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Signal crayfish are an internationally widespread invasive species that can have important detrimental ecological impacts. This thesis aims to determine whether signal crayfish have the potential to also impact the physical environment in rivers. A series of experiments were undertaken in purpose-built still-water aquaria using a laser scanner to obtain Digital Elevation Models (DEMs) of narrowly-graded gravel surfaces before and after exposure to crayfish. The difference between DEMs was used to quantify volumetric changes in surface topography due to crayfish activity. Two distinct types of topographic change were identified. The first was the construction of pits and mounds which resulted in an increase in surface roughness and grain exposure. The second was the rearrangement of surface material caused by crayfish brushing past grains when walking and foraging, reorientating grains and altering friction angles. A series of 80 flume runs were undertaken to quantify alterations made by crayfish to water-worked, as well as loose, gravel substrates at low velocity flows. Crayfish significantly altered the structure of water-worked substrates, reversing the imbrication of surface grains to a more random arrangement. Surfaces were entrained at a relatively high velocity flow subsequent to crayfish activity in order to directly link topographic and structural alterations to substrate stability. Nearly twice as many grains were mobilised from surfaces which had been disturbed by crayfish in comparison to control surfaces that were not exposed to crayfish. A field investigation aimed to determine the potential significance of the geomorphic impact of crayfish in rivers. Signal crayfish were tracked through a 20 m reach of a small, lowland alluvial river for 150 days using a Passive Integrated Transponder (PIT) system. Crayfish were active throughout the channel, although their activity became limited as water temperature dropped and flow stage increased. Substrate was not an important determinant of crayfish activity at this scale. Instead, crayfish tended to be found along the inner bank of a meander bend where there was a substantial cover of macrophytes. Consequently, signal crayfish were active for extended periods on substrates of a similar size to those that they could disturb in flume experiments. These results suggest that signal crayfish could have important geomorphic effects in rivers, disturbing bed structures and increasing the mobility of coarse material. This may have important implications for both the management of some rivers and benthic organisms that reside on the river bed.

Changes in vegetation may influence the quality and quantity of the underlying organic peat soils and have impacts on faunal populations. My goal was to determine whether shifts from native slough communities to invasive cattail in the Florida Everglades could affect peat characteristics that could cascade to impact the dry season survival of crayfish (Procambarus fallax). I contrasted peat soils from native slough and cattail-invaded sites as alternative dry-season burrowing substrates for crayfish. Cattail peat had higher average bulk density and inorganic content within the first ten centimeters of the soil profile. Crayfish showed marginally greater initial burrowing success in slough peat than in cattail peat but survival was equivalent in both peat soils and high overall. Understanding these indirect linkages between vegetation and crayfish populations in the Everglades can provide insight on the consequences of plant invasion on ecosystem trophic dynamics. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Many freshwater ecosystems sustain several invasive species. Here I examine multiple invasions in two highly invaded and well catalogued catchments; Lake Naivasha, Kenya and River Thames, England. New metrics, derived from stable isotope analysis, are used to provide measures of trophic diversity and to examine dietary interactions among species. I test the hypothesis that functionally similar sympatric species will occupy a smaller niche than their allopatric counterparts. Additionally, I quantify the impact of multiple invasive species on ecosystem structure and functioning in order to address the question; do interactions among species amplify or mitigate one another's impact? In Lake Naivasha, the stable isotope metrics revealed serial replacement of invasive species due to dietary interactions. Invasive red swamp crayfish were eventually excluded from the lake due to niche restriction in the presence of a more recent invader, the common carp. Now, the crayfish have migrated into the catchment where they overlap with a species of native river crab. Here, I found a novel mechanism of invasion, whereby the crayfish restricted their niche at the invasion front in order to reduce competition with crabs. Crayfish also caused significant changes in invertebrate community structure and increased decomposition rates, which indirectly resulted in displacement of the crabs. In the Thames catchment, I catalogue the non-indigenous species and show how invasion rates have increased significantly since 1800 due to globalisation. Using the four species of invasive crayfish present (red swamp, signal, Turkish and virile), I demonstrate their extensive diet plasticity using novel measures of niche width and individual specialisation based on stable isotope data. Interactions among the crayfish were examined and this revealed that each species has varying and independent impacts on invertebrate community structure, algal standing stock and decomposition rates. Hence, interactions among invaders are not expected to amplify or mitigate one another's impact and instead, the combined impact will be the sum of their allopatric impacts.

