The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
David M. Parichy - One of the best experts on this subject based on the ideXlab platform.
-
Conserved Vertebrate Chromosome Segments in the Large Salamander Genome
Genetics, 2001Co-Authors: S R Voss, J. Joshua Smith, David M. Gardiner, David M. ParichyAbstract:Urodele amphibians (salamanders) are important models for embryological, physiological, and natural history research and are also a biomedically important group because they are the only vertebrates capable of regenerating entire organ systems. To enhance the utility of salamanders for biomedical research and for understanding genome evolution, genetic linkage analysis was used to identify chromosome segments that are homologous between ambystomatid salamanders and distantly related vertebrate model organisms. A total of 347 loci (AFLPs, RAPDs, and protein-coding loci) were mapped using an interspecific meiotic mapping panel (Ambystoma mexicanum and A. tigrinum tigrinum; family Ambystomatidae). Genome size in Ambystoma was estimated to be 7291 cM, the largest linkage map estimate reported for any organism. However, the relatively large size of the salamander genome did not hinder efforts to map and identify conserved syntenies from a small sample of 24 protein-coding loci. Chromosomal segments that are conserved between fishes and mammals are also conserved in these salamanders. Thus, comparative gene mapping appears to be an efficient strategy for identifying orthologous loci between ambystomatid salamanders and genomically well-characterized vertebrate model organisms.
-
Genetic analysis of steel and the PG-M/versican-encoding gene AxPG as candidates for the white (d) pigmentation mutant in the salamander Ambystoma mexicanum.
Development genes and evolution, 1999Co-Authors: David M. Parichy, Michael Stigson, S R VossAbstract:Vertebrate non-retinal pigment cells are derived from neural crest (NC) cells, and several mutations have been identified in the Mexican axolotl Ambystoma mexicanum (Ambystomatidae) that affect the development of these cell lineages. In "white" (d) mutant axolotls, premigratory NC cells differentiate as pigment cells, yet fail to disperse, survive, or both, and this leads to a nearly complete absence of pigment cells in the skin. Previous studies revealed that d affects pigment cell development non-autonomously, and have reported differences between white and wild-type axolotls in the structure and composition of the extracellular matrix through which NC and pigment cells migrate. Here we test the correspondence of d and two candidate genes: steel and AxPG. In amniotes, Steel encodes the cytokine Steel factor (mast cell growth factor; stem cell factor; kit ligand), which is expressed along the migratory pathways of melanocyte precursors and is required by these cells for their migration and survival; mammalian Steel mutants resemble white mutant axolotls in having a deficit or complete absence of pigment cells. In contrast, AxPG encodes a PG-M/versican-like proteoglycan that may promote the migration of A. mexicanum pigment cells, and AxPG expression is reduced in white mutant axolotls. We cloned a salamander orthologue of steel and used a partial genetic linkage map of Ambystoma to determine the genomic locations of steel, AxPG, and d. We show that the three genes map to different linkage groups, excluding steel and AxPG as candidates for d.
-
Experimental analysis of character coupling across a complex life cycle: pigment pattern metamorphosis in the tiger salamander, Ambystoma tigrinum tigrinum.
Journal of morphology, 1998Co-Authors: David M. ParichyAbstract:Developmental relationships among characters are expected to bias patterns of morphological variation at the population level. Studies of character development thus can provide insights into processes of adaptation and the evolutionary diversification of morphologies. Here I use experimental manipulations to test whether larval and adult pigment patterns are coupled across metamorphosis in the tiger salamander, Ambystoma tigrinum tigrinum (Ambystomatidae). Previous investigations showed that the early larval pigment pattern depends on interactions between pigment cells and the lateral line sensory system. In contrast, the results of this study demonstrate that the major features of the adult pigment pattern develop largely independently of both the early larval pattern and the lateral lines. These results suggest that ontogenetic changes that occur across metamorphosis decouple larval and adult pigment patterns and could thereby facilitate independent evolutionary modifications to the patterns during different stages of the life cycle. J. Morphol. 237:53–67, 1998. © 1998 Wiley-Liss, Inc.
