Siredon Mexicanum Research Articles

A report of webbed feet in a mature female axolotl (Siredon mexicanum) and remarks on webbed feet in Urodela, generally

A report of webbed feet in a mature female axolotl (Siredon mexicanum) and remarks on webbed feet in Urodela, generally

Electrophysiological evidence of electroreception in the axoloyl Siredon mexicanum

Single unit recordings from a branch of the anterior lateral line nerve of the axolotl Siredon mexicanum, reveal the existence of two types of afferents. One type reacts to electric field square pulses below 100 μV/cm and is insensitive to weak mechanical stimuli. The other type is very sensitive to water displacements and can only be excited by electric square pulses above 3 mV/cm. We consider the fiber population with low electric thresholds to originate from electrosensitive receptors and the second population to represent fibers from ordinary mechanosensitive lateral line organs.

Morphological and functional aspects of the arrangement of connective tissue and muscle fibres in the tail of the Mexican axolotl, Siredon mexicanum (Shaw) (Amphibia, Urodela).

In the lateral musculature of the axolotl tail a multipennate arrangement of muscle fibres is found in the 3rd postanal myomere and all following myomeres. This arrangement appears in larval stages as soon as the myomeres concerned are fully differentiated. Within a myomere a uniform degree of contraction of the muscle fibres may be achieved either by helical arrangement as seen in Teleosts, by diminishing fibre length in medial direction or by a combination of both phenomena. The relation between muscle fibre length and angle of insertion in the myomeres showing pennate arrangement is approximated by the Benninghoff and Roll-häuser equation but the values recorded deviated systematically from the values calculated. In the rather slender tail of the axolotl the transition from the helical or parallel fibre system into the pennate arrangement will be in favour of the development of relatively strong bending moments in the region concerned while a reasonable uniformity of the rate of contraction is maintained.

Iron kinetics in axolotls ( Siredon mexicanum)

1. 1. Iron kinetics was studied on Siredon mexicanum originally from the valley of Mexico (7343 ft). 2. 2. Plasma iron clearance (T 1 2 59Fe) was estimated in 150 min. Circulating red-cells uptake was about 35 per cent. 3. 3. 59Fe bone marrow uptake had a peak after 2 hr of the radioisotope injection, with a later decrease. Spleen and liver increased their uptake up to a maximum between the first and the fifth day, with also a later decrease. 4. 4. It is concluded that mainly the spleen and in a lesser degree the liver and bone marrow are the most important organs of red-cell production in this animal. 5. 5. On the basis of the results obtained, we were able to compare axolotl erythropoiesis with that of the human foetus during the fourth to sixth lunar month of intra-uterine life.

Variations and developmental abnormalities in the sexual apparatus of the adult axolotl (Siredon mexicanum).

AbstractThe sexual apparatus was studied in 100 adult axolotls (Siredon mexicanum) for 13 different spawnings. The ages of the animals varied between two and six years. Additional material from Indiana University was also studied. Altogether there were 55 female and 52 male adult axolotls represented. The purpose of the study was to investigate the limits of the variations occurring in normal axolotls and to compare the incidences of variations and developmental abnormalities in adult animals of both sexes at various ages and belonging to different strains.Among the 13 spawnings examined, five strains were completely normal in 100% of the animals, but the remaining eight strains all included abnormal animals. The incidence of abnormal animals in some of these latter strains was 40% or even 50%. Since all of the animals were under the same conditions, the variability and the occurrence of developmental abnormalities most likely depended upon hereditary factors. Among 55 females, only seven (12.7%) were abnormal; only four of these had developmental abnormalities, and only one was hermaphrodite. Among 45 males from the author's axolotl colony, 16 (28%) were abnormal. Of these latter, six had no sex cells or very few; this variation must be regarded as a developmental abnormality. All of these malformations resulted from major degeneration processes and abnormal morphogenesis.Arrested development was also observed in many males. Spermatozoa were completely absent from the testes of eight animals. In the additional material from Indiana University (testes from 7 males), there was also one completely abnormal testis with major degeneration processes and complete absence of sex cells. It is evident that variability and the incidence of developmental abnormalities in the sexual apparatus in adult axolotls of some strains are very great.

