Spotted Salamanders Ambystoma Maculatum Research Articles

Taxonomy and nomenclature of Oophila amblystomatis (Chlorophyceae, Chlamydomonadales).

The unicellular green alga Oophila amblystomatis was named by Lambert in 1905 based upon its association with egg masses of the spotted salamander Ambystoma maculatum. We collected algal cells from Lambert's original egg capsule preparations that were contributed to Phycotheca Boreali-Americana (PBA) in 1905 and subjected them to DNA extraction and PCR with O. amblystomatis-specific 18S rRNA gene primers. DNA amplified from these preparations was cloned and nine clones were sequenced. Along with representative sequences from the Oophila clade and Chlorophyceae, a phylogenetic tree was inferred. Seven sequences clustered within the Oophila clade and two clustered with Chlamydomonas moewusii, which is included in a sister clade to Oophila. By sequencing algal material from the egg capsules of representative type material we can unambiguously characterize O. amblystomatis and define a monophyletic clade centered on this type material. Accordingly, we reject a recent proposal that this species be transferred to Chlorococcum.

Bacterial Diversity in Egg Capsular Fluid of the Spotted Salamander Ambystoma maculatum Decreases with Embryonic Development.

Egg capsules within egg masses of the spotted salamander Ambystoma maculatum host a symbiosis with the unicellular green alga Oophila amblystomatis. However, this alga is not the only microbe to inhabit those capsules, and the significance of these additional taxa for the symbiosis is unknown. Spatial and temporal patterns of bacterial diversity in egg capsules of A. maculatum have recently begun to be characterized, but patterns of bacterial diversity as a function of embryonic development are unknown. We sampled fluid from individual capsules in egg masses over a large range of host embryonic development in 2019 and 2020. We used 16S rRNA gene amplicon sequencing to examine how diversity and relative abundance of bacteria changed with embryonic development. In general, bacterial diversity decreased as embryos developed; significant differences were observed (depending on the metric) by embryonic development, pond, and year, and there were interaction effects. The function of bacteria in what is thought of as a bipartite symbiosis calls for further research.

Pond water is the principal source of algae that form a symbiosis with embryos of the spotted salamander Ambystoma maculatum: an experimental test

Pond water is the principal source of algae that form a symbiosis with embryos of the spotted salamander Ambystoma maculatum: an experimental test

Patterns of bacterial diversity in embryonic capsules of the spotted salamanderAmbystoma maculatum: an expanding view of a symbiosis

The unicellular green alga, Oophila amblystomatis, populates egg capsules of the spotted salamander Ambystoma maculatum. This nutrient-exchange mutualism is widely perceived as a bipartite interaction, but the presence and contributing effects of bacteria to this symbiosis are unknown. We used standard cultivation techniques and amplicon sequencing of the V4/V5 region of 16S rRNA gene to identify and compare diversity of bacterial taxa in embryonic capsules with that in the aquatic breeding habitat. Our sampling regime allowed us to investigate diversity among individual capsules of an egg mass and between two ponds and sampling years. Capsules contain much lower diversity of bacteria than pond water, and spatial and temporal variation in intracapsular and pond bacterial diversity was observed. Despite this variation, sequences corresponding to species in the orders Burkholderiales and Oligoflexales were either prevalent or abundant, or both. Isolates most commonly recovered from capsules were closely related to species in the genus Herbaspirillum (Burkholderiaceae); other isolates were pseudomonads, but in all cases are closely related to known vascular plant-associated species. We conclude that, despite observed variation, there are bacterial taxa whose presence is held in common spatially and temporally among capsules and that the symbiosis between O. amblystomatis and A. maculatum may involve these taxa.

