Recognition by Population and Genetic Similarity in the Mountain Dusky Salamander,Desmognathus ochrophaeus (Amphibia: Plethodontidae)

Adult males and females of Desmognathus ochrophaeus were tested in two-choice substrate discrimination trials in which salamanders were given a choice of the marked substrates of opposite-sex individuals from their own population and from a geographically distinct population. Females exhibited a significant preference for the marked substrates of extrapopulation males, whereas there was no evidence that males made any such discrimination of the marked substrates of females. We suggest that females may utilize substrate cues to make initial assessments of potential mates. We compared data from substrate discrimination trials to random amplified polymorphic DNA (RAPD) profiles generated for each individual. There was no evidence that females made any distinction of substrate odours based on our assessment of genetic similarity. The estimated genetic differences between the two populations were minimal.     

The courtship behaviour of the spotted dusky salamander, Desmognathus fuscus conanti (Amphibia: Caudata: Plethodontidae)

The courtship behaviour of the North American southern dusky salamander, Desmognathus fuscus conanti (Plethodontidae), is described for the first time. The male is the most active participant, as is typical for caudate amphibians, and much of his behaviour can be understood in terms of orientation to and stimulation (or persuasion) of the female. The latter is largely accomplished by the transfer of courtship pheromones from the male's mental (chin) gland. The orientation and persuasion phases of courtship appear necessary if sperm transfer by means of a spermatophore deposited upon the substratum is to be successful. The courtship of D. fuscus conanti is qualitatively identical to that of D. santeetlah , with which it is sexually compatible in the laboratory and with which it may hybridize in nature. However, a broader comparison of species in the genus Desmognathus reveals that the greatest interspecific differences occur during the orientation and persuasion phases of courtship. A complete understanding of the evolution of courtship behaviour in desmognathine salamanders awaits availability of ethograms for all other taxa and a robust, independent phytogeny for the entire subfamily.     

Divergence of mate recognition systems among conspecific populations of the plethodontid salamander Desmognathus santeetlah (Amphibia: Plethodontidae)

The disjunct geographic distribution of plethodontid salamanders of the genus Desmognathus provides excellent opportunities to test whether populations diverge in mate recognition systems so as to result in sexual incompatibility. Previous work has shown that sexual incompatibility may exist both among conspecific populations and between different species in this genus. Populations of the Santeetlah dusky salamander, Desmognathus santeetlah , are found at higher elevations in three mountain ranges in the southern Appalachian Mountains of eastern North America, where they are sympatric with congeneric species of similar body size. We report that statistically significant levels of sexual incompatibility exist among populations of D. santeetlah collected from across the species' range. Contrary to popular belief, but in accord with a growing body of empirical literature, aspects of mate recognition systems can diverge among conspecific populations of salamanders, resulting in incidental sexual incompatibility.     

Courtship Behavior of the Cumberland Plateau Woodland Salamander,Plethodon kentucki (Amphibia: Plethodontidae), with a Review of Courtship in the Genus Plethodon

Complete catalogs of courtship behavior are available for only seven of the 42 currently recognized species of Plethodon. Additional detailed studies of courtship behavior in Plethodon species are needed to analyze the evolution of courtship behavior in this genus. We investigated the courtship behavior of the Cumberland Plateau woodland salamander (Plethodon kentucki) and compared it to previous accounts of courtship in other Plethodon species. In the laboratory, we videotaped the complete courtship of 30 different P. kentucki pairs, which included 46 tail-straddling walks that resulted in spermatophore deposition. From a transition matrix of observed motor patterns, we constructed a flow diagram of significant motor-pattern transitions during courtship. In general, the courtship behavior of this species is very similar to that of other large eastern Plethodon; however, there are some notable differences. Prior to the tail-straddling walk, the male transfers courtship pheromone from his mental gland to the female's nasolabial grooves (via mental-gland tapping and ‘chin-to-chin’ behavior patterns) more frequently than in other Plethodon. In most courtships, the female initiates contact leading to the tail-straddling walk. Males exhibit a greater propensity to deposit multiple spermatophores per courtship (two deposited in 33% of courtships, three deposited in 10% of courtships, X = 1.53 spermatophores per courtship) than males of other plethodontids. Mean size of the spermatophore is smaller than in other large eastern Plethodon. Overall, the courtship behavior of this species is most similar to that of P. jordani.     

