Salamanders Desmognathus Quadramaculatus Research Articles

Host Phylogeny Is Not a Major Factor in Infection of the Salamander Desmognathus marmoratus by the Trematode Metagonimoides oregonensis

In the southern Appalachian Mountains, U.S.A., the trematode Metagonimoides oregonensis, a parasite of raccoons and mink, primarily uses larvae of the salamander Desmognathus quadramaculatus as a second intermediate host. However, evidence suggests that a cryptic, sympatric species, Desmognathus folkertsi is parasitized at a very low level or not at all. We tested the hypothesis that Desmognathus marmoratus, which is phylogenetically a sister to D. folkertsi, also has a low infection rate. We collected larvae of sympatric D. quadramaculatus and D. marmoratus from a stream (Beech Creek) in Towns County, Georgia, U.S.A. Although prevalence and mean visible metacercariae were different in June, no difference was seen between the species in either measure of infection in August. Our results support earlier work that suggests that factors other than host phylogeny can be more important in influencing infection.

A Female-Centered Evaluation of Growth, Survival, Reproduction, and Demography in the Salamander Desmognathus quadramaculatus

In the present report, I evaluate life history and demography for two populations of the Black-bellied Salamander, Desmognathus quadramaculatus, in the Cowee and Nantahala Mountains, North Carolina, using published data on growth of females, fecundity, and larval growth and development to generate life tables and metabolic life histories for each population. I assumed that females in these populations reproduce biennially, beginning at ages 7–8 years and 8–10 years in Cowee and Nantahala populations, respectively. In deriving life tables, I posited stationary populations wherein net reproductive rate (R0) equaled 1.0 and population growth rate (r) equaled 0. Fecundity (mx column of the life table) was based on counts of ovarian follicles in gravid females. Survival values (lx column of the life table) were generated by an iterative process that yielded a value of R0 = 1.0. I projected the life spans in each population to 25 years. The demographic models developed by the procedure allowed comparison with those reported earlier for D. monticola and D. ocoee. Age at first reproduction and generation time are key contributors to variation in body size and life history in Desmognathus.

Differential Infection of Two Sympatric, Cryptic Species of Appalachian Salamander (Genus Desmognathus) by the Trematode Metagonimoides oregonensis

In the southern Appalachian Mountains, U.S.A., the trematode Metagonimoides oregonensis, a parasite of raccoons and possibly mink, utilizes larvae of lungless salamanders as second intermediate hosts, most frequently using the salamander Desmognathus quadramaculatus. We tested whether there was a difference in parasite infection between this salamander and its sympatric, cryptic congener, Desmognathus folkertsi, in northern Georgia. Whereas larval D. quadramaculatus had a prevalence of 100% with intensities ranging from 18 to over 1,000, none of the D. folkertsi had visible metacercariae. These results indicate that M. oregonensis is more host-specific in salamander second intermediate hosts in the southern Appalachians than previously reported.

Host Specificity in the Appalachian Leech Placobdella biannulata

The Appalachian leech Placobdella biannulata is a presumed host generalist for an array of amphibian species. One species commonly parasitized by this leech is the salamander Desmognathus quadramaculatus because of its semiaquatic nature and relatively large size. We tested the null hypothesis that this leech species exhibits equal prevalence in large species of Desmognathus with the same level of aquatic tendency. We compared leech prevalence between D. quadramaculatus and sympatric Desmognathus folkertsi, which has the same extent of aquatic tendency. While smaller than D. quadramaculatus, D. folkertsi is still among the largest members of the genus. We found leech parasitism on 38/182 (21%) D. quadramaculatus from 2 different streams. Only 3 D. folkertsi out of 179 (<2%) from the same streams were parasitized. We concluded that the leech P. biannulata is more host specific than previously believed.

Critical Tail Autotomy for Reduction of Maximal Swimming Performance in a Plethodontid Salamander (Desmognathus quadramaculatus)

Although tail autotomy often has an immediate survival benefit, tail loss may subsequently hinder locomotion and the ability to escape from predators. Maximal locomotor performance can be reduced after tail autotomy in the plethodontid salamander Desmognathus quadramaculatus. The loss of a large proportion of the tail length (>60%) is costly for this semiaquatic species in terms of a reduction in maximal swimming performance (i.e., burst speed is about 50% less after such autotomy). However, the minimal amount of tail loss that causes a significant reduction in swimming performance (i.e., the “critical tail autotomy” for locomotion) is unknown. I examined the effect of partial tail loss (either 15% or 30% of tail length) on burst swimming performance. After the loss of about 15% of tail length in one experimental group (N = 15), burst speeds for individuals were not significantly different from preautotomy burst speeds. After the loss of about 30% of tail length in a second experimental group (N = 15), burst speeds for individuals were significantly less than preautotomy burst speeds. These results indicate that the critical tail autotomy for reduction of maximal swimming performance is between 15% and 30% of tail length. About 50% of individuals in the field (N = 69) experienced tail autotomy and most (80%) of these individuals lost more than 30% of their tails. This study shows that tail autotomy often results in a reduction in maximal swimming performance and thus a locomotor cost for individuals of this species.