Intracellularly recorded early receptor potential of the vertebrate photoreceptors

The early receptor potential was recorded intracellularly from single photoreceptors of Gekko gekko, Necturus maculosus and Siredon mexicanum. In the case of the gecko both the early and late receptor potentials have been recorded from both the inner and outer segments of the photoreceptor. The early receptor potential appears to be generated across the plasma membrane or a structure or structures electrically coupled to the plasma membrane. Moreover the membrane current associated with the ERP appears to be almost entirely capacitive. In the case of gecko the ERP decays with a time constant of 10.4 ± 0.4 msec. If this corresponds to the membrane time constant, the effective capacitance of the gecko photoreceptor is about 10 −9F.

Partial sex reversal in adult axolotls developing from cold‐treated eggs

AbstractOf 12 adult (4‐year‐old) axolotls (Siredon mexicanum) develoing from cold‐treated eggs, three were originally male, and the other nine were originally female. Only two of the animals, one male and one female, were normal. The second male was underdeveloped, with very small testes and abortive development of sex cells, which included only spermatogonia. The third male was greatly underdeveloped, with vestigial testes, complete degeneration of all germ cells, and entire absence of cloacal glands.The remaining eight females were greatly underdeveloped, with ovaries of almost microscopic size and partial sex reversal. In three of these females, only male cells could be observed, and the oviducts were very much diminished. In the other five females, the sexual glands were vestiges of hermaphrodite glands, with cells of both sexes (oogonia and spermatogonia) close together.The chief abnormalities observed in the great majority of the animals, partial sex reversal and development of hermaphrodite sex glands, were evidently due to triploidy developing as a result of cold treatment of the eggs. The normal male and female were most likely diploid. The under‐developed male with only spermatogonia was probably triploid, and the male with complete degeneration of the germ cells could have been triploid. All of the females with sex reversal were undoubtedly triploid.

Destructive Effects of Strictly Local Irradiation of the Eye of the Adult Axolotl (Siredon mexicanum)

In previous studies by the same author, axolotls underwent irradiation of the head with various doses, including 30,000 R. In the present study, axolotls were irradiated with 30,000 R limited to the right eye. Damage to the lens was different from such damage after irradiation with smaller doses. Immigration of macrophages was not observed. The lens fibers and nuclei disappeared, leaving inside the lens only a fibrous structure with many vacuoles. The fibers seem to have been transformed into a much softer material, perhaps even a liquid. The eye was completely destroyed whenever the orbital region was in the center of the field of irradiation. In all such cases, the cornea and lens were completely absent. Sometimes very small accumulations of retinal cells with mitotic figures were found. The tissues of the choroid coat and the sclera were the least radiosensitive, particularly the pigment layer and the ocular cartilage, but even they were left completely disorganized. The effects of the same dose of rad...

The effects of partial irradiation on tail regeneration in adult Siredon mexicanum.

1. The tails of 115 adult axolotls (Siredon mexicanum) were amputated, and the regenerates that developed were irradiated locally 1 to 2 months later with one or another of the following doses: 1,000 r, 2,000 r, 4,500 r, and 6,000 r. A more proximal amputation, performed a relatively long time (more than 1 year) after irradiation, was followed by the development of only 12 regenerates, all monstrous. Obviously these regenerates developed from the boundary zone, where irradiation of the cellular material had been only partial. In the other 103 animals, regeneration was completely suppressed.2. The 12 monstrous regenerates were the products of limited regeneration, and represented various types of abnormalities, ranging from narrow paddle-shaped formations with almost normal axial skeletons and spinal cords to small and narrow awl-shaped formations lacking both axial skeletons and spinal cords. Regression of the axial skeleton, which has been observed in previous study in 90 per cent of regenerates of axolo...