Comparative skull osteology of Karsenia koreana (Amphibia,Caudata, Plethodontidae)

The recent discovery of a plethodontid salamander, Karsenia koreana, in Korea challenged our understanding of the biogeographic history of the family Plethodontidae, by far the largest family of salamanders, which otherwise is distributed in the New World with a few European species. Molecular studies suggest that Karsenia forms a clade with Hydromantes (sensu lato), which includes among its species the only other Old World plethodontids. We studied the skull of K. koreana and compared it with that of other plethodontid genera, especially members of the subfamily Plethodontinae, which it resembles most closely in general anatomy. The anatomy of its skull corresponds to the most generalized and apparently ancestral condition for plethodontids. No clearly autapomorphic states were detected, and no synapomorphies can be found that would link it to other genera. The Karsenia skull is cylindrical and well ossified, giving an impression of strength. In contrast, the skull of Hydromantes is highly derived; the skull is flattened and the bones are weakly ossified and articulated. Hydromantes and Karsenia share no unique anatomical features; differences between them are especially evident in the hyobranchial skeleton, which is generalized in Karsenia but highly modified in Hydromantes, which is well known for its highly projectile tongue. Plethodon and Plethodon‐like species, including Karsenia and to a lesser degree Ensatina, represent the more generalized and apparently ancestral plethodontid morphology. Specialized morphologies have evolved along only a few morphological axes within the Plethodontidae, resulting in a pattern of rampant homoplasy. Our analysis of the anatomy of the new Asiatic lineage illuminates some potential mechanisms underlying adaptive morphological evolution within the Plethodontidae. J. Morphol. 2010. © 2009 Wiley‐Liss, Inc.     

Hydric constraints upon foraging in a terrestrial salamander,Desmognathus ochrophaeus (Amphibia: Plethodontidae)

Summary The time until salamanders voluntarily abandoned foraging (the water time limit) and the amount of water lost when salamanders abandoned foraging (dehydration deficit) were determined for terrestrial plethodontid salamanders, Desmognathus ochrophaeus, foraging at various vapor pressure gradients in the laboratory. Salamander activity was correlated with the rate of water loss and was inversely related to the water time limit. Animals at 0.35–0.86 kPa vapor pressure gradients abandoned foraging and returned to moist retreats significantly sooner than animals in water-saturated air. The early retreat of animals in dry air was related in part to high rates of water loss and in part to the modest dehydration deficit (3.8%) at which animals abandoned foraging. Locomotor performance and foraging ability were unaffected by dehydration until dehydration deficits exceeded 12%. This suggests that salamanders in unsaturated air abandoned foraging at a low dehydration deficit to conserve and replenish water reserves rather than to avoid outright incapacitation or death. Present address: Department of Zoology, University of Guelph, Guelph, Ontario N1G 2W1, Canada     

Space Use in Response to Conspecifics by the Red-backed Salamander (Plethodon cinereus, Plethodontidae, Caudata)

The presence of conspecifics, as well as the distribution and quality of resources, can influence habitat settlement decisions of animals. We studied the habitat preference and group size of the red-backed salamander, Plethodon cinereus , from the Upper Peninsula of Michigan. In contrast to previous work with P. cinereus from Virginia, we found groups of P. cinereus within higher quality habitat than solitary individuals and these groups contained both small and large individuals. Under identical conditions in the laboratory, salamanders from Virginia formed a uniform spatial distribution and individuals from northern Michigan displayed an aggregated spatial distribution. Our results suggest that P. cinereus from northern Michigan preferentially settle near conspecifics, while P. cinereus from Virginia avoid them. Our laboratory experiments also suggest that the aggregation behaviour of P. cinereus from northern Michigan may be the result of attraction to conspecifics rather than attraction to habitat features.     

