Desmognathine Salamanders Research Articles

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.

The courtship behaviour of the Apalachicola dusky salamander,Desmognathus apalachicolaeMeans & Karlin (Amphibia Caudata Plethodontidae)

This paper provides the first description of the courtship behaviour of the plethodontid salamander Desmognathus apalachicolae. After a brief phase of orientation of the male to the female, most courtship interactions consist of the male stimulating his partner (in effect, “persuading” her to mate). Tactile stimuli are produced by the behaviour patterns “head-rubbing” and “stroking”. Chemical stimuli are provided by secretions from the male's mental (= chin) gland, which are transferred to the female by the behaviour patterns “snapping” and “pulling”. Courtship ends with indirect sperm transfer by means of a spermatophore deposited on the substrate. This phase is marked by a behaviour pattern known as “tail-straddle walk”, exhibited only by plethodontid salamanders. A complete understanding of the evolution of courtship behaviour in desmognathine salamanders awaits availability of detailed ethograms for all taxa currently recognized. However, it appears that patterns of sexual incompatibility observed amo...

Prey processing in Leurognathus marmoratus and the evolution of form and function in desmognathine salamanders (Plethodontidae)

Function and biological role of morphological specialization in desmognathine salamanders are analysed in the light of studies of feeding in Leurognathus marmoratus . Nine morphological features uniquely characterize the Desmognathinae as compared to its sister group, the Plethodontinae, and other salamanders: (1) heavily ossified and strongly articulated skull and mandible; (2) flat, wedgelike head profile; (3) stalked occipital condyles; (4) modified atlas; (5) modified anterior trunk vertebrae; (6) atlanto-mandibular ligaments; (7) enlarged dorsal spinal muscles; (8) enlarged quadrato-pectoralis muscles; and (9) hind limbs relatively larger than forelimbs. Dorsoventral head mobility is increased at the atlanto-occipital joint by the stalked occipital condyles which simultaneously increase the mechanical advantage of the hypertrophied axial muscles that cross the joint. During head depression the atlanto-mandibular ligaments are placed in tension. Force generated by the quadrato-pectoralis muscles is transmitted directly to the mandible, creating a powerful bite with the jaws in full occlusion. Desmognathines use an efficient static pressure system for subduing and/or killing prey items held in the jaws, not a kinetic-inertial mechanism, as previously suggested. Leurognathus exhibits a behaviour ('head-tucking') unique to desmognathines that is consistent with the static-pressure hypothesis. Several desmognathine features (1, 2, 5, 7, 9) are not explicable as adaptations for feeding; these function as locomotory specializations for burrowing, especially for wedging under rocks within and alongside streams. Desmognathines use head-tucking during such wedging and burrowing movements, thus locomotory specializations act in concert with the feeding specializations. We suggest that origin of the atlanto-mandibular ligaments can be considered a 'key innovation' in that it allowed the secondary invasion of stream habitats by adults of ancestral desmognathines.

Prey processing in Leurognathus marmoratus and the evolution of form and function in desmognathine salamanders (Plethodontidae)

Function and biological role of morphological specialization in desmognathine salamanders are analysed in the light of studies of feeding in Leurognathus marmoratus . Nine morphological features uniquely characterize the Desmognathinae as compared to its sister group, the Plethodontinae, and other salamanders: (1) heavily ossified and strongly articulated skull and mandible; (2) flat, wedgelike head profile; (3) stalked occipital condyles; (4) modified atlas; (5) modified anterior trunk vertebrae; (6) atlanto-mandibular ligaments; (7) enlarged dorsal spinal muscles; (8) enlarged quadrato-pectoralis muscles; and (9) hind limbs relatively larger than forelimbs. Dorsoventral head mobility is increased at the atlanto-occipital joint by the stalked occipital condyles which simultaneously increase the mechanical advantage of the hypertrophied axial muscles that cross the joint. During head depression the atlanto-mandibular ligaments are placed in tension. Force generated by the quadrato-pectoralis muscles is transmitted directly to the mandible, creating a powerful bite with the jaws in full occlusion. Desmognathines use an efficient static pressure system for subduing and/or killing prey items held in the jaws, not a kinetic-inertial mechanism, as previously suggested. Leurognathus exhibits a behaviour ('head-tucking') unique to desmognathines that is consistent with the static-pressure hypothesis. Several desmognathine features (1, 2, 5, 7, 9) are not explicable as adaptations for feeding; these function as locomotory specializations for burrowing, especially for wedging under rocks within and alongside streams. Desmognathines use head-tucking during such wedging and burrowing movements, thus locomotory specializations act in concert with the feeding specializations. We suggest that origin of the atlanto-mandibular ligaments can be considered a 'key innovation' in that it allowed the secondary invasion of stream habitats by adults of ancestral desmognathines.

