Publications (14)23.65 Total impact
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Article: Making sense of electrical sense in crayfish.
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ABSTRACT: The five sensory modalities of humans are also found in a wide range of invertebrates. Other vertebrates have evolved additional special senses, such as the magnetic sense, which are also found in some invertebrates. However, there remain a few sensory abilities that curiously appear to be found in either vertebrates or invertebrates, but not both. For example, electrosensitivity - the ability to detect electric fields in water - which should benefit vertebrates and invertebrates alike, is apparently only used by vertebrates. However, recent reports suggest that some invertebrates could have an electric sense. Here we examine that possibility further and demonstrate a behavioural threshold to low-level electrical fields in two freshwater invertebrates. The responses are not low enough for them to detect the Earth's magnetic field as some other electroreceptive species can do, but sufficiently low for them to use in navigation or prey and predator detection. This finding challenges the current view of the sensory world of aquatic invertebrates and has implications for the evolution of this ability.Journal of Experimental Biology 02/2010; 213(4):651-7. · 3.00 Impact Factor -
Article: Video tracking in the extreme: video analysis for nocturnal underwater animal movement.
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ABSTRACT: Computer analysis of video footage is one option for recording locomotor behavior for a range of neurophysiological and behavioral studies. This technique is reasonably well established and accepted, but its use for some behavioral analyses remains a challenge. For example, filming through water can lead to reflection, and filming nocturnal activity can reduce resolution and clarity of filmed images. The aim of this study was to develop a noninvasive method for recording nocturnal activity in aquatic decapods and test the accuracy of analysis by video tracking software. We selected crayfish, Cherax destructor, because they are often active at night, they live underwater, and data on their locomotion is important for answering biological and physiological questions such as how they explore and navigate. We constructed recording arenas and filmed animals in infrared light. Wethen compared human observer data and software-acquired values. In this article, we outline important apparatus and software issues to obtain reliable computer tracking.Behavior Research Methods 12/2007; 39(4):783-8. · 2.12 Impact Factor -
Article: Exploring with damaged antennae: do crayfish compensate for injuries?
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ABSTRACT: Appendages are important sources of sensory information for all animals that possess them but they are commonly damaged in nature. We describe how the tactile system of the crayfish Cherax destructor functioned when subjected to the kind of damage found in wild-caught or cultured animals. Touch information was methodically varied by the removal of antennae and chelae. The resulting behaviour was analysed in a T-maze. Crayfish with a single antenna ablated turned toward the intact appendage, however, those with only a partial ablation did not, suggesting that a tactile information threshold exists for normal behaviour. When exposed to the same environment after an antennal ablation but with no prior experience in that terrain, crayfish also turned toward the side of the intact antenna. By contrast, when animals with experience obtained in a previous trial with intact antennae were tested after ablation of one antenna, they did not turn into one arm of the maze more than the other. These two outcomes indicate that behaviour is affected by an interaction between the time at which an injury occurs and an animal's knowledge of the topography, and that an injury may affect learning. We also tested to see if other appendages could provide tactile information to compensate for antennal loss. Input from the chelae did not affect the turning behaviour of crayfish in the maze.Journal of Experimental Biology 09/2006; 209(Pt 16):3226-33. · 3.00 Impact Factor -
Article: Corners and bubble wrap: the structure and texture of surfaces influence crayfish exploratory behaviour.
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ABSTRACT: Touch is a principal sense in all animals. It is potentially important in species of freshwater crayfish that encounter murky waters or are nocturnal. Little is known about how tactile (touch) stimuli affect exploratory behaviour under these conditions. We placed animals in different tactile situations at the start of an exploration in a dark arena and tracked the position of the body and antennae to test whether subsequent search behaviour was affected. Individuals were exposed to differently textured walls, channelled out along a wall, or released in contact with no, one, or two walls. A corner arrangement of surfaces, where individuals started near two walls at right angles, produced behaviour that differed from that of other configurations; animals chose one wall and then maintained a close distance from the wall along which they were moving. The distance from a wall adopted by a crayfish walking parallel to it was affected by the texture of the wall. These results on the influence of tactile stimuli on crayfish exploratory behaviour may have implications for other taxa.Journal of Experimental Biology 03/2006; 209(Pt 3):567-75. · 3.00 Impact Factor -
Article: The activity of abdominal stretch receptors during non-giant swimming in the crayfish Cherax destructor and their role in hydrodynamic efficiency.
