The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Elizabeth T. Snow - One of the best experts on this subject based on the ideXlab platform.
-
Arsenic speciation in the freshwater crayfish, Cherax Destructor Clark
The Science of the total environment, 2009Co-Authors: Gemma Williams, Jan M. West, Iris Koch, Kenneth J. Reimer, Elizabeth T. SnowAbstract:Abstract Arsenic is a proven carcinogen that is found in the soil in gold mining regions at concentrations that can be thousands of times greater than gold. During mining arsenic is released into the environment, easily entering surrounding water bodies. The yabby ( Cherax Destructor ) is a common freshwater crustacean native to Australia's central and eastern regions. Increasing aquaculture and export of these animals has led us to question the effects of mine contamination on the yabbies themselves and to assess any potential risks to consumers. This study determined the species of arsenic present in a number of organs from the yabby. Several arsenic contaminated dam sites in the goldfields of western Victoria were sampled for yabby populations. Yabbies from these sites were collected and analysed for arsenic speciation using high performance liquid chromatography–inductively coupled plasma-mass spectrometry (HPLC–ICP-MS). Results showed that type of exposure influenced which arsenic species was present in each organ, and that as arsenic exposure increased the prevalence of inorganic arsenic species, mostly As(V), within the tissues increased. The bioaccessibility of the arsenic present in the abdominal muscle (the edible portion for humans) of the yabbies was assessed. It was found that the majority of the bioaccessible arsenic was present as inorganic As(III) and As(V).
-
Total arsenic accumulation in yabbies (Cherax Destructor clark) exposed to elevated arsenic levels in victorian gold mining areas, Australia
Environmental toxicology and chemistry, 2008Co-Authors: Gemma Williams, Jan M. West, Elizabeth T. SnowAbstract:Arsenic is a proven carcinogen often found at high concentrations in association with gold and other heavy metals. The freshwater yabby, Cherax Destructor Clark (Decapoda, Parastacidae), is a ubiquitous species native to Australia's central and eastern regions, with a growing international commercial market. However, in this region of Australia, yabby farmers often harvest organisms from old mine tailings dams with elevated environmental arsenic levels. Yabbies exposed to elevated environmental arsenic were found to accumulate and store as much as 100 μg/g arsenic in their tissues. The accumulation is proportional to the concentration of arsenic in the sediment and is high enough to be of concern for people who eat the yabbies. A comparison of arsenic levels in wild and lab-fed animals also was performed. Although there was no significant difference in the level of arsenic in the various organs of the wild animals, the animals purchased from a yabby farm showed a significantly higher arsenic concentration in their hepatopancreas (3.7 ± 0.9 μg/g) compared to other organs (0.6–1.8 μg/g). Furthermore, after a 40-d exposure to food containing 200 to 300 μg/g inorganic arsenic, arsenate (As[V])-exposed animals showed a significant increase in tissue-specific arsenic accumulation, whereas arsenite (As[III])-exposed animals showed a lower, nonsignificant increase in As uptake, primarily in the hepatopancreas. These results have important implications for yabby growers and consumers alike.
-
Total Arsenic Accumulation in Yabbies (Cherax Destructor Clark) Exposed to Elevated Arsenic in Victorian Gold Mining Areas
Environmental Toxicology and Chemistry, 2007Co-Authors: Gemma Williams, Jan M. West, Elizabeth T. SnowAbstract:Arsenic is a proven carcinogen often found at high concentrations in association with gold and other heavy metals. The freshwater yabby, Cherax Destructor Clark (Decapoda, Parastacidae), is a ubiquitous species native to Australia's central and eastern regions, with a growing international commercial market. However, in this region of Australia, yabby farmers often harvest organisms from old mine tailings dams with elevated environmental arsenic levels. Yabbies exposed to elevated environmental arsenic were found to accumulate and store as much as 100 μg/g arsenic in their tissues. The accumulation is proportional to the concentration of arsenic in the sediment and is high enough to be of concern for people who eat the yabbies. A comparison of arsenic levels in wild and lab-fed animals also was performed. Although there was no significant difference in the level of arsenic in the various organs of the wild animals, the animals purchased from a yabby farm showed a significantly higher arsenic concentration in their hepatopancreas (3.7 ± 0.9 μg/g) compared to other organs (0.6-1.8 μg/g). Furthermore, after a 40-d exposure to food containing 200 to 300 μg/g inorganic arsenic, arsenate (As[V])-exposed animals showed a significant increase in tissue-specific arsenic accumulation, whereas arsenite (As[III])-exposed animals showed a lower, nonsignificant increase in As uptake, primarily in the hepatopancreas. These results have important implications for yabby growers and consumers alike. © 2008 SETAC.