Effects of Sex and Size on Agonistic Encounters between Juvenile and Adult Lizards, Sceloporus jarrovi

JAEGER, R. G. 1986. Pheromonal markers as territorial advertisement by terrestrial salamanders. In D. Duvall, D. Muller-Schwarze, and R. M. Silverstein (eds.), Chemical Signals in Vertebrates 4, pp. 191203. Plenum Publishing Corp., New York. ROUDEBUSH, R. E., AND D. H. TAYLOR. 1987. Chemical communication between two species of desmognathine salamanders. Copeia 1987:744-748. SIMONS, R. R., AND B. E. FELGENHAUER. 1992. Identifying areas of chemical signal production in the red-backed salamander, Plethodon cinereus. Copeia 1992:776-781. WATSON, P. 1986. Chemical communication in the courtship ritual of the red-spotted newt: investigations into the role of the genial gland pheromone. 1986 Abstracts of Joint Meeting of Herpetologists' League and SSAR, Springfield, Missouri, p. 115.

Motor Neurons and Motor Columns of the Anterior Spinal Cord of Salamanders: Posthatching Development and Phylogenetic Distribution

The posthatching development of rostral (1st-4th) spinal motor neurons was studied in ten species of salamanders, using horseradish peroxidase and cobaltic lysine tracing techniques. Development of spinal motor neurons differs among species in association with differences in life history and general developmental patterns (i.e., between species with aquatic larvae versus those with direct development, with or without ontogenetic repatterning). In the plesiomorphic state, represented by species with aquatic larvae, five types of motor neurons are present: (1) large, multipolar neurons, believed to be primary motor neurons; (2) medial, pear-shaped neurons; (3) larger, spindle-shaped neurons, which increase in number during posthatching development; (4) cone-shaped neurons, and (5) bilaterally arborizing neurons (found only at the rostral pole of the first spinal nucleus). Direct-developing desmognathine salamanders have the plesiomorphic set of motor neurons, but appear to lack Mauthner neurons. Direct-developing plethodontine salamanders have cone-shaped, pear-shaped, and spindle-shaped neurons, but lack primary motor neurons and Mauthner neurons. Direct-developing bolitoglossine salamanders, which exhibit both pedomorphosis and ontogenetic repatterning, have only medial, pear-shaped neurons, and lack primary motor neurons, spindle-shaped neurons, cone-shaped and bilaterally arborizing neurons. At all developmental stages in all species studied, pear-shaped neurons are always found in medial positions and spindle-shaped neurons are always found in lateral positions. Spindle-shaped neurons are found more laterally as development proceeds. The medial and lateral motor columns of salamanders and amniotes differ in their connections with peripheral targets (i.e., axial muscles vs. limbs). This implies a lack of homology of neuron types in salamanders and amniotes, which has been obscured by the current terminology.

Helminth Parasites of Sympatric Salamanders: Ecological Concepts at Infracommunity, Component and Compound Community Levels

