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PubMed1995

The ontogeny of aquatic feeding behavior in Salamandra salamandra: stereotypy and isometry in feeding kinematics

To examine the extent to which aquatic prey-capture behavior in salamanders is stereotyped and how feeding kinematics scales with size, the ontogenetic variability of aquatic feeding behavior was examined in eight Salamandra salamandra. Feeding kinematics (seven duration and angular displacement variables), kinematic variance and capture performance were quantified and compared in the first several feedings after birth with a series of feedings 8 weeks later, just prior to metamorphosis. Analysis of variance revealed no statistically significant ontogenetic differences in the kinematic variables, and individual differences were found in only two variables (maximum gape angle and gape cycle time). A comparison of the relative kinematic variance within individuals revealed no significant differences in variance during ontogeny. In addition, capture success rate did not change. The strike is significantly faster than that of other salamanders. These results indicate that the initial prey-capture behavior remains unchanged throughout larval ontogeny. Thus, aquatic strike behavior in S. salamandra is developmentally fixed (innate) and does not appear to be influenced by learning or improvement in 'skill', supporting the hypothesis that aquatic salamander feeding is a highly stereotyped, unmodulated behavior. In addition, the lack of kinematic change through ontogeny indicates that feeding kinematics do not scale with body size, contrary to predictions that movements should be slower in larger animals.

Journal Article↗
PubMed1982

Further evidence for calcitonin gene duplication: the identification of two different calcitonins in a fish, a reptile and two mammals.

In order to investigate the possibility of the simultaneous expression of two different calcitonin genes during evolution, we studied the nature of calcitonin in: eel pericardium, salamander branchial region, rat thyroid, ox thyroid, medullary carcinoma of the human thyroid and human thyrotoxic goitre. Sensitive and specific RIAs for human calcitonin (hCT) and salmon calcitonin (sCT) were used in combination with high pressure liquid chromatography (HPLC). We found that two different immunoreactive calcitonins resembling hCT and sCT exist in eels, salamanders and rats. The major form is i-sCT-like in eels and salamanders, while it is i-hCT-like in rats. Extracts of ox thyroid contained, in addition to the major artiodactyl-CT, an i-hCT-like material. The various human thyroid extracts studied, contained i-hCT but no i-sCT-like material. This study demonstrates the simultaneous expression of two different calcitonin genes in several species. Taken with the presence of molecules resembling sCT and hCT in birds, this further evidence is consistent with duplication of the calcitonin gene early in vertebrate evolution.

Animals↗
PubMed2001

Transmission of the Ambystoma tigrinum virus to alternative hosts.

Ambystoma tigrinum virus (ATV) is a lethal virus originally isolated from Sonora tiger salamanders Ambystoma tigrinum stebbinsi in the San Rafael Valley in southern Arizona. USA. ATV is implicated in several salamander epizootics. We attempted to transmit ATV experimentally to fish and amphibians by injection, water bath exposure, or feeding to test whether ATV can cause clinical signs of infection or be recovered from exposed individuals that do not show clinical signs. Cell culture and polymerase chain reaction of the viral major capsid protein gene were used for viral detection. Salamanders and newts became infected with ATV and the virus was recovered from these animals, but virus could not be recovered from any of the frogs or fish tested. These results suggest that ATV may only infect urodeles and that fish and frogs may not be susceptible to ATV infection.

Ambystoma↗
PubMed1988

Cell rearrangement and directional migration in pronephric duct development.

The morphology of the directed migration of the pronephric duct rudiment of three vertebrates, the salamander, chick and sturgeon, has been examined by scanning electron microscopy. Of particular interest in this paper are the morphology of the duct tip, the role of cell rearrangement, and the relation of duct extension to somite segmentation. The duct rudiments of all three species have motile cell processes (lamellipodia and filopodia) largely confined to their posterior tips. The salamander and sturgeon embryos extend their duct rudiments by extensive cell rearrangements. A short, wide rudiment is elongated to form a long, thin one. The chick duct rudiment stays about the same width and apparently gains volume by cell proliferation. The salamander duct rudiment's posterior tip is always two somites behind the last formed somite. Both the sturgeon and chick embryo's duct rudiments lie well posterior of the last segmented somite adjacent to segmental plate mesoderm. There is still a close coupling, however, between the posterior progression of the duct rudiments and the advancing wave of somite segmentation.