Oophila is monophyletic within a three-taxon eukaryotic microbiome in egg masses of the salamander Ambystoma maculatum

Tests of hypotheses of vertical transmission and competitive exclusion for particular resource-exchange mutualisms require assessments of the number and identity of partners. Unicellular green algae form a symbiosis with embryos of the northeastern yellow spotted salamander Ambystoma maculatum. The extent to which the composition of egg mass-associated taxa depends on temporal or spatial factors is unknown and the discovery of an endosymbiotic component to this symbiosis has increased the importance of knowing the specificity of the association. We assessed the diversity and relative abundance of algal and other unicellular eukaryotes in egg masses by subjecting DNA harvested from cells in egg capsules or water from breeding habitat to 18S amplicon sequencing. A nested sampling regime for two breeding seasons allowed comparisons among capsules within egg masses, among egg masses in ponds, between breeding locales, between pond water and capsule fluid, and between years. Based upon 4.33 X106 reads, we found no evidence inside fifty-eight egg capsules of algal lineages outside the Oophila clade and report that, whereas non-algal eukaryotic sequence diversity was low, cercozoan protists and chytridomycete fungi were sometimes abundant. There were weak or inconsistent egg mass, year or locale effects, but there was a very strong localization effect, indicating that capsules are rarefied spaces for eukaryotic aquatic taxa. This work provides a foundation for comparing microbial community structure within and among egg masses across the geographic range of the host.

The roles of oxygen and ammonia in the symbiotic relationship between the spotted salamander Ambystoma maculatum and the green alga Oophila amblystomatis during embryonic development

Some of the positive benefits of the symbiotic relationship between the yellow spotted salamander Ambystoma maculatum and the green alga Oophila amblystomatis on salamander embryonic development have been well documented. However, the fundamental basis of the relationship, in terms of the exchange of metabolic and photosynthetic products, is under debate, especially as it relates to newly discovered endosymbiotic aspects of the relationship. We developed a novel experimental approach in which we liberated egg capsules from egg masses and compared de-capsulated embryos to capsulated embryos. We were able to discern the contribution of salamander embryo respiration and ammonia excretion and algal photosynthesis to oxygen and ammonia dynamics within the egg capsules under light and dark conditions. Algal photosynthesis drove oxygen production under light conditions, while salamander respiration caused hypoxia during dark conditions. Ammonia was consumed to such an extent that it may be the limiting factor for algal growth. Algal cells actively penetrated the developing gut of embryos through the blastopore from an early developmental stage, and some algae came to reside in the vicinity of liver primordia towards later embryonic development, perhaps explaining the lack of detectable ammonia production by de-capsulated embryos. We suggest that oxygen and ammonia may influence A. maculatum growth and O. amblystomatis population dynamics. We have also demonstrated the extent to which algal cells penetrate internal spaces of embryos, which may be the precursor to endosymbiosis between these two species.

Population of origin and environment interact to determine oomycete infections in spotted salamander populations

Spatial variation in disease risk in wild populations can depend both on environmental and genetic factors. Understanding the various contributions of each factor requires experimental manipulation of both the environment and genetic composition of populations under natural field conditions. We first examined natural patterns of oomycete composition and infection in the eggs of 13 populations of the spotted salamander Ambystoma maculatum. We then performed a fully factorial field transplant of the eggs of six populations to separate the contributions from population of origin and the environment on oomycete resistance in spotted salamanders. Among wild ponds, we found strong variation in oomycete infections in spotted salamander populations and differences in the composition of oomycete communities. In transplant experiments, salamander populations differed in their resistance to oomycete infections via a significant interaction between population of origin and environment. However, not all populations were locally adapted to local conditions. One population was significantly adapted to its home environment, and another one was significantly maladapted. These population effects could originate from differential adaptation of salamander populations to local oomycete communities or environmental conditions that mediate resistance, local adaptation and maladaptation of oomycetes to hosts, or from maternal transmission. Accounting for both environment and population of origin will often be necessary to understand disease dynamics in wild populations.

