Trait Performance Correlations across Life Stages under Environmental Stress Conditions in the Common Frog,Rana temporaria

If an organism''s juvenile and adult life stages inhabit different environments, certain traits may need to be independently adapted to each environment. In many organisms, a move to a different environment during ontogeny is accompanied by metamorphosis. In such organisms phenotypic induction early in ontogeny can affect later phenotypes. In laboratory experiments we first investigated correlations between body morphology and the locomotor performance traits expressed in different life stages of the common frog, Rana temporaria: swimming speed and acceleration in tadpoles; and jump-distance in froglets. We then tested for correlations between these performances across life stages. We also subjected tadpoles to unchanging or decreasing water levels to explore whether decreasing water levels might induce any carry-over effects. Body morphology and performance were correlated in tadpoles; morphology and performance were correlated in froglets: hence body shape and morphology affect performance within each life stage. However, performance was decoupled across life stages, as there was no correlation between performance in tadpoles and performance in froglets. While size did not influence tadpole performance, it was correlated with performance of the metamorphosed froglets. Experiencing decreasing water levels accelerated development time, which resulted in smaller tadpoles and froglets, i.e., a carry-over effect. Interestingly, decreasing water levels positively affected the performance of tadpoles, but negatively affected froglet performance. Our results suggest that performance does not necessarily have to be correlated between life stages. However, froglet performance is size dependent and carried over from the tadpole stage, suggesting that some important size-dependent characters cannot be decoupled via metamorphosis.     

Odorous and Non-Fatal Skin Secretion of Adult Wrinkled Frog (Rana rugosa) Is Effective in Avoiding Predation by Snakes

The roles played by nonfatal secretions of adult anurans in the avoidance of predation remain unknown. The adult Wrinkled frog (Rana rugosa) has warty skin with the odorous mucus secretion that is not fatal to the snake Elaphe quadrivirgata. We fed R. rugosa or Fejervarya limnocharis, which resembles R. rugosa in appearance and has mucus secretion, to snakes and compared the snakes’ responses to the frogs. Compared to F. limnocharis, R. rugosa was less frequently bitten or swallowed by snakes. The snakes that bit R. rugosa spat out the frogs and showed mouth opening (gaping) behavior, while the snakes that bit F. limnocharis did not show gaping behavior. We also compared the responses of the snakes to R. rugosa and F. limnocharis secretions. We coated palatable R. japonica with secretions from R. rugosa or F. limnocharis. The frogs coated by R. rugosa secretion were less frequently bitten or swallowed than those coated by F. limnocharis secretion. We concluded that compared to different frog species of similar sizes, the adult R. rugosa was less frequently preyed upon by, and that its skin secretion was effective in avoiding predation by snakes.     

Force-Velocity Relationship of Shortening of Blood Vessel of the Common Frog Rana temporaria during Phasic and Tonic Contractions

The relationship between shortening velocity and the applied external load (force-velocity) was studied for vena cava posterior of the frog Rana temporaria. This relationship was determined in 15 s, 2 and 20 min after the beginning of isometric contraction induced by a high KCl concentration (110 mmole/l). It was found that maximal shortening velocity (V₀) was the highest at the 15th s after the beginning of the isometric contraction and amounted to 0.125 ± 0.009 L₀/s (n = 4); then it decreased progressively to 0.058 ± 0.005 L₀/s at the 20th min, respectively. On the contrary, the isometric tension value increased and reached its peak in 5 min after the beginning of contraction, then it decreased slightly. Such phenomenon indicates the occurrence of attached non-cycling bridges. The a/P₀ parameter was equal to 0.15 ± 0.03 and 0.33 ± 0.06 at the 15th s and the 20th min, respectively.     

Spawning Female-Specific Egg Envelope Glycoprotein-Like Substances in Oryzias latipes

In addition to the spawning female-specific (SF) substance (3, 6), a group of new higher molecular weight proteins cross-reacting with anti-egg envelope (chorion) glycoprotein (F1) antibody (original antibody) were found in the liver, blood plasma and the ovary of spawning female fish and in the ascites of the estrogenized fish of Oryzias latipes . Exploiting the antibodies specific for the SF substance and the new proteins, which were made of the original antibody by absorbing with the new proteins or the SF substance, the new proteins were found to behave very similarly to the SF substance concerning their localization in the inner layer of the oocyte envelope, intrahepatic formation in response to estrogen etc. They include the protein bands corresponding to Zl-1 and -2, two major constituent glycoproteins of the oocyte envelope, while the SF substance corresponds to ZI-3, the third major constituent of the envelope. Thus the three major constituent proteins of the inner layer of oocyte envelope are probably formed in the liver under the influence of estrogen in this fish.     

