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Rhanor Gillette - One of the best experts on this subject based on the ideXlab platform.
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the sea slug Pleurobranchaea californica a signpost species in the evolution of complex nervous systems and behavior
2015Co-Authors: Rhanor Gillette, Jeffrey W. BrownAbstract:How and why did complex brain and behavior evolve? Clues emerge from comparative studies of animals with simpler morphology, nervous system, and behavioral economics. The brains of vertebrates, arthropods, and some annelids have highly derived executive structures and function that control downstream, central pattern generators (CPGs) for locomotion, behavioral choice, and reproduction. For the vertebrates, these structures-cortex, basal ganglia, and hypothalamus-integrate topographically mapped sensory inputs with motivation and memory to transmit complex motor commands to relay stations controlling CPG outputs. Similar computations occur in the central complex and mushroom bodies of the arthropods, and in mammals these interactions structure subjective thought and socially based valuations. The simplest model systems available for comparison are opisthobranch molluscs, which have avoided selective pressure for complex bodies, brain, and behavior through potent chemical defenses. In particular, in the sea-slug Pleurobranchaea californica the functions of vertebrates' olfactory bulb and pallium are performed in the peripheral nervous system (PNS) of the chemotactile oral veil. Functions of hypothalamus and basal ganglia are combined in Pleurobranchaea's feeding motor network. The actions of basal ganglia on downstream locomotor regions and spinal CPGs are analogous to Pleurobranchaea's feeding network actions on CPGs for agonist and antagonist behaviors. The nervous systems of opisthobranch and pulmonate gastropods may conserve or reflect relations of the ancestral urbilaterian. Parallels and contrasts in neuronal circuits for action selection in Pleurobranchaea and vertebrates suggest how a basic set of decision circuitry was built upon in evolving segmentation, articulated skeletons, sociality, and highly invested reproductive strategies. They suggest (1) an origin of olfactory bulb and pallium from head-region PNS; (2) modularization of an ancestral feeding network into discrete but interacting executive modules for incentive comparison and decision (basal ganglia), and homeostatic functions (hypothalamus); (3) modification of a multifunctional premotor network for turns and locomotion, and its downstream targets for mid-brain and hind-brain motor areas and spinal CPGs; (4) condensation of a distributed serotonergic network for arousal into the raphe nuclei, with superimposed control by a peptidergic hypothalamic network mediating appetite and arousal; (5) centralization and condensation of the dopaminergic sensory afferents of the PNS, and/or the disperse dopaminergic elements of central CPGs, into the brain nuclei mediating valuation, reward, and motor arousal; and (6) the urbilaterian possessed the basic circuit relations integrating sensation, internal state, and learning for cost-benefit approach-avoidance decisions.
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2001) The role of escape swim motor network in the organization of behavioral hierarchy and arousal in Pleurobranchaea
2015Co-Authors: Rhanor Gillette, Jian JingAbstract:SYNOPSIS. The escape swimming pattern generator of the notaspid opisthobranch Pleurobranchaea drives a high threshold, override behavior. The pattern generator is integrated with neural networks of other behaviors so as to coordinate unitary behavioral expression and to promote general behavioral arousal. These functions are separately produced by different swim network elements. One set of swim premotor neurons, the A1/A10 ensemble, A3 and IVS, generate the swim pattern and, through corollary activity, suppress potentially conflicting feeding behavior by exerting broad inhibition at major feeding network interneurons. A second set of swim neurons, the serotonergic As1–4 neurons, provides intrinsic neuromodu-latory excitation to the swim pattern generator that sustains the escape swim ep-isode through multiple cycles. The As1–4 also provide neuromodulatory excitation to important modulatory, serotonergic cells in the feeding motor network and lo-comotor network, and may have a general regulatory role in the distributed se-rotonergic arousal network of the mollusk. The As1–4 appear to be also necessary to both avoidance and orienting turning, and are therefore likely to be critical
