Frog Limb Research Articles

Design, Analysis, and Tests of an Impulsive Aquatic Jumping Mechanism Inspired by Frog Limbs

Design, Analysis, and Tests of an Impulsive Aquatic Jumping Mechanism Inspired by Frog Limbs

Frog limbs in deep time: is jumping locomotion at the roots of the anuran Bauplan?

AbstractThe unique body plan of frogs (Lissamphibia: Anura) has been largely conserved from at least 200 Myr, and its evolution from a more generalized tetrapod condition is still poorly understood, in part due to the scarce early fossil record of Salientia, the anuran total-group. The origin of the anuran Bauplan has been classically explained as an adaptation to jumping, but recent studies incorporating new data in a phylogenetic context have challenged the popular jumping hypothesis. Here we revisit and test this hypothesis from a paleobiological perspective by integrating limb data from a wide range of extant and fossil frogs. We first explored the evolution of limb proportions from the Jurassic to the Paleogene to understand when the present limb diversity originated and whether, and to what extent, limb proportions have been conserved over the last 200 Myr. We then inferred the locomotor capabilities of extinct species by phylogenetic flexible discriminant analysis, and from these inferences, we studied the locomotor diversity of frogs over geological time and reconstructed the ancestral state for frog-like salientians. The evolution of limb proportions is characterized by an early diversification that was underway in the Jurassic, followed by a repeated convergence over a limited area of the morphospace that was already explored by the Early Cretaceous. In agreement with this early limb diversity, the Jurassic stem species were also locomotory diverse, and their inferred locomotor modes do not support the jumping hypothesis. We propose that the patterns found herein of repeated convergent evolution of both limb proportions and locomotor capabilities over geological time hamper any attempt to confidently infer the ancestral locomotion mode and, it therefore might be time to start focusing on other hypotheses on the origin of the anuran Bauplan that are not related to locomotion.

A novel kinematics analysis method using quaternion interpolation–a case study in frog jumping

Spherical Linear Interpolation (SLERP) has long been used in computer animation to interpolate movements between two 3D orientations. We developed a forward kinematics (FK) approach using quaternions and SLERP to predict how frogs modulate jump kinematics between start posture and takeoff. Frog limb kinematics have been studied during various activities, yet the causal link between differences in joint kinematics and locomotor variation remains unknown. We varied 1) takeoff angle from 8 to 60°; 2) turn angle from 0 to 18°; and 3) initial body pitch from 0 to 70°. Simulations were similar to experimentally observed frog kinematics. Findings suggest a fundamental mechanism whereby limb elevation is modulated by thigh and shank adduction. Forward thrust is produced by thigh and proximal foot retraction with little contribution from the shank except to induce asymmetries for turning. Kinematic shifts causing turns were subtle, marked only by slight counter-rotation of the left versus right shank as well as a 10% timing offset in proximal foot adduction. Additionally, inclining initial body tilt influenced the centre of mass trajectory to determine direction of travel at takeoff. Most importantly, our theory suggests firstly that the convergence of leg segment rotation axes toward a common orientation is crucial both for limb extension and for coordinating jump direction; and, secondly, the challenge of simulating 3D kinematics is simplified using SLERP because frog limbs approximately follow linear paths in unit quaternion space. Our methodology can be applied more broadly to study living and fossil frog taxa as well as to inspire new control algorithms for robotic limbs.

Imparting Regenerative Capacity to Limbs by Progenitor Cell Transplantation

The frog Xenopus can normally regenerate its limbs at early developmental stages but loses the ability during metamorphosis. This behavior provides a potential gain-of-function model for measures that can enhance limb regeneration. Here, we show that frog limbs can be caused to form multidigit regenerates after receiving transplants of larval limb progenitor cells. It is necessary to activate Wnt/β-catenin signaling in the cells and to add Sonic hedgehog, FGF10, and thymosin β4. These factors promote survival and growth of the grafted cells and also provide pattern information. The eventual regenerates are not composed solely of donor tissue; the host cells also make a substantial contribution despite their lack of regeneration competence. Cells from adult frog legs or from regenerating tadpole tails do not promote limb regeneration, demonstrating the necessity for limb progenitor cells. These findings have obvious implications for the development of a technology to promote limb regeneration in mammals.