Ambystoma↗
PubMed1996

Acid efflux from retinal glial cells generated by sodium bicarbonate cotransport.

Sodium bicarbonate cotransport was studied in freshly dissociated Müller cells of the salamander retina. Variations in intracellular and extracellular pH evoked extracellular potassium concentration ([K+]o were recorded. Intracellular pH was measured by standard ratio imaging of the pH-sensitive dye BCECF, whereas extracellular pH was monitored by imaging BCECF fixed to coverslips under dissociated cells. Increasing [K+]o from 2.5 to 50 mM resulted in an intracellular alkalinization. The rate of alkalinization, 0.047 pH units/min, was reduced to 42% of control when HEPES was substituted for HCO3- and was reduced to 36% of control by the addition of 0.5 mM DIDS, a Na+/HCO3- cotransport blocker. The K(+)-evoked alkalinization was Cl(-)-independent and was not substantially reduced by amiloride or bumetanide. Increasing [K+]o to 50 mM also produced a rapid extracellular acidification, 0.01 to 0.05 pH units in amplitude. HEPES substitution and addition of 0.5 mM DIDS reduced the acidification to 7-8% of control, respectively. These results confirm the presence of a Na+/HCO3- cotransport system in salamander Müller cells and provide definitive evidence that glial cells can generate an extracellular acidification when [K+]o is increased. The K(+)-evoked extracellular acidification measured beneath cell endfeet was 304% of the amplitude of the acidification beneath cell somata, confirming that cotransporter sites are preferentially localized to the endfoot. The carbonic anhydrase inhibitor benzolamide (2 x 10(-5) M), which is poorly membrane permeant, increased the K(+)-evoked extracellular acidification to 269% of control, demonstrating that salamander Müller cells possess extracellular carbonic anhydrase.

Acids↗
PubMed1995

-Structure of the respiratory system of the Ulodera Hynobius neblosus tokyoensis Tago, with special reference to the distribution of serotonin-immunoreactive cells in its respiratory tract epithelium.

The respiratory tract epithelium in many vertebrate species has a neuroepithelial endocrine (NEE) system. This system is composed of solitary NEE cells or organoid cell groups called neuroepithelial bodies (NEBs). In response to chemical and physical stimuli, NEE cells may release bioactive substances. Serotonin, one of the biogenic amines, well-known as a constricter of smooth muscle, can be found in NEE cells, serotonin-immunoreactive cells can be used as a marker for these cells. Comparative histological studies of lower vertebrates can improve our understanding of mammalian respiratory systems. The Tokyo salamander (Hynobius neblosus tokyoensis Tago), classified as Ulodera, is particularly useful for comparative studies of respiration. In this study, the serial sections of respiratory tract of the Tokyo salamander were stained by a commonly used staining method and by an immunocytochemical method for serotonin, and the distribution of serotonin-immunoreactive cells in the respiratory tract was examined. The respiratory tract was found to be connected to the alimentary tract via an aditus laryngis, which opens on the medio-ventral side of the esophagus. The laryngotrachea was slit-like or elliptically shaped with a total length of about 3.5 mm, joining the aditus laryngis. The laryngotrachea was supported by a pair of lateral cartilages, and a fibromuscular layer was seen between the cartilages and the epithelium. In the cranial region, a laryngeal sphincter was seen around the laryngotrachea. The laryngotrachea branches into a pair of tube-like lungs, that are about 17-20 mm in length. Two apposed primary trabeclae run along the entire length of the lung wall, perpendicular to the axis, and containing the pulmonary arteries and veins. The lungs were divided into two portions: 1) an airway portion (trabeclae, septa) in which smooth muscles surrounding the large vessels were well developed, and 2) a respiratory portion which was give that name because it has well developed capillary networks that were assumed to be involved in gas exchange. The lumen of the laryngotrachea and the pulmonary airway portion contained pseudostratified cilio-mucous epithelium. In the caudaldorsal region of the laryngotrachea adjacent to the lungs, the non-ciliated respiratory epithelium was seen lining the capillaries. In cilio-mucous epithelium of the laryngotrachea, all serotonin-immunoreactive cells were solitary. They apposed to be columnar, cuboidal, triangular, oval, and flask- or spindle-shaped. Solitary serotonin-immunoreactive cells were classified "open type cell" with appical process reaching to the luminal surface and "closed type cell" insulated from the lumen by an epithelial lining. In the pulmonary airway portion, serotonin-immunoreactive cells were solitary cells and in clusters. Serotonin-immunoreactive cells were widely distributed throughout the respiratory tract, but they tended to be found mainly in the cranial portion. The density was highest in the area with the laryngeal sphincter, and decreased caudally in the laryngotrachea and lung. No serotonin-immunoreactive cells were found in the respiratory portion of the dorsal-caudal area of the laryngotrachea or in the part of the lung with non-ciliated cells. So the structure and distribution of serotonin-immunoreactive cells in the respiratory tract of the Tokyo salamander are similar to those of NEE cells and NEBs in mammalian respiratory systems. The density of serotonin-immunoreactive cells appears to be related to the distribution of smooth muscles in the fibromuscular layer and airway portion. The cells may be involved in regulation of the respiratory system. Serotonin is released in response to stimulation, which could result in constriction of the fibromuscular layer and shrinkage of the laryngotracheal cavity, and may regulate pulmonary volume by constricting smooth muscles

