Muscle activity at the ilio‐sacral articulation of frogs
TL;DR: The firing pattern of the ilio‐sacral musculature is essentially similar during swimming and jumping, and suggests that differences in medium (water vs. air) are responsible for differences in propulsive thrust in the two types of locomotion.
Abstract: Electromyographic recording indicates that the sequence of muscle firing around the ilio-sacral joint is similar for three species of frogs during locomotion, despite differences in gross morphology at the articulation. The ilio-sacral musculature is most active during the take-off phase of a jump, and there is a correlation between the degree of muscle activity and height of jump. This muscle activity is involved in aligning the center of mass of the frog with the direction of the propulsive force of the jump. The firing pattern of the ilio-sacral musculature is essentially similar during swimming and jumping, and suggests that differences in medium (water vs. air) are responsible for differences in propulsive thrust in the two types of locomotion.
Citations
More filters
TL;DR: The discovery of the earliest known frog is reported, associated with caecilians that retained limbs7, that exhibits primitive characters but shares with later anurans such features as fusion of the caudal vertebrae (urostyle), a rod-like ilium, and elongate hind limbs.
Abstract: WITH nearly 4,000 living species1, frogs are numerically the most successful of modern amphibian groups. Their distinctive anatomy, which exhibits numerous unique features in both the axial and appendicular skeletons2a¤-6, represents a major departure from the body plan of Palaeozoic amphibians. We report here the discovery of the earliest known frog, associated with caecilians that retained limbs7, that exhibits primitive characters but shares with later anurans such features as fusion of the caudal vertebrae (urostyle), a rod-like ilium, and elongate hind limbs. The evolution of saltation in anurans entailed translocation of the ilium below the sacral rib, recruitment of the primitive tail musculature to transmit force from the hind limb to the axial skeleton during a jump, and development of iliosacral mobility. We reinterpret the caudopelvic transition from Palaeozoic amphibians to modern frogs with reference to Triadobatrachm massinoti, an Early Triassic amphibian that possesses some frog-like features8. The Early Jurassic age and Laurasian provenance of the new frog support the hypothesis4 that the widespread occurrence of primitive extant anurans reflects an ancient Pangaean distribution.
159 citations
TL;DR: It is shown here that the predicted power output during takeoff in Cuban tree frogs Osteopilus septentrionalis exceeds that available from the muscles by at least sevenfold, and muscle work output during jumping is temperature-dependent, with greater work being produced at higher temperatures.
Abstract: It has been suggested that small frogs use a catapult mechanism to amplify muscle power production during the takeoff phase of jumping. This conclusion was based on an apparent discrepancy between the power available from the hindlimb muscles and that required during takeoff. The present study provides integrated data on muscle contractile properties, morphology and jumping performance that support this conclusion. We show here that the predicted power output during takeoff in Cuban tree frogs Osteopilus septentrionalis exceeds that available from the muscles by at least sevenfold. We consider the sartorius muscle as representative of the bulk of the hindlimb muscles of these animals, because this muscle has properties typical of other hindlimb muscles of small frogs. At 25 degrees C, this muscle has a maximum shortening velocity (Vmax) of 8.77 +/- 0.62 L0 s-1 (where L0 is the muscle length yielding maximum isometric force), a maximum isometric force (P0) of 24.1 +/- 2.3 N cm-2 and a maximum isotonic power output of 230 +/- 9.2 W kg-1 of muscle (mean +/- S.E.M.). In contrast, the power required to accelerate the animal in the longest jumps measured (approximately 1.4 m) is more than 800 W kg-1 of total hindlimb muscle. The peak instantaneous power is expected to be twice this value. These estimates are probably conservative because the muscles that probably power jumping make up only 85% of the total hindlimb muscle mass. The total mechanical work required of the muscles is high (up to 60 J kg-1), but is within the work capacities predicted for vertebrate skeletal muscle. Clearly, a substantial portion of this work must be performed and stored prior to takeoff to account for the high power output during jumping. Interestingly, muscle work output during jumping is temperature-dependent, with greater work being produced at higher temperatures. The thermal dependence of work does not follow from simple muscle properties and instead must reflect the interaction between these properties and the other components of the skeletomuscular system during the propulsive phase of the jump.
156 citations
Cites background from "Muscle activity at the ilio‐sacral ..."
...The muscles in the back that act to ext the sacral joint are active during jumping (Emerson and Jong, 1980), but in total these muscles are very sm amounting to less than 0.5 % of body mass....
[...]
