Salamander Locomotion

Cross references:   Amphioxus Locomotion    Lamprey Locomotion       
Salamander     Brain of the Tiger Salamander    Salamander Brain Diagram    
Amphibian Muscles        Salamander GABA     

    The list of links in "Cross references", above, to pages in  Children of the Amphioxus  is intended to provide general background to salamander locomotion. 

salamander locomotion - Mozilla Yahoo Search Results - 143,000 references 
salamander locomotion - Google Search - 105,000 references 
salamander locomotion - PubMed - 344 references   

Striatal afferents in the newt Triturus cristatus.    
    I'm very surprised.  I had the impression from Herrick that striatal afferents were mostly olfactory, but this article says: 
    "Striatal injections of HRP revealed that the main striatal afferent systems originate within the diencephalon, specifically in the dorsal thalamus and paraventricular organ of the hypothalamus. Several small groups of neurons in other diencephalic areas also participate in striatal innervation: proeminentia ventralis, amygdala, contralateral corpus striatum, preoptic area, posterior tuberal nucleus, locus coeruleus and raphe nuclei. 
Degeneration experiments after mechanical lesion of the paraventricular organ established the existence of a hypothalamostriatal projection. Degenerating axonal profiles were also found in many of the structures already identified as projecting to the striatum, suggesting that the paraventricular organ might influence the striatum not only directly but also indirectly through these other afferent systems.  
    In the paraventricular organ, glyoxylic acid fluorescence histochemistry showed numerous monoamine neurons that corresponded in distribution and morphology to the retrogradely HRP-labeled neurons. Paraventricular-organ-lesioned males displayed a severe impairment of courtship behavior in the form of decreased tail beating and head stepping by the females. This suggests that the regulation of stereotyped hypermotricity might involve the monoamine component of the hypothalamo-striatal projection."  

119 Related citations
1 Cited by
See the paper. 

My comment:            
    I need to come back to this. 


Epaxial and limb muscle activity during swimming and terrestrial stepping in the adult newt, Pleurodeles waltl.      
    "During swimming, the epaxial myomeres are rhythmically active, with a strict alternation between opposite myomeres located at the same longitudinal site. The pattern of intersegmental coordination consists of three successively initiated waves of EMG activity passing posteriorly along the anterior trunk, the midtrunk, and the posterior trunk, respectively. Swimming is also characterized by a tonic activation of forelimb (dorsalis scapulae and extensor ulnae) and hindlimb (puboischiotibialis and puboischiofemoralis internus) muscles and a rhythmic activation of muscles (latissimus dorsi and caudofemoralis) acting both on limb and body axis. The latter matched the activation pattern of epaxial myomeres at the similar vertebral level.  
    During overground stepping, the midtrunk myomeres express single synchronous bursts whereas the myomeres of the anterior trunk and those of the posterior trunk display a double bursting pattern in the form of two waves of EMG activity propagating in opposite directions. During overground stepping, the limb muscles and muscles acting on both limb and body axis were found to be rhythmically active and usually displayed a double bursting pattern.
    The main conclusion of this investigation is that the patterns of intersegmental coordination during both swimming and overground stepping in the adult newt are related to the presence of limbs and that they can be considered as hybrid lampreylike patterns. Thus it is hypothesized that, in newt, a chain of coupled segmental oscillatory networks, similar to that which constitutes the central pattern generator (CPG) for swimming in the lamprey, can account for both trunk motor patterns if it is influenced by limb CPGs in a way depending on the locomotor mode. During swimming, the segmental networks located close to the girdles receive extra tonic excitation coming from the limb CPGs, whereas during stepping, the axial CPGs are entrained to some extent by the limb oscillators."  