Four species assemblages of desmognathine salamanders are sympatric in and along many mountain streams of the southern Appalachians. The species, Leurognathus marmorata, Desmognathus quadramaculatus, D. monticola and D. ochrophaeus, span an aquatic to terrestrial habitat continuum ranging from totally aquatic (L. marmorata) to primarily terrestrial (D. ochrophaeus). Such a system afforded the opportunity of examining concepts of helminth parasite ecology within the context of several recent theoretical predictions. Parasite infracommuinities (populations of all helminth species within individual hosts) in salamanders are isolationist in character. That is, parasite prevalence (percentage of hosts infected with a given parasite species) and mean intensity (mean number of parasites of a given species within a species of host) are low, and as a consequence there is little potential for competitive interactions. Isolationist infracommunities in salamanders arise from factors including a simple enteric system, restricted vagility and ectothermic generalist insectivory. Salamanders have a broad prey base and they do not focus on any particular prey species. Transmission of helminths by intermediate hosts is unimportant and contributes to depauperate helminth faunas dominated by nematodes with direct life cycles. The least diverse infracommunities were associated with Leurognathus marmorata while Desmognathus quadramaculatus had the most diverse fauna. Patterns of prevalence and intensity of infection revealed that salamander helminths were, in general, not host specific. Rather, they are generalists and their distributions can be correlated with host size (age), diet and habitat preferences. INTRODUCTION A principal focus of community ecology is to interpret the effects of competition, predation, mutualism and parasitism, as well as abiotic factors, in determining community structure. Ecological theory has been largely derived from studies on free-living animals with little attention focused on specialist organisms such as parasites. Price (1980, 1984) emphasized that small, highly specialized organisms are very different in many aspects of their biology from larger, more generalized animals so that communities of specialists may be organized in fundamentally different ways from generalist communities. The current literature reveals a predominance of nonequilibrial communities in nature among specialists, in which biotic interactions play a minor role in maintaining community structure (Price, 1984). These are in marked contrast to the equilibrium communities, many of which conform to the predictions of classic competition-based theory (see Strong et al., 1984; Price et al., 1984, and references therein). As stated by Price (1984), It is valuable to examine the extent to which specialist communities support or contradict the paradigms' Despite their biological uniqueness and complexity, helminth parasites possess certain attributes which should permit them to contribute significantly to several basic concepts in community theory. First, helminth communities have unambiguous boundaries

Chemical Communication between Two Species of Desmognathine Salamanders

ticola was investigated in the laboratory. The salamanders were divided into four species-size groups (i.e., large and small D. quadramaculatus and large and small D. monticola). Extracts were collected by housing salamanders individually on filter paper for 3 d. Salamander responses to filter paper extracts from each species-size group were monitored in a pheromone test apparatus. Each speciessize group was attracted to its own extract. Desmognathus monticola exhibited a species-specific avoidance of D. quadramaculatus extracts, but the converse was not true. The detection of chemical cues by D. monticola may lower its risk to predation from D. quadramaculatus. A chemical communication system in these salamanders has broad implications for the analysis and interpretation of desmognathine community structure.

A Test of Competition in Two Sympatric Populations of Desmognathine Salamanders

The effect of competition on foraging success and density in two sympatric populations of salamanders (Desmognathus monticola and D. quadramaculatus) was examined by density and cover—object manipulation experiments from June 1980 to April 1982. A second—order mountain stream in southwestern North Carolina was divided into experimental and control sections, and four treatments were performed: (1) addition of D. monticola, (II) addition of D. quadramaculatus, (III) addition of cover objects (rocks), (IV) addition of rocks and D. monticola. Treatments III and IV were performed for D. monticola only. Salamanders were marked individually for mark—release—recapture data. After experiments were terminated, salamanders were collected from control and treatment plots. Total lipid contents were determined and were used as an indirect measure of foraging success. Additions of D. monticola increased the total number of conspecific salamanders on plots and decreased their lipid content; congeners were not affected by the additions. Additions of D. quadramaculatus did not affect the total lipid content or the density of conspecifics or congeners. Addition of rocks significantly increased the density of D. monticola but did not affect their lipid content. Addition of rocks and D. monticola increased conspecific density and total lipid content. Results of salamander additions indicated that intraspecific competition for limited cover objects and energy resources may be important for adults and juveniles of D. monticola but not for D. quadramaculatus; interspecific competition was not detected.

Substrate selection by three species of desmognathine salamanders from southwestern Pennsylvania: an experimental approach

Substrate selection by three species of desmognathine salamanders from southwestern Pennsylvania: an experimental approach

CORRELATIONS OF QUANTITATIVE PARAMETERS OF FECUNDITY IN AMPHIBIANS.