TL;DR: In this article, comparative and evolutionary studies of Xenopus laevis and its relatives have been conducted and it has been shown that Xenopus is monophyletic and that Silurana is its sister group.
Abstract: Model organisms are often assumed to be representative of some more inclusive taxon of which the species is a part. This assumption leads to mistaken generalizations about the evolutionary and comparative significance of the data gathered. This paper reviews comparative and evolutionary studies of Xenopus laevis and its relatives. Phylogenetic analysis of data from DNA sequences and morphology indicate that Xenopus is monophyletic and that Silurana is its sister group. The most basal lineages of Pipidae diverged prior to the breakup of Gondwana. The bizarre morphology of Xenopus is in part due to changes in the mode of metamorphosis
140 citations
TL;DR: Cranial features of Prosalirus bitis, an Early Jurassic anuran from the Kayenta Formation, include a dentigerous premaxilla and maxilla; a parasphenoid with a lanceolate cultriform process and posterolateral alae; a well ossified, unpaired sphenethmoid; and a stapes of modern form.
Abstract: Cranial features of Prosalirus bitis, an Early Jurassic anuran from the Kayenta Formation, include a dentigerous premaxilla and maxilla; a parasphenoid with a lanceolate cultriform process and posterolateral alae; a well ossified, unpaired sphenethmoid; and a stapes of modern form. The atlas bears a notochordal fossa between the cotyles. The number of vertebrae is unknown but anterior, middle, and posterior presacrai vertebrae are represented. The sacrum, which lacks postzygapophyses, possesses elongate, narrow alae and a cartilaginous intercentral articulation with a short urostyle. The appendicular skeleton exhibits a relatively primitive glenoid, prolongation of the iliac shaft, elongation of the hind limbs, radio-ulnar and tibiofibular fusion, and unfused, elongate proximal tarsals. Mobile sacro-urostylic and ilio-sacral joints are important kinetic links in the anuran caudopelvic mechanism for saltation. The angular appearance of the back common among living anurans reflects a pronounced fle...
114 citations
TL;DR: It appears that toad hindlimb function is altered between jumping and swimming, and these functional differences are influenced by passive effects associated with physical differences between the external environments, but are also actively mediated by shifts in the motor output and mechanical behavior of several muscles.
Abstract: Many anurans use their hindlimbs to generate propulsive forces during both jumping and swimming. To investigate the musculoskeletal dynamics and motor output underlying locomotion in such physically different environments, we examined patterns of muscle strain and activity using sonomicrometry and electromyography, respectively, during jumping and swimming in the toad Bufo marinus. We measured strain and electromyographic (EMG) activity in four hindlimb muscles: the semimembranosus, a hip extensor; the plantaris, an ankle extensor; and the gluteus and cruralis, two knee extensors. During jumping, these four muscles are activated approximately simultaneously; however, joint extension appears to be temporally staggered, with the hip beginning to extend prior to or initially faster than the more distal knee and ankle joints. Mirroring this pattern, the gluteus and plantaris shorten quite slowly and over a small distance during the first half of limb extension during take-off, before beginning to shorten rapidly. The hip and knee extensors finish shortening near the point of take-off (when the feet leave the ground), while the ankle-extending plantaris, which exhibits the longest-duration EMG burst, on average, always completes its shortening after take-off (mean 26 ms). During swimming, activation of the four muscles is also nearly synchronous at the start of a propulsive stroke. The onset of fascicle shortening is temporally staggered, with the knee extensors beginning to shorten first, prior to the hip and ankle extensors. In addition, the knee extensors also often exhibit some degree of slow passive shortening prior to the onset of EMG activity. The offset of muscle shortening during swimming is also staggered, and to a much greater extent than during jumping. During swimming, the cruralis and gluteus finish shortening first, the semimembranosus finishes 30-60 ms later, and the plantaris, which again exhibits the longest EMG burst, finishes shortening last (mean 150 ms after the cruralis). Interestingly, much of this extended shortening in the plantaris occurs at a relatively slow velocity and may reflect passive ankle extension caused by fluid forces, associated with previously generated unsteady (accelerative) limb movements, acting on the foot. Average EMG burst intensity tends to be greater during jumping than during swimming in all muscles but the gluteus. However, EMG burst duration only changes between jumping and swimming in the cruralis (duration during jumping is nearly twice as long as during swimming). The cruralis is also the only muscle to exhibit substantially greater fractional shortening during jumping (mean 0.28) than during swimming (mean 0.20 active strain, 0.22 total strain). On the basis of these results, it appears that toad hindlimb function is altered between jumping and swimming. Moreover, these functional differences are influenced by passive effects associated with physical differences between the external environments, but are also actively mediated by shifts in the motor output and mechanical behavior of several muscles.