David L. Macmillan - One of the best experts on this subject based on the ideXlab platform.
-
reducing aggression between freshwater crayfish Cherax Destructor clark decapoda parastacidae by increasing habitat complexity
Aquaculture Research, 2006Co-Authors: Helena P Baird, Blair W. Patullo, David L. MacmillanAbstract:The culture of decapod crustaceans occurs worldwide. Aggressive behaviour is common in many of the species, including crayfish. This is problematic when it physically damages stock and reduces quality. Numerous biological factors influence crayfish fighting behaviour but the influence of environmental factors is not well known. This study investigated the effect of habitat complexity on the agonistic interactions of Australian freshwater crayfish, more commonly referred to locally as ‘yabbies’ (Cherax Destructor Clark). Solid objects that provided structure but not shelter were used to manipulate the complexity of the environment. The number, duration and dynamic of aggressive interactions within groups of animals were observed and recorded in simple and complex environments. Habitat complexity reduced both the number of agonistic interactions and the total time spent interacting. It is suggested that the structure in the environment distracts crayfish from the presence of others or physically blocks contact between them. These results extend our knowledge of crayfish social behaviour and may provide opportunities for reducing detrimental aggressive interactions in the aquaculture industry.
-
Exploration in a T-maze by the crayfish Cherax Destructor suggests bilateral comparison of antennal tactile information.
The Biological bulletin, 2005Co-Authors: Adrian Mcmahon, Blair W. Patullo, David L. MacmillanAbstract:Many crayfish species inhabit murky waters or have a crepuscular lifestyle, which forces them to rely on chemical and mechanical information rather than visual input. Information on how they use one form of mechanical information-tactile cues-to explore their local environment is limited. We observed the exploratory behavior of the crayfish Cherax Destructor in a T-maze under red light. Animals moved forward along the long arm of the maze and then moved equally in one of two available directions. The arm chosen by one crayfish did not affect that selected by a second crayfish tested immediately after in an unwashed maze. Previous experience in the maze also did not affect the choice. We found, however, that crayfish with one antenna denervated or splinted back to the carapace turned more often toward the unaltered side. Our data support the hypothesis that crayfish bilaterally compare information from their antennae.
-
Morphology and connections of the abdominal accessory neurons of the crayfish Cherax Destructor.
The Journal of comparative neurology, 2004Co-Authors: Joanne M. Drummond, David L. MacmillanAbstract:Associated with the abdominal muscle receptor organs of crayfish are accessory neurons that inhibit the activity of the stretch receptors. Cobalt infusion into their cut axons reveals four accessory somata associated with each hemiganglion in the abdomen of the crayfish Cherax Destructor. These conform to the pattern described previously for these neurons: The cell bodies are in the ganglion posterior to the one from which they exit. We recorded intracellularly from the largest accessory neurons, Acc-1 and Acc-2, and stained them with intracellular dye to establish unambiguously the characteristics defining their identity and structure. We describe their branching patterns in the ganglion of origin and the ganglion of exit. This morphological information permitted us to distinguish all four accessory neurons in preparations with dye infused through their cut axons, and we propose a revised, unambiguous nomenclature for the two smaller ones. Our intracelluar recordings allowed us to reexamine the physiological relationships of Acc-1 and Acc-2, the only accessory neurons for which there are data in the literature. In general, the connections and inputs described in previous studies were substantiated, although there has clearly been confusion between the two, and they differ in a number of significant ways. We found that they are seldom active together, have different firing patterns, and may operate with different clusters of extensor and flexor motorneurons. The results illustrate the level at which the accessory neurons operate within the abdominal control system but do not distinguish between competing hypotheses concerning their role in behavior. The data are consistent with the view that accessory neurons assist in timing between adjacent segments.