Lack of Evidence for the Prior Residence Effect in the Allegheny Mountain Dusky Salamander (Desmognathus ochrophaeus)

Territorial disputes are frequently settled by an advantage afforded to one of the contestants by asymmetries such as size difference, strength and motivation. Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus) are reported to defend cover objects, a form of territorial behaviour. We conducted an experiment to determine whether or not adult salamanders of this species exhibit prior residence effect during staged encounters involving size‐matched, same sex conspecifics (i.e. does familiarity with a territory predict successful defence?). We tested 154 adult salamanders (72 female, 82 male) in reciprocal trials in which each animal acted as a resident and as an intruder. We recorded multiple agonistic behaviours including: front‐trunk raised, all‐trunk raised, nudge, bite, bite‐and‐hold and jaw‐lock. We assigned these behaviours scaled point values and calculated an index of aggression for each animal as a resident and as an intruder. We found that in same sex trials, males were significantly more aggressive than females. Although D. ochrophaeus exhibited stereotypical, agonistic behaviours similar to those reported for Plethodon, unlike Plethodon the outcomes of symmetrical social encounters were not influenced by residential status. Prior residence is documented to be a major determinant of territorial disputes among diverse animal taxa, including salamanders. However, our research suggests that the phenomenon is not universal and may depend on qualities of the microhabitat in which a species has evolved.     

Dusky salamanders (Desmognathus, Plethodontidae) from the Coastal Plain: multiple independent lineages and their bearing on the molecular phylogeny of the genus

Recent phylogenetic reassessment of the lungless salamanders (Plethodontidae) confirmed a major life-history reversal-from direct development to an aquatic larval stage-in the dusky salamanders (Desmognathus) of eastern North America. This reversal initiated high rates of lineage accumulation, reputedly generating the species richness and ecological breath that now characterize Desmognathus. Certain important aspects of the radiation, e.g., ecomorphological evolution, have been identified through intense sampling effort of Appalachian Highland lineages. However, the research preoccupation on montane species has left overlooked a significant component of dusky salamander distribution-the Coastal Plain. We present the first molecular phylogeny for Desmognathus to incorporate extensive coverage from the Atlantic and Gulf coastal plains. We examined 38 Coastal Plain populations in conjunction with 45 additional populations, representing 16 of the 19 nominal species. Bayesian analysis of 88 mitochondrial cox1 haplotypes diagnosed eight independent population lineages within the Coastal Plain, a number at odds with the region's three currently recognized species. Desmognathus has apparently experienced a complex biogeographic history in this physiographic region, one involving multiple invasions and several ecological transitions from lotic to lentic habitats.     

Systematics of dusky salamanders, Desmognathus (Caudata: Plethodontidae), in the mountain and Piedmont regions of Virginia and North Carolina, USA

We analysed mitochondrial (cytochrome  b ) nucleotide sequences, nuclear allozyme markers, and morphometric characters to investigate species boundaries and phylogenetic relationships among dusky salamanders ( Desmognathus ) in the southern Blue Ridge and adjacent Piedmont Physiographic Provinces of Virginia and North Carolina. Our results revealed four distinct mitochondrial DNA clades that are also characterized by distinct allozyme markers. One clade consists of sequences derived from populations distributed from New England to south-western Virginia that are referable to Desmognathus fuscus Rafinesque, 1820, although there is considerable sequence and allozyme divergence within this clade. A second clade consists of sequences derived from populations referable to Desmognathus planiceps Newman, 1955, a form that we resurrect from its long synonymy under D. fuscus . Desmognathus planiceps and D. fuscus also differ in mandibular tooth shape. Two other cytochrome  b sequences recovered from populations along the Blue Ridge escarpment in southern Virginia are quite divergent from those of the previous two clades, and these populations may represent yet another distinct species. Sequences from a population in the Brushy Mountains in the Piedmont of northern North Carolina are similar to those of Desmognathus carolinensis . Population groupings indicated by allozyme data generally correspond to the cytochrome  b clades. Cryptic diversity in Appalachian desmognathan salamanders clearly requires further study. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 115–130.     

Osseous pathologies in the lungless salamander Desmognathus fuscus (Plethodontidae)

The majority of reported pathologies in lissamphibians (salamanders, caecilians and frogs) include limb deformities such as missing limbs, multiple extra limbs and digits, or incomplete limb formation. However, comparatively little is known about congenital vertebral malformations or posttraumatic pathologies (e.g. injuries, infections) in the vertebral column of salamanders. In the present study, we describe eight vertebral deformities in three cleared and stained specimens of Desmognathus fuscus. Two specimens display developmental deformities which range from a potential non-segmented wedge vertebra to fully segmented hemivertebrae. The vertebral pathology in the third specimens possibly results from a parasitic infection. Apparently, these osseous deformities were not severe enough to prohibit survival of the specimens.     