Micro‐Computed Tomography for Visualizing Limb Skeletal Regeneration in Young Xenopus Frogs

For studies of vertebrate limb regeneration it is often desirable to visualize the regenerated skeleton, which is mostly cartilage, and also section the specimen for histological or immunohistochemical visualization of other tissues. However, the normal skeletal staining techniques are incompatible with immunohistochemistry. Here, we describe a contrast-based micro-computed tomography (microCT) method for direct and nondestructive observation of regenerated cartilage spikes in Xenopus frog limbs. In addition, we show that contrast based microCT imaging is compatible with immunohistochemistry protocols. This approach provides versatile and high contrast images of the cartilage allowing us to measure the regenerated skeletal structure in detail as well as carrying out the other types of analysis. It opens a wide range of potential microCT applications in research on vertebrate limb regeneration.

Lbx1 expression and frog limb development

In order to identify prospective limb muscle cells in a frog, we cloned Lbx1 from the direct developing frog Eleutherodactylus coqui. Like in embryos of the frog Xenopus laevis but unlike in other vertebrates, EcLbx1 is expressed in all trunk somites. Like in embryos of chick, mouse, and zebrafish, cells expressing EcLbx1 are then found in limb buds, consistent with migration of those cells from somites. EcLbx1 is also expressed in the dorsal spinal cord as in other vertebrates.

Amphibians of France, Belgium and Luxemburg

As a general trend, accounts on regional and local herpetofaunas tend to become more and more colourful and extensive, and the classical borders between fieldguide, distribution atlas and handbook are fading. The book reviewed here is a good example for this trend. Edited by Remi Duguet und Frederic Melki for the “Association pour la Connaissance et l’Etude du Monde Animal et Vegetal” (ACEMAV), it summarizes the state of knowledge on the amphibians of France, Luxembourg and Belgium. Thereby it bridges a very important gap, because no comprehensive account on this region was so far available – despite its “batrachophilic” character, expressed in the yearly import of over 2970 tons of frog limbs to France, 2100 t to Belgium and 34 t to Luxembourg for consumption. These detailed figures (referring to 1999) exemplify the high density of detailed and original data that are woven into the text by the 18 authors who contributed to the book. The first 200 pages are devoted to introduce amphibians and place them into the context of the animal kingdom (chapter 1) and to discuss the basic patterns of their biology (chapter 2), biogeography and ecology (chapter 3) as well as their relationships to human culture and society (chapter 4). These chapters have an ample perspective, illustrating, for instance, representatives of many tropical amphibian families to be able to sort the European taxa into a world-wide context. Many aspects of the biology and behaviour of European amphibian species are documented photographically, and the same is true for many of the regionally typical habitats. All species are allocated to different biogeographic clusters depending on their distribution pattern, and much effort is devoted to discussing the possible geological and climatic explanations of these patterns. Amphibian conservation is another focus, and the many detailed reports of regional conservation measures are especially interesting. Precise instructions are given to carry out successful amphibian conservation measures, and state-of-the-art methods for inventorization, mapping and monitoring of these animals are described. The latter bears relevance because previous efforts of herpetofaunal mapping in France have heavily been criticized by part of the scientific community because of their presumably too uncritical approach.

Where the Tadpole Meets the World—Observations and Speculations on Biomechanical and Biochemical Factors that Influence Metamorphosis in Anurans