Effect of body size on tail regeneration and recovery of swimming performance after caudal autotomy in a plethodontid salamander

I examined the effect of body size on the locomotor cost of caudal autotomy in the plethodontid salamander Desmognathus quadramaculatus. In this primarily aquatic species, larger individuals autotomize the tail less readily than smaller individuals, and this may be related to a greater locomotor cost of tail loss for larger individuals. To determine whether the rate of regeneration for tail length and the recovery of maximal locomotor performance after caudal autotomy vary with body size, I measured the rate of tail re-growth and the swimming burst speed for 14 individuals (snout-vent length = 42-106 mm) as they regenerated their tails. Burst speeds of individuals were significantly reduced after caudal autotomy. With the loss of about 62% of tail length, mean burst speed declined about 50%. Thus, caudal autotomy was costly in terms of a reduction in maximal locomotor performance in an aquatic environment. After the regeneration of 50% of the tail length that was lost, post-autotomy swimming speeds were not significantly different from pre-autotomy swimming speeds. The time required for this amount of tail length regeneration (about 63-143 d) increased significantly with body size. The rate of re-growth for the lost tail length declined significantly after the regeneration of 50% of tail length. These results demonstrate that the locomotor cost of tail loss is greater for larger individuals of D. quadramaculatus, and this may be related to a lower propensity for caudal autotomy and a greater propensity for alternative antipredator mechanisms (e.g., biting) for such individuals.

Formation of Hypoxic Boundary Layers and Their Biological Implications in a Skin-Breathing Aquatic Salamander,Desmognathus quadramaculatus

We examined hypoxic boundary layers surrounding the skin-breathing aquatic plethodontid salamander Desmognathus quadramaculatus and investigated the flow regime in the natural habitat of this species. In slow-flowing water (<10 cm · s⁻¹), which we found to be the preferred microhabitat in nature, the boundary layer is the major resistance to oxygen uptake. Consequently, PO₂ at the skin surface in slow-flowing water falls below 60 Torr even though Po₂ in the free stream exceeds 150 Torr, and aerobic metabolism is severely impaired. Four salamanders survived reduced aerobic metabolism for 4 mo in the laboratory, implying that D. quadramaculatus can severely restrict overall metabolic needs and/ or makes extensive use of anaerobic metabolic pathways.

Time courses of thermal acclimation for critical thermal minima in the salamanders Desmognathus quadramaculatus, Desmognathus monticola, Desmognathus ochrophaeus, and Plethodon jordani

1. 1. We examined the time courses of thermal acclimation for critical thermal minima (CTMin) in the salamanders Desmognathus quadramaculatus, D. monticola, D. ochrophaeus, and Plethodon jordani. 2. 2. D. quadramaculatus showed no annual differences in their time courses, but we noted seasonal differences in the CTMin with these salamanders having lower CTMin in the spring. 3. 3. Gain in CTMin (25°C to 5°C transfer) was faster than its corresponding loss (5°C to 25°C transfer) in D. quadramaculatus. 4. 4. Comparison of all three Desmognathus species revealed no differences in the CTMin for the 5°C to 25°C time courses, but P. jordani had lower CTMin than corresponding D. quadramaculatus. 5. 5. Our results indicate that the pattern of CTMin acclimation correlates with the constraints acting on salamanders in their natural environment.

Coexistence of Three Congeneric Salamanders: The Importance of Habitat and Body Size

In the southern Appalachians three congeneric salamanders–Desmognathus quadramaculatus, D. monticola, and D. ochrophaeus–are broadly sympatric. D. monticola is intermediate to the others species in body size and in degree of terrestrial habit. This study analyzed the roles of competition, predation, and habitat conditions in limiting the abundance of this "ecologically intermediate" species and in directing its evolution. In field observations, D. monticola regularly used both stream—bank and forest—floor habitats; experimental exclusion from either of these habitats resulted in poor survival. Field enclosure experiments also showed that growth, survival, and habitat selection of D. monticola were altered by the presence of congeners. Interference from conspecifics and from congeners of equal size decreased growth and reduced survival of D. monticola. Predation by large D. quadramaculatus sharply reduced survival of juveniles and caused shifts in activity and habitat selection. I suggest that predation has controlled the evolution of body size and habitat selection in D. monticola and that populations of this intermediate species are limited by the availability of streambank cover as a refuge from predation. Competition may also be important among species of similar size when food is limited.

Larval Periods, Population Structure and the Effects of Stream Drift in Larvae of the Salamanders Desmognathus quadramaculatus and Leurognathus marmoratus in a Southern Appalachian Stream

Non-destructive sampling of salamander larvae at East Fork Overflow Creek and its tributaries in the Blue Ridge Mountains of North Carolina provided information on larval life histories of Desmognathus quadramaculatus and Leurognathus marmoratus. Snout-vent length data indicated that both D. quadramaculatus and L. marmoratus have larval periods of three years, which is considerably longer than estimates provided by previous investigators. Individual growth rates were higher and metamorphic sizes larger in D. quadramaculatus than in L. marmoratus. In both species, first-year larvae were under-represented in the samples from East Fork Overflow Creek. Sampling in tributaries yielded higher frequencies of young larvae of D. quadramaculatus. These data suggested that in the latter species, reproduction was concentrated in headwater tributaries and that the downstream larval populations were constituted in part from stream drift. Although drift may thus account for the population structure of D. quadramaculatus, it does not explain similar findings for L. marmoratus, inasmuch as the latter species was nearly absent from the tributaries.