-
Pigment Patterns of Larval Salamanders (Ambystomatidae, Salamandridae): The Role of the Lateral Line Sensory System and the Evolution of Pattern-Forming Mechanisms
Developmental biology, 1996Co-Authors: David M. ParichyAbstract:In many species of salamanders, pigment cells derived from the neural crest give rise to a horizontal stripe pattern in hatchling larvae. A defining element of these horizontal stripe patterns is a region over the middle of the myotomes that is relatively free of melanophores. This study shows that formation of a "melanophore-free region" and horizontal stripe pattern in Ambystoma tigrinum tigrinum (family Ambystomatidae) correlates with the development of the trunk lateral line sensory system. Moreover, prevention of lateral line development results in greater densities of melanophores in the middle of the flank, essentially eliminating the melanophore-free region in this taxon. A phylogenetic survey also revealed that ablation of the lateral lines has qualitatively similar effects on melanophores in seven of eight additional taxa (Ambystomatidae: A. barbouri, A. maculatum, A. talpoideum; Salamandridae: Notophthalmus viridescens, Pleurodeles waltl, Taricha granulosa, T. rivularis). In Taricha torosa, however, a superficially similar melanophore-free region forms prior to lateral line development, and ablation of the lateral lines does not perturb the horizontal stripe pattern. Finally, heterospecific grafting experiments demonstrated that T. torosa lateral lines are competent to generate a melanophore-free region, and T. torosa melanophores are competent to respond to cues associated with the lateral lines. These results indicate that lateral line-dependent pattern-forming mechanisms are common and probably ancestral within the families Ambystomatidae and Salamandridae and suggest that these ancestral mechanisms have been retained in T. torosa as redundant, lateral line-dependent mechanisms for stripe formation have evolved.
-
When Neural Crest and Placodes Collide: Interactions between Melanophores and the Lateral Lines That Generate Stripes in the SalamanderAmbystoma tigrinum tigrinum(Ambystomatidae)
Developmental biology, 1996Co-Authors: David M. ParichyAbstract:Abstract A prominent element of the early larval pigment pattern in the salamanderAmbystoma tigrinum tigrinum(family Ambystomatidae) is a horizontal stripe over the lateral surface of the myotomes where otherwise abundant, neural crest-derived melanophores are not found. This study examines the formation of this “melanophore-free region.” When the trunk lateral lines were ablated (by removing cranial lateral line placodes), the melanophore-free region did not form; instead, melanophores populated the middle of the flank and the distribution of yellow, neural crest-derived xanthophores was perturbed. Time-lapse videomicrography demonstrated that during normal development, the melanophore-free region is established because melanophores retreat from the midbody lateral line primordium as it migrates caudally along the inner side of the epidermis. Melanophores do not repopulate the middle of the flank after primordium migration and heterochronic grafting experiments suggest that extracellular factors contribute to maintaining the melanophore-free region during these later stages. Finally, photographic series, microsurgical manipulations, electron microscopy, and staining for molecules of the extracellular matrix (peanut agglutinin-binding components, tenascin, chondroitin sulfate proteoglycans, fibronectin, laminin) suggest that several factors contribute to establishing and maintaining the melanophore-free region, including steric effects of the lateral lines, interactions between melanophores and xanthophores, lateral line-dependent alterations of the subepidermal basement membrane, and a general elaboration of the extracellular matrix. Lateral line effects on melanophores are inferred to be a shared, ancestral feature of pigment pattern development for the families Ambystomatidae and Salamandridae (D. M. Parichy,Dev. Biol.174, 265–282. 1996). The results of this study thus provide insights into a phylogenetically primitive mechanism for stripe formation, and a context for interpreting evolutionary innovations in pattern-forming mechanisms.
Raymond D. Semlitsch - One of the best experts on this subject based on the ideXlab platform.
-
Recommended Citation
2016Co-Authors: Travis J. Ryan, Raymond D. SemlitschAbstract:Growth and the expression of alternative life cycles in the salamander Ambystoma talpoideum (Caudata: Ambystomatidae
-
Growth and the expression of alternative life cycles in the salamander Ambystoma talpoideum (Caudata: Ambystomatidae)
Biological Journal of the Linnean Society, 2003Co-Authors: Travis J. Ryan, Raymond D. SemlitschAbstract:Complex life cycles (CLCs) contain larval and adult phases that are morphologically and ecologically distinct. Simple life cycles (SLCs) have evolved from CLCs repeatedly in a wide variety of lineages but the processes that may underlie the transition have rarely been identified or investigated experimentally. We examined the influence of larval growth rate on the facultative expression of alternative life cycles (metamorphosis or maturation as gill-bearing adults [= paedomorphosis]) in the salamander Ambystoma talpoideum. We manipulated growth rates by altering the amount of food individuals received throughout larval development. The expression of alternative life cycles in A. talpoideum is influenced by growth via food levels, but the same growth rates at different points in the larval period elicit different responses. Individuals were more likely to metamorphose (i.e. express a CLC) when food levels and growth rates were high later in development and more likely to mature without metamorphosing (SLC) when growth rates were comparatively low during the same point in development. Growth rates at particular points in development, rather than overall larval growth rate, may be an important proximate factor in salamander life-cycle evolution.