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Neuromodulatory Control of a Goal-Directed Decision
2014Co-Authors: Leonid L. Moroz¤b, Nathan G. Hatcher¤c, Rhanor GilletteAbstract:Many cost-benefit decisions reduce to simple choices between approach or avoidance (or active disregard) to salient stimuli. Physiologically, critical factors in such decisions are modulators of the homeostatic neural networks that bias decision processes from moment to moment. For the predatory sea-slug Pleurobranchaea, serotonin (5-HT) is an intrinsic modulatory promoter of general arousal and feeding. We correlated 5-HT actions on appetitive state with its effects on the approach-avoidance decision in Pleurobranchaea. 5-HT and its precursor 5-hydroxytryptophan (5-HTP) augmented general arousal state and reduced feeding thresholds in intact animals. Moreover, 5-HT switched the turn response to chemosensory stimulation from avoidance to orienting in many animals. In isolated CNSs, bath application of 5-HT both stimulated activity in the feeding motor network and switched the fictive turn response to unilateral sensory nerve stimulation from avoidance to orienting. Previously, it was shown that increasing excitation state of the feeding network reversibly switched the turn motor network response from avoidance to orienting, and that 5-HT levels vary inversely with nutritional state. A simple model posits a critical role for 5-HT in control of the turn network response by corollary output of the feeding network. In it, 5-HT acts as an intrinsic neuromodulatory factor coupled to nutritional status and regulates approach-avoidance via the excitation state of the feeding network. Thus, the neuromodulator is a key organizing element in behavioral choice of approach or avoidance through its actions in promoting appetitive state, in large part via th
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Selective prey avoidance learning in the predatory sea slug Pleurobranchaea californica.
2013Co-Authors: Vanessa Noboa, Rhanor GilletteAbstract:Predator-prey interactions involving aposematic signaling, where predators learn the warning cues of well-defended prey, are clear examples of cost-benefit decisions in foraging animals. However, knowledge of the selectivity of predator learning and the natural conditions where it occurs is lacking for those foragers simpler in brain and body plan. We pursued the question in the sea slug Pleurobranchaea californica, a generalist forager of marked simplicity of body form, nervous system and behavior. This predator exploits many different types of prey, some of which are costly to attack. When offered Flabellina iodinea, an aeolid nudibranch with a stinging defense, biting attack was followed by rapid rejection and aversive turns. The predatory sea slug rapidly learned avoidance. Notable exceptions were animals with extremely high or low feeding thresholds that either ignored F. iodinea or completely consumed it, respectively. Experienced slugs showed strong avoidance of F. iodinea for days after exposure. Aposematic odor learning was selective: avoidance was not linked to change in feeding thresholds, and trained animals readily attacked and consumed a related aeolid, Hermissenda crassicornis. For P. californica, aposematic learning is a cognitive adaptation in which sensation, motivation and memory are integrated to direct cost-benefit choice, and thereby lend flexibility to the generalist's foraging strategy.
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Reviewed by:
2012Co-Authors: Keiko Hirayama, Rhanor Gillette, Jeffrey W. Brown, Marianne Catanho, Björn Brembs, Freie UniversitätAbstract:A simple circuit for cost-benefit decision derived from behavioral and neural studies of the predatory sea-slug Pleurobranchaea may closely resemble that upon which the more complex valuation and decision processes of the social vertebrates are built. The neuronal natures of the pathways in the connectionist model comprise classic central pattern gener-ators, bipolar switch mechanisms, and neuromodulatory state regulation. Marked potential exists for exploring more complex neuroeconomic behavior by appending appropriate circuitry in simulo
Susanna A Wood - One of the best experts on this subject based on the ideXlab platform.