Animals↗
PubMed1998

Species, sex, and seasonal differences in VNO size.

Differences in the sizes of sensory and neural structures are used as an indication of differences in the function of those structures. Large VNOs often are interpreted to mean that this sense is particularly important in the life history of the animal. They also are assumed to be associated with more primitive animals. I examined VNO sizes across mammalian, reptilian, and amphibian lineages while attempting to account for total body size, because VNO and total body sizes are related. Most descriptions of VNO size and development are not quantified and often ambiguous. Large VNOs in a lineage should not be interpreted necessarily as primitive. Comparisons across smaller taxonomic ranges are easier to interpret. Plethodontid salamanders are a diverse set of species for which VNO descriptions show trends in size associated with habitat, sex, and season. Semiaquatic species tend to have proportionately larger VNOs than terrestrial species, males have larger organs than females, and VNOs can show increases and decreases in size that may be associated with seasonal activities. Salamanders may use their VNOs to locate and identify mates, as part of the courtship sequences, or to identify and assess neighboring territory holders.

Animals↗
PubMed1988

Role of monocarboxylate transport in the regulation of intracellular pH of renal proximal tubule cells.

Traditional models of acid-base transport and intracellular pH (pHi) regulation in the renal proximal tubule have been based on the existence of a Na+/H+ exchanger at the luminal membrane and a simple HCO3- conductance at the basolateral membrane. Our recent work, in which we used pH-sensitive microelectrodes or dyes to monitor pHi in isolated renal tubules perfused in the nominal absence of HCO3-, has demonstrated the existence of a novel mechanism of acid extrusion in amphibian and mammalian proximal tubule cells. The salamander proximal tubule, for example, possesses an electroneutral Na+ monocarboxylate (Na+-X-) co-transporter, but only at the luminal membrane. It also possesses an electroneutral H+-X- co-transporter, but only at the blood side or basolateral membrane. In the presence of lactate, the luminal Na+-lactate co-transporter mediates a net influx of lactate, driven by the Na+ gradient. The cell-to-blood lactate gradient, in turn, drives the coupled efflux of H+ and lactate across the basolateral membrane. The net effect is the reabsorption of lactate, the luminal uptake of Na+ and the basolateral extrusion of H+. Acid extrusion mediated by this monocarboxylate system in the salamander is comparable in magnitude to that mediated by the Na+/H+ exchanger. In the S3 segment of the rabbit proximal tubule, a similar monocarboxylate system (studied with acetate instead of lactate) extrudes acetate at twice the rate of the Na+/H+ exchanger. Thus, monocarboxylate transport, at least in the nominal absence of HCO3-, can have a major impact on pHi regulation.