Habitat type and distance to edge affect movement behavior of juvenile pond‐breeding salamanders

AbstractBehavioral strategies of natal dispersers in response to human‐altered habitat have far‐reaching implications for functional connectivity and local population dynamics. Spotted salamanders Ambystoma maculatum are forest‐dependent, pond‐breeding amphibians which metamorphose and disperse out of aquatic habitat with limited knowledge of the terrestrial habitat. We quantified the fine‐scale movement behavior and search strategies of recently metamorphosed spotted salamanders in three different habitat types (field, early successional forest and forest) and at varying distances from both hard (field and forest) and soft (early successional forest and forest) edges using fluorescent powder tracking. We found that salamanders moved straighter and with fewer turns through field habitat compared with both forest and early successional habitat. Salamanders significantly oriented movement toward forest when released in the field and when released on the edge between the forest and field. We found that salamander movement in the forest and early successional forest was approximated by a correlated random walk. Based on these results, dispersing spotted salamanders exhibit strong edge‐mediated behavior when differences between habitats are stark (forest and field) and can perceive forest habitat from distances of at least 10 m. These results indicate that dispersing juvenile salamanders exhibit reasonable behavioral rules when moving through habitat types of differing quality. Knowledge of these behavioral rules will improve predictions of the effects of habitat type and configuration on amphibian survival and dispersion in altered landscapes.

Salamander evolution across a latitudinal cline in gape‐limited predation risk

General predictions of community dynamics require that insights derived from local habitats can be scaled up to explain phenomena across geographic scales. Across these larger spatial extents, adaptation can play an increasing role in determining the outcome of species interactions. If local adaptation is common, then our ability to generalize measures of species interaction strength across communities will be limited without an additional understanding of the genetic variation underlying interaction traits. In the context of predator–prey interactions, prey individuals commonly are expected to reduce risky foraging behaviors and subsequent growth under predation threat. However, rapid growth into a large body size can defend against gape‐limited predators, creating a tradeoff between increased predation risk due to elevated foraging activity and decreased predation risk due to large size. Here I combine field observations, natural selection experiments, and common garden assays to understand potential adaptations of spotted salamander Ambystoma maculatum larvae to gape‐limited and gape‐unconstrained predators. Field observations and natural selection trials suggested antagonistic selection on prey body size among ponds dominated by gape‐limited predator salamanders A. opacum and gape‐unconstrained beetle larvae Dytiscus. In common garden experiments, prey from sites with high gape‐limited predation risk grew larger than those from other sites, suggesting the evolution of rapid growth into a prey size refuge. Larvae from all sites grew to a large size when exposed to the gape‐limited N. viridescens predator's kairomones. Hence, induced rapid growth into a size refuge may be an adaptive response to gape‐limited predation risk. Results point to an important role for cross‐community generalizations based on functional classifications of predators by their gape constraints and inter‐site genetic variation in prey growth rates and behaviors.

Intermittent hypoxia in eggs ofAmbystoma maculatum: embryonic development and egg capsule conductance

The spotted salamander Ambystoma maculatum breeds in shallow freshwater pools and imbeds its eggs within a common outer jelly matrix that can limit oxygen availability. The eggs are impregnated with the unicellular alga Oophilia amblystomatis, which produces oxygen during the day but consumes oxygen at night. This daily cycle of algal oxygen production drives a diurnal fluctuation of oxygen partial pressure (PO2) within the eggs, the magnitude of which depends on the distance of an egg from the exterior of the jelly matrix and on the ambient PO2 of the pond. We subjected A. maculatum eggs to fluctuating oxygen levels with a variable minimum PO2 and an invariable maximum, to simulate natural conditions, and measured differences in developmental rate, day and stage at hatching, and egg capsule conductance (GO2). Lower minimum PO2 slowed development and resulted in delayed, yet developmentally premature hatching. GO2 increased in all treatments throughout development, but PO2 had no detectable effect on the increase. Intermittent hypoxia caused comparable but less pronounced developmental delays than chronic hypoxia and failed to elicit the measurable change in GO2 seen in ambystomatid salamander eggs exposed to chronic hypoxia.