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In situ accumulation of tetrodotoxin in non-toxic Pleurobranchaea maculata (Opisthobranchia)
2017Co-Authors: Lauren Salvitti, Susanna A Wood, Paul Mcnabb, Rex Fairweather, David Culliford, S. Craig CaryAbstract:Tetrodotoxin (TTX) is a highly potent neurotoxin targeting voltage gated sodium channels. It is found in numerous phyla, including both marine and terrestrial taxa, however, its origin is a topic of considerable debate. The aim of this study was to investigate the origin of TTX in the Opisthobranch Pleurobranchaea maculata using in situ experimentation. Sixteen individuals sourced from non-toxic populations were transplanted to a habitat with toxic populations. These were kept in mesh net cages either; (1) anchored to the seafloor, or (2) deployed 0.5 m off the benthos. They were fed a non-toxic diet for 8 weeks before being sacrificed, and either the entire organisms or specific organs analysed for TTX via liquid chromatography–mass spectrometry. Four of the six remaining individuals from cages on the benthos contained TTX (max. 0.79 mg kg^−1), whilst only two of eight from the suspended cages contained TTX and concentrations were lower (max. 0.43 mg kg^−1). These were similar to the lowest concentrations (min. 0.4 mg kg^−1) detected in free-living specimens collected during the experimental period. Among positive individuals the highest concentrations were detected in gonad tissues. These data, in concert with previous studies, suggest an environmental source of TTX for P. maculata , which may be bacterial or dietary in origin. High-Throughput Sequencing (18S ribosomal RNA gene metabarcoding) of foregut contents from toxic and non-toxic individuals was used to investigate their diet. High abundances of Cnidaria and Annelida sequences were identified and these groups should be targeted in future efforts to identify TTX-containing organisms.
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first identification of tetrodotoxin ttx in the flatworm stylochoplana sp a source of ttx for the sea slug Pleurobranchaea maculata
2015Co-Authors: Lauren R Salvitti, Susanna A Wood, David I Taylor, Paul Mcnabb, Craig S CaryAbstract:High concentrations of the neurotoxin tetrodotoxin (TTX) were detected by liquid chromatography–mass spectrometry (LC–MS) in the Platyhelminthes Stylochoplana sp. from Pilot Bay (Tauranga, New Zealand). This is the first detection of TTX in this genus. Concentrations were monitored from March to November (2013) and found to significantly decrease from a peak in July (avg. 551 mg kg−1) to November (avg. 140 mg kg−1). Stylochoplana sp. co-occurred with TTX-containing Pleurobranchaea maculata (Opisthobranchia). A Stylochoplana sp.-specific real-time PCR assay was developed targeting the mitochondrial cytochrome c oxidase subunit I gene to determine if P. maculata consumed Stylochoplana sp. Positive Stylochoplana sp. signals were obtained for 7 of 19 P. maculata tested. Mass calculations indicate Stylochoplana sp. could supply Pilot Bay P. maculata with the TTX required to account for the concentrations reported in previous studies (ca. 1.04 mg TTX per individual) based on an ingestion rate of one individual every 2–3 days throughout their lifetime. However, due to the lack of Stylochoplana sp. in areas with dense P. maculata populations, and high concentration (ca. 1400 mg kg−1) of TTX detected in some individuals, it is unlikely that Stylochoplana sp. represent the sole source of TTX in P. maculata.
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no evidence for a culturable bacterial tetrodotoxin producer in Pleurobranchaea maculata gastropoda pleurobranchidae and stylochoplana sp platyhelminthes polycladida
2015Co-Authors: Lauren R Salvitti, Susanna A Wood, Paul Mcnabb, Stephen Craig CaryAbstract:Tetrodotoxin (TTX) is a potent neurotoxin found in the tissues of many taxonomically diverse organisms. Its origin has been the topic of much debate, with suggestions including endogenous production, acquisition through diet, and symbiotic bacterial synthesis. Bacterial production of TTX has been reported in isolates from marine biota, but at lower than expected concentrations. In this study, 102 strains were isolated from Pleurobranchaea maculata (Opisthobranchia) and Stylochoplana sp. (Platyhelminthes). Tetrodotoxin production was tested utilizing a recently developed sensitive method to detect the C9 base of TTX via liquid chromatography—mass spectrometry. Bacterial strains were characterized by sequencing a region of the 16S ribosomal RNA gene. To account for the possibility that TTX is produced by a consortium of bacteria, a series of experiments using marine broth spiked with various P. maculata tissues were undertaken. Sixteen unique strains from P. maculata and one from Stylochoplana sp. were isolated, representing eight different genera; Pseudomonadales, Actinomycetales, Oceanospirillales, Thiotrichales, Rhodobacterales, Sphingomonadales, Bacillales, and Vibrionales. Molecular fingerprinting of bacterial communities from broth experiments showed little change over the first four days. No C9 base or TTX was detected in isolates or broth experiments (past day 0), suggesting a culturable microbial source of TTX in P. maculata and Stylochoplana sp. is unlikely.