-
Multimodal individual recognition in the crayfish Cherax Destructor
Marine and Freshwater Behaviour and Physiology, 2004Co-Authors: Robyn J. Crook, Blair W. Patullo, David L. MacmillanAbstract:There is some evidence that macrurans recognize each other as individuals. In freshwater crayfish there are conflicting reports and there is limited information about the sensory mechanisms involved. To determine the extent to which the crayfish Cherax Destructor is capable of individual recognition, we performed experiments that familiarized animals with each other and then manipulated their recent success in dominance contests. Crayfish were more likely to win an encounter when paired against a familiar opponent than an unfamiliar one after the manipulation stage. In other experiments, animals were attracted to familiar conspecifics when only visual or chemical cues were present. This demonstrates that C. Destructor is able to discriminate between a familiar and an unfamiliar opponent. The results highlight the complex nature of intraspecific communication in crayfish and suggest elements likely to be of importance in the social interactions of groups in the wild state.
-
The cord stretch receptors in the abdominal nerve cord of the crayfish Cherax Destructor: physiology and relationships.
Journal of comparative physiology. A Neuroethology sensory neural and behavioral physiology, 2002Co-Authors: J. M. Drummond, David L. MacmillanAbstract:The physiology and relationships of tonic cord stretch receptor neurons in the crayfish Cherax Destructor were examined with intracellular and extracellular recording. Cord stretch evoked slow depolarisations leading to action potentials in tonic cord stretch receptor neurons. Intermittent post-synaptic potentials were also seen in cord stretch receptor neurons but were not the primary cause of the action potentials. Cord stretch still evoked action potentials in cord stretch receptor neurons when all synaptic activity, monitored at another known chemical synapse, was blocked using high [Mg2+] and low [Ca2+] in the bath. One source of facilitating excitatory post-synaptic potentials in the cord stretch receptor neurons was from mechanosensory hairs on the dorsal abdominal surface. Tonic cord stretch receptor neuron activity was associated with an increase in the activity of the abdominal slow extensor inhibitor motor neuron and at least one abdominal flexor excitor motor neuron in its segment, and reduced activity in the abdominal slow flexor inhibitor motor neuron. Activation of individual cord stretch receptor neurons produced a local resistance reflex. Cord stretch, activating many receptors, produced several other outcomes. One was the "extensor state" described in earlier literature. The tonic cord stretch receptor neurons of Cherax Destructor appear to be stretch-sensitive interneurons that receive inputs from other elements of the abdominal control system and mediate polysynaptic reflex activity in postural motor neurons.
Margaret E. Katz - One of the best experts on this subject based on the ideXlab platform.
-
Thelohania montirivulorum sp. nov. (Microspora: Thelohaniidae), a parasite of the Australian freshwater crayfish, Cherax Destructor (Decapoda: Parastacidae): fine ultrastructure, molecular characteristics and phylogenetic relati
Parasitology Research, 2003Co-Authors: Elizabeth G. Moodie, Leo F. Jambre, Margaret E. KatzAbstract:Thelohania montirivulorum sp. nov., a new species of microsporidian parasite, was found in a highland population of the Australian yabby, Cherax Destructor . Data are presented on fine ultrastructure, developmental morphology and DNA sequence of the small subunit ribosomal DNA (SSU rDNA) and internal transcribed spacer region. The phylogenetic relationships of T. montrivulorum sp. nov. and other crayfish parasites in the genus Thelohania , based on the SSU rDNA sequence, are investigated. Fine ultrastructure, patterns of sporogony and SSU rDNA sequence similarities indicate T. montirivulorum sp. nov. is congeneric with T. parastaci , a parasite of lowland populations of C. Destructor , and with T. contejeani , a parasite of European freshwater crayfish. SSU rDNA data suggests Thelohania species found in crustacean hosts are more closely related to the Vairimorpha / Nosema clade of species from insect and crustacean hosts than to the fire ant parasites, T. solenopsae and Thelohania sp.