155 Related citations
   - Free full text -  


From swimming to walking: a single basic network for two different behaviors. 
    "In this paper we consider the hypothesis that the spinal locomotor network controlling trunk movements has remained essentially unchanged during the evolutionary transition from aquatic to terrestrial locomotion. The wider repertoire of axial motor patterns expressed by amphibians would then be explained by the influence from separate limb pattern generators, added during this evolution.  
    This study is based on EMG data recorded in vivo from epaxial musculature in the newt Pleurodeles waltl during unrestrained swimming and walking, and on a simplified model of the lamprey spinal pattern generator for swimming. Using computer simulations, we have examined the output generated by the lamprey model network for different input drives. Two distinct inputs were identified which reproduced the main features of the swimming and walking motor patterns in the newt.  
    The swimming pattern is generated when the network receives tonic excitation with local intensity gradients near the neck and girdle regions.  
    To produce the walking pattern, the network must receive (in addition to a tonic excitation at the girdles) a phasic drive which is out of phase in the neck and tail regions in relation to the middle part of the body. To fit the symmetry of the walking pattern, however, the intersegmental connectivity of the network had to be modified by reversing the direction of the crossed inhibitory pathways in the rostral part of the spinal cord.  
    This study suggests that the input drive required for the generation of the distinct walking pattern could, at least partly, be attributed to mechanosensory feedback received by the network directly from the intraspinal stretch-receptor system. Indeed, the input drive required resembles the pattern of activity of stretch receptors sensing the lateral bending of the trunk, as expressed during walking in urodeles. Moreover, our results indicate that a nonuniform distribution of these stretch receptors along the trunk can explain the discontinuities exhibited in the swimming pattern of the newt.  
    Thus, separate limb pattern generators can influence the original network controlling axial movements not only through a direct coupling at the central level but also via a mechanical coupling between trunk and limbs, which in turn influences the sensory signals sent back to the network. Taken together, our findings support the hypothesis of a phylogenetic conservatism of the spinal locomotor networks generating axial motor patterns from agnathans to amphibians."    

307 Related citations:   



    Activation of NMDA receptors is required for the initiation and maintenance of walking-like activity in the mudpuppy (Necturus Maculatus).  
We hypothesized that blocking the activation of N-methyl-D-aspartate (NMDA) receptors prevents the initiation of walking-like activity and abolishes the ongoing rhythmic activity in the spinal cord-forelimb preparation from the mudpuppy.  
    Robust walking-like movements of the limb and rhythmic alternating elbow flexor-extensor EMG pattern characteristic of walking were elicited when continuous perfusion of the spinal cord with solution containing D-glutamate. The frequency of the walking-like activity was dose-dependent on the concentration of D-glutamate in the bath over a range of 0.2 to 0.9 mmol/L.  
    Elevation of potassium concentrations failed to induce walking-like activity.  
    Application of the selective antagonist 2-amino-5-phosphonovalerate (AP-5) produced dose-dependent block of the initiation and maintenance of walking-like activity induced by D-glutamate. Complete block of the activity was achieved when the concentration of AP-5 reached 20 micromol/L. Furthermore, application of L-701,324 (a selective antagonist of the strychnine-insensitive glycine site of NMDA receptor) (1-10 micromol/L) also resulted in complete block of the walking-like activity. In contrast, application of the non-NMDA receptor antagonist 6-cyno-7-nitroquinoxaline-2,3-dione (CNQX) (1-50 micromol/L) induced a dose-dependent inhibition of the burst frequency but failed to result in a complete block. Only at concentration as high as 100 micromol/L, did CNQX cause complete block of the rhythmic activity, presumably through nonspecific action on the strychnine-insensitive glycine site of NMDA receptors.  
    These results suggest that activation of NMDA receptors is required for the initiation and maintenance of walking-like activity. Operation of non-NMDA receptors plays a powerful role in the modulation of the walking-like activity in the mudpuppy."  

99 Related citations:   
2 Cited by's
See the PubMed abstract. 

Organisation of the spinal central pattern generators for locomotion in the salamander: biology and modelling.  
Among living tetrapods, salamanders are regarded as most closely resembling the first terrestrial vertebrates, and are therefore an interesting group in which the evolutionary changes in the locomotor behaviour from aquatic to terrestrial habitats can be inferred.  
    Salamanders exhibit two locomotor modes: swimming and terrestrial stepping. The swimming is anguilliform and resembles closely that of the lamprey. On the ground, the salamander switches to a stepping gait with axial undulations that is also observed in many reptiles. The salamander is therefore ideally suited for examining the neural mechanisms for the generation of these two locomotor modes, as well as the neural mechanisms of gait transition.  
    In the present paper, we describe the kinematics and patterns of activation of axial and limb muscles during stepping and swimming in adult salamanders. We then review the current neurobiological data about the organisation of the spinal networks underlying swimming and stepping, and the mechanisms of gait transition. Finally we report modelling studies aimed at understanding the organisation and operation of the salamander locomotor circuits.  
    Altogether, the neurobiological and the modelling data support the hypothesis of a phylogenetic conservatism from agnathians to amphibians of the spinal locomotor networks generating axial motor patterns."   