-
Cloacal anatomy of paedomorphic female Ambystoma talpoideum (Caudata: Ambystomatidae), with comments on intermorph mating and sperm storage
Canadian Journal of Zoology, 1994Co-Authors: Stanley E. Trauth, David M. Sever, Raymond D. SemlitschAbstract:The cloacal anatomy of paedomorphic female Ambystoma talpoideum was examined using light microscopy and histochemical techniques. Three types of cloacal glands (anterior ventral glands, dorsal glan...
Wilfred C. Mccain - One of the best experts on this subject based on the ideXlab platform.
-
Exposure Regime on a Terrestrial Salamander, Ambystoma tigrinum
2011Co-Authors: Mark S. Johnson, Steven D. Holladay, Kelly S. Lippenholz, Jennifer L. Tenkins, Wilfred C. MccainAbstract:Trinitrotoluene (TNT) is a defense-related environmental contaminant present at high concentrations in soil at some military installations. Tiger salamanders (Ambystoma tigrinum, family Ambystomatidae) were exposed to TNT in a soil matrix and fed earth- worms that had also been exposed to TNT via contaminated soil. Such exposure was previously shown to result in significant accumulation of both TNT and TNT metabolites by salamanders. Following 14 days of combined oral and dermal exposures, sala- manders were evaluated for signs of toxicity. Control and TNT-exposed salamanders gained weight (p < 0.025). In addition, organ to body weight ratios (kidney, liver, and spleen) were not affected by treatment. The function of splenic phagocytic cells was evaluated because these cells are sensitive to certain environmental chemical exposures. Neither the chemiluminescence response (H pro- duction) nor the phagocytic capacity of such cells were different between controls and treatment groups. In like manner, no changes were seen in the peripheral hematologic parameters investigated. Histopathologic evaluations were inconclusive, yet the liver revealed the presence of heavily pigmented iron-rich phagocytes (melanomacrophages). This investigation presents a realistic approach and preliminary data for investigating the effects of xenobiotic exposure in a soil matrix on a terrestrial vertebrate.
-
Effects of 2,4,6-trinitrotoluene in a holistic environmental exposure regime on a terrestrial salamander, Ambystoma tigrinum.
Toxicologic pathology, 2000Co-Authors: Mark S. Johnson, Steven D. Holladay, Kelly S. Lippenholz, J L Jenkins, Wilfred C. MccainAbstract:2,4,6-Trinitrotoluene (TNT) is a defense-related environmental contaminant present at high concentrations in soil at some military installations. Tiger salamanders (Ambystoma tigrinum, family Ambystomatidae) were exposed to TNT in a soil matrix and fed earthworms that had also been exposed to TNT via contaminated soil. Such exposure was previously shown to result in significant accumulation of both TNT and TNT metabolites by salamanders. Following 14 days of combined oral and dermal exposures, salamanders were evaluated for signs of toxicity. Control and TNT-exposed salamanders gained weight (p < 0.025). In addition, organ to body weight ratios (kidney, liver, and spleen) were not affected by treatment. The function of splenic phagocytic cells was evaluated because these cells are sensitive to certain environmental chemical exposures. Neither the chemiluminescence response (H2O2 production) nor the phagocytic capacity of such cells were different between controls and treatment groups. In like manner, no changes were seen in the peripheral hematologic parameters investigated. Histopathologic evaluations were inconclusive, yet the liver revealed the presence of heavily pigmented iron-rich phagocytes (melanomacrophages). This investigation presents a realistic approach and preliminary data for investigating the effects of xenobiotic exposure in a soil matrix on a terrestrial vertebrate.
Stanley E. Trauth - One of the best experts on this subject based on the ideXlab platform.