Acetates↗
PubMed1984

Cytophotometric comparisons of DNA levels in neuronal and glial cells of the cerebellum: a comparative study.

Several cytochemical studies of the DNA content and ploidy status of neuronal cell nuclei in the central nervous system have reported the occurrence of hyperdiploid amounts of DNA in Purkinje cells and suggest the existence of some type of 'extra' DNA, the biological significance of which is, as yet, unknown. To explore this phenomenon further, the DNA content of glial and Purkinje cell nuclei was determined in several vertebrate species, using the DNA-specific fluorochrome 4',6-diamidino-2-phenylindole (DAPI) to stain isolated cerebellar nuclei for analysis with a single parameter flow cytometer. The Feulgen reaction for DNA was used to stain liver and cerebellar tissue imprints for the measurement of individual nuclei with a Vickers M86 integrating microdensitometer. In both types of analyses, chicken erythrocyte nuclei served as an internal reference standard of 2.5 pg DNA per cell. The mean DNA content of Purkinje cells and glial or granule cells was essentially the same as that found for diploid (2C) non-neuronal cells, such as hepatocytes, in rainbow trout, Amazon molly fish, salamander (Plethodon), mouse, rat, rabbit, cat, dog, monkey and human. Although Purkinje cell nuclei with 4C DNA levels were found in all of these species, except salamander and rabbit, the frequency of such cells was low (1-7%) and varied with the species. There was a low incidence of Purkinje cell nuclei with interclass DNA amounts in all species examined. Our data show that most neuronal cell nuclei in the cerebellum contain 2C levels of DNA.

Animals↗
PubMed1989

Distribution of muscarinic acetylcholine receptors on processes of isolated retinal cells.

Binding of propylbenzilylcholine mustard, a muscarinic acetylcholine receptor antagonist, to isolated retinal cells was examined with light microscopic autoradiography. Dissociation of the adult tiger salamander retina yielded identifiable rod, cone, horizontal, bipolar, amacrine/ganglion, and Müller cells. Preservation of fine structure was assessed with conventional electron microscopy. For all cell types, the plasmalemma was intact and free of adhering debris; in addition, presynaptic ribbon complexes were present in photoreceptor and bipolar axon terminals indicating that synaptic structures were retained. Specific binding to cell bodies and processes was analyzed separately by using morphometric and statistical techniques. The highest grain densities occurred on processes of amacrine/ganglion cells and axons and 2 degrees and 3 degrees dendrites of bipolar neurons. Bipolar cells, however, seemed to be a heterogeneous population because there was great variation in the density of binding sites on both their axons and distal dendrites. Intermediate levels of binding were found on bipolar 1 degree dendrites and horizontal cells. No specific binding was detected on Müller cells and most parts of photoreceptors. Comparisons between cells showed that grain densities were similar for bipolar axons and amacrine/ganglion cell processes but bipolar dendrites were richer in binding sites than horizontal cell dendrites. Thus, muscarinic receptors in the salamander retina are located on amacrine/ganglion, bipolar, and horizontal cells and primarily confined to the processes which compose the two synaptic layers. In the inner plexiform layer, muscarinic receptors reside on processes from all three inner retinal neurons: in the outer synaptic layer, receptors are only on second-order cells and are more numerous along bipolar than horizontal cell dendrites.

Animals↗
PubMed2002

Expression of fibroblast growth factors 4, 8, and 10 in limbs, flanks, and blastemas of Ambystoma.

