Salamandridae Research Articles

Phylogeny and biogeography of the family Salamandridae (Amphibia: Caudata) inferred from complete mitochondrial genomes

Phylogenetic relationships of members of the salamander family Salamandridae were examined using complete mitochondrial genomes collected from 42 species representing all 20 salamandrid genera and five outgroup taxa. Weighted maximum parsimony, partitioned maximum likelihood, and partitioned Bayesian approaches all produce an identical, well-resolved phylogeny; most branches are strongly supported with greater than 90% bootstrap values and 1.0 Bayesian posterior probabilities. Our results support recent taxonomic changes in finding the traditional genera Mertensiella, Euproctus, and Triturus to be non-monophyletic species assemblages. We successfully resolved the current polytomy at the base of the salamandrid tree: the Italian newt genus Salamandrina is sister to all remaining salamandrids. Beyond Salamandrina, a clade comprising all remaining newts is separated from a clade containing the true salamanders. Among these newts, the branching orders of well-supported clades are: primitive newts ( Echinotriton, Pleurodeles, and Tylototriton), New World newts ( Notophthalmus-Taricha), Corsica-Sardinia newts ( Euproctus), and modern European newts ( Calotriton, Lissotriton, Mesotriton, Neurergus, Ommatotriton, and Triturus) plus modern Asian newts ( Cynops, Pachytriton, and Paramesotriton).Two alternative sets of calibration points and two Bayesian dating methods (BEAST and MultiDivTime) were used to estimate timescales for salamandrid evolution. The estimation difference by dating methods is slight and we propose two sets of timescales based on different calibration choices. The two timescales suggest that the initial diversification of extant salamandrids took place in Europe about 97 or 69 Ma. North American salamandrids were derived from their European ancestors by dispersal through North Atlantic Land Bridges in the Late Cretaceous (∼69 Ma) or Middle Eocene (∼43 Ma). Ancestors of Asian salamandrids most probably dispersed to the eastern Asia from Europe, after withdrawal of the Turgai Sea (∼29 Ma).

A Bayesian approach on molecules and behavior: reconsidering phylogenetic and evolutionary patterns of the Salamandridae with emphasis on Triturus newts

The monophyly of European newts of the genus Triturus within the family Salamandridae has for decades rested on presumably homologous behavioral and morphological characters. Molecular data challenge this hypothesis, but the phylogenetic position of Triturus within the Salamandridae has not yet been convincingly resolved. We addressed this issue and the temporal divergence of Triturus within the Salamandridae with novel Bayesian approaches applied to DNA sequence data from three mitochondrial genes (12S, 16S and cytb). We included 38 salamandrid species comprising all 13 recognized species of Triturus and 16 out of 17 salamandrid genera. A clade comprising all the "Newts" can be separated from the "True Salamanders" and Salamandrina clades. Within the "Newts" well-supported clades are: Tylototriton-Pleurodeles, the "New World Newts" (Notophthalmus-Taricha), and the "Modern Eurasian Newts" (Cynops, Pachytriton, Paramesotriton=together the "Modern Asian Newts", Calotriton, Euproctus, Neurergus and Triturus species). We found that Triturus is a non-monophyletic species assemblage, which includes four groups that are themselves monophyletic: (i) the "Large-Bodied Triturus" (six species), (ii) the "Small-Bodied Triturus" (five species), (iii) T. alpestris and (iv) T. vittatus. We estimated that the last common ancestor of Triturus existed around 64 million years ago (mya) while the root of the Salamandridae dates back to 95 mya. This was estimated using a fossil-based molecular dating approach and an explicit framework to select calibration points that least underestimated their corresponding nodes. Using the molecular phylogeny we mapped the evolution of life history and courtship traits in Triturus and found that several Triturus-specific courtship traits evolved independently.