An experimental assessment of invertebrate/vertebrate predation: the interaction between wolf spiders (Gladicosa pulchra) and terrestrial salamanders (Ambystoma maculatum)

AbstractA series of laboratory experiments were conducted to determine if adult wolf spiders Gladicosa pulchra were capable of acting as predators of juvenile spotted salamanders Ambystoma maculatum. Spiders preyed upon salamanders in two of 20 trials and attacked salamanders in five trials. As attacks did not always kill salamanders, multiple attacks per trial were possible. A total of 11 attacks was observed: two complete attacks, and nine incomplete attacks. Attacks were considered complete if the spider inserted its chelicerae into the salamander and incomplete if the spider did not. In response to complete attacks, the salamander would flip onto its back. Salamanders occasionally responded to incomplete attacks by continuously raising and lowering their heads. To our knowledge, this behaviour is undescribed in this group of salamanders. An additional experiment investigated the influence of increased levels of salamander movement on this interaction. In this experiment, spiders preyed upon salamanders in one of eight trials and attacked salamanders in six trials (28 total attacks: four complete attacks, 24 incomplete attacks). The results of this study indicate that wolf spiders can prey upon juvenile spotted salamanders, and that the ecological relationship between wolf spiders and amphibians may be quite complex.

Impact of guthion on survival and growth of the frog Pseudacris regilla and the salamanders Ambystoma gracile and Ambystoma maculatum.

The effects of the insecticides Guthion (technical grade) and Guthion 2S (commercial formulation) on survival and growth of tadpoles of the Pacific treefrog Pseudacris regilla, and larvae of the Northwestern salamander Ambystoma gracile and the spotted salamander Ambystoma maculatum were determined in continuous-flow exposures in the laboratory. Ninety-six-hour LC50 values were >3.6 mg/L for P. regilla with technical grade Guthion and 1.47 mg/L with the formulation Guthion 2S (measured as active ingredient Guthion). Ten-day LOAEL and NOAEL values based on length and weight for P. regilla with Guthion were 3.60 and 0.98 mg/L. LOAEL and NOAEL values based on length and weight for P. regilla with Guthion 2S were 0.17 and 0.07 mg/L. The 96-h LC50 for Guthion 2S was 1.67 and 1.90 mg/L for A. gracile and A. maculatum, respectively. LOAEL and NOAEL values based on length and weight for A. gracile with Guthion 2S were 0.22 and 0.10 mg/L; they were 0.11 and 0.03 mg/L for A. maculatum based on weight. These species are as similar in sensitivity as some fish species but are more tolerant to Guthion than most invertebrates.

Erpobdella punctata (Hirudinea: Erpobdellidae) as phoronts on Ambystoma maculatum (Amphibia: Ambystomatidae)

Adult spotted salamanders Ambystoma maculatum with leeches Erpobdella punctata attached were observed frequently during a survey of the amphibians from a temporary woodland pond in southern Beaufort County in South Carolina. In the present study, the occurrence of E. punctata was examined in a population of A. maculatum with regards to the salamander's sex and body length. In February 1994, 57 salamanders were collected using minnow traps and examined for leeches. The main attachment site was near the forelimb of the salamander. The percentage of salamanders used as hosts by the leeches was 49·12% (28/57); only male salamnders served as hosts. The mean intensity of occurrence was 1·04 leeches per salamander. No significant difference in occurrence was observed based on host body length; nor were the body lengths of the host correlated with those of the phoronts. This salamander-leech association appears to be a phoretic relationship. Phoresy may provide the leech with mobility within and without the original habitat as well as with food particles which are expelled by the salamander during feeding. This is the first record of E. punctata using a salamander as a phoretic agent.

Variation in Metamorphosis in Spotted Salamanders Ambystoma maculatum from Eastern Missouri

-I examined timing of metamorphosis in the spotted salamander Ambystoma maculatum for five years at a pond in east-central Missouri. Timing of metamorphosis was variable both among and within years. In three years most larvae failed to undergo metamorphosis by November and either died or overwintered and metamorphosed from the pond in the following spring. In two other years most larvae apparently metamorphosed by October and did not overwinter. In 1986, 81 newly transformed animals were captured from June to September. Individuals that metamorphosed later exhibited larger body sizes than those that left the pond early in the season. Variation in time and size at metamorphosis may be important in population regulation by affecting adult traits that contribute to fitness.

