Alejandra Rua

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.

Two features of this study have furnished direct evidence for the material continuity and individuality of the chromosomes in the epithelial cells of the larvae of Ambystoma tigrinum (1) the tracing of the complete history of a specific chromosome, the nucleolus-containing chromosome, throughout the successive stages of mitosis and interkinesis, (2) the following of the exact parallelism in behavior (during mitosis) of the chromosomes in a given nuclear group with that in a single chromosome which has been isolated in the cytoplasm from the main chromosomal complex.Each of the two nucleoli is subterminally located in the short arm of one of two particular V-shaped chromosomes. The latter are probably homologues.78: In this subterminal chromosomal position the nucleolus exhibits in fixed and stained preparations an achromatic character in late prophase, metaphase, anaphase and early telophase, while it presents itself as a chromatic element in middle telophase, late telophase, interkinesis and early prophase.The nucleolus is not a simple homogeneous body, but rather a complex structure, the nature of which is revealed in the study of its evolution during the chromatic phase of its cycle in mitosis.

... Further. he found younger larvae "in the stomachs of a nuniber of second-year larvae shortly after they nrere collected." He did not quantify canni-balism by older animals, but argued that older larvae ate most, if not all, younger larvae in ponds llear Crested Butte, CO. ...

High speed cinematography was used to record the feeding activities of terrestrial Ambystoma tigrinum melanostictum. A description of these activities based on films of more than 50 feeding sequences is presented, and the mechanical units involved are defined, described, and functionally analyzed. Evolutionary implications of the feeding system are discussed.In a typical feeding sequence, A. t. melanostictum stations and maintains its lower jaw 3-5 mm from the prey. The mouth is then opened to form a gape of ∼60° by raising the anterior end of the flexed skull and by elevating and advancing the trunk while the mental symphysis of the lower jaw remains stationary. As the mouth opens the bulging tongue is recontoured so that the posterior glandular region becomes the tip of the fully protruded tongue, which may extend 3 to 7 mm beyond the symphysis. Dorsally the protruded tongue has a deep central depression and pronounced anterolateral rims. The anterior rim collapses on contact, thereby engulfing the prey in a sticky trough that retains it during tongue withdrawal. The cervical region is then flexed and the skull snaps downward. If the prey resists the tongue and is captured by marginal teeth, A. t. melanostictum relies on repeated tongue protraction and retraction, in some cases accompanied by inertial feeding. Swallowing involves gular expansion and contraction, and is accompanied by eye depression. When the mouth is opened during ingestive activities, the lower jaw remains in place.Apparently, A. t. melanostictum uses the dorsal trunk, the cucullaris major and the robust heads of the depressor mandibulae muscles to open the mouth. During skull elevation the lower jaw is partially immobilized by the geniohyoideus, and rectus cervicis superficialis muscles. The subarcualis rectus I muscles are prime movers in tongue projection. Hebosteoypsiloideus muscles assist in tongue protrusion by slackening the rectus cervicis profundus muscles that would otherwise restrict anterior displacement of the otoglossal cartilage and copula. Tongue contouring is performed by the complex genioglossus musculature. Sublingual and anterolingual sinuses facilitate protrusion and contouring by providing space and lubrication. Rectus cervicis muscles (profundus and superficialis) are responsible for tongue withdrawal. Closure of the mouth is accomplished by the four levator mandibulae muscles, and again the lower jaw is immobilized, mostly by ventral longitudinal muscles.Skull-trunk elevation during prey capture and ingestion was also observed and filmed in several other species of Ambystoma, in Dicamptodon ensatus, and in two salamandrid species. Apparently raising and straightening the craniovertebral axis, while the mental symphysis retains contact with the substratum, is a common feature of urodele feeding systems, and does not require peculiar morphological adaptations.