SYNOPSIS. A diversity of issues related to metamorphosis are discussed in this paper, ranging from biomechanical constraints on behavior in premetamorphic anurans, to environmental factors that regulate metamorphosis. I begin by reviewing key behavioral features of tadpoles that have implications to their form and locomotion. Tadpoles lack all visceral behaviors, such as emesis, coughing, and egg-laying, that require major elevations of pressure in the pleuroperitoneal cavity. I suggest that the inability to forcefully elevate pleuroperitoneal pressure is a consequence of the tadpoles' short and inflexible spine. Although postmetamorphic frogs have a similarly short vertebral column, they can compress viscera by movement at sacroiliac joints, which are absent in tadpoles. I argue that the short torso of tadpoles is a necessary consequence of the need to innervate the frog's limbs early in development so that they can be fully functional by the end of metamorphosis. The short torso is a good mechanical design for the saltatory frog, but afflicts the tadpoles with a distinctly globous shape that intuitively appears inefficient for aquatic locomotion. Computational fluid dynamics (CFD) models, however, reveal that tadpoles are, in fact, efficient undulatory swimmers compared to subcarangiform fishes and that their swimming kinematics work in concert with their shape to help generate thrust. Furthermore the CFD models show that the crease in the dorsal profile of tadpoles, where the body abruptly meets the tail, produces a dead water zone immediately behind the body of the tadpole. As a result, tadpoles can grow hindlimbs in this region without those limbs seriously impeding flow. Thus the shape of tadpoles nicely matches their need to transform into limbed tetrapods. In the latter half of this paper I review ideas on how environmental factors could influence metamorphosis in anurans. One speculation is that tadpoles may secrete a metamorphic inhibitor in their oral mucus, which they then ingest with their food, with the result that metamorphosis is delayed when food is abundant. An epidermal growth factor-like peptide has been suggested as a possible metamorphic inhibitor along the pathway just proposed. Strengths and weaknesses of this hypothesized agent and pathway are reviewed. An experiment to test the hypothesis that orally ingested EGF inhibits metamorphosis yielded inconclusive results. Orally secreted EGF-like peptide may not inhibit metamorphosis of the tadpole gut, but other yet-to-be-identified factors in tadpole oral mucus could still play a role in regulating metamorphosis of the alimentary tract in anurans. The essay ends with some broad speculations on the role that peptides in frogs' skin may play in the metamorphic process as well as several unanswered questions about how other organisms and the physical environment influence tadpole metamorphosis.

Thyroid hormone-induced gene expression changes in the developing frog limb.

Greater than 120 genes are up-regulated in Xenopus laevis limb buds within the first 24 h after induction of metamorphosis by thyroid hormone. Fourteen of these have been isolated and characterized. Four encode heat shock proteins. The identified regulated genes have in common a relatedness with cell growth as exemplified by the serum response of quiescent fibroblasts. Some of the genes respond directly to hormone. However, the majority appear to be secondary response genes judging from their delayed kinetics and cycloheximide sensitivity. This indicates that there are at least two periods of gene expression change in the first 24 h. DNA replication increases in the second 24 h. Growth of the limb bud occurs for several days before the genes that characterize terminal differentiation of its cell types are up-regulated.

The regeneration of axolotl limbs covered by frog skin

Forearm skin of Stage XXIV Rana pipiens, which cannot regenerate limbs, was removed and placed upon the skinned forearms of young axolotls. The axolotl limbs were amputated immediately through the level of the grafts. Frog epidermis migrated to cover the amputation surface. Dedifferentiation and early blastema formation occurred beneath the frog wound epidermis. Limb regeneration continued, but in time axolotl epidermis overgrew the frog epidermis. The experiment shows that epidermis from nonregenerating frog limbs is still capable of supporting typical epimorphic regeneration.

Role of subdermal current shunts in the failure of frogs to regenerate

Large, uniform, skin-driven currents (20-40 muamp/cm2) leave the ends of limb stumps of post-metamorphic frogs (Rana pipiens) from about the first through the tenth day after amputation. However, right after amputation, while currents of comparable density may leave the periphery of the cut surface, current densities are greatly depressed in the center of this surface. We suggest that this depression is brought about by shunting through the subdermal lymph space (characteristic of anurans but not urodeles); continues in covert form after formation of a wound epithelium; and helps explain the ability of small, imposed currents to initiate frog limb regeneration.

Bioelectricity and regeneration: large currents leave the stumps of regenerating newt limbs.

Electrical currents near regenerating newt limbs were measured with a recently developed vibrating probe. Steady currents with local surface densities of 10 to 100 muA/cm2 or more leave the end of the stump during the first 5-10 days after amputation and are balanced by currents with densities of only 1-3 muA/cm2 that enter the intact skin around the stump. They are immediately dependent upon the entry of sodium ions into this skin and are therefore inferred to be skin-driven. The outward currents are comparable in direction, density, duration, and position to artificially imposed currents previously found sufficient to induce significant regeneration of amputated adult frog limbs. This comparison suggests that the endogenous stump currents play some causal role in initiating regeneration.