Members of the fibroblast growth factor (FGF) family of molecules are critical to limb outgrowth. Here, we examine the expression of Fgfs in three types of limbs-embryonic (developing), mature (differentiated), and regenerating-as well as in the surrounding non-limb tissues in the Mexican axolotl, Ambystoma mexicanum. We have previously cloned partial cDNAs of Fgf4, 8, and 10 from the axolotl (Christensen et al., 2001); the complete Fgf10 cDNA sequence is presented here. Axolotl Fgf10 showed deduced amino acid sequence identity with all other vertebrate Fgf10 coding sequences of >62%, and also included conserved 5' and 3' untranslated regions in nucleotide sequence comparisons. Semiquantitative reverse transcriptase-polymerase chain reaction showed that fibroblast growth factors are differentially expressed in axolotl limbs. Only Fgf8 and 10 were highly expressed during axolotl limb development, although Fgf4, 8, and 10 are all highly expressed during limb development of other vertebrates. Fgf4 expression, however, was highly expressed in the differentiated salamander limb, whereas expression levels of Fgf8 and 10 decreased. Expression levels of Fgf8 and 10 then increased during limb regeneration, whereas Fgf4 expression was completely absent. In addition, axolotl limb regeneration contrasted to limb development of other vertebrates in that Fgf8 did not seem to be as highly expressed in the distal epithelium; rather, its highest expression was found in the blastema mesenchyme. Finally, we investigated the expression of these Fgfs in non-limb tissues. The Fgfs were clearly expressed in developing flank tissue and then severely downregulated in mature flank tissue. Differential Fgf expression levels in the limb and shoulder (limb field) versus in the flank (non-limb field) suggest that FGFs may be instrumental during limb field specification as well as instrumental in maintaining the salamander limb in a state of preparation for regeneration.

3' Untranslated Regions↗
PubMed2004

Cloning and analysis of axolotl ISL2 and LHX2 LIM-homeodomain transcription factors.

We cloned and characterized the ISL2 and LHX2 LIM-homeodomain transcription factors of the Mexican salamander, or axolotl, Ambystoma mexicanum. Using a degenerate PCR approach, partial cDNAs representing five LIM-homeodomain genes were cloned, indicating conservation of this class of transcription factors in urodeles. Full-length cDNAs for Isl2 and Lhx2 were identified and sequenced. The predicted ISL2 and LHX2 proteins are well conserved, especially in the LIM and DNA-binding domains. The Isl2 and Lhx2 genes are expressed at all examined stages of embryogenesis and display tissue-restricted expression patterns in adults. In functional tests, axolotl LHX2 was inactive compared to homologous mammalian factors and adopted unusual DNA/protein complexes. However, axolotl ISL2 bound and induced transcription from the rat insulin gene. These experiments demonstrate conservation of key developmental regulatory proteins in salamanders and will allow future studies of their potential roles in the molecular regulation of tissue regeneration in such species.

Animals↗
PubMed1994

Neuroepithelial endocrine and nervous system in the respiratory tract of Cynops pyrrhogaster with special reference to the distribution of nitric oxide synthase and serotonin.

The respiratory tract of urodeles harbours an intramural nerve network comprising an innervated system of neuroepithelial endocrine (NEE) cells. However, striking differences have been noted between phylogenetically closely related species. Zamboni- or formaldehyde-fixed whole-mount preparations and sections of the saclike lungs of a Japanese salamander, Cynops salamander, Cynops pyrrhogaster, have been investigated for the immunocytochemical detection of nitric oxide synthase (NOS), serotonin (5-HT), VIP, somatostatin, calcitonin, and bombesin; for the enzyme-cytochemical demonstration of NADPH diaphorase (NADPHd); and for formaldehyde-induced fluorescence. In addition, the ultrastructural morphology has been examined by using glutaraldehyde/osmium tetroxide fixed lung tissues. Ovoid 5-HT-immunoreactive (IR) NEE cells occur singly or grouped in the ciliomucous epithelium of the trachea and lungs of Cynops, and a few somatostatin-, calcitonin-, and bombesin-like IR NEE cells are also observed. These cells exhibit a characteristic neuroendocrine morphology as seen with the electron microscope. In addition, large numbers of 5-HT-IR interstitial cells, with round to oval cell bodies and two or three long, slender, sometimes branching processes, are located preferentially along large blood vessels in the connective tissue capsule of the lung and trachea. Immunoelectronmicroscopy shows that 5-HT is localized over large dense granules in the cell bodies and processes of these interstitial cells. NOS-like immunoreactivity occurs in a nerve plexus composed of thick nerve bundles and nerve cells, and in a fine varicose nerve network that originates at least partly from intrapulmonary NOS-containing nerve cells. VIP-like immunoreactivity appears to be colocalized with NOS in the latter network. All NOS-positive nerve fibres in the lungs of Cynops pyrrhogaster and Ambystoma mexicanum stain for NADPHd. It is concluded that the pulmonary NEE cells observed in Cynops pyrrhogaster are similar to those described in other vertebrate species and that the 5-HT-IR interstitial cells resemble mast cells. In addition, nitric oxide is likely to be a bioactive substance involved in nonadrenergic, noncholinergic inhibitory neurotransmission in the pulmonary nervous system of urodeles, where it may be colocalized with VIP.