Records of Salamandrina perspicillata (Savi, 1821) in the Colli Albani (Latium, central Italy), with some ecological notes (Urodela, Salamandridae)

The distribution of the Northern Spectacled Salamander in the Colli Albani (= Albani Hills), together with some ecological aspects at eight sites are reported. In four sites, oviposition took place between February and April, but in the other four it probably started at least in the first half of december. Eggs were deposited into the water of either temporary or perennial spring ponds or inside flooded man-made tuff tunnels. In some sites, which do not undergo summer drought, some larvae surpassed the summer and even the following winter. For one site, length and weight of 52 ovipositing females were recorded and larval development was monitored. A clear relation between larval body size and limb development did not appear.

A molecular assessment of phylogenetic relationships and lineage accumulation rates within the family Salamandridae (Amphibia, Caudata)

We examine phylogenetic relationships among salamanders of the family Salamandridae using approximately 2700 bases of new mtDNA sequence data (the tRNA Leu, ND1, tRNA Ile, tRNA Gln, tRNA Met, ND2, tRNA Trp, tRNA Ala, tRNA Asn, tRNA Cys, tRNA Tyr, and COI genes and the origin for light-strand replication) collected from 96 individuals representing 61 of the 66 recognized salamandrid species and outgroups. Phylogenetic analyses using maximum parsimony and Bayesian analysis are performed on the new data alone and combined with previously reported sequences from other parts of the mitochondrial genome. The basal phylogenetic split is a polytomy of lineages ancestral to (1) the Italian newt Salamandrina terdigitata, (2) a strongly supported clade comprising the “true” salamanders (genera Chioglossa, Mertensiella, Lyciasalamandra, and Salamandra), and (3) a strongly supported clade comprising all newts except S. terdigitata. Strongly supported clades within the true salamanders include monophyly of each genus and grouping Chioglossa and Mertensiella as the sister taxon to a clade comprising Lyciasalamandra and Salamandra. Among newts, genera Echinotriton, Pleurodeles, and Tylototriton form a strongly supported clade whose sister taxon comprises the genera Calotriton, Cynops, Euproctus, Neurergus, Notophthalmus, Pachytriton, Paramesotriton, Taricha, and Triturus. Our results strongly support monophyly of all polytypic newt genera except Paramesotriton and Triturus, which appear paraphyletic, and Calotriton, for which only one of the two species is sampled. Other well-supported clades within newts include (1) Asian genera Cynops, Pachytriton, and Paramesotriton, (2) North American genera Notophthalmus and Taricha, (3) the Triturus vulgaris species group, and (4) the Triturus cristatus species group; some additional groupings appear strong in Bayesian but not parsimony analyses. Rates of lineage accumulation through time are evaluated using this nearly comprehensive sampling of salamandrid species-level lineages. Rate of lineage accumulation appears constant throughout salamandrid evolutionary history with no obvious fluctuations associated with origins of morphological or ecological novelties.

5-HT-like immunoreactivity in the brains of plethodontid and salamandrid salamanders (Hydromantes italicus, Hydromantes genei, Plethodon jordani, Desmognathus ochrophaeus, Pleurodeles waltl): an immunohistochemical and biocytin double-labelling study.

The distribution of 5-HT-like-immunoreactive cell bodies and fibres was studied in the brains of the salamanders Hydromantes italicus, H. genei, Plethodon jordani, Desmognathus ochrophaeus (family Plethodontidae), and Pleurodeles waltl (family Salamandridae). In addition, double-labelling experiments with biocytin were carried out to identify the relationship between serotonergic fibres and neurons involved in the processing of sensory and sensorimotor information. In all species, 5-HT-immunopositive somata are found in the ventral thalamus close to the ventricle forming the paraventricular organ. In the hypothalamus, cells are labelled in the ependymal layer around the infundibular recess and at the lateral edge of the periventricular grey. In the pretectum, a few immunoreactive cells are situated dorsolaterally in the grey matter. In the tegmentum and medulla oblongata, cells of the raphe nuclei are regularly distributed along the midline; labelled perikarya are occasionally found in the cervical spinal cord. 5-HT-like-immunoreactive fibres are widely distributed throughout the nervous system. Densely arborizing fibres are found in the olfactory bulb, striatum and amygdala. Distinct fibre projections extend in the ventral thalamus and tectum. Biocytin tracing of striatal and tectal projection neurons and ascending reticular neurons combined with the demonstration of 5-HT suggest that the striatum, the tectum and the ascending activating system are strongly influenced by 5-HT.