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intracellular immunohistochemical detection of tetrodotoxin in Pleurobranchaea maculata gastropoda and stylochoplana sp turbellaria
2015Co-Authors: Lauren R Salvitti, Susanna A Wood, Leigh Winsor, Stephen Craig CaryAbstract:Tetrodotoxin (TTX), is a potent neurotoxin targeting sodium channels that has been identified in multiple marine and terrestrial organisms. It was recently detected in the Opisthobranch Pleurobranchaea maculata and a Platyhelminthes Stylochoplana sp. from New Zealand. Knowledge on the distribution of TTX within these organisms is important to assist in elucidating the origin and ecological role of this toxin. Intracellular micro-distribution of TTX was investigated using a monoclonal antibody-based immunoenzymatic technique. Tetrodotoxin was strongly localized in neutral mucin cells and the basement membrane of the mantle, the oocytes and follicles of the gonad tissue, and in the digestive tissue of P. maculata. The ova and pharynx were the only two structures to contain TTX in Stylochoplana sp. Using liquid chromatography-mass spectrometry, TTX was identified in the larvae and eggs, but not the gelatinous egg cases of P. maculata. Tetrodotoxin was present in egg masses of Stylochoplana sp. These data suggest that TTX has a defensive function in adult P. maculata, who then invest this in their progeny for protection. Localization in the digestive tissue of P. maculata potentially indicates a dietary source of TTX. Stylochoplana sp. may use TTX in prey capture and for the protection of offspring.
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first detection of tetrodotoxin in the bivalve paphies australis by liquid chromatography coupled to triple quadrupole mass spectrometry with and without precolumn reaction
2014Co-Authors: Paul Mcnabb, Susanna A Wood, David I Taylor, Shaun Ogilvie, Larn Wilkinson, Alice Anderson, David Hamon, Barrie M PeakeAbstract:Two methods for the determination of tetrodotoxin (TTX) in marine biota have been developed and validated using ultra-performance LC coupled to triple quadrupole MS. The direct analysis of TTX is completed in one method, while the other method detects the dehydration product of TTX after reaction with base. The methods were validated in a single-laboratory trial and used to test Paphies australis (pipi) samples collected from Whangapoua, New Zealand during April 2011. Pa. australis is a commonly eaten species of bivalve that was found to contain TTX at levels up to 0.80 mg/kg in this study. The methods exhibited recoveries ranging from 94 to 120%, and the within laboratory reproducibility ranged from 6 to 27% for Pleurobranchaea maculata (grey-side gilled sea slug) and bivalve matrixes. Use of the method using a dehydration step showed no evidence of TTX analogs in any of the samples.
Stephen Craig Cary - One of the best experts on this subject based on the ideXlab platform.