Osteological Variation among Extreme Morphological Forms in the Mexican Salamander Genus Chiropterotriton (Amphibia: Plethodontidae): Morphological Evolution And Homoplasy

Osteological variation is recorded among and within four of the most distinctive species of the Mexican salamander genus Chiropterotriton. Analysis of the data is consistent with the monophyletic status of the genus and documents previously unrecorded intraspecific and interspecific variation. Most of the recorded variation involves qualitative and quantitative proportional differences, but four fixed differences constitute autapomorphic states that affirm and diagnose some species (C. dimidiatus, C. magnipes). Osteological variation in 15 characters is analyzed with respect to predictions generated from four hypotheses: 1) phylogeny, 2) adaptation to specific habitats (the four species include cave-dwelling, terrestrial, and arboreal forms), 3) size-free shape, and 4) size. High levels of intraspecific variation suggest that the characters studied are not subject to rigid functional constraints in salamanders, regardless of size. The pattern predicted by the hypothesis based on size differences seen among these four Chiropterotriton species matches most closely the observed pattern of relative skull robustness. Since size change and heterochrony are often associated in plethodontid evolution, it is likely that changes in developmental timing play a role in the morphological transitions among these morphologically diverse taxa. Webbed feet, miniaturization, body shape, and an unusual tarsal arrangement are morphologies exhibited in species of Chiropterotrition that are shown to be homoplastic with other clades of tropical plethodontids. Although extensive homoplasy in salamanders might be seen as a roadblock to unraveling phylogenetic hypotheses, the homologous developmental systems that appear to underlie such homoplasy may reveal common and consistent evolutionary processes at work.     

Male Mating Success in the Mountain Dusky Salamander,Desmognathus ochrophaeus: Are Small,Young, Inexperienced Males at a Disadvantage?

Young, small, sexually-inexperienced males suffer lower mating success than older, larger, more experienced males in many species of animals. I compared the mating success of male Desmognathus ochrophaeus (Amphibia: Caudata: Plethodontidae) reared to maturity in the laboratory with that of males collected as adults in the field. Courtship trials were staged in the laboratory between single males and females. Laboratory-reared males were significantly smaller in body size than adult males collected in the field, were certainly inexperienced sexually and were probably younger. No difference was found between laboratory-reared males and field-collected males in any measure of mating success, although the former apparently produced smaller sperm masses. I conclude that newly-mature male D. ochrophaeus are not discriminated against by females in the context of mate choice, and do not need to “rehearse” courtship in order to obtain successful inseminations. However, newly-mature males are probably at a disadvantage in terms of aggressive and sperm competition with larger males.     

Cytogenetics of the Brazilian Bolitoglossa paraensis (Unterstein, 1930) salamanders (Caudata,Plethodontidae)

Plethodontid salamanders of genus Bolitoglossa constitute the largest and most diverse group of salamanders, including around 20% of living caudate species. Recent studies have indicated the occurrence of five recognized species in the Brazilian Amazon Rainforest. We present here the first cytogenetic data of a Brazilian salamander, which may prove to be a useful by contribution to the cytotaxonomy of the genus. Specimens were collected near the “type” locality (Utinga, Belém, PA, Brazil). Chromosomal preparations from duodenal epithelial cells and testes were subjected to Giemsa staining, C-banding and DAPI/CMA₃ fluorochrome staining. All specimens showed a karyotype with 13 bi-armed chromosome pairs (2n = 26). Nucleolar Organizer Regions, evidenced by CMA₃, were located distally on the long arm of pair 7 (7q). DAPI+ heterochromatin was predominantly centromeric, with some small pericentromeric bands. Although the C-banding patterns of other Bolitoglossa species are so far unknown, cytogenetic studies conducted in other Plethodontid salamanders have demonstrated that pericentromeric heterochromatin is a useful cytological marker for identifying interspecific homeologies. Species diversification is usually accompanied by chromosomal changes. Therefore, the cytogenetic characterization of Bolitoglossa populations from the middle and western Brazilian Amazon Basin could identify differences which may lead to the identification of new species.     