-
Thelohania parastaci sp. nov. (Microspora: Thelohaniidae), a parasite of the Australian freshwater crayfish, Cherax Destructor (Decapoda: Parastacidae)
Parasitology Research, 2003Co-Authors: Elizabeth G. Moodie, Leo F. Jambre, Margaret E. KatzAbstract:Thelohania parastaci sp. nov. infects the Australian freshwater crayfish, Cherax Destructor. Data on morphology, developmental patterns and sequences from the small subunit (SSU) and internal transcribed spacer (ITS) regions of the ribosomal DNA (rDNA) of T. parastaci sp. nov. are described. The ultrastructural features of different life cycle stages are very similar to those of the European crayfish parasite Thelohania contejeani . T. parastaci sp. nov. exhibits simultaneous dimorphic sporogony in muscle tissue. Meronts, sporonts and spores are found in muscle tissue, within haemocytes in the hepatopancreas, and in the intestinal wall of infected crayfish. T. parastaci sp. nov. shows 92% sequence identity with T. contejeani and only 67% sequence identity with the fire ant pathogen T. solenopsae , when SSU rDNA sequences are compared. Analysis of SSU rDNA and ITS sequences of T. parastaci sp. nov. from crayfish from Victoria, Western Australia, and New South Wales indicate that the parasite has a wide geographical distribution in Australia.
Gemma Williams - One of the best experts on this subject based on the ideXlab platform.
-
Arsenic speciation in the freshwater crayfish, Cherax Destructor Clark
The Science of the total environment, 2009Co-Authors: Gemma Williams, Jan M. West, Iris Koch, Kenneth J. Reimer, Elizabeth T. SnowAbstract:Abstract Arsenic is a proven carcinogen that is found in the soil in gold mining regions at concentrations that can be thousands of times greater than gold. During mining arsenic is released into the environment, easily entering surrounding water bodies. The yabby ( Cherax Destructor ) is a common freshwater crustacean native to Australia's central and eastern regions. Increasing aquaculture and export of these animals has led us to question the effects of mine contamination on the yabbies themselves and to assess any potential risks to consumers. This study determined the species of arsenic present in a number of organs from the yabby. Several arsenic contaminated dam sites in the goldfields of western Victoria were sampled for yabby populations. Yabbies from these sites were collected and analysed for arsenic speciation using high performance liquid chromatography–inductively coupled plasma-mass spectrometry (HPLC–ICP-MS). Results showed that type of exposure influenced which arsenic species was present in each organ, and that as arsenic exposure increased the prevalence of inorganic arsenic species, mostly As(V), within the tissues increased. The bioaccessibility of the arsenic present in the abdominal muscle (the edible portion for humans) of the yabbies was assessed. It was found that the majority of the bioaccessible arsenic was present as inorganic As(III) and As(V).
-
Total arsenic accumulation in yabbies (Cherax Destructor clark) exposed to elevated arsenic levels in victorian gold mining areas, Australia
Environmental toxicology and chemistry, 2008Co-Authors: Gemma Williams, Jan M. West, Elizabeth T. SnowAbstract:Arsenic is a proven carcinogen often found at high concentrations in association with gold and other heavy metals. The freshwater yabby, Cherax Destructor Clark (Decapoda, Parastacidae), is a ubiquitous species native to Australia's central and eastern regions, with a growing international commercial market. However, in this region of Australia, yabby farmers often harvest organisms from old mine tailings dams with elevated environmental arsenic levels. Yabbies exposed to elevated environmental arsenic were found to accumulate and store as much as 100 μg/g arsenic in their tissues. The accumulation is proportional to the concentration of arsenic in the sediment and is high enough to be of concern for people who eat the yabbies. A comparison of arsenic levels in wild and lab-fed animals also was performed. Although there was no significant difference in the level of arsenic in the various organs of the wild animals, the animals purchased from a yabby farm showed a significantly higher arsenic concentration in their hepatopancreas (3.7 ± 0.9 μg/g) compared to other organs (0.6–1.8 μg/g). Furthermore, after a 40-d exposure to food containing 200 to 300 μg/g inorganic arsenic, arsenate (As[V])-exposed animals showed a significant increase in tissue-specific arsenic accumulation, whereas arsenite (As[III])-exposed animals showed a lower, nonsignificant increase in As uptake, primarily in the hepatopancreas. These results have important implications for yabby growers and consumers alike.
