The control of walking movements in the leg of the rock lobster

Cruse H, Clarac F, Chasserat C. The control of walking movements in the leg of the rock lobster. Biological Cybernetics. 1983;47(2):87-94

Innervation of the receptors present at the various joints of the pereiopods and third maxilliped of Homarus gammarus (L.) and other macruran decapods (crustacea)

This paper gives a full account of the number and structure of the chordotonal organs present at all joints between the coxopodite and dactylopodite of the pereiopods and 3rd maxilliped of the macruran Homarus gammarus L. ( H. vulgaris M. Ed.). Some comparative data is supplied for other macruran decapods. As the form of the receptors depends to some degree upon the structure of the joint we have included details of musculature, planes of movement and degrees of freedom at each of the joints.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47101/1/359_2004_Article_BF00297736.pd

Neural circuits controlling behavior and autonomic functions in medicinal leeches

In the study of the neural circuits underlying behavior and autonomic functions, the stereotyped and accessible nervous system of medicinal leeches, Hirudo sp., has been particularly informative. These leeches express well-defined behaviors and autonomic movements which are amenable to investigation at the circuit and neuronal levels. In this review, we discuss some of the best understood of these movements and the circuits which underlie them, focusing on swimming, crawling and heartbeat. We also discuss the rudiments of decision-making: the selection between generally mutually exclusive behaviors at the neuronal level

Nanostructural Diversity of Synapses in the Mammalian Spinal Cord

This work for funded by the Biotechnology and Biological Sciences Research Council (BBSRC; BB/M021793/1), RS MacDonald Charitable Trust, Motor Neurone Disease (MND) Association UK (Miles/Apr18/863-791), the Engineering and Physical Sciences Research Council (EPSRC; EP/P030017/1), Welcome Trust (202932/Z/16/Z), European Research Council (ERC; 695568) and the Simons Initiative for the Developing Brain.Functionally distinct synapses exhibit diverse and complex organisation at molecular and nanoscale levels. Synaptic diversity may be dependent on developmental stage, anatomical locus and the neural circuit within which synapses reside. Furthermore, astrocytes, which align with pre and post-synaptic structures to form “tripartite synapses”, can modulate neural circuits and impact on synaptic organisation. In this study, we aimed to determine which factors impact the diversity of excitatory synapses throughout the lumbar spinal cord. We used PSD95-eGFP mice, to visualise excitatory postsynaptic densities (PSDs) using high-resolution and super-resolution microscopy. We reveal a detailed and quantitative map of the features of excitatory synapses in the lumbar spinal cord, detailing synaptic diversity that is dependent on developmental stage, anatomical region and whether associated with VGLUT1 or VGLUT2 terminals. We report that PSDs are nanostructurally distinct between spinal laminae and across age groups. PSDs receiving VGLUT1 inputs also show enhanced nanostructural complexity compared with those receiving VGLUT2 inputs, suggesting pathway-specific diversity. Finally, we show that PSDs exhibit greater nanostructural complexity when part of tripartite synapses, and we provide evidence that astrocytic activation enhances PSD95 expression. Taken together, these results provide novel insights into the regulation and diversification of synapses across functionally distinct spinal regions and advance our general understanding of the ‘rules’ governing synaptic nanostructural organisation.Publisher PDFPeer reviewe

Muscle precursor cells in the developing limbs of two isopods (Crustacea, Peracarida): an immunohistochemical study using a novel monoclonal antibody against myosin heavy chain

In the hot debate on arthropod relationships, Crustaceans and the morphology of their appendages play a pivotal role. To gain new insights into how arthropod appendages evolved, developmental biologists recently have begun to examine the expression and function of Drosophila appendage genes in Crustaceans. However, cellular aspects of Crustacean limb development such as myogenesis are poorly understood in Crustaceans so that the interpretative context in which to analyse gene functions is still fragmentary. The goal of the present project was to analyse muscle development in Crustacean appendages, and to that end, monoclonal antibodies against arthropod muscle proteins were generated. One of these antibodies recognises certain isoforms of myosin heavy chain and strongly binds to muscle precursor cells in malacostracan Crustacea. We used this antibody to study myogenesis in two isopods, Porcellio scaber and Idotea balthica (Crustacea, Malacostraca, Peracarida), by immunohistochemistry. In these animals, muscles in the limbs originate from single muscle precursor cells, which subsequently grow to form multinucleated muscle precursors. The pattern of primordial muscles in the thoracic limbs was mapped, and results compared to muscle development in other Crustaceans and in insects