Intermediate heterochromatic zones in Triturus (Amphibia: Caudata)

Employment of the C-banding procedure disclosed the presence of slightly stained bands in some chromosome regions of several Triturus species. These regions have been previously described in other organisms as 'grey C-bands'. Possible explanations for the presence of these bands in Triturus karyotypes are discussed.     

Courtship in the Zig-Zag Salamander (Plethodon dorsalis): Insights into a Transition in Pheromone-Delivery Behavior

Courtship in plethodontid salamanders includes the delivery of male courtship pheromones by two distinct modes. Within the eastern Plethodon clade of the tribe Plethodontini, members of the Plethodon cinereus species group use an ancestral ‘vaccination’ mode of delivery, while members of the P. glutinosus group use an olfactory delivery mode. In order to shed light on this transition in delivery mode, I observed courtship behavior in P. dorsalis, a species that is phylogenetically intermediate to the P. cinereus and P. glutinosus groups. My observations indicate that P. dorsalis also is intermediate to the P. cinereus and P. glutinosus species groups in terms of courtship behavior. The context of delivery of male courtship pheromones in P. dorsalis is similar to that of the P. cinereus species group; however, the mode of pheromone delivery in P. dorsalis is olfactory. Thus, a transition in the context of pheromone delivery underlies the more obvious change in pheromone delivery mode. I discuss these findings in terms of the evolution of courtship pheromone delivery across the eastern Plethodon clade. I also report the first observations of ‘premature’ spermatophore deposition by male plethodontids.     

Allozymic variation of Hynobius kimurae Dunn (Amphibia, Caudata)

An electrophoretic survey was conducted to examine genetic divergence among 21 populations of a lotic-breeding salamander Hynobius kimurae from Honshu, Japan. Genetically H. kimurae proved to be specifically distinct from H. naevius. Hynobius kimurae is divided genetically into two groups of local populations, and the five populations from the eastern area are genetically distinct from the remaining populations of the central and western areas. Less prominent genetic differentiation was revealed between the western and central populations. Separation of the eastern and central-western groups are discussed in relation to the formation of the Japanese mainland.     

Ultrastructure of the bone marrow of the salamander Plethodon glutinosus (Caudata: Plethodontidae)

The unusual lymphogranulopoietic bone marrow of the large lungless salamander Plethodon glutinosus was examined by light and electron microscopy. Developing neutrophils, eosinophils, and fat cells were found in large numbers, while lymphocytes of various sizes, plasma cells, plasmablasts, macrophages, pigment cells, and fibroblasts were present in more moderate numbers. Basophils were observed only rarely. Macrophages were found in extravascular locations and did not appear to be associated directly with the walls of the blood vessels supplying the marrow. Both neutrophils and eosinophils seemed to arise from small precursor cells whose ultrastructural features bore a resemblance in some ways to those of mammalian myeloblasts described by Bainton and Farquhar ('66). Developing neutrophils and eosinophils seemed to produce only single populations of specific cytoplasmic granules, rather than both primary (azurophilic) and secondary (specific) inclusions, as are produced typically by mammalian granulocytes. Both eosinophilic and neutrophilic granules were formed in association with Golgi complexes; and eosinophilic granules were much larger, more densely stained, and more regularly rounded in shape than the inclusions of developing neutrophils. Peroxidase activity was associated with the specific granules of neutrophils but seemed to be lacking in the granules of eosinophils. The specific granules of eosinophils were especially unusual because they contained irregularly shaped, lightly stained cores which occasionally displayed a distinctly crystalline substructural organization. The specific granules of basophils also possessed a prominent crystalline organization. The overall appearance of the marrow of Plethodon suggests that it functions not only as a valuable source of neutrophils, eosinophils, and cells of the lymphoid series, but also as a part of the phagocytic system of the animals and as an important repository for fat.     

Chromosome differentiation in the Triturus alpestris complex (Amphibia: Caudata)

Several individuals from distinct populations of 7 subspecies included in the Triturus alpestris complex have been analysed to obtain characteristic C-banding patterns.The differences found among the populations as regards the amount, complexity and distribution of heterochromatin bands have been employed to test a pattern of chromosome evolution.Relevant similarities and dissimilarities of these populations are discussed in the light of the tentative evolutionary history inferred from a rooted tree.