Distribution of GABA-immunoreactive neurons in the brain of adult and developing salamanders (Pleurodeles waltli, Triturus alpestris)

The distribution of GABAergic neurons in brains of the family Salamandridae (Pleurodeles waltli, Triturus alpestris) has been investigated immunohistochemically with an antibody against gamma-aminobutyric acid (GABA). In adult animals, immunoreactive neurons, fibers, and terminals are abundantly labeled. In the telencephalon, pallial areas contain fewer GABAergic neurons and fibers than basal forebrain areas. The amygdalar complex and the habenulae have a complex pattern of GABA-immunoreactivity that is especially pronounced within the neuropil. The pretectal and basal optic systems are provided with GABAergic neurons, corroborating electrophysiological results. The dorsal thalamus and parts of the torus semicircularis are almost completely devoid of GABA-immunoreactive neurons. In the torus, magnocellular neurons known to project to the contralateral counterpart are distinctly GABA-immunoreactive. During ontogeny, GABAergic neurons arise early when the first reflexive movements occur after mechanical stimulation. At stage 28, cells are labeled initially near the nucleus of the medial longitudinal fasciculus, which is the first supraspinal tract to appear in ontogeny. At stage 30 (still before hatching), GABAergic neurons are found in the pretectum, immunoreactive neurons arising in the dorsal tegmentum slightly later. Both systems are known to mediate basic reflexes in gaze stabilization. The commissura posterior is GABAergic at early stages suggesting an important functional role in homonymous inhibition between both sides. Thus in salamanders, the neurotransmitter GABA displays a complex distribution, similar to that in other vertrebrates. This pattern emerges early in ontogeny.

Molecular cytogenetics of the ribosomal (18S + 28S and 5S) DNA loci in primitive and advanced urodele amphibians

In the present work we performed a cytogenetic analysis of the ribosomal (18S + 28S and 5S) loci in amphibian species belonging to the advanced family Salamandridae (genera Triturus, Salamandra, and Salamandrina) and in the primitive hynobiid Salamandrella keyserlingii (family Hynobiidae). In each analyzed karyotype the 5S rDNA sites appear to be stable, and definite in number, while an intraspecific variability both in number and chromosomal location of the 18S + 28S rDNA loci has been found in some Triturus species. In particular, an evolutionary trend toward a large intraspecific variability of the 18S + 28S rDNA loci has been found in the T. vulgaris species group. A structural analysis of the ribosomal repetition units demonstrates the occurrence of a length polymorphism within the 18S + 28S rDNA repeats in the examined species of the family Salamandridae; however, this polymorphism is rather limited, even in those Triturus species characterized by high intragenomic variability of the ribosomal sites. We show that in T. vulgaris meridionalis the variant repetition units actually segregate with individual chromosomes. This implies that they are not intermingled in the ribosomal clusters.