Madagascar's freshwater crayfish, belonging to the endemic genus Astacoides, are harvested throughout their range in the eastern highlands of the country. They provide an important source of protein and revenue to local communities but there is concern that the harvest may be unsustainable. In this thesis I assess the sustainability of crayfish harvesting in and around Ranomafana National Park, an area well known for its reliance on crayfish harvesting. Six taxa (belonging to four described species) are found in the Ranomafana area. Most families in villages with access to forest carry out some harvesting for subsistence use. Due to variation in local taboos (fady) and in access to forest, commercial crayfish harvesting is very important in only three of the 27 villages I visited. However, in these villages crayfish revenue is very important, particularly to poorer households. One species, Astacoides granulimanus, dominates the harvest: more than 95% of crayfish caught in the harvesting village of Vohiparara are of this species. I used a mark-and-recapture study involving more than 26,000 A. granulimanus across 79 sites under a range of harvesting intensities to estimate demographic parameters (growth, fecundity and survival) and investigate density-dependent control of growth and fecundity. No evidence for density-dependent control of growth was found, but the density of large crayfish negatively influenced the proportion of females of a given size which reproduced. I investigated the sustainability of the harvest of A. granulimanus using two approaches: I) comparing population structure and density under varying harvesting intensity and II) using population models to investigate the forest area necessary to provide the observed annual harvest from one harvesting village and comparing that with the area available. The conclusions are encouraging as they suggest that the A. granulimanus harvest in the Ranomafana area may be sustainable under current conditions. Preliminary work suggests habitat loss may be a more immediate threat, so scarce conservation resources should perhaps be concentrated on reducing habitat loss rather than enforcing a ban on harvesting.

Os lagostins são crustáceos decápodos límnicos que podem ser encontrados em água corrente, outros preferem água com pouca ou nenhuma corrente, como pequenos riachos, lagos, reservatórios e pântanos. Muitas espécies vivem em galerias subterrâneas com níveis mais baixos de oxigênio; assim, estas espécies podem mostrar adaptações metabólicas às condições hipóxicas. O objetivo desta pesquisa foi comparar o metabolismo de duas espécies de lagostins com diferentes hábitos, Parastacus defossus e Parastacus brasiliensis. P. defossus é uma espécie fossorial, vive em galerias com baixos níveis de oxigênio e P. brasiliensis é encontrado em ambientes lóticos com maiores níveis de oxigênio. Amostragens sazonais foram realizadas da primavera de 2006 ao inverno de 2007 para determinações metabólicas sazonais e posteriormente, amostragens foram realizadas durante o inverno de 2008 para análises metabólicas dos animais submetidos à hipóxia e recuperação pós-hipóxia. P. brasiliensis foi amostrado em Mariana Pimentel, Rio Grande do Sul (Brasil) e P. defossus foi amostrado no Lami, Porto Alegre, Rio Grande do Sul (Brasil). Nos experimentos de hipóxia, grupos de animais foram submetidos à hipóxia por 1, 2, 4 e 8 horas. Períodos de recuperação póshipóxia também foram analisados, após 4 hs de hipóxia, grupos de animais foram colocados em aquários com água aerada e foram removidos em intervalos de 1, 3, 6 e 9 hs. Após esse período foram extraídas amostras de hemolinfa e removidos o hepatopâncreas, o músculo, as brânquias e as gônadas para a determinação de glicose, lactato, glicose livre, glicogênio, proteínas totais, lipídios totais, colesterol total, arginina e arginina fosfato. Os resultados das análises sazonais mostraram diferentes respostas entre as estações do ano e entre as espécies, para todos os parâmetros metabólicos, com exceção das proteínas nas brânquias e do lactato na hemolinfa. As variações metabólicas em P. defossus foram principalmente relacionadas com o período reprodutivo e os períodos de baixa concentração de oxigênio nas galerias, enquanto os resultados em P. brasiliensis sugerem uma alocação significativa dos nutrientes da dieta para o tecido gonadal durante o período reprodutivo, com uma menor transferência das reservas de diferentes tecidos para as gônadas. Em relação ao metabolismo dos animais submetidos à hipóxia foi observado que em ambas as espécies, os níveis de glicose e de lactato aumentaram significativamente em hipóxia. Reduções de glicogênio, lipídios e colesterol foram registradas no hepatopâncreas e no tecido muscular, especialmente de P. defossus. Todos os tecidos de P. defossus e P. brasiliensis mostraram reduções nos níveis de glicose livre, mas essas reduções não foram significativas. Todas as reservas das brânquias anteriores e posteriores, com exceção das reservas de glicogênio, mostraram comportamento semelhante em ambas as espécies. As duas espécies de Parastacus armazenaram e utilizaram arginina fosfato, principalmente P. defossus. Entre os resultados do metabolismo dos animais submetidos à recuperação pós-hipóxia foram observadas que a restauração