Behavior and Approximate Entropy of Right-eye Lateralization During Predation in the Music Frog

Brain asymmetry for processing visual information is widespread in animals. However, it is still unknown how the complexity of the underlying neural network activities represents this asymmetrical pattern in the brain. In the present study, we investigated this complexity using the approximate entropy(ApEn)protocol for electroencephalogram(EEG) recordings from the forebrain and midbrain while the music frogs(Nidirana daunchina) attacked prey stimulus. The results showed that(1) more significant prey responses were evoked by the prey stimulus presented in the right visual field than that in the left visual field,consistent with the idea that right-eye preferences for predatory behaviors exist in animals including anurans;(2) in general, the ApEn value of the left hemisphere(especially the left mesencephalon) was greatest under various stimulus conditions, suggesting that visual lateralization could be reflected by the dynamics of underlying neural network activities and that the stable left-hemisphere dominance of EEG ApEn may play an important role in maintaining this brain asymmetry.     

Context-dependent aggregation in Common Frog Rana temporaria tadpoles: influence of developmental stage, predation risk and social environment

1. This study examines the aggregation behaviour and activity of larvae of the Common Frog Rana temporaria in relation to the early social environment, ontogeny and the presence of chemical cues from a predatory fish to address three main questions: (i) Does previous social interaction influence aggregation behaviour in later developmental stages? (ii) To what extent does aggregation behaviour depend upon the risk level perceived by the individual? (iii) Does aggregation behaviour change through ontogeny?
2. Tadpoles were reared from eggs either in small groups or in complete isolation. In relatively early stages of development, tadpoles showed no preference for the side of the test container containing siblings over the side containing no larvae regardless of the social context experienced (isolation or contact with siblings).
3. The presence of chemical cues from a potential predator did not trigger the aggregation behaviour of tadpoles, but it had a remarkable effect on their activity and spatial distribution. Tadpoles exposed to water preconditioned by a predator spent significantly less time swimming and avoided the central area of the test container more frequently than did controls exposed to unconditioned water.
4. Tadpoles were more active, avoided the central section and associated preferentially with conspecifics (siblings) at later stages of development regardless of the social conditioning they had previously experienced.
5. Individuals reared in groups were twice as active as individuals reared in isolation. This suggests that the early social environment experienced by larvae can influence future behaviour and thereby growth and development rates.
6. The expression of conspecific attraction is probably linked to an ontogenetic shift in larval behaviour. However, reduced activity, rather than aggregation, appears to be the basic antipredator mechanism in larval Common Frog.     

Ultrastructural Aspects of the Endolymphatic Organ in the Frog Rana esculenta

Morphological evidence indicates that the endolymphatic sac of anuran amphibians is involved in the morphogenesis of most statoconia (aragonite crystals). The cells frequently show the aspect of an intense secretory activity, their cytoplasm being totally occupied by a number of vesicles the contents of which might be expelled into the lumen forming the organic—or at times mineral—components of statoconia. Moreover, evidence is presented that another function of the endolymphatic sac might be involvement in a resorptive mechanism for endolymph and for CaCO₃ mobilization from aragonite crystals. In fact, these show clear signs of erosion, consistent with a role as a labile calcium deposit played by the calcareous formations of the endolymphatic sac.     

Spawning Site Selection and Contingent Behavior in Common Snook,Centropomus undecimalis

Reproductive behavior affects spatial population structure and our ability to manage for sustainability in marine and diadromous fishes. In this study, we used fishery independent capture-based sampling to evaluate where Common Snook occurred in Tampa Bay and if it changed with spawning season, and passive acoustic telemetry to assess fine scale behavior at an inlet spawning site (2007–2009). Snook concentrated in three areas during the spawning season only one of which fell within the expected spawning habitat. Although in lower numbers, they remained in these areas throughout the winter months. Acoustically-tagged snook (n = 31) showed two seasonal patterns at the spawning site: Most fish occurred during the spawning season but several fish displayed more extended residency, supporting the capture-based findings that Common Snook exhibit facultative catadromy. Spawning site selection for iteroparous, multiple-batch spawning fishes occurs at the lifetime, annual, or intra-annual temporal scales. In this study we show colonization of a new spawning site, indicating that lifetime spawning site fidelity of Common Snook is not fixed at this fine spatial scale. However, individuals did exhibit annual and intra-seasonal spawning site fidelity to this new site over the three years studied. The number of fish at the spawning site increased in June and July (peak spawning months) and on new and full lunar phases indicating within population variability in spawning and movement patterns. Intra-seasonal patterns of detection also differed significantly with sex. Common Snook exhibited divergent migration tactics and habitat use at the annual and estuarine scales, with contingents using different overwintering habitat. Migration tactics also varied at the spawning site at the intra-seasonal scale and with sex. These results have important implications for understanding how reproductive behavior affects spatio-temporal patterns of fish abundance and their resilience to disturbance events and fishing pressure.     