Amino Acid Oxidoreductases↗
PubMed1986

Requisites for growth and myelination of urodele sensory neurons in tissue culture.

We describe a system for long-term culture of adult salamander dorsal root ganglia and present initial observations on the regulation of nonneuronal cell proliferation in this system. Observations of the region of axonal outgrowth in these cultures indicated that, on the one hand, fibroblasts proliferate equally well with neurons present or absent. Schwann cells, on the other hand, require not only the presence of neurons but also proximity to or contact with their neurites. These results indicate that neural tissue is not mitogenic for all cell types represented in the limb regeneration blastema. Further, we describe, for the first time, myelination of salamander axons in vitro. The critical factors found to be required for this high degree of differentiation were the use of long culture periods and addition to the culture medium of ascorbic acid, which is shown to promote extracellular matrix deposition. These observations correlate with extensive observations made on mammalian tissues in vitro, indicating a linkage between deposition of extracellular matrix and full expression of other Schwann cell functions. We anticipate this culture system will be useful in studies of limb blastema cell proliferation.

Ambystoma↗
PubMed1990

Explanation for naturally occurring supernumerary limbs in amphibians.

The occasional occurrence of high frequencies of limb abnormalities, including extra limbs, in natural populations of amphibians has long been a puzzle. In this paper we report the discovery of a population in which such limb abnormalities appear to be caused by a parasitic flatworm (trematode) that uses amphibians as intermediate hosts. The cercarial larval stage of the trematode attacks amphibians, penetrating the skin to form cysts (metacercariae). The cysts are preferentially localized in the cloacal region, including the developing hind limb regions in larvae of both frogs (Hyla regilla) and salamanders (Ambystoma macrodactylum). A wide range of limb abnormalities are seen, including duplicated limb structures ranging from extra digits to several extra whole limbs. We hypothesize that these limb abnormalities result from localized regulatory responses of developing and regenerating limb tissues to mechanical disruption caused by the trematode cysts. We have tested this idea by implanting inert resin beads into developing limb buds of frogs and salamanders. Since this treatment can cause supernumerary limb structures, our hypothesis is sufficient to explain the naturally occurring extra limbs.

Animals↗
PubMed1991

Reduced calcium and inhibition of protein kinase C mimic the enhancement of ornithine decarboxylase activity of prolactin in Ambystoma tigrinum tissues.

We previously reported that prolactin (PRL) could increase the activity of ornithine decarboxylase (ODC) in liver slices taken from larval tiger salamanders (Ambystoma tigrinum). This action of the hormone was inhibited by oxytocin (OT), the calcium ionophore A23187, and diacyglycerol (DG) and was duplicated by 10 microM verapamil (VML), a calcium channel blocker. Here, we expand these results to show that 1) a higher dose of VML (50 microM) produces an additive effect with PRL; 2) addition of small amounts of calcium (0.1 mM) to the liver culture medium blocks PRL action; 3) neither nifedipine (NIF), a different type of calcium channel blocker, nor EDTA alter PRL action; and 4) gossypol, a reported inhibitor of protein kinase C, mimics PRL action. Additionally, we show that PRL increases ODC activity in tiger salamander tail skin in vitro, a tissue previously demonstrated to be a PRL target tissue in this species. The same set of treatments which we have shown to modify PRL effects on ODC in liver slices affects PRL action in the tail skin in a parallel manner. Thus, the mechanism whereby PRL enhances ODC activity appears to be the same in both these tissues. These results are discussed in conjunction with the findings from similar studies using mammalian tissues in an attempt to assess the current picture of the mechanism of PRL action and the possible role of inositol phospholipid turnover, calcium, and protein kinase C in the action of this hormone.