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ABSTRACT: Recordings were made from the nerve innervating the stretch receptors of the abdominal muscle receptor organs and slow extensor muscles of tethered crayfish, Cherax destructor, during so-called "non-giant swimming". The stretch receptors were active during the flexor phase of swimming but the duration and pattern of activity varied from cycle to cycle. Their pattern of firing was modified by the activity of the large accessory neurons which make direct inhibitory synapses upon them. Neither the stretch receptors nor the accessory neurons were active during the extensor phase of the cycle. The timing and extent of tailfan movements during the period of stretch receptor activity were measured from video records before and after the stretch receptor nerves were cut in the second to fifth segments. The promotion of the tailfan during flexion was significantly delayed and the minimum angle to which the uropods were remoted at the end of flexion significantly larger in denervated animals. We propose that afferent information from the stretch receptors coordinates the timing and extent of tailfan movements according to variations in the positioning and movement of the abdominal segments such that the hydrodynamic efficiency of the tailfan is enhanced on a cycle by cycle basis during non-giant swimming.Journal of Comparative Physiology 05/2004; 190(4):291-9. · 2.01 Impact Factor -
Article: The cord stretch receptors in the abdominal nerve cord of the crayfish Cherax destructor: physiology and relationships.
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ABSTRACT: 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 [Mg(2+)] and low [Ca(2+)] 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.Journal of Comparative Physiology 07/2002; 188(5):349-57. · 2.01 Impact Factor -
Article: Muscle receptor organs do not mediate load compensation during body roll and defense response extensions in the crayfish Cherax destructor.
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ABSTRACT: It has been proposed that the abdominal muscle receptor organ (MRO) of decapod crustaceans acts in a sensory feedback loop to compensate for external load. There is not yet unequivocal evidence of MRO activity during slow abdominal extension in intact animals, however. This raises the possibility that MRO involvement in load compensation is context-dependent. We recorded from MRO tonic stretch receptors (SRs) in freely behaving crayfish (Cherax destructor) during abdominal extension occurring during two different behaviors: body roll and the defense response. Abdominal extensions are similar in many respects in both behaviors, although defense response extensions are more rapid. In both situations, SR activity typically ceased when the abdominal extension commenced, even if the joint of the SR being monitored was mechanically prevented from extending by a block. Since extensor motor neuron activity increased when the abdomen was prevented from extending, we concluded that the load compensation occurring in these behaviors was not mediated by the MROs.Journal of Experimental Zoology 01/2002; 290(7):783-90. -
Article: Laboratory and field studies on the effect of molinate, clomazone, and thiobencarb on nontarget aquatic invertebrates.
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ABSTRACT: The midge Chironomus tepperi was used in laboratory experiments to assess the relative toxicity of formulated molinate, clomazone, and thiobencarb, three herbicides used in Australian rice crops. Static bioassays were initiated with first-instar larvae at herbicide concentrations between 0.0625 and 2 times the anticipated field concentrations (AFCs) expected from the registered application rates. Adult emergence success, development time, and wing length were used as indices of the effect of each herbicide. Clomazone had no effect on any parameters at concentrations up to 0.288 mg/L (p > 0.05). Molinate significantly increased development time at concentrations equivalent to the AFC (3.6 mg/L) and above (p < 0.05). Thiobencarb reduced emergence success of adult C. tepperi at 0.0625 times the AFC (0.1875 mg/L) as well as decreasing male adult size and increasing development time for males and females at 0.125 times the AFC (p < 0.05). Nontarget effects of the herbicides on aquatic invertebrate communities were assessed in shallow experimental ponds using commercial application rates. One week after treatment, only thiobencarb had a significant effect, suppressing populations of chironomids, calanoids, and cyclopoids (p < 0.05). Four weeks later, all populations had recovered, equaling or exceeding control densities.Environmental Toxicology and Chemistry 10/2001; 20(10):2229-36. · 2.81 Impact Factor -
Article: Embryonic and postembryonic neurogenesis in the ventral nerve cord of the freshwater crayfish Cherax destructor.
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ABSTRACT: Previous studies of neurogenic activity in the thoracic neuromeres of indirect developing crustaceans indicated that the temporal patterns of neurogenesis can be correlated with the appearance of the thoracic appendages during larval and metamorphic development. To test further the idea that the temporal patterns of neurogenesis in crustaceans are related to their life histories, we examined neurogenesis in the ventral nerve cord of a direct developing crustacean, the freshwater crayfish Cherax destructor, whose life history contains neither larval stages nor metamorphoses. Neurogenesis was examined using the in vivo incorporation of bromodeoxyuridine into DNA. During late embryonic development the thoracic neuromeres of the crayfish contain arrays of mitotically active neuroblasts similar to those previously described in the spider crab and lobster. The arrays in the crayfish abdomen are, however, greatly reduced compared with those of the thorax. On hatching, both the thoracic and abdominal appendages of C. destructor are capable of movement. The pleopods, however, do not beat rhythmically until the second postembryonic stage whereas the pereiopods are not used in coordinated walking movements until the third stage. An examination of the time course of neurogenesis in the ventral nerve cord revealed that neurogenic activity in each neuromere ceases during or before the moult to the developmental stage in which its segmental appendage is first used in coordinated movements. These findings indicate that the patterns of neurogenesis in crustaceans are indeed related to the maturation of the segmental appendages and, in particular, to the maturation of motor behaviours.Journal of Experimental Zoology 07/2001; 290(1):49-60. -
Article: Insights for robotic design from studies of the control of abdominal position in crayfish.