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no evidence for a culturable bacterial tetrodotoxin producer in Pleurobranchaea maculata gastropoda pleurobranchidae and stylochoplana sp platyhelminthes polycladida
2015Co-Authors: Lauren R Salvitti, Susanna A Wood, Paul Mcnabb, Stephen Craig CaryAbstract:Tetrodotoxin (TTX) is a potent neurotoxin found in the tissues of many taxonomically diverse organisms. Its origin has been the topic of much debate, with suggestions including endogenous production, acquisition through diet, and symbiotic bacterial synthesis. Bacterial production of TTX has been reported in isolates from marine biota, but at lower than expected concentrations. In this study, 102 strains were isolated from Pleurobranchaea maculata (Opisthobranchia) and Stylochoplana sp. (Platyhelminthes). Tetrodotoxin production was tested utilizing a recently developed sensitive method to detect the C9 base of TTX via liquid chromatography—mass spectrometry. Bacterial strains were characterized by sequencing a region of the 16S ribosomal RNA gene. To account for the possibility that TTX is produced by a consortium of bacteria, a series of experiments using marine broth spiked with various P. maculata tissues were undertaken. Sixteen unique strains from P. maculata and one from Stylochoplana sp. were isolated, representing eight different genera; Pseudomonadales, Actinomycetales, Oceanospirillales, Thiotrichales, Rhodobacterales, Sphingomonadales, Bacillales, and Vibrionales. Molecular fingerprinting of bacterial communities from broth experiments showed little change over the first four days. No C9 base or TTX was detected in isolates or broth experiments (past day 0), suggesting a culturable microbial source of TTX in P. maculata and Stylochoplana sp. is unlikely.
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intracellular immunohistochemical detection of tetrodotoxin in Pleurobranchaea maculata gastropoda and stylochoplana sp turbellaria
2015Co-Authors: Lauren R Salvitti, Susanna A Wood, Leigh Winsor, Stephen Craig CaryAbstract:Tetrodotoxin (TTX), is a potent neurotoxin targeting sodium channels that has been identified in multiple marine and terrestrial organisms. It was recently detected in the Opisthobranch Pleurobranchaea maculata and a Platyhelminthes Stylochoplana sp. from New Zealand. Knowledge on the distribution of TTX within these organisms is important to assist in elucidating the origin and ecological role of this toxin. Intracellular micro-distribution of TTX was investigated using a monoclonal antibody-based immunoenzymatic technique. Tetrodotoxin was strongly localized in neutral mucin cells and the basement membrane of the mantle, the oocytes and follicles of the gonad tissue, and in the digestive tissue of P. maculata. The ova and pharynx were the only two structures to contain TTX in Stylochoplana sp. Using liquid chromatography-mass spectrometry, TTX was identified in the larvae and eggs, but not the gelatinous egg cases of P. maculata. Tetrodotoxin was present in egg masses of Stylochoplana sp. These data suggest that TTX has a defensive function in adult P. maculata, who then invest this in their progeny for protection. Localization in the digestive tissue of P. maculata potentially indicates a dietary source of TTX. Stylochoplana sp. may use TTX in prey capture and for the protection of offspring.
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investigating diet as the source of tetrodotoxin in Pleurobranchaea maculata
2013Co-Authors: Serena Khor, Susanna A Wood, David I Taylor, Lauren R Salvitti, Paul Mcnabb, Janet Adamson, Stephen Craig CaryAbstract:The origin of tetrodotoxin (TTX) is highly debated; researchers have postulated either an endogenous or exogenous source with the host accumulating TTX symbiotically or via food chain transmission. The aim of this study was to determine whether the grey side-gilled sea slug (Pleurobranchaea maculata) could obtain TTX from a dietary source, and to attempt to identify this source through environmental surveys. Eighteen non-toxic P. maculata were maintained in aquariums and twelve were fed a TTX-containing diet. Three P. maculata were harvested after 1 h, 24 h, 17 days and 39 days and TTX concentrations in their stomach, gonad, mantle and remaining tissue/fluids determined using liquid chromatography-mass spectrometry. Tetrodotoxin was detected in all organs/tissue after 1 h with an average uptake of 32%. This decreased throughout the experiment (21%, 15% and 9%, respectively). Benthic surveys at sites with dense populations of toxic P. maculata detected very low or no TTX in other organisms. This study demonstrates that P. maculata can accumulate TTX through their diet. However, based on the absence of an identifiable TTX source in the environment, in concert with the extremely high TTX concentrations and short life spans of P. maculata, it is unlikely to be the sole TTX source for this species.