-
Total Arsenic Accumulation in Yabbies (Cherax Destructor Clark) Exposed to Elevated Arsenic in Victorian Gold Mining Areas
Environmental Toxicology and Chemistry, 2007Co-Authors: Gemma Williams, Jan M. West, Elizabeth T. SnowAbstract:Arsenic is a proven carcinogen often found at high concentrations in association with gold and other heavy metals. The freshwater yabby, Cherax Destructor Clark (Decapoda, Parastacidae), is a ubiquitous species native to Australia's central and eastern regions, with a growing international commercial market. However, in this region of Australia, yabby farmers often harvest organisms from old mine tailings dams with elevated environmental arsenic levels. Yabbies exposed to elevated environmental arsenic were found to accumulate and store as much as 100 μg/g arsenic in their tissues. The accumulation is proportional to the concentration of arsenic in the sediment and is high enough to be of concern for people who eat the yabbies. A comparison of arsenic levels in wild and lab-fed animals also was performed. Although there was no significant difference in the level of arsenic in the various organs of the wild animals, the animals purchased from a yabby farm showed a significantly higher arsenic concentration in their hepatopancreas (3.7 ± 0.9 μg/g) compared to other organs (0.6-1.8 μg/g). Furthermore, after a 40-d exposure to food containing 200 to 300 μg/g inorganic arsenic, arsenate (As[V])-exposed animals showed a significant increase in tissue-specific arsenic accumulation, whereas arsenite (As[III])-exposed animals showed a lower, nonsignificant increase in As uptake, primarily in the hepatopancreas. These results have important implications for yabby growers and consumers alike. © 2008 SETAC.
Christopher M Austin - One of the best experts on this subject based on the ideXlab platform.
-
Population structure and life history characteristics of Euastacus bispinosus and Cherax Destructor (Parastacidae) in the Grampians National Park, Australia
2008Co-Authors: Kerrylyn Johnston, Belinda J. Robson, Christopher M AustinAbstract:Despite being the most widely distributed and cultured freshwater crayfish species in Australia, relatively little is known about the ecology of Cherax Destructor outside of captivity. Similarly, few ecological studies have been conducted on the large and threatened stream dwelling Australian freshwater crayfish Euastacus bispinosus. A series of seasonal sampling surveys over two years investigated the population structure, life history and reproductive timing of C. Destructor in fire dam habitats, and of E. bispinosus in channel (stream) habitats, in the Grampians National Park in south-west Victoria, Australia. Cherax Destructor individuals in the largest size class (50 – 59.95 mm OCL) were not abundant during the study, while those belonging to the 0 – 9.95 mm OCL size class were more frequent in summer than at other times of year, suggesting synchronous recruitment in fire dam habitats. Individuals in the reproductively active mid-size classes were also frequent in summer. For E. bispinosus, sex ratios in spring always favoured females, although there were no clear trends for other times of year. Gravid E. bispinosus females were found in winter and spring throughout the study, and were sexually mature at a smaller size than has previously been reported.
-
Population genetic studies on the australian freshwater crayfish, Cherax Destructor (Crustacea: Parastacidae) using allozyme and RAPD markers
Aquatic Living Resources, 2005Co-Authors: Thuy T T Nguyen, Christopher P. Burridge, Christopher M AustinAbstract:Allozyme and Random Amplified Polymorphic DNA (RAPD) variation was surveyed in the freshwater crayfish Cherax Destructor Clark, an ecologically and commercially important species that is widespread throughout the freshwater systems of central Australia. At the intra-population level, allozymes revealed a similar level of variation to that found in other freshwater crayfish; RAPDs showed less diversity than allozymes, which was unexpected. At the inter-population level, both techniques revealed significant population structure, both within and between drainages. RAPD results were consistent with phylogeographic patterns previously identified using mtDNA. Although allozyme data showed little geographic pattern in relation to genetic variation based on multidimensional-scaling (MDS) plots on matrices of genetic distance, results of AMOVA and Mantel tests indicated significant population structuring. Each of the mtDNA lineages proposed in a previous study also showed significant genetic structure at similar levels as revealed by RAPDs but different levels by allozymes. These results reject hypotheses previously put forward on genetic homogenisation within the species due to wide-scale translocation. The implications of the findings for conservation and aquaculture of C. Destructor are also discussed.