Bioelectricity and regeneration. I. Initiation of frog limb regeneration by minute currents

AbstractWe have applied 0.2 μamps of current to the forelimb stump of Rana adults for several weeks. The stimulator was designed to avoid introduction of any physiologically active electrode products into the tissue. Current was applied to the dorsal postaxial region of the stump. Cathodal (i.e., distally negative) current initiated partial regeneration; anodal (i.e., distally positive) current initiated extensive destruction of the limb; while implantation of sham stimulators (delivering no current) yielded limbs showing just a healing response. Regeneration was indicated by organized extension of the severed radio‐ulna, newly formed muscle, ligament, and isolated cartilage rods that were partially segmented. Moreover, extraordinarily large amounts of nerve developed in the regenerated tissue. We conclude that the cathodally initiated regeneration was mediated by small electrical fields within the stump and not by electrode products. However, an electrode product (Ag+ ion) cannot be completely excluded as a possible mediator of anodal destruction.

Induction of growth in newt and frog limbs after perfusion with extracts from newt blastemas.

IT has been suggested that the nerves required for regeneration of the amphibian limb produce a “trophic material”1,2. Lentz3 has suggested a “hormonal” role for the nervous system, but otherwise the nature of trophic material is undefined4.

The Ferrier Lecture: The nature of central inhibition

I feel greatly honoured by the invitation to give the Ferrier Lecture. I attended the first Ferrier Lecture, given by Sherrington in 1929, and I learned from Sherrington to value and admire the pioneer contributions of David Ferrier to neurology. In choosing the subject of inhibition for my lecture I was prompted by the peculiar challenge that inhibition has presented to physiologists ever since it was first demonstrated by the Weber brothers in 1846 that stimulation of the vagus nerve could stop the heart and by Setchenov in 1863 that stimulation of areas in the brain could slow or prevent reflex responses of frog limbs. It was Sherrington who greatly extended and organized knowledge of inhibition in the central nervous system; first, by a series of remarkable investigations, and finally by a theoretical paper published by the Royal Society in 1925, in which excitation and inhibition were given equivalent status in the synaptic mechanisms controlling neuronal discharge. His interest in central inhibition continued to the end of his scientific life, and was the subject of his Nobel Lecture in 1932. I might mention that both my first scientific paper and my D.Phil. thesis were concerned with inhibition, and that I have continued to be more interested in the problem of synaptic inhibition than in any other aspect of neurophysiology. In recent years progress has been so rapid that our understanding of the nature of central inhibition is in several respects more complete than that of central excitation. This illumination has followed rather rapidly upon a long period of ingenious theorizing which is now only of historical interest

The effects of implantation of embryonic and tadpole tissues into adult frog limbs. II. Histological observations.

The effects of implantation of embryonic and tadpole tissues into adult frog limbs. II. Histological observations.

The effects of implantation of embryonic and tadpole tissues into adult frog limbs. I. Regeneration after amputation.

Journal of Experimental ZoologyVolume 139, Issue 2 p. 307-327 Article The effects of implantation of embryonic and tadpole tissues into adult frog limbs. I. Regeneration after amputation Theodore Malinin, Theodore Malinin Department of Anatomy, University of Virginia, Charlottesville, Virginia Public Health Service Fellow, Medical School Post-Sophomor Research Training Program, 1957–58.Search for more papers by this authorJ. David Deck, J. David Deck Department of Anatomy, University of Virginia, Charlottesville, VirginiaSearch for more papers by this author Theodore Malinin, Theodore Malinin Department of Anatomy, University of Virginia, Charlottesville, Virginia Public Health Service Fellow, Medical School Post-Sophomor Research Training Program, 1957–58.Search for more papers by this authorJ. David Deck, J. David Deck Department of Anatomy, University of Virginia, Charlottesville, VirginiaSearch for more papers by this author First published: November 1958 https://doi.org/10.1002/jez.1401390205Citations: 12 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume139, Issue2November 1958Pages 307-327 RelatedInformation

Selectivity of nerve fibers from the dorsal and ventral roots in the development of the frog limb

Selectivity of nerve fibers from the dorsal and ventral roots in the development of the frog limb