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tetrodotoxin concentrations in Pleurobranchaea maculata temporal spatial and individual variability from new zealand populations
2012Co-Authors: Susanna A Wood, David I Taylor, Paul Mcnabb, Janet Adamson, Jarrod Walker, Stephen Craig CaryAbstract:Tetrodotoxin (TTX) is a potent neurotoxin that has been identified in a range of phylogenetically unrelated marine and terrestrial organisms. Tetrodotoxin was recently detected in New Zealand in Pleurobranchaea maculata (the grey side-gilled sea slug). From June 2010 to June 2011 wild specimens were collected from 10 locations around New Zealand. At one site (Narrow Neck Beach, Auckland) up to 10 individuals were collected monthly for 6 months. Attempts were also made to rear P. maculata in captivity. Tetrodotoxin was detected in samples from eight of the ten sites. The highest average (368.7 mg kg−1) and maximum (1414.0 mg kg−1) concentrations were measured in samples from Illiomama Rock (Auckland). Of the toxic populations tested there was significant variability in TTX concentrations among individuals, with the highest difference (62 fold) measured at Illiomama Rock. Tetrodotoxin concentrations in samples from Narrow Neck Beach varied temporally, ranging from an average of 184 mg kg−1 in June 2010 to 17.5 mg kg−1 by December 2010. There was no correlation between TTX levels and mass. The highest levels correspond with the egg laying season (June–August) and this, in concert with the detection of high levels of TTX in eggs and early larval stages, suggests that TTX may have a defensive function in P. maculata. Only one larva was successfully reared to full maturation and no TTX was detected.
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Tetrodotoxin Concentrations in Pleurobranchaea maculata: Temporal, Spatial and Individual Variability from New Zealand Populations
2012Co-Authors: Susanna A Wood, David I Taylor, Paul Mcnabb, Janet Adamson, Jarrod Walker, Stephen Craig CaryAbstract:Abstract: Tetrodotoxin (TTX) is a potent neurotoxin that has been identified in a range of phylogenetically unrelated marine and terrestrial organisms. Tetrodotoxin was recently detected in New Zealand in Pleurobranchaea maculata (the grey side-gilled sea slug). From June 2010 to June 2011 wild specimens were collected from 10 locations around New Zealand. At one site (Narrow Neck Beach, Auckland) up to 10 individuals were collected monthly for 6 months. Attempts were also made to rear P. maculata in captivity. Tetrodotoxin was detected in samples from eight of the ten sites. The highest average (368.7 mg kg −1) and maximum (1414.0 mg kg −1) concentrations were measured in samples from Illiomama Rock (Auckland). Of the toxic populations tested there was significant variability in TTX concentrations among individuals, with the highest difference (62 fold) measured at Illiomama Rock. Tetrodotoxin concentrations in samples from Narrow Neck Beach varied temporally, ranging from an average of 184 mg kg −1 in June 2010 to 17.5 mg kg −1 by December 2010. There was no correlation between TTX levels and mass. The highest levels correspond with the egg laying season (June–August) and this, in concert with theMar. Drugs 2012, 10 164 detection of high levels of TTX in eggs and early larval stages, suggests that TTX ma
Paul Mcnabb - One of the best experts on this subject based on the ideXlab platform.
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In situ accumulation of tetrodotoxin in non-toxic Pleurobranchaea maculata (Opisthobranchia)
2017Co-Authors: Lauren Salvitti, Susanna A Wood, Paul Mcnabb, Rex Fairweather, David Culliford, S. Craig CaryAbstract:Tetrodotoxin (TTX) is a highly potent neurotoxin targeting voltage gated sodium channels. It is found in numerous phyla, including both marine and terrestrial taxa, however, its origin is a topic of considerable debate. The aim of this study was to investigate the origin of TTX in the Opisthobranch Pleurobranchaea maculata using in situ experimentation. Sixteen individuals sourced from non-toxic populations were transplanted to a habitat with toxic populations. These were kept in mesh net cages either; (1) anchored to the seafloor, or (2) deployed 0.5 m off the benthos. They were fed a non-toxic diet for 8 weeks before being sacrificed, and either the entire organisms or specific organs analysed for TTX via liquid chromatography–mass spectrometry. Four of the six remaining individuals from cages on the benthos contained TTX (max. 0.79 mg kg^−1), whilst only two of eight from the suspended cages contained TTX and concentrations were lower (max. 0.43 mg kg^−1). These were similar to the lowest concentrations (min. 0.4 mg kg^−1) detected in free-living specimens collected during the experimental period. Among positive individuals the highest concentrations were detected in gonad tissues. These data, in concert with previous studies, suggest an environmental source of TTX for P. maculata , which may be bacterial or dietary in origin. High-Throughput Sequencing (18S ribosomal RNA gene metabarcoding) of foregut contents from toxic and non-toxic individuals was used to investigate their diet. High abundances of Cnidaria and Annelida sequences were identified and these groups should be targeted in future efforts to identify TTX-containing organisms.