Cytological study of transplanted neuroepithelioma in Siredon mexicanum

By phase contrast microscopy, cells from the surface epithelium covering a neuroepithelioma in a Mexican axolotl ( Siredon mexicanum), as well as cells from the interior of the tumor, were examined in various stages of mitosis and in interphase. In the surface epithelium, abnormal cells with one or three nucleoli were comparatively uncommon, and mitosis was extremely rare. In the interior of the tumor, the number of abnormal cells was very high. Cells large in size but with only one nucleolus, and cells the same size as diploid cell but with three nucleoli, could be found. Small cells with one nucleolus (haploid), and large cells with three nucleoli (triploid) or many nucleoli (polyploid), were also present. Giant cells of extremely large size, usually having several nuclei and clear cndoplasmic reticulum, were highly characteristic of the tumor. Such cells were not observed in the process of division. Most of the metaphases in the interior of the tumor, including those in nonmalignant stroma (interstitial loose connective tissue between the lobes of the tumor), had the normal diploid chromosome number (2 n = 28), but aneuploid and polyploid numbers were comparatively frequent. Abnormal chromosome numbers such as 12, 14 (the haploid number), 20, 30, 32, 34, 35, or 36 were observed in the tumor, but never in normal tissues. Evidently the karyotype of tumor cells tends towards instability in the axolotl, as in other vertebrates.

Induced metamorphosis: Rectification of a genetic disability by thyroid hormone in the Mexican axolotl Siredon mexicanum

Evidence is presented to show that the pituitary-thyroid axis functions at an elevated level in axolotls induced to metamorphose by single injections of triiodothyronine. Investigations conducted were: (1) changes in premetamorphic skin grafts in intact and thyroidectomized postmetamorphic axolotls. (2) changes in the histological picture of the thyroid of hypophysectomized pre- and postmetamorphic animals. (3) effect of thyroidectomy on the pituitary of the pre- and postmetamorphic animals. (4) thin-layer chromatography of thyroid hormones in serum and thyroid and 131I uptake by thyroid gland of pre- and postmetamorphic animals. Premetamorphic skin grafts metamorphosed on intact postmetamorphic animals but not on thyroidectomized animals. Hypophysectomy affected the thyroid in both pre- and postmetamorphic animals. The most pronounced change was the loss of granular texture in the colloid of operated animals. The cell height of the follicle epithelium showed a reduction in the animals as follows: Intact postmetamorphic > hypophysectomized postmetamorphic > intact premetamorphic > hypophysectomized premetamorphic. Histological variations in pituitary cytology could not be detected. Monoiodotyrosine was detected in the blood stream of all animals except those that were hypophysectomized or thyroidectomized. 131I uptake by thyroid of premetamorphic axolotl was much lower than that seen in postmetamorphic animals. The implications of the observations mentioned above are discussed.

Stability of chondrocyte differentiation and contribution of muscle to cartilage during limb regeneration in the axolotl (Siredon mexicanum).

AbstractIn order to determine whether chondrocytes are stable as to type during limb regeneration and whether any cells from limb muscle become chondrocytes in the regenerate, labeled cartilage and muscle were transplanted into limbs which were then allowed to regenerate. Transplanted cells were identified after redifferentiation in the regenerate by three kinds of label: H3‐thymidine detected by radioautography; triploidy as judged by the presence of three nucleoli per nucleus; or a combination of the two.The results of this investigation indicate that limb chondrocytes are intrinsically stable with respect to cell type, for grafts of both triploid and H3‐thymidine labeled chondrocytes gave rise to morphologically dedifferentiated blastema cells which almost exclusively differentiated into chondrocytes. The small percentage of labeled noncartilage cells observed could have been the result of metaplasia, although it is more likely that all or most of them arose as spontaneous polyploids or as contaminants of the original grafts. Isotope dilution in H3‐thymidine labeled chondrocytes indicated that they had usually divided at least five times. Hence, the basis for the intrinsic stability of chondrocytes must be heritable.Chondrocytes from the coracoid, scapula, and visceral arch cartilages also contributed cells to cartilage of limb regenerates, and the available evidence indicates that cells released from these cartilages are similarly stable as to type. These cartilages did not dedifferentiate and participate in limb regeneration to the same extent as did limb cartilage.Results from transplanted limb muscle, labeled by all three methods used in this study, indicate that certain cells of muscle can become chondrocytes during limb regeneration. The exact cellular origin of these chondrocytes, however, is uncertain, for muscle is a mixture of cell types.

Lethal effect and visible irradiation damage.