dos níveis de lactato foi mais rápido em P. defossus quando comparado com P. brasiliensis. Essa espécie restabeleceu suas reservas de glicogênio do hepatopâncreas e do tecido muscular. Já os níveis de glicose livre foram rapidamente restabelecidos em todos os tecidos das duas espécies. Em relação às reservas de arginina fosfato, P. defossus mostrou maiores concentrações que P. brasiliensis. As duas espécies mostraram capacidade de restaurar os níveis de arginina fosfato, mas também utilizaram essas reservas durante períodos de recuperação. Nas espécies, as reservas de lipídios totais e colesterol parecem ser uma importante fonte de energia durante a recuperação. / Some species of crayfish live in flowing water, and others prefer water with little or no current such as small streams, lakes, reservoirs, and swamps. Many species live in subterranean burrows with lower oxygen levels, and can show metabolic adaptations to hypoxic conditions. The aim of this study was to compare the metabolism of two crayfish species with different habitats, Parastacus defossus and Parastacus brasiliensis. P. defossus is fossorial, living in burrows with low oxygen levels, and P. brasiliensis lives in lotic environments with higher oxygen levels. Seasonal sampling was conducted from spring 2006 to winter 2007 for seasonal metabolic determinations, and samples were taken during the winter of 2008 for metabolic analyses of the animals subjected to hypoxia and during the post-hypoxia recovery. P. brasiliensis was collected in Mariana Pimentel, Rio Grande do Sul (Brazil) and P. defossus at Lami, Porto Alegre, Rio Grande do Sul. In the hypoxia experiments, groups of animals were subjected to hypoxia for 1, 2, 4, and 8 h. Periods of post-hypoxia recovery were also analyzed; after 4 h of hypoxia, groups of animals were placed in tanks with oxygenated water and were then removed at intervals of 1, 3, 6, and 9 h. The hemolymph was extracted, and the hepatopancreas, muscle, gills, and gonads were removed for determination of glucose, lactate, free glucose, glycogen, total proteins, total lipids, total cholesterol, arginine, and arginine phosphate. The results of the seasonal analysis showed, for all metabolic parameters, different seasonal responses between the species, with the exception of proteins in gills, and of lactate in hemolymph. The metabolic variations in P. defossus were mainly related to reproductive period and periods of low oxygen concentration in the burrows. The results for P. brasiliensis suggested a significant allocation of dietary nutrients to gonadal tissue during the reproductive period, with a smaller transfer of reserves from different tissues to gonads. In both species, glucose and lactate levels increased significantly in hypoxia. Reductions of glycogen, lipids, and cholesterol were recorded in hepatopancreas and muscle tissue, especially of P. defossus. In all tissues of P. defossus and P. brasiliensis were observed reductions in the free glucose levels, but these reductions weren’t significant. All reserves in the anterior and posterior gills, except glycogen, behaved similarly in both species. Both Parastacus species, mainly P. defossus, stored and used arginine phosphate. During post-hypoxia recovery, lactate was restored more rapidly in P. defossus than in P. brasiliensis. P. defossus restored its glycogen reserves in the hepatopancreas and muscle tissue. Free glucose was quickly restored in all tissues of both species. In relation to the reserves of arginine phosphate, P. defossus showed higher concentrations than P. brasiliensis. The two species showed ability to restore this metabolite, but they also used this metabolite during longer periods of recovery. In both species, the reserves of total lipids and cholesterol seemed be an important source of energy during the recovery period.

In previous studies, some channels, called the “sleeper channels,” were reported to contribute to the shaping of the action potential (AP) only under non-physiological conditions. These channels have been hypothesized to play a role in providing a protective mechanism to prevent damage from neuronal hyperexcitation. Here we applied two-electrode current clamp at the primary branch point (1°BP) and the presynaptic terminal simultaneously on crayfish axons. Cadmium had minimal effects on AP shaping, suggesting the absence of calcium-activated potassium channels. Application of 1 mM TEA had minimal impact on AP waveform. In the presence of 4-Aminopyridine (4-AP), the same tetraethylammonium (TEA) concentration significantly prolonged AP duration, resembling the behaviors of sleeper channels. The kinetics of the TEA-sensitive channel (Kv(TEA)) is similar to the Kv2 family of mammalian K+ channels. TEA depolarized the potential after an AP and increased the AP duration in a dose-dependent manner, indicating that these channels contributed to maintaining AP waveform majorly during the hyperpolarization. The terminals were more sensitive to the blockers, suggesting a probability of regulation on neurotransmitter release. However, the TEA-sensitive channels at the crayfish axon had a higher affinity to TEA than the Kv2 channels. Pharmacological profiles, spatial distinction and function of the Kv(TEA) in the crayfish axon require further study.