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first identification of tetrodotoxin ttx in the flatworm stylochoplana sp a source of ttx for the sea slug Pleurobranchaea maculata
2015Co-Authors: Lauren R Salvitti, Susanna A Wood, David I Taylor, Paul Mcnabb, Craig S CaryAbstract:High concentrations of the neurotoxin tetrodotoxin (TTX) were detected by liquid chromatography–mass spectrometry (LC–MS) in the Platyhelminthes Stylochoplana sp. from Pilot Bay (Tauranga, New Zealand). This is the first detection of TTX in this genus. Concentrations were monitored from March to November (2013) and found to significantly decrease from a peak in July (avg. 551 mg kg−1) to November (avg. 140 mg kg−1). Stylochoplana sp. co-occurred with TTX-containing Pleurobranchaea maculata (Opisthobranchia). A Stylochoplana sp.-specific real-time PCR assay was developed targeting the mitochondrial cytochrome c oxidase subunit I gene to determine if P. maculata consumed Stylochoplana sp. Positive Stylochoplana sp. signals were obtained for 7 of 19 P. maculata tested. Mass calculations indicate Stylochoplana sp. could supply Pilot Bay P. maculata with the TTX required to account for the concentrations reported in previous studies (ca. 1.04 mg TTX per individual) based on an ingestion rate of one individual every 2–3 days throughout their lifetime. However, due to the lack of Stylochoplana sp. in areas with dense P. maculata populations, and high concentration (ca. 1400 mg kg−1) of TTX detected in some individuals, it is unlikely that Stylochoplana sp. represent the sole source of TTX in P. maculata.
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no evidence for a culturable bacterial tetrodotoxin producer in Pleurobranchaea maculata gastropoda pleurobranchidae and stylochoplana sp platyhelminthes polycladida
2015Co-Authors: Lauren R Salvitti, Susanna A Wood, Paul Mcnabb, Stephen Craig CaryAbstract:Tetrodotoxin (TTX) is a potent neurotoxin found in the tissues of many taxonomically diverse organisms. Its origin has been the topic of much debate, with suggestions including endogenous production, acquisition through diet, and symbiotic bacterial synthesis. Bacterial production of TTX has been reported in isolates from marine biota, but at lower than expected concentrations. In this study, 102 strains were isolated from Pleurobranchaea maculata (Opisthobranchia) and Stylochoplana sp. (Platyhelminthes). Tetrodotoxin production was tested utilizing a recently developed sensitive method to detect the C9 base of TTX via liquid chromatography—mass spectrometry. Bacterial strains were characterized by sequencing a region of the 16S ribosomal RNA gene. To account for the possibility that TTX is produced by a consortium of bacteria, a series of experiments using marine broth spiked with various P. maculata tissues were undertaken. Sixteen unique strains from P. maculata and one from Stylochoplana sp. were isolated, representing eight different genera; Pseudomonadales, Actinomycetales, Oceanospirillales, Thiotrichales, Rhodobacterales, Sphingomonadales, Bacillales, and Vibrionales. Molecular fingerprinting of bacterial communities from broth experiments showed little change over the first four days. No C9 base or TTX was detected in isolates or broth experiments (past day 0), suggesting a culturable microbial source of TTX in P. maculata and Stylochoplana sp. is unlikely.