Brain of the Tiger Salamander     

Index    p.  399    
    Locomotor apparatus, 15, 40, 50, 63, 282   

Pages 14 - 16:     

In Devonian times, probably about three hundred million years ago, various species of fishes made excursions to the land and acquired structures adapted for temporary sojourn out of water. Some of the primitive crossopterygian fishes went further and, after a fishlike larval period, experienced a metamorphosis into air-breathing tetrapods. They became amphibians. These were fresh-water species, and the immediate cause of this evolutionary change was extensive continental desiccation during the Devonian period. While their streams and pools were drying up, those fishes which had accessory organs of respiration in addition to the gills of typical fishes, were able to survive and, through further transformations, become air breathing land animals. An excellent summary of the paleontological evidence upon which the history of the evolution of fishes has been reconstructed has been published by Romer ('46). 

Two prominent features of this revolutionary change involved the organs of respiration and locomotion, with corresponding changes in the nervous apparatus of control. These systems of organs are typical representatives of the two major subdivisions of all vertebrate bodies and their functions — the visceral and the somatic. The visceral functions and the visceral nervous system will receive scant consideration

Page 15

 in this work, for the material at our disposal is not favorable for the study of these tissues. Here we are concerned primarily with the nervous apparatus of overt behavior, that is, of the somatic adjustments. 

The most important change in these somatic adjustments during the critical evolutionary period under consideration is the transition from swimming to walking. The fossil record of the transformation of fins into legs is incomplete, but it is adequate to show the salient features of the transformation of crossopterygian fins into amphibian legs (Romer, '46). In the individual development of every salamander and every frog the internal changes in the organization of the nervous system during the transition from swimming to walking can be clearly seen. And these changes are very significant in our present inquiry because they illustrate some general principles of morphogenesis of the brain more clearly than do any other available data. 

In fishes, swimming is a mass movement requiring the co-ordinated action of most of their muscles in unison, notably the musculature of the trunk and tail. The paired fins are rudders, not organs of propulsion. 

The young salamander larva has no paired limbs but swims vigorously. This is a typical total pattern of action as defined by Coghill. The adult salamander after metamorphosis may swim in the water like the larva; and he can also walk on land with radically different equipment. Some fishes can crawl out on land, but the modified fins are clumsy and inefficient makeshifts compared with the amphibian's mobile legs. 

Quadrupedal locomotion is a very complicated activity compared with the simple mass movement of swimming. The action of the four appendages and of every segment of each of them must be harmoniously co-ordinated, with accurate timing of the contraction of many small muscles. These local activities are "partial patterns" of behavior, in Coghill's sense. From the physiological standpoint there is great advance, in that the primitive total pattern is supplemented, and in higher animals largely replaced, by a complicated system of co-ordinated partial patterns. This is emphasized here because it provides the key to an understanding of many of the differences between the nervous systems of fishes, salamanders, and mammals. Motility, and particularly locomotion, have played a major role in vertebrate evolution, as dramatically told by Gregory ('43). This outline has been filled in by Howell's ('45) interesting comparative survey of the

Page 16   

mechanisms of locomotion, and I have elsewhere discussed ('48) Coghill's contributions to this theme. 

Page 40:   

Amblystoma possesses the equipment of sensory and motor organs typical for vertebrates at a rather low level of specialization and in evenly balanced relations. All the usual systems are present, and none shows unusual size or aberrant features. The great lateral-line system of sense organs so characteristic of fishes is preserved, though somewhat reduced after metamorphosis. On the motor side the organs of locomotion and respiration have advanced from the fish-like to the quadrupedal form, but in very simple patterns. In early phylogeny the specialization of the motor systems seems to lag behind that of the sensory systems because the aquatic environment of primitive forms is more homogeneous than that of terrestrial animals, and, accordingly, fewer and simpler patterns of behavior are needed.       


The spinal cord and rhombic brain contain the central adjustors of the basic vital functions — respiration, nutrition, circulation, reproduction, locomotion, among others. This apparatus is elaborately organized in the most primitive living vertebrates, as also no doubt it must have been in their extinct ancestors. The cerebrum, on the

Page 41

other hand, except for the olfactory component, is a later acquisition.   

The spinal cord is not described in this report except for some features closely related to the brain, to which reference is made in the next paragraph. The cord segments are organized for the regulation

Page 42

of local reflexes of the limbs and the integration of these reflexes with one another and with the action of the trunk musculature, as in ordinary locomotion.   