The process of metamorphosis in tiger salamanders, Ambystoma tigrinum, is used to investigate motor pattern conservatism in vertebrates. Specifically, we examined cranial muscle activity to determine if changes in the motor pattern are correlated with the morphological or environmental changes that occur at metamorphosis.Twenty-three variables were measured from electromyographic recordings from six cranial muscles in 13 tiger salamanders. These variables described the configuration of the motor pattern: the peak amplitude of activity, duration, relative onset, and time to peak amplitude were measured for each of the six muscles. Univariate and multivariate statistical analyses showed that there was no change in the mean motor pattern associated with the morphological transformation at metamorphosis: larval and metamorphosed individuals feeding in the water have very similar motor patterns. This was true despite significant morphological changes in the design of the feeding mechanism at metamorphosis and despite a significant decrease in aquatic feeding performance following metamorphosis.There was a change in the mean motor pattern to jaw muscles when metamorphosed individuals fed in water and on land: metamorphosed terrestrial feedings tend to have longer bursts of muscle activity then do aquatic feedings. The environmental changes in the motor pattern cannot be attributed to effects of differing fluid density or viscosity between water and air and are instead related to the shift to feeding by tongue projection on land.The decrease in aquatic feeding performance that occurs after metamorphosis is not correlated with changes in the motor pattern. Instead, the results suggest that changes in behavioral performance during ontogeny are associated with the transformation of hydrodynamic design of the feeding mechanism from uni- to bidirectional, and that motor patterns driving complex rapid behaviors may be conserved when behavior is altered by changes in peripheral morphology.

The two species of mole salamander that occur in the Ithaca, New York, region (Ambystoma maculatum and A. jeffersonianum) breed in temporary ponds that are formed by accumulation of melted snow and spring rains. Water in many of these pools during the breeding season is acid; pH values as low as 3.5 have been measured. In laboratory experiments A. maculatum tolerated pHs from 6 to 10 and had greatest hatching success at pH 7 to 9. Ambystoma jeffersonianum tolerated pH 4 to 8 and was most successful at pH 5 to 6. Mortality rose abruptly beyond the tolerance limits. The pH optimum shifted upward with increasing temperature for A. jeffersonianum and downward for A. maculatum. Judging from our laboratory studies, the acidity measured in breeding ponds should cause mortality in A. maculatum and permit normal development in A. jeffersonianum. In a 4 yr study of a large, acidic vernal pond, 938 adult A. maculatum produced 486 metamorphosed juveniles (0.52 juvenile/adult), while 686 adult A. jeffersonianum produced 2157 juveniles (3.14 juveniles/adult). Because the effects of acid precipitation on the salamanders' breeding ponds are cumulative from year to year, profound changes in the salamander populations can be anticipated.

Solitary rod inner segments were isolated from salamander retinae. Their Ca current was studied with the 'whole-cell, gigaseal' technique (Hamill, Marty, Neher, Sakmann & Sigworth, 1981). The soluble constituents of the cytoplasm exchanged with the solution in the pipette. The external solution could be changed during continuous perfusion. Membrane voltage was controlled with a voltage clamp. After permeant ions other than Ca were replaced with impermeant ions (i.e. tetraethylammonium as a cation, and aspartate or methanesulphonate as an anion), an inward current remained. It activated at approximately -40 mV, reached a maximum at approximately 0 mV, and decreased as the membrane was further depolarized. The size of the current increased when Ba was substituted for external Ca. The current was blocked when Ca was replaced with Co. The voltage at which the current was half-maximum shifted from approximately -22 to -31 mV during the initial 3 min of an experiment. The maximum amplitude of the current continuously declined during the entire course of an experiment. The time course for activation of the Ca current following a step of depolarization could be described by the sum of two exponentials. The time constant of the slower exponential was voltage dependent. Deactivation following repolarization could also be described by the sum of two exponentials. Both time constants for deactivation were independent of voltage (between -30 and 0 mV) and faster than the slower time constant for activation. When the internal Ca concentration was buffered by 10 mM-EGTA, the Ca current did not inactivate during several seconds of maintained depolarization. When the concentration of EGTA was reduced to 0.1 mM, the Ca current declined and the membrane conductance decreased during several seconds of maintained depolarization. This inactivation was incomplete and only occurred after a substantial quantity of Ca entered. Following repolarization the Ca conductance recovered from inactivation. In contrast, the continuous decline observed during the course of an experiment (item 3) was not reversible. The difference suggests that inactivation and the decline are distinct processes.

The oocytes of naturally occurring triploid females of the Ambystoma jeffersonianum complex each contain 84 lampbrush chromosomes. This constitutes hexaploidy (n = 14). The chromosomes are joined into pairs by chiasmata and form 42 bivalents. It is suggested that meiosis in triploid females is preceded by an endomitosis and the resulting sister chromosomes synapse to form pseudo-bivalents. Sperm from diploid males stimulate development of the triploid eggs but do not contribute chromosomes to the triploid nucleus. Bivalents in the oocytes of triploids have twice as many chiasmata as the corresponding bivalents in diploid animals. Such chiasmata cannot result in genetic recombination.