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ABSTRACT: Studies of the control of position and movement of the abdomen of crayfish illustrate a number of features of invertebrate sensory-motor systems that have implications for their use to inform robotic design. We use the abdominal slow extensor motor system to illustrate three of them here: first, the way in which a behaviorally flexible length-servo device can be achieved with very few elements; second, the importance of knowledge of the biological and behavioral context in which the elements operate; third, that design solutions resulting from natural selection have been constrained by the previous evolutionary history of the animal, which can affect the outcomes in ways that may not be immediately apparent in a design context.Biological Bulletin 05/2001; 200(2):201-5. · 1.70 Impact Factor -
Article: The abdominal motor system of the crayfish, Cherax destructor. II. Morphology and physiology of the deep extensor motor neurons
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ABSTRACT: Two opposing muscle systems underlie abdominal contractions during escape swimming in crayfish. In this study we used extracellular and intracellular stimulation, recording and dye-filling to systematically identify each of the five deep extensor excitors and single inhibitor of the crayfish, Cherax destructor. Functional associations of each neuron were characterised by recording its responses to sensory and abdominal cord inputs, its extensor muscle innervation pattern, and its relationships with other neurons. Each excitor receives excitatory input from the tonic abdominal stretch receptors and the largest neuron also receives input from the phasic stretch receptor. The two largest excitors innervate the muscle bundle containing the fastest fibres and may be electronically coupled. The smaller neurons may also be electronically coupled and innervate the remaining deep extensor fibres which display dynamic characteristics from fast to medium-fast. The inhibitor does not receive input from the stretch receptors, but is strongly excited by tactile afferents. The implications of these findings for the current models of the control of abdominal tailflips and swimming are discussed.Journal of Comparative Physiology 10/1998; 183(5):603-619. · 2.01 Impact Factor -
Article: The abdominal motor system of the crayfish, Cherax destructor. I. Morphology and physiology of the superficial extensor motor neurons
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ABSTRACT: Using extracellular and intracellular stimulation, recording and dye-filling, we identified and studied the superficial extensor motor neurons of the crayfish, Cherax destructor. Functional associations of each neuron were characterised by recording its responses to sensory and abdominal cord inputs, its extensor muscle innervation pattern and its relationships with other neurons. Two clear associations were found among the six neurons of each segment. A medium-sized excitor (no. 3), that innervates a substantial percentage of extensor muscle fibres, and the largest excitor (no. 6), recruited during peak, excitation, were inhibited by input from unknown interneurons that excited the common inhibitor (no. 5). Likewise, these excitors received excitatory input when the inhibitor was silent. Another medium-sized neuron (no. 4) that innervates many muscle fibres was co-active with one of the small excitors (no. 2). The two medium-sized neurons were never active at the same time, and these two groupings may be determined by pre-motor interneurons. The implications of these findings for our understanding of motor control in this system are discussed.Journal of Comparative Physiology 01/1998; 183(5):583-601. · 2.01 Impact Factor -
Article: Lactic acid formation in crustaceans and the liver function of the midgut gland questioned.
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ABSTRACT: 1. The possibility of the midgut gland of the crustacean (Cherax destructor) functioning as a liver has been investigated. 2. Seven species of crustaceans accumulate lactic acid in the haemolymph when exercised. The rate of disappearance of lactate in Homarus gammarus and in C. destructor is very slow when compared with man. 3. In the midgut gland of C. destructor no firm evidence was obtained for gluconeogenesis from lactate and for ketogenesis from fatty acids. 4. It is concluded that there is at present no justification for the common practice of calling the midgut gland an hepatopancreas.Comparative biochemistry and physiology. B, Comparative biochemistry 02/1977; 56(4):427-33. -
Article: Lactic acid formation in crustaceans and the liver function of the midgut gland questioned
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ABSTRACT: 1.1. The possibility of the midgut gland of the crustacean (Cherax destructor) functioning as a liver has been investigated.2.2. Seven species of crustaceans accumulate lactic acid in the haemolymph when exercised. The rate of disappearance of lactate in Homarus gammarus and in C. destructor is very slow when compared with man.3.3. In the midgut gland of C. destructor no firm evidence was obtained for gluconeogenesis from lactate and for ketogenesis from fatty acids.4.4. It is concluded that there is at present no justification for the common practice of calling the midgut gland an hepatopancreas.Comparative Biochemistry and Physiology Part B: Comparative Biochemistry.
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1977–2010
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University of Melbourne
- Department of Zoology
Melbourne, Victoria, Australia
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