The present study utilized 650 axolotls (Siredon mexicanum), 12 days after hatching. In one series of experiments involving 500 animals from one spawning, nine groups of 50 animals each received totalbody irradiation with 200, 300, 400, 600, 800, 1,000, 1,500, 2,000, and 3,000 r, respectively. In another series of experiments involving 150 animals from another spawning, two groups of 50 animals each received 100 and 200 r, respectively. In each series of experiments, the remaining 50 animals served as untreated controls.1. All doses from 200 r up very definitely suppressed growth.2. The response of the skin epithelium to irradiation, even with a dose as large as 3,000 r, was highly diverse, and at most only partial. Not a single animal with totally damaged skin epithelium could be found, but the skin epithelium was completely normal in some instances even after 3,000 r. In some areas of the skin epithelium of irradiated animals, giant cells developed and the simple squamous epithelium was transformed into...

Light and electron microscope observations on the taste buds of the axolotl tongue

The investigation of the taste buds in the tongue of the neotene Mexican axolotl (Siredon mexicanum) by light and electron microscopy demonstrates 4 different cell types: 1) R-cells, marginal cells of less differentiated character. 2) G-cells, granulated cells in basal position. 3) Cells of type A with fibrills, vesicular elements, and dark bodies, showing supporting and secretory function. 4) Cells of type B with an agranular endoplasmic reticulum in stripe like arrangement, supposed to be receptor cells.

The response of the gil epithelium of the adult axolotl (Siredon mexicanum) to roentgen radiation.

1. The right gills of adult axolotls (Siredon mexicanum), 5 to 6 years old, were locally irradiated with 2,000 r in 10 animals, 4,000 r in 10, and 8,000 r in 10; 10 animals served as untreated controls.2. Disappearance of the gill filaments is possible in the course of normal development, especially in old axolotls, but was the rule after irradiation. In the present study, normal filaments were never seen after irradiation.3. The gill filament and the gill epithelium are very sensitive to roentgen radiation, much more so than the skin epithelium. The gill epithelium is one of the most sensitive types of epithelium in the adult axolotl. Even as little as 2,000 r, the smallest dose used, completely disorganized and destroyed the gill filaments and the gill epithelium, which were later replaced with skin epithelium containing many Leydig cells.4. After irradiation with 8,000 r, giant cells developed in the skin epithelium that replaced the destroyed gill epithelium. Such giant cells were probably caused by m...

The effects of X-radiation on the eye of the one-year-old axolotl ( Siredon mexicanum)

The anterior portion of each head of 30 1-year-old axolotls ( Siredon mexicanum ) was irradiated with 4000 r; 5 animals served as untreated controls. Specimens fixed at various intervals following irradiation were studied histologically. Considerable differences were found between specimens undergoing early fixation (about 53–100 days after irradiation) and specimens undergoing late fixation (about 230–280 days after irradiation). The corneas of the eyes undergoing early fixation were damaged in 100% of the animals, the injury being moderate in most cases, but serious in some. The lenses and retinas were normal or only slightly damaged in most cases and severely damaged only in rare cases. The corneas of the eyes undergoing late fixation, however, were normal or only slightly damaged in most cases; obviously, the cornea was never entirely destroyed by the dose of radiation used and was able to recover more or less completely during the course of the experiment. The lenses were damaged in 100% of the animals, the injury being severe in most cases, moderate in some, and slight in none. The gradual destruction of the lens was due to the activity of macrophages, which partially phagocytosed the lens fibers and partially dissolved them. The retinas were damaged severely in rare cases, moderately in most cases, slightly in some cases, and not at all in one case. Evidently, the lens is the most radiosensitive part of the eye of 1-year-old axolotls, but the injury takes time to become mainfest. In contrast, the cornea is appreciably less sensitive, undergoing moderate to severe injury at first, but recovering later. The most sensitive part of the retina is the rod-and-cone layer. The response of the eye of the 1-year-old axolotl to radiation was similar to that of younger animals, but showed some peculiarities. For example, in the lens of the 1-year-old axolotl, the irradiation was followed by the development of pigmentation, but such pigmentation never developed in the lenses of younger animals; also, recovery of the cornea has never been observed in younger axolotls.

The influence of temperature on the water exchange in amphibian eggs and embryos.