Comparative kinematics of terrestrial prey capture in Salamanders and newts (Amphibia:Urodela:Salamandridae)

AbstractHigh‐speed cinematography was used to compare the kinematics of terrestrial prey capture among postmetamorphic individuals of the family Salamandridae that have a) terrestrial (Salamandra, Salamandrina, and Tylototriton), b) amphibious (Pleurodeles, Cynops, and Paramesotriton), and c) aquatic (Pachytriton) lifestyles. Tongue projection was common during prey capture attempts in Salamandra, Salamandrina, and Tylototriton, occurred frequently in Cynops and Paramesotriton, but was absent during terrestrial feeding by Pachytriton. The gape cycle consisted of four distinct phases that were associated with discrete movements of the hyolingual apparatus. In all salamandrids that projected the tongue, the gape 1) increased rapidly while the tongue was elevated from the floor of the mouth in preparation for protraction, 2) was stabilized while the tongue was protracted, 3) increased to maximum during retraction and 4) decreased rapidly while the tongue transported the prey into the oral cavity. The absence of tongue projection during some (Cynops, Paramesotriton), or all prey capture attempts (Pachytriton) resulted in gape profiles distinctly different from those described above. Most notably, these profiles lacked the gape stabilization component characteristic of tongue projection. The maximum distance that the tongue was projected beyond the mandible approached 6% snout‐vent length (SVL) in most salamandrids, but reached 20% SVL in Salamandrina. Several elements of the feeding system in Salamandrina are functionally related to the evolution of its specialized tongue projection apparatus. These include a gape cycle of relatively long duration (200 ms) and the absence of a head‐body surge and of eye retraction during the strike.

An integrative analysis of phylogenetic relationships among newts of the genus Triturus (family Salamandridae), using comparative biochemistry, cytogenetics and reproductive interactions

AbstractAll the currently available data with regard to morphology, palaeontology, biochemical genetics, reproductive interactions and behaviour have been collated and analysed with combinations of phenetic and numerical phylogenetic methods, and integrated into a consensus evolutionary tree for European newts of the genus Triturus.A range of cytogenetic data are presented including genome sizes (amount of DNA per haploid chromosome set), Giemsa C‐banded karyotypes for mitotic chromosomes, maps of lampbrush chromosomes and locations of nucleolus organisers (genes for ribosomal RNA). We have examined these data in search of evolutionary trends within the genus.The degree to which cytogenetic data accord with the consensus tree, and the general usefulness of cytogenetic data for the reconstruction of evolutionary history are discussed.A revised scheme for the taxonomy of Triturus is presented in which the genus is subdivided into two subgenera, Triturus and Palaeotriton is suggested. Subgenus Triturus should include all of the large bodied newts belonging to the T. cristatus species group as well as T. alpestris and T. vittatus. All other species are included in subgenus Palaeotriton.The elevation of the former subspecies of T. cristatus to full species status is recommended mainly on the basis of information from studies of mitochrondrial DNA.

Feeding performance in aquatic postmetamorphic newts (Urodela: Salamandridae): Are bidirectional flow systems necessarily inefficient?

There are two basic designs of suction-feeding mechanisms in aquatic salamanders. Premetamorphic salamanders use a unidirectional flow system in which water is drawn into the mouth anteriorly and expelled posteriorly through the gill slits. Postmetamorphic salamanders use a bidirectional flow system in which water enters and then exits through the mouth. It has been suggested that bidirectional flow results in an inefficient feeding mechanism. To test this hypothesis, we compared the structure of the feeding system and the proficiency of aquatic prey capture among postmetamorphic individuals from (i) predominantly terrestrial (Tylototriton verrucosus), (ii) amphibious (Pleurodeles waltl, Cynops pyrrhogaster, Notophthalmus viridescens, Taricha granulosa, and Paramesotriton hongkongensis), and (iii) aquatic (Pachytriton brevipes) species of newts (family Salamandridae). Ossification of the hyolingual skeleton, size of the labial lobes, and taper of the snout increase with increasing preference for an aquatic habitat. All species studied except T. verrucosus captured prey in water. Feeding efficiency was similar among all the amphibious species; each was highly successful at capturing immobile prey (90–98%), successful at capturing mobile prey (40–58%), and less successful at capturing evasive prey (18–23%). Fully aquatic P. brevipes was highly successful in taking immobile (100%) and mobile (90%) prey and successful at capturing evasive prey (65%). We attribute the superior feeding performance of this newt to several morphological specializations of its feeding system, including a strongly tapered snout and greatly enlarged labial lobes. We reject the hypothesis that bidirectional flow is always inefficient for prey capture by metamorphosed salamanders. The degree of feeding proficiency in water is influenced by the morphological and behavioral attributes of aquatic salamanders, rather than just by the presence or absence of gill slits and, hence, by unidirectional flow.