-
Phylogeny of the Australian freshwater crayfish Cherax Destructor-complex (Decapoda:Parastacidae) inferred from four mitochondrial gene regions
Invertebrate Systematics, 2005Co-Authors: Thuy T T Nguyen, Christopher M AustinAbstract:The phylogenetic relationships among 32 individuals of Australian freshwater crayfish belonging to the Cherax Destructor-complex were investigated using a dataset comprising sequences from four mitochondrial gene regions: the large subunit rRNA (16S rRNA), cytochrome oxidase I (COI), adenosine triphosphatase 6 (ATPase 6), and cytochrome oxidase III (COIII). A total of 1602 bp was obtained, and a combined analysis of the data produced a tree with strong support (bootstrap values 94–100%) for three divergent lineages, verifying the phylogenetic hypotheses of relationships within the C. Destructor species-complex suggested in previous studies. Overall, sequences from the 16S rRNA gene showed the least variation compared to those generated from protein coding genes, which presented considerably greater levels of divergence. The level of divergence within C. Destructor was found to be greater than that observed in other species of freshwater crayfish, but interspecific variation among species examined in the present study was similar to that reported previously.
-
Phylogeography of the freshwater crayfish Cherax Destructor Clark (Parastacidae) in inland Australia: historical fragmentation and recent range expansion
Biological Journal of the Linnean Society, 2004Co-Authors: Thuy T T Nguyen, Christopher M Austin, Maliwan Meewan, Mark B. Schultz, Dean R. JerryAbstract:The yabby, Cherax Destructor Clark, is the most widespread species in the most widespread genus of Australian freshwater crayfish. It has a distribution that spans several distinct drainage basins and biogeographical regions within semiarid and arid inland Australia. Here we report a study designed to investigate patterns of genetic variation within the species and hypotheses put forward to account for its extensive distribution using DNA sequences from the mitochondrial 16S rRNA gene region. Results of phylogenetic analyses contradicted previous allozyme data and revealed relatively deep phylogenetic structure in the form of three geographically correlated clades. The degree of genetic divergences between clades (8–15 bp) contrasted with the relatively limited haplotype diversity within clades (1–3 bp). Network-based analyses confirmed these results and revealed genetic structure on both larger and more restricted geographical scales. Nevertheless some haplotypes and 1-step clades had large distributions, some of which crossed boundaries between river basins and aquatic biogeographical regions. Thus both older and more recent historical processes, including fragmentation on a larger geographical scale and more recent range expansion on a local scale, appear to be responsible for the observed pattern of genetic variation within C. Destructor . These results support elements of alternative hypotheses previously put forward to account for the evolutionary history of C. Destructor and the origin of its large distribution.
-
Complete mitochondrial DNA sequence of the Australian freshwater crayfish, Cherax Destructor (Crustacea: Decapoda: Parastacidae): a novel gene order revealed.
Gene, 2004Co-Authors: Adam D. Miller, Thuy T T Nguyen, Christopher P. Burridge, Christopher M AustinAbstract:The complete mitochondrial DNA sequence was determined for the Australian freshwater crayfish Cherax Destructor (Crustacea: Decapoda: Parastacidae). The 15,895-bp genome is circular with the same gene composition as that found in other metazoans. However, we report a novel gene arrangement with respect to the putative arthropod ancestral gene order and all other arthropod mitochondrial genomes sequenced to date. It is apparent that 11 genes have been translocated (ND1, ND4, ND4L, Cyt b, srRNA, and tRNAs Ser(UGA), Leu(CUN), Ile, Cys, Pro, and Val), two of which have also undergone inversions (tRNAs Pro and Val). The 'duplication/random loss' mechanism is a plausible model for the observed translocations, while 'intramitochondrial recombination' may account for the gene inversions. In addition, the arrangement of rRNA genes is incompatible with current mitochondrial transcription models, and suggests that a different transcription mechanism may operate in C. Destructor.