-
Comparative Histomorphology of Oviducts from Metamorphic and Paedomorphic Ambystoma talpoideum (Caudata: Ambystomatidae)
Copeia, 2019Co-Authors: Dustin S. Siegel, Cody L. Long, Madison Herrboldt, Stanley E. TrauthAbstract:Oviducts of paedomorphic and metamorphic Ambystoma talpoideum were examined to determine if previously observed differences in egg mass characteristics between the two morphs originated from differences in oviductal histomorphology/histochemistry. We found no evidence to support this hypothesis. At least seven oviductal regions were easily identified in the oviducts of both paedomorphic and metamorphic individuals; these were as follows (from cranial to caudal): 1) pars recta (termed Region A), 2) pars convoluta (termed Regions B through F), and 3) the uterine region (termed Region G). While slight structure and staining differences were evident in Region D of the pars convoluta when paedomorphic A. talpoideum from South Carolina were compared with metamorphic A. talpoideum from Arkansas, there were no differences observed between paedomorphic and metamorphic individuals of A. talpoideum from Arkansas. Thus, any observed oviductal variation was most likely the result of geographic variation and not from differences involving metamorphosis between paedomorphic and metamorphic A. talpoideum. The number of oviductal regions of A. talpoideum was comparable with previous studies on plethodontids and salamandrids, and this study represents the first treatise of oviductal anatomy of an ambystomatid using a histochemical approach beyond general staining with hematoxylin and eosin.
-
The testicular sperm ducts and genital kidney of male Ambystoma maculatum (Amphibia, Urodela, Ambystomatidae)
Journal of morphology, 2012Co-Authors: Dustin S. Siegel, David M. Sever, Kevin M. Gribbins, Robert D. Aldridge, Justin L. Rheubert, Stanley E. TrauthAbstract:The ducts associated with sperm transport from the testicular lobules to the Wolffian ducts in Ambystoma maculatum were examined with transmission electron microscopy. Based on the ultrastructure and historical precedence, new terminology for this network of ducts is proposed that better represents primary hypotheses of homology. Furthermore, the terminology proposed better characterizes the distinct regions of the sperm transport ducts in salamanders based on anatomy and should, therefore, lead to more accurate comparisons in the future. While developing the above ontology, we also tested the hypothesis that nephrons from the genital kidney are modified from those of the pelvic kidney due to the fact that the former nephrons function in sperm transport. Our ultrastructural analysis of the genital kidney supports this hypothesis, as the basal plasma membrane of distinct functional regions of the nephron (proximal convoluted tubule, distal convoluted tubule, and collecting tubule) appear less folded (indicating decreased surface area and reduced reabsorption efficiency) and the proximal convoluted tubule possesses ciliated epithelial cells along its entire length. Furthermore, visible luminal filtrate is absent from the nephrons of the genital kidney throughout their entire length. Thus, it appears that the nephrons of the genital kidney have reduced reabsorptive capacity and ciliated cells of the proximal convoluted tubule may increase the movement of immature sperm through the sperm transport ducts or aid in the mixing of seminal fluids within the ducts.
-
Metacercariae of Clinostomum (Trematoda: Digenea) from Three Species of Ambystoma (Caudata: Ambystomatidae) from Arkansas and Illinois, U.S.A
Comparative Parasitology, 2010Co-Authors: Chris T Mcallister, Charles R. Bursey, John A. Crawford, Andrew R. Kuhns, Corey Shaffer, Stanley E. TrauthAbstract:Thirteen of 51 (25.5%) Jefferson salamanders, Ambystoma jeffersonianum, and 4 of 69 (5.8%) small-mouthed salamanders, Ambystoma texanum, from east-central Illinois were found to be infected with metacercariae of Clinostomum marginatum; 1 of 72 (1.4%) spotted salamanders, Ambystoma maculatum from north-central Arkansas was found to be infected with metacercariae of Clinostomum attenuatum. We provide a new host record for C. attenuatum and 2 new host records and a new locality record for metacercariae of C. marginatum. In addition, a list of the amphibian hosts of metacercariae of Clinostomum spp. is provided.