Ambystoma↗
PubMed2003

Anatomical features of Leiopelma embryos and larvae: implications for anuran evolution.

A controversial issue in anuran systematics is the relationship of Leiopelma to other anurans because recent phylogenetic constructions imply different relationships among the basal frogs. Of particular evolutionary interest is whether early development of Leiopelma resembles an ancestral salamander-like larva, an anuran tadpole, or neither. In the 1950s, Neville G. Stephenson hypothesized that direct development is the primary mode of development in amphibians, based on the fact that Leiopelma spp. lack a free-living (=feeding) larval stage. Although this hypothesis has not been generally accepted, it has not been formally refuted. We review Stephenson's work on Leiopelma and examine the anatomy of embryos/"larvae" of the four extant Leiopelma species for evidence of vestigial larval features that might refute the "direct-developing ancestor" hypothesis. We describe internal oral features in early developmental stages of Leiopelma and compare Leiopelma with a closely related basal anuran, Ascaphus, to assess whether their early developmental stages share any derived features. In Leiopelma hochstetteri, embryos/larvae have open gill slits and some faint rugosities around one gill slit that may be vestiges of gill rakers or filters. They also have more intestinal loops, indicative of an elongated alimentary tract, at earlier rather than late embryonic/larval stages. Collectively, these features support the view that the ancestor of Leiopelma had a free-swimming, free-feeding, aquatic larva. The palatoquadrate of Leiopelma archeyi reorients approximately 40 degrees from a more horizontal to a more vertical position through embryonic/"larval" development. This amount of cranial remodeling is intermediate between that seen in salamanders (17-27 degrees) and that reported for Ascaphus (64 degrees ) and other basal frogs (71-78 degrees) at metamorphosis. We found no internal oral features that Leiopelma shares specifically with Ascaphus. However, Leiopelma embryos have a ventrally positioned mouth and a downturned rostrum, characteristic of Ascaphus and other stream-adapted tadpoles.

Animals↗
PubMed2003

Ultrastructure of the mature spermatozoa of caecilians (Amphibia: Gymnophiona).

The spermatozoa of Gymnophiona show the following autapomorphies: 1) penetration of the distal centriole by the axial fiber; 2) presence of an acrosomal baseplate; 3) presence of an acrosome seat (flattened apical end of nucleus); and 4) absence of juxta-axonemal fibers. The wide separation of the plasma membrane bounding the undulating membrane is here also considered to be apomorphic. Three plesiomorphic spermatozoal characters are recognized that are not seen in other Amphibia but occur in basal amniotes: 1) presence of mitochondria with a delicate array of concentric cristae (concentric cristae of salamander spermatozoa differ in lacking the delicate array); 2) presence of peripheral dense fibers associated with the triplets of the distal centriole; and 3) presence of a simple annulus (a highly modified, elongate annulus is present in salamander sperm). The presence of an endonuclear canal containing a perforatorium is a plesiomorphic feature of caecilian spermatozoa that is shared with urodeles, some basal anurans, sarcopterygian fish, and some amniotes. Spermatozoal synapomorphies are identified for 1) the Uraeotyphlidae and Ichthyophiidae, and 2) the Caeciliidae and Typhlonectidae, suggesting that the members of each pair of families are more closely related to each other than to other caecilians. Although caecilian spermatozoa exhibit the clear amphibian synapomorphy of the unilateral location of the undulating membrane and its axial fiber, they have no apomorphic characters that suggest a closer relationship to either the Urodela or Anura.

Acrosome↗