Why tadpole has a tail

Although apoptosis-related proteins such as caspases are generally considered to contribute to tail resorption, the specific gene expression necessary for the suicide induction of tail muscle cells during spontaneous metamorphosis is unknown.

Several ECM-degrading enzymes can cleave collagens, elastin, and other ECM molecules, but no study thus far has identified an enzyme essential for the murder of tail muscle cells, and the possibility remains that multiple enzymes complement each other in this process.

Addressing these issues in future studies by performing comprehensive RNAseq analyses and using genomic-editing methods to create knockouts of genes of interest will lead to the clarification of the entire mechanism of tail resorption. The author confirms being the sole contributor of this work and has approved it for publication. The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

I thank Drs. Nakajima, K. Fujimoto, M. Okada, and Y. Nakai for their contribution to this review, and Ms. Nakajima for technical assistance. I also thank Editage for English language editing. Highnam KC.

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Biomol Concepts. Thyroid hormone controls the development of connections between the spinal cord and limbs during Xenopus laevis metamorphosis. Wong J, Shi YB. Coordinated regulation of and transcriptional activation by Xenopus thyroid hormone and retinoid X receptors. J Biol Chem. Leloup J, Buscaglia M. Triiodothyronine, the hormone of amphibian metamorphosis La triiodothyronine, hormone de la metamorphose des Amphibiens.

C R Acad Sc. Google Scholar. Regulation of thyroid hormone sensitivity by differential expression of the thyroid hormone receptor during Xenopus metamorphosis. The c-erb-A protein is a high-affinity receptor for thyroid hormone.

The c-erb-A gene encodes a thyroid hormone receptor. Yoshizato K, Frieden E. Increase in binding capacity for triiodothyronine in tadpole tail nuclei during metamorphosis. Yaoita Y, Brown DD. A correlation of thyroid hormone receptor gene expression with amphibian metamorphosis. Genes Dev. Wang Z, Brown DD.

Thyroid hormone-induced gene expression program for amphibian tail resorption. PubMed Abstract Google Scholar. The sensitivity of Xenopus laevis tadpole tail tissue to the action of thyroid hormones.

The type 2 and type 3 iodothyronine deiodinases play important roles in coordinating development in Rana catesbeiana tadpoles. Timing of metamorphosis and the onset of the negative feedback loop between the thyroid gland and the pituitary is controlled by type II iodothyronine deiodinase in Xenopus laevis. One of the duplicated matrix metalloproteinase-9 genes is expressed in regressing tail during anuran metamorphosis.

After the hind legs have started to form, a pair of front legs will begin to develop and the tail will start to disappear. You might also notice that the tadpole has started to form a frog-like face. When the tadpole reaches the froglet stage, it is almost a full adult. This means it is ready to leave the water and live on land. Once its tail disappears, it will become an adult frog. This is a fully grown frog. As you have just read, frogs go through a lot to get to this phase. Contact us: membership earthrangers.

Read our F. In both cases the regeneration process was inhibited and the tadpole tail did not grow back. Our research suggests that ROS are essential to initiate and sustain the regeneration response. We also found that ROS production is essential to activate Wnt signalling, which has been implicated in essentially every studied regeneration system, including those found in humans.

It was also striking that our study showed that antioxidants had such a negative impact on tissue regrowth, as we are often told that antioxidants should be beneficial to health. Professor Amaya comments: "It's very interesting that two papers suggesting that antioxidants may not always be beneficial have been published recently.

Our findings and those of others are leading to a reversal in our thinking about the relative beneficial versus harmful effects that oxidants and antioxidants may have on human health, and indeed that oxidants, such as ROS, may play some important beneficial roles in healing and regeneration.

With a better understanding, Professor Amaya and his team hope to apply their findings to human health to identify whether manipulating ROS levels in the body could improve our ability to heal and regenerate tissues better. Ablation of the most caudal portion of the tail fin results in a clear reduction in maximum swimming velocity Fig. As already noted from our EMG studies, the musculature near the tip of the tail is not recruited when tadpoles swim naturally at their preferred speed.

However it may be called into play during starting, turning, stopping, and during both very slow and very fast swimming. In our previous studies of the tadpole tail, we suggested that the absence of a skeleton in the tail permitted: 1 high maneuverability and 2 rapid metamorphosis.

To this we can now add the fact that the tail plays a role in how tadpoles interact with their predators, which goes beyond simply swimming out of range. The tails of tadpoles from several species exhibit polyphenism, which allows them to rapidly change shape and color in response to predators.

We suggest that this developmental plasticity is facilitated by the fact that the tadpoles do not need to buildup or breakdown mineralized tissue in order to change tail shape. One might suppose that what tadpoles lose in mechanical efficiency by having such a flexible tail Liu et al.

Axial movements in tadpoles are regulated by a diverse array of muscle activity in a manner similar to anguilliform fishes Gillis, Under various circumstances, tadpoles manifest all of the patterns of muscle recruitment noted by Blight , in his studies of axial muscle activity.