The sector of the bulbo-spinal junction includes the upper segments of the spinal cord and the lower part of the medulla oblongata.   

It is the first center of correlation to become functional in embryonic development (Coghill, '14, Paper I). Its dorsal part around the calamus scriptorius receives fibers from the entire sensory zone of the bulb and cord, so that this gray of the funicular and commissural nuclei is a general clearing-house for all exteroceptive, proprioceptive, and visceral functions of the body except vision and olfaction.   

Here these functions are integrated in the interest of control of posture, locomotion, visceral activity, and other basic components of mass-movement type. Some of these connections are shown diagrammatically in
BTS Fig 003  , BTS Fig 007 , BTS Fig 008 , BTS Fig 087 ; for details and discussion see chapter IX. Spinal Cord   and a recent paper ('44b).   

Page 50:   

The "peduncle" described here is not the equivalent of the human cerebral peduncle (p. 21). The intimate relations of this field with the overlying tecto-thalamic field have been commented upon in the preceding paragraphs. This ventral field is a well-defined column of cells, differentiated at the anterior end of the basal plate of the embryonic neural tube. It is the head of the primary motor column (of Coghill), which in all vertebrates, from early embryonic stages to the adult, contains the nucleus of the oculomotor nerve and a much larger mass of nervous tissue, which activates the primitive mass movements of locomotion. It maintains cerebral control of the lower bulbo-spinal segments of the latter systems, and some other motor functions also are represented here. Into it fibers converge from all other parts of the cerebrum (
BTS Fig 012  , BTS Fig 014 , BTS Fig 015 , BTS Fig 017 , BTS Fig 018 , BTS Fig 020 , BTS Fig 021  , BTS Fig 022 , BTS Fig 023  BTS Fig 024 ), and from it efferent fibers go out in four groups: (1) Ventromedial tracts go to the medulla oblongata and spinal cord. The longest of these fibers are in the f. longitudinalis medialis ( BTS Fig 006). (2) The oculomotor nerve supplies intrinsic and extrinsic muscles of the eyeball ( BTS Fig 022 , BTS Fig 024).   

Page 63

The motor field of this brain is smaller and more simply organized than the sensory field because most of the activities are mass movements of total-pattern type. Within this larger frame of total behavior, the partial patterns of local reflexes are individuated with more or less capacity for autonomous action. The number of these local partial patterns is smaller than in higher animals, and all of them are far more closely bound to the total patterns of which they are parts. The segments of each limb, for instance, may, upon appropriate stimulation, move independently; but in ordinary locomotion they move in a sequence related to the action of the entire limb, the other limbs, and the musculature of the trunk.       

Page 282:   

The fascicles of group (5) also receive some fibers from other systems, as will appear below. For their courses as seen in horizontal sections see 
  BTS Fig 027  ,    BTS Fig 028 ,    BTS Fig 029  ,    BTS Fig 030  ,    BTS Fig 031  ,    BTS Fig 032;   in transverse sections, BTS Fig 091  ,    BTS Fig 092  ,    BTS Fig 093  ,    BTS Fig 094    and '36,

Page 282

figures 9-16; in sagittal sections, '36, figures 3, 18-21. The thalamo and pedunculo-tegmental fibers of this group are similar in many respects to the crossed and uncrossed fibers of tr. thalamo-tegmentalis ventralis of groups (4), (6), and (8). Those of group (5) arise chiefly from the peduncle, the others from the thalamus. In the aggregate these thick descending paths comprise the chief final common paths from the cerebrum to the peripheral neuromotor apparatus of the primary activities of the skeletal musculature, notably those of locomotion and feeding. In early larval development these long fibers from the peduncle and ventral thalamus are among the first to appear in the cerebrum. Their adult distribution in the several tegmental fascicles seems to be determined primarily not by the arrangement in space of the groups of cells from which they arise but by the lower motor fields into which they discharge their nervous impulses. Those in groups (4), (5), and (6) descend more medially and ventrally, the longest in the f. longitudinalis medialis. These longer fibers evidently activate the trunk and limbs. Collaterals of these fibers and accompanying shorter fibers end throughout the isthmic and bulbar tegmentum ('39b, figs. 84, 93), thus insuring coordination of head movements with those of the trunk and limbs. These more ventromedial fibers, accordingly, comprise the final common paths of fundamental mass movements, total patterns of behavior.