Crayfish plague is an emerging disease caused by the oomycete Aphanomyces astaci, a pathogen listed among the 100 World's Worst Invasive Alien Species. It was introduced into Europe in the second half of 19th century from North America and caused collapses of European native crayfish populations. Nowadays, A. astaci is widespread in Europe and has spread also to other parts of the world, threatening all susceptible crayfish of non-North American origin. The aims of this MSc thesis were 1) to provide information about crayfish plague outbreaks from recent years, and by using microsatellite and mtDNA markers reveal A. astaci genotypes involved; 2) to test healthy-looking indigenous crayfish for potential occurrence of chronic infections by A. astaci in Czechia. Six new crayfish plague outbreaks were confirmed from 2016 to 2018, involving at least five distinct pathogen strains. My results provide first evidence of the A. astaci genotype group D causing Astacus astacus and Austropotamobius torrentium mass mortalities in Czechia. MtDNA sequencing revealed two haplotypes of the D haplogroup, indicating two independent sources of infection presumably either from ornamental crayfish or spreading from neighbouring countries. The genotype group A was recorded in two A. astacus mortalities and genotype group...

Research into the polyculture of finfish and crayfish has been conducted in Western Australia for over a decade now. This research was instigated out of a need to increase revenues from freshwater crayfish farmers wishing to diversify their income base with a view to increasing profitability and reducing risk. It has become clear that several key variables dictate how the polyculture system (i.e. polysystem) will perform. These include biological factors like: size of participating species, relative densities, gender, planktonic turbidity, natural feeds; and abiotic factors like: light intensity, clay turbidity, floating cages for segregation, water quality, and habitat/shelter complexity. Many of these factors can be controlled / adjusted by the manager of the polysystem to maximise performance, production and profitability.While much of the research to date has focussed on the marron (Cherax tenuimanus) industry, it is also important to realise that an understanding of these factors can also assist other crayfish polysystems, like integrated agri-aquaculture systems containing yabbies (Cherax albidus). Some of the factors that influence how the system will perform may become more prevalent, like suspended clay turbidity and the associated role of light intensity in species interactions, or shelter complexity and the resulting choice of shelter material. But overall, they are the same basic variables and we must understand how they affect the particular multi-species system that we are dealing with. There is a lot to be learned from the literature on how these variables affect multi-species aquatic environments in the wild. Perhaps aquaculturists have not considered this enough in the past. Some farmers seem to believe that these variables are different JUST because it is a culture system. This is not true. / The variables will take on different levels in a culture system (i.e. a manager will stimulate turbidity, provide artificial feeds, stock different sizes, and supply particular types of shelter) BUT the actual variables themselves (e.g. food, density, light, shelter) are basic to ALL aquatic ecosystems. Other researchers have looked at important factors like density, gender, and light intensity / turbidity in crayfish polysystems - but the issue of habitat complexity and the role of shelter has not been adequately addressed. This thesis will investigate some basic questions about shelter and endeavour to apply them to crayfish polysystems, with the emphasis on marron (C. tenuimanus) and yabbies (C. albidus) because these are the two most commercially important species of crayfish in Western Australia. Importantly, it should be noted that due to the invasive nature of yabbies, and their apparent ability to displace native marron in the wild, findings will be related to yabby-marron competition / displacement where relevant. We need to know many things about shelter: what type is best in a multi-species system? Should the shelter size match the crayfish size? Do marron have different requirements for shelter than yabbies? Does it matter who gets first use of a shelter (i.e. prior residence effect)? Can we learn about crayfish shelter requirements by examining the behaviour / plasticity of crayfish species? If crayfish are stocked with finfish and they retreat into shelter as a predator-avoidance measure, is the complexity important given that their densities will be higher? If densities of crayfish inside shelters are higher in polysystems, will cannibalism be a concern, particularly when conditions are right for moulting? Does visual recognition and / or chemo-detection of a predator affect the shelter usage by marron or yabbies? / Does temperature affect shelter usage behaviour for a burrowing species like yabbies? Shelter is an important factor in the life history of a freshwater crayfish and an understanding of its influence on different species is important for maximising system performance. Crayfish are categorised depending on their ability to construct shelters (i.e. burrows). Yabbies have evolved in systems with fluctuating water quality and many