of salinity on the various stages in the life cycle are discussed. Freezing point studies show C. volutator to be a hyperosmotic regulator, having a tissue tolerance range of 13 - 50‰ . The effect of size, sex, feeding and moulting on the freezing point have been investigated. C. volutator was found to produce urine hypoosmotic to the blood when acclimated to low salinities, and isosmotic urine at salinities above 20‰ . Over a range of salinities from 1 - 35‰ , C. volutator was found to maintain Na+, K+,Ca ++,Cl-, more concentrated than the medium, and Mg++ less concentrated. The restricted permeable areas of the cuticle have been localised by silver staining. The oxygen consumption of animals of the same size, at the same level of activity, and at the same temperature, did not differ significantly between animals in different salinities. A salinity preference range of 10 - 30‰ has been demonstrated. Relevant literature on estuarine life, and osmoregulation of crustacea is reviewed. The adaptations of C. volutator to an environment with varying salinity are discussed.