-
new host records for myxidium serotinum protozoa myxosporea from north american amphibians
Journal of Parasitology, 1995Co-Authors: Chris T Mcallister, Stanley E. TrauthAbstract:Three hundred twenty-five amphibians (80 salamanders, 245 frogs and toads) from Arkansas and Texas, representing 28 species within 9 families (Ambystomatidae, Plethodontidae, Salamandridae, Sirenidae, Bufonidae, Hylidae, Leptodactylidae, Microhylidae, Ranidae) were examined for gall bladder myxosporeans. Of these, 32 (10%) were found to harbor Myxidium serotinum Kudo and Sprague, 1940, including 3 (4%) of the salamanders and 29 (12%) of the frogs and toads. This report documents 6 new host records for M. serotinum in Ambystoma opacum, Bufo americanus charlesmithi, Bufo speciosus, Acris crepitans blanchardi, Gastrophryne olivacea, and Pseudacris streckeri illinoensis. In addition, the Great Plains narrowmouth toad G. olivacea represents the first microhylid host of Myxidium spp. worldwide.
-
Cloacal anatomy of paedomorphic female Ambystoma talpoideum (Caudata: Ambystomatidae), with comments on intermorph mating and sperm storage
Canadian Journal of Zoology, 1994Co-Authors: Stanley E. Trauth, David M. Sever, Raymond D. SemlitschAbstract:The cloacal anatomy of paedomorphic female Ambystoma talpoideum was examined using light microscopy and histochemical techniques. Three types of cloacal glands (anterior ventral glands, dorsal glan...
Mark S. Johnson - One of the best experts on this subject based on the ideXlab platform.
-
Exposure Regime on a Terrestrial Salamander, Ambystoma tigrinum
2011Co-Authors: Mark S. Johnson, Steven D. Holladay, Kelly S. Lippenholz, Jennifer L. Tenkins, Wilfred C. MccainAbstract:Trinitrotoluene (TNT) is a defense-related environmental contaminant present at high concentrations in soil at some military installations. Tiger salamanders (Ambystoma tigrinum, family Ambystomatidae) were exposed to TNT in a soil matrix and fed earth- worms that had also been exposed to TNT via contaminated soil. Such exposure was previously shown to result in significant accumulation of both TNT and TNT metabolites by salamanders. Following 14 days of combined oral and dermal exposures, sala- manders were evaluated for signs of toxicity. Control and TNT-exposed salamanders gained weight (p < 0.025). In addition, organ to body weight ratios (kidney, liver, and spleen) were not affected by treatment. The function of splenic phagocytic cells was evaluated because these cells are sensitive to certain environmental chemical exposures. Neither the chemiluminescence response (H pro- duction) nor the phagocytic capacity of such cells were different between controls and treatment groups. In like manner, no changes were seen in the peripheral hematologic parameters investigated. Histopathologic evaluations were inconclusive, yet the liver revealed the presence of heavily pigmented iron-rich phagocytes (melanomacrophages). This investigation presents a realistic approach and preliminary data for investigating the effects of xenobiotic exposure in a soil matrix on a terrestrial vertebrate.
-
Effects of 2,4,6-trinitrotoluene in a holistic environmental exposure regime on a terrestrial salamander, Ambystoma tigrinum.
Toxicologic pathology, 2000Co-Authors: Mark S. Johnson, Steven D. Holladay, Kelly S. Lippenholz, J L Jenkins, Wilfred C. MccainAbstract:2,4,6-Trinitrotoluene (TNT) is a defense-related environmental contaminant present at high concentrations in soil at some military installations. Tiger salamanders (Ambystoma tigrinum, family Ambystomatidae) were exposed to TNT in a soil matrix and fed earthworms that had also been exposed to TNT via contaminated soil. Such exposure was previously shown to result in significant accumulation of both TNT and TNT metabolites by salamanders. Following 14 days of combined oral and dermal exposures, salamanders were evaluated for signs of toxicity. Control and TNT-exposed salamanders gained weight (p < 0.025). In addition, organ to body weight ratios (kidney, liver, and spleen) were not affected by treatment. The function of splenic phagocytic cells was evaluated because these cells are sensitive to certain environmental chemical exposures. Neither the chemiluminescence response (H2O2 production) nor the phagocytic capacity of such cells were different between controls and treatment groups. In like manner, no changes were seen in the peripheral hematologic parameters investigated. Histopathologic evaluations were inconclusive, yet the liver revealed the presence of heavily pigmented iron-rich phagocytes (melanomacrophages). This investigation presents a realistic approach and preliminary data for investigating the effects of xenobiotic exposure in a soil matrix on a terrestrial vertebrate.