The contralateral coordination of walking legs in the crayfish Astacus leptodactylus. I. Experimental results

Müller U, Cruse H. The contralateral coordination of walking legs in the crayfish Astacus leptodactylus. I. Experimental results. Biol. Cybern. 1991;64(5):429-436.The coupling mechanisms which coordinate the movement of ipsilateral walking legs in the crayfish have been described in earlier investigations. Concerning the coupling between contralateral legs it was only known that these influences are weaker than those acting between ipsilateral legs. The nature of these coupling mechanisms between contralateral legs of the crayfish are investigated here by running left and right legs on separate walking belts at different speeds. The results show that coordination is performed by a phase-dependent shift of the anterior extreme position of the influenced leg. This backward shift leads to a shortening of both the return stroke and the following power stroke. As the coupling influence is only weak, several steps might be necessary to retain normal coordination after a disturbance. This corresponds to v. Holst's relative coordination. The influences act in both directions, from left to right and vice versa. However, one side may be more or less dominant. A gradient was found in the way that anterior leg pairs show less strong coordination than posterior legs. In some cases the coupling between diagonally neighbouring legs was found to be stronger than between contralateral legs of the same segment. The interpretation of this result is still open

Invertebrate presynaptic inhibition and motor control.

International audienc

Functional multimodality of axonal tree in invertebrate neurons.

International audienceThis review, based on invertebrate neuron examples, aims at highlighting the functional consequences of axonal tree organization. The axonal organization of invertebrate neurons is very complex both morphologically and physiologically. The first part shows how the transfer of information along sensory axons is modified by presynaptic inhibition mechanisms. In primary afferents, presynaptic inhibition is involved in: 1) increasing the dynamic range of the sensory response; 2) processing the sensory information such as increasing spatial and/or temporal selectivity; 3) discriminating environmental information from sensory activities generated by the animal's own movement; and 4) modulating the gain of negative feedback (resistance reflex) during active rhythmic movements such as locomotion. In a second part, the whole organization of other types of neurons is considered, and evidence is given that a neuron may not work as a unit, but rather as a mosaic of disconnected 'integrate-and-fire' units. Examples of invertebrate neurons are presented in which several spike initiating zones exist, such as in some stomatogastric neurons. The separation of a neuron into two functionally distinct entities may be almost total with distinct arborizations existing in different ganglia. However, this functional separation is not definitive and depends on the state of the neuron. In conclusion, the classical integrate-and-fire representation of the neuron, with its dendritic arborization, its spike initiating zone, its axon and axonal tree seems to be no more applicable to invertebrate neurons. A better knowledge of the function of vertebrate neurons would probably demonstrate that it is the case for a large number of them, as suggested by the complex architecture of some reticular interneurons in vertebrates

The contralateral coordination of walking in the crayfish Astacus leptodactylus. II. Model calculations

Müller U, Cruse H. The contralateral coordination of walking in the crayfish Astacus leptodactylus. II. Model calculations. Biol. Cybern. 1991;64(5):437-446

Influence of walking on swimmeret beating in the lobster Homarus gammarus.

International audienceInfluence of walking on swimmeret beating in intact lobsters, Homarus gammarus, has been analyzed using a treadmill experimental device. Belt movement activates both leg stepping and swimmeret beating. The simultaneity of the onset of the two motor systems in this situation is demonstrated to be the result of a startle response initiated when the belt begins to move. This reaction consists of a non-specific motor activity involving several antagonist postural and dynamic muscles. Abdominal extension and vigorous swimmeret beating are the main features of this reaction. The main characteristics of the swimmeret beating as defined by Davis (1969) has been observed here in sequences without walking. However during long walking sequences a very different swimmeret beating pattern occurs. It is suggested that this slow swimmeret beating is completely subordinate to the walking rhythm during sequences of absolute coordination. In more rapid swimmeret beating a relative coordination with leg stepping is very common. The functional meaning of this linkage between legs and swimmerets is discussed