When we combine the results from our studies on the regulation of axial propulsion in tadpoles with what we currently know about predator influences on tadpole tails, we arrive at a picture of an axial structure—the tadpole tail—that is functionally and developmentally as adaptable as the caudal fin of most teleosts. Overall our studies demonstrate that, despite their relatively simple morphology, tadpoles have an elegant array of mechanisms for controlling their axial locomotion.

But in the absence of a solid skeleton, the soft tissue—be it the loose connective tissue of the fins or the muscles themselves—must, literally, take up the load. Electromyographic EMG recordings were made from bipolar electrodes Evenohm size 51, 25 c nickel-chromium alloy, with approximately 0.

Synchronization of EMG signal and animal movements was determined by split-screen video analysis of tadpole activity and polygraph pen movements. Kinematic parameters following Wassersug and Hoff, were taken from the video tape with an effective framing rate of 60 fps.

Animals had a maximum of three electrodes in place during any recording session. They swam spontaneously or were induced to swim by prodding with a plastic rod. Each animal was used with only one set of electrodes and those specimens from which good recordings were obtained were anaesthetized 0. The stippled area in the cross-section indicates the thin band of small-diameter, red fibers in most places only 2 or 3 cell layers surrounding the larger-diameter, white fibers that comprise the bulk of the musculature.

Two animals were sectioned and stained to verify that the population of Rana ca-tesbeiana we used conformed to previously published accounts of muscle fiber type distribution in Rana Watanabe et al.

At the most posterior site 0. EMG for starting, turning and stopping: A During starting there was no detectable rosto-caudal lag in muscle activity between 0. The image shows a C—shaped kinematic pattern of the initial bend of a start. B This series of images is taken from simultaneous video recordings at ms intervals from two turns using different tadpoles with electrodes on opposite sides.

The sequences were selected for near perfect movement match, but differed slightly in turning speed. These sequences illustrate that electrodes on the concave side showed no detectable rostro-caudal lag in initial muscle activity, while muscle activity on the convex side did show a rostro-caudal lag. Note also that the EMG preceded body bending. Note that opposing side EMG activity started fairly early in the turn and continued into the next tail beat.

C During a gliding stop the tadpole's body remains straight. There is little anterior EMG activity, but there was prolonged low amplitude EMG activity simultaneously on both sides at 0. Tadpoles also stopped by bending the tail at the end and forming a J shape.

In that case EMG activity was confined to the end of the tail 0. EMG signal for steady rectilinear swimming. The rostral portion of the tail 0. Rostral muscles at 0. Mass distribution of Rana catesbeiana tadpoles. The striped area indicates axial muscle. The center of axial muscle mass is at the base of the tail and is caudal to the center of mass of the body. Rostro-caudal lag in muscle activity was apparent in most, but not all, EMG records.

A For tail beat periods less than ms frequencies above 3 Hz EMG onset lag on the Y-axis was a fixed portion of period for electrodes at 0. The regression equation does not include the three instances where no lag was measurable. B At slower swimming speeds 3 Hz and below muscle activity sometimes started earlier in the kinematic cycle and lasted slightly longer at 0.

The figure shows mean onset, offset and duration of EMG activity in relation to kinematic cycle. Mean onset of EMG at 0. Duration and offset were more variable and did not differ by t -test.

Ninety degrees corresponds to maximal body bending and presumably muscle fibers at maximum length following Wardle et al. Preferred tail beat frequencies of Rana catesbeiana tadpoles. Frequencies of approximately 3 Hz and 10 Hz were selected far more often than other tail beat frequencies in response to mechanical stimulation. B During spontaneous swimming 19 of 20 tadpoles selected tail beat frequencies of approximately 3 Hz.

Each bar represents a frequency range of 0. Flow around a virtual Rana tadpole swimming at Reynolds number of 7, established through computational fluid dynamic modeling taken from Fig.

Instantaneous streamlines allow the flow over the body and tail to be visualized. The body of the tadpole is covered in false colored isopressure contours, with higher pressures represented by the red end of the spectrum. Note the high pressure region on the tail where maximum thrust is being generated at this instant in the tail beat cycle. A comparison between the color markings on an Ascaphus truei tadpole and the pattern of injury seen in a population of 81 A.

Top drawing, taken from Stebbins , shows the white dot surrounded by the black band at the tip of the A. The bottom figure is a composite illustration made by marking the portion of the tail lost to injury in each individual tadpole and then layering the digitized images of each tadpole one upon the other. Using false color representation, the portions of the figures nearest the red end of the spectrum are those most often injured in the population as a whole.

See Blair and Wassersug for details on the image processing procedures. Effects of tail fin ablations on maximum specific velocity. Fin was removed rostrally B or caudally C without damaging muscle. A third pair of tadpoles A had no fin ablations. Maximum velocity was calculated following Wassersug and Hoff and compared by rank for 5 swimming bouts for each tadpole among the three groups. The maximum velocity of normal and rostral tail fin ablated tadpoles did not differ.

We thank J. Blair, P. Doherty, K. Kawachi, J. Lee, and H. Liu for collaborating with us on various studies of tadpole functional morphology.

Manuscript production was greatly facilitated by T. Lownds and S. In addition we thank J. Caldwell, B. Jayne, G. Gillis, J. Long, Jr. Marlow, S. McCollum and G. Thiemann for helpful discussion and encouragement along the way.

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