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first detection of tetrodotoxin in the bivalve paphies australis by liquid chromatography coupled to triple quadrupole mass spectrometry with and without precolumn reaction
2014Co-Authors: Paul Mcnabb, Susanna A Wood, David I Taylor, Shaun Ogilvie, Larn Wilkinson, Alice Anderson, David Hamon, Barrie M PeakeAbstract:Two methods for the determination of tetrodotoxin (TTX) in marine biota have been developed and validated using ultra-performance LC coupled to triple quadrupole MS. The direct analysis of TTX is completed in one method, while the other method detects the dehydration product of TTX after reaction with base. The methods were validated in a single-laboratory trial and used to test Paphies australis (pipi) samples collected from Whangapoua, New Zealand during April 2011. Pa. australis is a commonly eaten species of bivalve that was found to contain TTX at levels up to 0.80 mg/kg in this study. The methods exhibited recoveries ranging from 94 to 120%, and the within laboratory reproducibility ranged from 6 to 27% for Pleurobranchaea maculata (grey-side gilled sea slug) and bivalve matrixes. Use of the method using a dehydration step showed no evidence of TTX analogs in any of the samples.
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investigating diet as the source of tetrodotoxin in Pleurobranchaea maculata
2013Co-Authors: Serena Khor, Susanna A Wood, David I Taylor, Lauren R Salvitti, Paul Mcnabb, Janet Adamson, Stephen Craig CaryAbstract:The origin of tetrodotoxin (TTX) is highly debated; researchers have postulated either an endogenous or exogenous source with the host accumulating TTX symbiotically or via food chain transmission. The aim of this study was to determine whether the grey side-gilled sea slug (Pleurobranchaea maculata) could obtain TTX from a dietary source, and to attempt to identify this source through environmental surveys. Eighteen non-toxic P. maculata were maintained in aquariums and twelve were fed a TTX-containing diet. Three P. maculata were harvested after 1 h, 24 h, 17 days and 39 days and TTX concentrations in their stomach, gonad, mantle and remaining tissue/fluids determined using liquid chromatography-mass spectrometry. Tetrodotoxin was detected in all organs/tissue after 1 h with an average uptake of 32%. This decreased throughout the experiment (21%, 15% and 9%, respectively). Benthic surveys at sites with dense populations of toxic P. maculata detected very low or no TTX in other organisms. This study demonstrates that P. maculata can accumulate TTX through their diet. However, based on the absence of an identifiable TTX source in the environment, in concert with the extremely high TTX concentrations and short life spans of P. maculata, it is unlikely to be the sole TTX source for this species.
Nathan G Hatcher - One of the best experts on this subject based on the ideXlab platform.
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nitric oxide potentiates camp gated cation current by intracellular acidification in feeding neurons of Pleurobranchaea
2010Co-Authors: Kurt Potgieter, Rhanor Gillette, Nathan G Hatcher, C R MccrohanAbstract:A pH-sensitive cAMP-gated cation current (INa,cAMP) is widely distributed in neurons of the feeding motor networks of gastropods. In the sea slug Pleurobranchaea this current is potentiated by nitric oxide (NO), which itself is produced by many feeding neurons. The action of NO is not dependent on either cGMP or cAMP signaling pathways. However, we found that NO potentiation of INa,cAMP in the serotonergic metacerebral cells could be blocked by intracellular injection of MOPS buffer (pH 7.2). In neurons injected with the pH indicator BCECF, NO induced rapid intracellular acidification to several tenths of a pH unit. Intracellular pH has not previously been identified as a specific target of NO, but in this system NO modulation of INa,cAMP via pHi may be an important regulator of the excitability of the feeding motor network.
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nitric oxide potentiates camp gated cation current in feeding neurons of Pleurobranchaea californica independent of camp and cgmp signaling pathways
2006Co-Authors: Nathan G Hatcher, Leonid L. Moroz, Leland C. Sudlow, Rhanor GilletteAbstract:Critical roles for nitric oxide (NO) in regulating cell and tissue physiology are broadly appreciated, but aspects remain to be explored. In the mollusk Pleurobranchaea, NO synthase activity is hig...