AbstractThe water exchange has been measured in oocytes of siredon mexicanum and rana temporaria, and in unfertilized eggs and early gastrulae of the former species, by recording the D2OH2O exchange with the cartesian diver balance.In oocytes, where no diffusion barrier to water is demonstrable, the temperature coefficient Q10 for the exchange of water is about 1.3–1.4, corresponding to that of free diffusion. in unfertilized eggs, and in early gastrulae the exchange is considerably slowed down, indicating that a surface membrane to some extent limits the rate of exchange. at the same time the Q10 value is increased, lying in the range 2.3–3.8. since it is most likely that the exchange even in this case occurs by diffusion, but through membrane pores, it is concluded that the area available for diffusion (pore size or number, or both) increases with temperature.

Histopathology of the development of the axial skeleton and spinal cord in the irradiated tail of the young axolotl (Siredon mexicanum).

The tails of axolotls (Siredon mexicanum) were irradiated locally in five groups of 25 animals each, receiving 500, 1,000, 2,000, 3,000 and 6,000 r, respectively, 1 month after hatching, and in one group of 20 animals, receiving 3,000 r 38 days after hatching; 35 animals served as untreated controls.1. In control animals, the development of the axial skeleton of the tail is completely different during the later stages than during the earlier stages. The first period of development lasts 2 or 3 months. During this period, development of the axial skeleton of the tail is limited to growth and differentiation of the notochord. The second period begins with the formation of the cartilaginous trunk from the end of the notochord or from the distal end of the last caudal vertebra. Further development is characterized by growth and differentiation of the cartilaginous trunk.2. During the first 20 days after irradiation, the appearance of the axial skeleton usually is approximately normal. Around the 20th day, mac...

The response of the cornea of the adult axolotl ( Siredon mexicanum) to X-radiation

The anterior portion of the head was irradiated in 70 adult axolotls (Mexican salamanders of the species Siredon mexicanum), 4–5 years old, using 1000 r in 9 animals, 3000 r in 20, 6000 r in 10, 8000 r in 11, and 10,000 r in 20; 5 animals served as untreated controls. Specimens fixed at various intervals following irradiation were studied histologically. After irradiation with 1000 r, the substantia propria of the cornea was almost normal. The corneal epithelium, however, became much thicker, and melanophores and Leydig cells developed in it. After irradiation with 3000 r, the substantia propria was much thicker than normal, and underwent stratification; cavities and pigment cells developed in it. In the epithelium, melanophores and Leydig cells developed, and sometimes cavities formed between the cells, and vacuoles appeared in the cytoplasm. After irradiation with 6000–10,000 r, the substantia propria underwent thickening and stratification, and blood vessels penetrated into it. The epithelium became much thicker, giant cells developed, and melanophores and Leydig cells were formed. Sometimes the corneal epithelium disappeared and was replaced by skin epithelium. Some phenomena typical of the response of young axolotls to radiation (e.g., the formation of abnormal outgrowths on the cornea) were not observed in adult animals. On the other hand, the development of melanophores and blood vessels in the substantia propria occurred in the adults, but not in the young animals. The development of melanophores and blood vessels in areas of the irradiated cornea where they do not occur in the nonirradiated cornea may be considered a result of X-ray stimulation. Most of the histopathological changes that were observed in the irradiated cornea in axolotls are not peculiar to amphibians; they have been reported by various investigators to occur in mammals, including man.

Vergleichende Untersuchungen �ber die Feinstruktur der Bipolarzellschicht der Vertebratenretina

1. The ultrastructure of the retinal cells of the inner granular layer has been studied in diurnal animals (species: Carassius auratus auratus, Siredon mexicanum, Lacerta muralis, Gallus domesticus, Passer domesticus, Rhesus). 2. Three different types of neurons can be discriminated which correspond to horizontal, bipolar and amacrin cells seen in light microscopy. 3. The classification of the horizontal and amacrin cells as neurons is based on their synaptic contacts with receptors and other cells. 4. The demonstration of synaptic contacts appears to be the only reliable criterion of a neuron concerning cells situated in the inner granular layer, for obvious Nissl substance (granulated ER) is not detectable in most of these cells.