predators and, as such, have learned to burrow (to escape drought and also to escape predators). Marron, on the other hand, are a non-burrowing native crayfish species that have existed with relatively few predators in the South-West. As a result, marron are less capable of modifying their behaviour when confronted with a predator (i.e. low behavioural plasticity). Species with high plasticity, like yabbies, are more capable of adapting to new environments, because they can change their behaviour to increase their chance of survival. Therefore we can expect yabbies and marron to utilize habitats differently and we should compare these behaviours as a basis to developing management strategies. This type of knowledge may also assist with managing the translocation and spread of yabbies in the wild and their displacement of native marron.Within multi-species systems, the physical structure of shelter plays an important role inprotecting crayfish and the perfect shelter would not only provide safety from co-stocked finfish, but also from conspecific cannibalism. Given the different life histories and behaviours, it is probable that both species of crayfish will have different refuge requirements.Over the course of this four-year investigation, trials were conducted in four culture systems (72L aquariums, 300L circular tanks, 80t mesocosm tank, and 720m2 earthen ponds) using marron and yabbies as the species of interest. / Silver perch and Murray cod were chosen as the finfish species of interest as they appear to have the highest aquaculture potential for native freshwater finfish in Australia at the present time. Further, both of these fish have been documented as potential predators of crayfish, resulting in a challenge to understand the role of shelter in minimising the negative effects of fish-crayfish interactions within a polysystem. This study has confirmed that shelter plays a critical role in multi-species system dynamics. In the case of polysystems, it will affect both interspecific and intra-specific interactions, ultimately governing production and profitability, along with the other, previously defined factors. This means that the manager of a polysystem can influenceproductivity by understanding: a) the behavioural characteristics and biology of the crayfish; b) the feeding biology of the finfish; and c) the system variables (both biotic and abiotic) that will affect the overall well being of the fish and crayfish. In the case ofshelter, the manager should understand the available shelter types, the appropriatedensities, the importance of matching complexity to the crayfish size, and the prior residence effect when choosing a timing strategy for stocking and harvesting. Prior residence increased resource holding potential for both marron and yabbies in the short term. In fact, prior residence was a stronger determinant of successful sheltering than crayfish gender or species. However, in longer-term trials the physical size of the crayfish (larger animals evicted smaller animals) and reproductive status (berried females were successful at evicting all other crayfish) were more important factors in determining successful shelter acquisition, although the temporal variations (i.e. growth and release of young) complicate the issue. / When stocking crayfish of different sizes, and in polysystems, the correct size of shelter becomes critical, as smaller individuals will be forced to leave over-sized shelter and locate a shelter commensurate with their own body size to avoid predators. This is relevant to crayfish nurseries where complex habitat is paramount for juvenile cohorts that display variation in sizes and gender. The expansion of crayfish polyculture holds considerable promise; however, furtherinvestigations are required into shelter complexity within floating fish cages, shelter types and arrangement of shelters within ponds (for increased production and ease-of-harvesting), potential of yabbies in polyculture (comparison of monosex and hybrid strains), and the impact of shelter on escape behaviour of marron in a polysystem.

<p>Prophenoloxidase (proPO) is a key enzyme for generation of melanin and is activated by the proPO activating enzyme (ppA) to its active form, PO. The active ppA was purified and cloned from crayfish hemocytes and it is a typical serine proteinase containing a clip, a proline-rich, and a glycine-rich domain. A recombinant protein containing the clip-domain, with homology to horseshoe crab big defensin and mammalian â-defensin, had antibacterial activity <i>in vitro</i> against gram-positive bacteria.</p><p>The proPO activating system (proPO system) is triggered by lipopolysaccharides (LPS) or â-1,3-glucans. An LPS and â-1,3-glucan binding protein (LGBP) was characterized from crayfish hemocytes. The results of an LGBP antibody inhibition assay suggest that LGBP is directly involved in the proPO system.</p><p>The primary structure of a crayfish masquerade-like (mas) protein has homology to serine proteinases except for a substitution within the catalytic triad, which renders it without proteinase activity. The crayfish mas-like protein has also binding activity to various gram-negative bacteria and yeast. When the mas-like protein binds to microorganisms, it is processed by a proteolytic enzyme. The mas-like protein exhibited cell adhesion and opsonic activities suggesting that it plays a role in defense against parasites.</p>