The terrestrial activity and summer home range of Ambystoma talpoideum is described in two populations in South Carolina. Emigration of adults from breeding sites occurred from March through May during 1979 and 1980. Adults spent 237-354 days in terrestrial ...

To investigate possible biological effects of acidic deposition in the western United States, we performed population censuses and dose-response experiments at a subalpine watershed in the Rocky Mountains of Colorado, An adult tiger salamander (Ambystoma tigrinum nebulosum) population declined by 65% over seven years, while larval recruitment declined over all but the last year of his period A. tigrinum eggs had an LD-50 pH of 5.6, which is within the range encountered by eggs at this site during snow melt. Although the decline of A. tigrinum at this watershed could be a natural fluctuation, the available evidence is consistent with the bypothesis that acidic deposition is its cause. Thus, the decline of A. tigrinum at the watershed may be the first indication of biological damage from acidic deposition in the western United StatesPara investigar los posibles efectos biológicos de lluvia ácaida en el oeste de los Estados Unidos, se llevaron a cabo censos poblacionales de salamandras y experimentos deevaluación de respuesta a varias dosijicaciones en una cuenca subalpina en las Montañas Rocosas del Estado de Colorado. Una población adulta de salamundras tigre (Ambystoma tigrinum nebulosum) tuvo un descenso de 65% ensiete años, mientras el reclutamiento de larvas disminuyó en general salvo en el ultimo año de este perí'odo. Huatos de A. tigrinum tuvieron un pH de 5.6(LD-50), valor que se encuentra en el rango usual para este luagar medido durante el período de desahielo. Aunque el descenso de A. tigrinurn en esta cuenca puede deberse a una fluctuación natural la evidencia disponible es consistente con la hipótesis de que su causa se debe a las deposiciones por lluvia ácida Por. lo tanto, el descenso de A. tigrinurn en la cuenca puede ser la primera indicación de daño biológico de los llivia acida en el oeste de los Estados Unidos.

The reproductive strategy of the salamander Ambystoma talpoideum was studied on an age-specific basis in five breeding populations using ponds subjected to different annual probabilities of drying. Ambystoma talpoideum is facultatively paedomorphic in semi-permanent ponds but sexually mature individuals occur only as terrestrial morphs in temporary ponds. Larvae of paedomorphs and terrestrial morphs mature at the same age but different body sizes. Body mass and snout-vent length increased with age in both morphs. One-year old terrestrial morphs had larger snoutvent lengths than 1-year-old paedomorphs but were smaller in body mass. Clutch mass, number of ova, and diameter of ova increased with snout-vent length. After removing the effects of snout-vent length with an analysis of covariance, only the diameter of ova and the resultant clutch mass increased with age. One-year-old terrestrial morphs produced more ova than 1-year-old paedomorphs but paedomorphs have the potential to reproduce earlier than terrestrial morphs. Parental investment, as shown by the relationship between clutch size and egg size, increased with age. This suggested that as potential energy increased with age, A. talpoideum produced more eggs and larger eggs. Rather than optimizing egg size, individuals may produce a range of egg sizes that theoretically fare better in spatially and temporally varying environments.

Migrating Ambystoma maculatum tend to utilize the same track on entering and leaving breeding ponds. The movements are usually accom plished at night in rain, fog, or cloudy, weather when visible celestial cues may not be available. The sensory basis for the orienting ability is unknown.

Abstract. Populations of six species of amphibians were manipulated in field enclosui es to study the biological tractability of current concepts of the organization of natural com-munities. Experimental communities with a known composition of mature eggs were intro-duced into screen ...

Abstract. Two species of salamander (Ambystoma) and a frog (Rana sylvatica) were raised at a variety of initial densities in enclosures in a pond to study the effect of population density on survival and body size at metamorphosis. The relationship between the probability of ...

... Sand Point Way NE, Seattle, Washington 98115-0070, USA 3 Department of Microbiology and Molecular and Cellular Biology Program, Arizona State University, Tempe, Arizona 85287-1144, USA. *Addressee for correspondence. E-mail: e.davidson@asu.edu. The Sonora tiger ...

Factors that affect traits of aquatic larvae of amphibians may have long-lasting effects on terrestrial juveniles and adults. I manipulated larval densities of marbled salamanders, Ambystoma opacum, in large-scale field enclosures during 2 yr, released the juveniles ...