The Selective Advantage of the Defensive Posture of the Newt, Taricha granulosa

The newt, Taricha granulosa (family Salamandridae) is toxic and noxious; bright ventral coloration is exhibited by a rigid defensive posture (unken reflex). Feeding studies using Taricha were conducted to determine if the bright ventral coloration and the defen- sive posture are important aposematic cues eliciting avoidance by birds. Trials were conducted using three groups of five chickens, previously conditioned to eat palatable salamanders (Desmognathus). Anesthe- tized Taricha were offered to each group in one of three positions: dorsum-up, venter-up or defensive posture. A trial consisted of placing a chicken in an enclosure with a salamander for 3 min and noting if the salamander was eaten, contacted but not eaten, or not contacted. Each chicken was offered an equal number of Taricha and Desmogna- thus at random. Postured newts were avoided more rapidly and to a greater extent than dorsum-up newts. Intermediate avoidance was exhibited in response to venter-up Taricha. Experience with either postured or venter-up Taricha facilitated avoidance learning of dorsum- up Taricha in later trials. The defensive posture of Taricha is an apose- matic cue which elicits avoidance by birds, but the aposematic influence of the posture and that of the ventral coloration cannot be separated. Prey species have evolved several lines of defense against predators using visual cues; the most important of these are crypsis, aposematic coloration and pseudoaposematic coloration (Robinson, 1969a). Those organisms that have aposematic coloration also have some attribute that renders them undesirable to the predator and often have some

The Morphology and Evolution of the Tongue and Associated Structures in Salamanders and Newts (Family Salamandridae)

Within the family Salamandridae, a relatively great diversity of feeding mechanisms is found. Dissections of the jaw, tongue, and throat musculature combined with serial section analysis, studies of osteology, and behavioral observations provide data which are used to analyze functional morphology of feeding mechanisms among the 14 genera. There are two distinct classes of feeding mechanisms in the family. One class, characterized by those species with tongues, involves specializations associated primarily with feeding in aquatic habitats. Included are those salamandrids which are aquatic at least during the breeding season, Tylototriton, Pleurodeles, Triturus, Neurergus, Euproctus, Paramesotriton, Cynops, Hypselotriton, Pachytriton, Taricha, and Notophthalmus. These genera utilize the gape and suck method of feeding in aquatic situations, but most utilize a modified jaw-feeding mechanism on land. Some of the genera (e. g., Pachytriton) are exclusively aquatic, and in these specializations for aquatic feeding are extreme. Tylototriton and Pleurodeles are much more generalized than the other genera. A general trend in genera with water tongues is for an elaboration of the posterior parts of the hyobranchial apparatus and associated musculature together with a reduction in structure and function of the anterior parts of the functional unit. In addition, the hyobranchial apparatus becomes increasingly ossified and rigid as specializations for gape and suck feeding, such as throat expansion, increase. Land tongues are found in Salamandra, Chioglossa, and Salamandrina, and are especially highly developed in the last two. These genera are specialized for feeding in terrestrial situations. Here the general trend is for an elaboration of the anterior parts of the functional unit, especially the tongue pad, and a reduction in the posterior parts. The hyobranchial apparatus is quite flexible and permits extensive flipping of the tongue pad from the mouth. Prey is captured through tongue pad flipping, but in quite a different manner than in tongue feeders in other families.

E-and I-retinae of urodeles

Two representatives of the same urodele family (Salamandridae) demonstrate in their electroretinograms 2 different types of light response. These 2 types correspond well withGranit's concept of E-retinae and I-Retinae.