Breeding biology of the spotted salamander Ambystoma maculatum (Shaw) in acidic temporary ponds at Cape Cod, USA

The relationship between water chemistry and breeding success of spotted salamanders Ambystoma maculatum (Shaw) was examined in temporary woodland ponds on outer Cape Cod, Massachusetts in 1985 and 1986. Most pond waters were dilute (3median coductivity = 57 umhos cm −1 (1 umhos cm −1 = 0·1 mSm −1)), acidic (median pH = 4·82), and highly colored (median = 140 Pt-Co units). Most acidity was due to abundant organic acids. Salamander survival to hatching was over 80% at 8 of 12 ponds monitored. Complete mortality, preceded by gross abnormalities, was observed only among embryos in the most acidic spawning pond (pH 4·3−4·5) in both years. Embryo transfers between ponds and laboratory studies indicated that reduced survival was due to the interaction of low pH with high tannin-lignin concentration. The use of amphibian embryonic survival to indicate acid rain effects is complicated by multiple habitat parameters and should only be attempted in conjunction with long-term population monitoring.

Survival of spotted salamander eggs in temporary woodland ponds of coastal Maryland.

Temporary ponds on the Atlantic Coastal Plain in maryland were characterized according to water chemistry, rain input, phytoplankton, zooplankton and use by the spotted salamander Ambystoma maculatum during March-October 1983-1984. Neither the number of egg masses per unit of pond surface (abundance) nor the survival of spotted salamander embryos was significantly correlated (P>0.05) with pond pH. Rainfall during May-July significantly increased the hydrogen ion concentration of 5 of 11 ponds evaluated for the impact of rainfall during the previous 48h and the previous week. Survival of egg masses transferred among eight ponds with pH3.66-4.45 and one pond with pH5.18 was significantly reduced (P<or=0.05) only at pH 3.66. Embryonic survival was negatively correlated (P<or=0.05) with the concentration of aluminium in the pond water. The abundance of egg masses was positively correlated (P<or=0.05) with water temperature and magnesium concentration, and total chlorophyll during the larval period. Yearly variability of pond characteristics (e.g. water chemistry, pond longevity) and amphibian reproduction make it difficult to determine the effects of acidic deposition on the spotted salamander. At the present time, pond longevity, water temperature and possibly, oxygen content, seem more important to spotted salamander reproduction than chemical changes caused by annual acidic deposition.

Effects of acid precipitation on embryonic mortality of Ambystoma salamanders in the Connecticut Valley of Massachusetts

The phenomenon of increased embryonic mortality of the spotted salamander Ambystoma maculatum concomitant with breeding pond acidification from acid rainfall was investigated in the Connecticut Valley of Massachusetts. The pH and chemistry of rain and pond water were analysed, and embryonic mortality of spotted and Jefferson salamanders A. jeffersonianum was monitored in 1976 and 1977. Rainfall pH, 4·16 and 4·07 in 1976 and 1977, respectively, indicates that acid rain continues to occur in the area. Ambystoma breeding ponds are acidic, due to background and rainfall acidity. The average pH of six ponds dropped from 5·62 in 1976 to 5·10 in 1977. Pond pH decreased up to 0·75 pH units following heavy rainfall. These trends indicate that pond acidification from acid rain is occurring. Despite pond acidity, embryonic mortality of spotted and Jefferson salamanders was low. For spotted salamanders, mortality ranged from 2·1 to 30·2%, with 15 of 17 ponds below 16%. Embryonic mortality of Jefferson salamanders ranged from 12·4 to 40·3%. No significant correlation between pond pH and percent embryonic mortality was found. Estimates based on numbers of breeding females showed Connecticut Valley spotted salamander populations to be larger than in areas where their decline has been correlated with acid rain. The size of present populations, and the embryonic acid tolerance exhibited by spotted and Jefferson salamanders, indicate that acid rain has not affected their populations in the Connecticut Valley of Massachusetts.