Salthe (1969), Salthe and Duellman (1973), and Salthe and Mecham (1974) generalized the published data on body size of the females, clutch size, ovum size, and reproductive mode of various amphibian species. For example, they recognized a positive interspecific correlation between ovum size and female body size in frogs within a given reproductive mode and a negative correlation between clutch size and ovum size regardless of differences in reproductive mode. Since these relationships of body size, clutch size, and ovum size should have been established during the evolutionary process as one of the adaptive features in each species, it is an interesting problem to examine whether the same sort of relationships are also found within each species. The data on which the above studies were based were from a large literature, and close examination of this literature reveals several defects for drawing relevant conclusions on the relationships of these parameters within as well as between species. There are only a few papers describing precise number and size of eggs from individual females, and, in most papers, the statistics are obtained from indirect methods. For instance, Tilley (1968) counted the number of follicles larger than 1 mm as the clutch size of five desmognathine salamanders, Bruce (1969) estimated the clutch size of four plethodontid salamanders from the yolked oocytes in the ovary, and Inger and Bacon (1968) determined the number of eggs of six Bornean frogs from the ratio of left ovary volume to 50 eggs removed from it. All these investigations were based on the preserved specimens. Only two papers deal with live animals. H6nig (1966) counted and measured the eggs obtained by spontaneous ovulation from the common frog, Rana temporaria, and Pettus and Angleton (1967) made the same kind of observations on eggs obtained by induced ovulation from the chorus frog, Pseudacris triseriata. The former study is obviously superior to the others in that it deals with weight, instead of length or volume, of females and eggs, although no correlation coefficient nor regression is given. Because the reproductive cost to the female of a given species should be expressed in terms of weight relationships, the weight parameters are more pertinent than the length or volume parameters. Since the intraspecific relationships between the reproductive parameters probably precede the interspecific relationships (Salthe and Duellman, 1973), comparative analyses on relationships both within and between species are critical for elucidating the adaptive evolution of reproductive strategies. From this point of view, the quantitative relationships among the weight parameters of eggs and adult females of 12 amphibian species from Japan were examined.

Some Aspects of the Life History and Ecology of the Salamander Leurognathus

Leurognathus inhabits trout streams in the southern Appalachian Mountains from southwestern Virginia to northeastern Georgia. These salamanders have a discontinuous distribution; they are strangely absent from some drainages. Specimens are best collected by diverting the flow of water so that a part of the stream bed is drained. This area is then carefully searched and the routed animals captured with the use of a funnel-shaped trap made of screen or fine-mesh hardware cloth. Some individuals attain a maximum snout-vent length of 78 mm and a weight of 13 grams. Generally males are larger than females, have a relatively wider head, less vomerine teeth, enlarged maxillary teeth, a larger and papillated cloaca, and an enlarged (but not conspictious) mental gland. Spawning occurs chiefly in June. Eggs are attached to the underside of a rock located in the main current. They average about 40 per clutch and hatch in about three months. Hatchlings average 11 mm in snoutvent length. The larval stage may be as short as 10 months or as long as 20 months. The average size at metamorphosis varies seasonally and geographically. It ranges from 25 to 38 mm; the over-all average is near 30 mm. Males reach sexual maturity when about 50 mm in snout-vent length and at least two years of age. Females mature when they are three years old and about 55 mm in size. Maximum size is probably approached at the age of five years. There is no evidence that either sex prefers a special habitat or that the sex ratio is other than one to one. Leurognathus are mainly noctural and secretive. They spend much time under rocks and feed almost exclusively on the larval or nymphal forms of aquatic insects. Much geographic and individual variation in body proportions and in coloration and markings occurs in this species. One of the most interesting types of variation involves the absence of dark pigment. These specimens are mostly whitish-yellow but may have dark blotches over both venter and dorsum. Some completely lack dark markings, but all have normal colored eyes and soles of the feet. The incidence of albinistic specimens has gradually increased from less than one per cent in 1954 to nine per cent in 1960. No albinistic larvae have been found. The smallest specimen showing such albinism measured 39 mm from snout to vent. However, some specimens as small as 45 mm were among the most albinistic ones collected. Thus a very conspicuous change in phenotype may occur in individuals and in populations within a relatively short period of time. A survey of the morphological features and adaptive trends of desmognathine salamanders supports retention of the genus Leurognathus. This content downloaded from 207.46.13.86 on Sun, 16 Oct 2016 04:35:27 UTC All use subject to http://about.jstor.org/terms 2 THE AMERICAN MIDLAND NATURALIST 67(1)