104 citations
References
More filters
519 citations
TL;DR: This work has shown that when subjects perform two-handed movements to targets of widely disparate difficulty they do so simultaneously, and that the brain produces simultaneity of action not by controlling each limb independently, but by organizing functional groupings of muscles that are constrained to act as a single unit.
Abstract: Movement time varies as a function of amplitude and requirements for precision, according to Fitts' law, but when subjects perform two-handed movements to targets of widely disparate difficulty they do so simultaneously. The hand moving to an "easy" target moves more slowly to accommodate its "difficult" counterpart, yet both hands reach peak velocity and acceleration synchronously. This result suggests that the brain produces simultaneity of action not by controlling each limb independently, but by organizing functional groupings of muscles that are constrained to act as a single unit.
518 citations
TL;DR: A correlated examination of allometry and locomotor behavior provides an approach for testing two alternative hypotheses of jump function: jump distance vs. quickness of movement.
Abstract: Superficially, anurans appear stereotyped in body shape, with short trunks and relatively long hindlimbs. This uniformity has been characterized by Inger (1967), who, borrowing from Gertrude Stein, wrote a frog is a frog is a frog. Because frogs preserve a generally similar body shape over a wide size range, they are an interesting group in which to study the relationship of locomotor function to body geometry and size. On land, jumping is the dominant locomotor mode of anurans. Previous studies of frog jumping (e.g., Wermel, 1934; Rand and Rand, 1966; Zug, 1972) have assumed that the principal function of this locomotor mode is to maximize distance between the animal and a potential predator, and have focused on the relationship between morphology and jump distance. There are, however, other parameters of jumping, such as quickness of movement (acceleration) that may be important and related to frog morphology. A correlated examination of allometry and locomotor behavior provides an approach for testing two alternative hypotheses of jump function: jump distance vs. quickness of movement.
229 citations
TL;DR: The masticatory apparatus in the albino rat was studied by means of electromyography and subsequent estimation of muscular forces.
Abstract: The masticatory apparatus in the albino rat was studied by means of electromyography and subsequent estimation of muscular forces. The activity patterns of the trigeminal and suprahyoid musculature and the mandibular movements were recorded simultaneously during feeding. The relative forces of the individual muscles in the different stages of chewing cycles and biting were estimated on the basis of their physiological cross sections and their activity levels, as measured from integrated electromyograms. Workinglines and moment arms of these muscles were determined for different jaw positions. In the anteriorly directed masticatory grinding stroke the resultants of the muscle forces at each side are identical; they direct anteriorly, dorsally and slightly lingually and pass along the lateral side of the second molar. Almost the entire muscular resultant force is transmitted to the molars while the temporo-mandibular joint remains unloaded. A small transverse force, produced by the tense symphyseal cruciate ligaments balances the couple of muscle resultant and molar reaction force in the transverse plane. After each grinding stroke the mandible is repositioned for the next stroke by the overlapping actions of three muscle groups: the pterygoids and suprahyoids produce depression and forward shift, the suprahyoids and temporal backward shift and elevation of the mandible while the subsequent co-operation of the temporal and masseter causes final closure of the mouth and starting of the forward grinding movement. All muscles act in a bilaterally symmetrical fashion. The pterygoids contract more strongly, the masseter more weakly during biting than during chewing. The wide gape shifts the resultant of the muscle forces more vertically and moreposteriorly. The joint then becomes strongly loaded because the reaction forces are applied far anteriorly on the incisors. The charateristic angle between the almost horizontal biting force and the surface of the food pellet indicates that the lower incisors produce a chisel-like action. Tooth structure reflects chewing and biting forces. The transverse molar lamellae lie about parallel to the chewing forces whereas perpendicular loading of the occlusal surfaces is achieved by their inclination in the transverse plane. The incisors are loaded approximately parallel to their longitudinal axis, placement that avoids bending forces during biting. It is suggested that a predominantly protrusive musculature favors the effective force transmission to the lower incisors, required for gnawing. By grinding food across transversely oriented molar ridges the protrusive components of the muscles would be utilized best. From the relative weights of the masticatory muscles in their topographical relations with joints, molars and incisors it may be concluded that the masticatory apparatus is a construction adapted to optimal transmission of force from muscles to teeth.
217 citations