Heterogeneity of Mechanisms of Olfactory Transduction in the Frog Rana temporaria

In experiments on the isolated olfactory lining of the frog Rana temporaria, using the method of supravital fluorescent microscopy and pharmacological analysis, it has been shown that olfactory reception of camphor, unlike that of amyl alcohol, is provided not by one, but by two intracellular signaling systems: the tyrosine kinase and phosphoinositide ones. Heterogeneity of the mechanisms of olfactory reception seems to be due to their evolution associated with the appearance of novel odorants in environment.     

Trade-off between larval development rate and Post-metamorphic Traits in the Frog Rana latastei

Development rate early in the ontogeny is believed to correlate positively with fitness. Geographic variation in intrinsic development rate suggests the existence of trade-offs between development rate and other fitness related traits. We investigated whether these trade-offs exist between intrinsic larval development rate and post-metamorphic traits in an organism with a complex life cycle. In laboratory, we measured if the tadpoles of the frog Rana latastei with fast intrinsic development rate have a suboptimal post-metamorphic morphology, by comparing froglets from five populations. Then, we evaluated the relationship between age at metamorphosis, hindlimb length and jumping performance for frogs grown in nature in two populations. Under laboratory conditions, froglets with fast intrinsic development had shorter absolute and shorter size-adjusted tibiofibulas. We observed a strong, positive relationship between tibiofibula length and jumping performance. In nature, froglets from the last metamorphosing population had longer absolute and size-adjusted tibiofibulas, and were able to jump further. The cost of fast development could be the shorter legs of early metamorphosing frogs, and their poor jumping performance. Thus, a fast intrinsic development rate may not always be positively related to lifetime fitness, since delayed effects of larval development persist also across life history stages. Co-ordinating editor: V. Jormalainen     

Local Adaptation and Genetics of Acid-Stress Tolerance in the Moor Frog, Rana arvalis

As potential to adapt to environmental stress can be essential for population persistence, knowledge on the genetic architecture of local adaptation is important for conservation genetics. We investigated the relative importance of additive genetic, dominance and maternal effects contributions to acid stress tolerance in two moor frog (Rana arvalis) populations originating from low and neutral pH habitats. Experiments with crosses obtained from artificial matings revealed that embryos from the acid origin population were more tolerant to low pH than embryos from the neutral origin population in embryonic survival rates, but not in terms of developmental stability, developmental and growth rates. Strong maternal effect and small additive genetic contributions to variation were detected in all traits in both populations. In general, dominance contributions to variance in different traits were of similar magnitude to the additive genetic effects, but dominance effects outweighed the additive genetic and maternal effects contributions to early growth in both populations. Furthermore, the expression of additive genetic variance was independent of pH treatment, suggesting little additive genetic variation in acid stress tolerance. The results suggest that although local genetic adaptation to acid stress has taken place, the current variation in acid stress tolerance in acidified populations may owe largely to non-genetic effects. However, low but significant heritabilities (h ² 0.07–0.22) in all traits – including viability itself – under a wide range of pH conditions suggests that environmental stress created by low pH is unlikely to lower moor frog populations' ability to respond to selection in the traits studied. Nevertheless, acid conditions could lower populations' ability to respond to selection in the long run through reduction in effective population size.     

Habitat Impoverishment and Egg Predation by <Emphasis Type="Italic">Alouatta caraya</Emphasis>

Species response to habitat loss, fragmentation, or alteration ranges from intolerance and extinction to tolerance and population growth. An ability to increase trophic niche breadth is likely to play a key role in promoting tolerance to habitat change in many species. Howlers (Alouatta spp.) are good examples of these tolerant species. Researchers have related their capacity to thrive well in disturbed habitats to their ability to exploit an eclectic vegetarian diet. Despite >50,000 h of observation of habituated free-ranging groups throughout the distribution of Alouatta, no case of intentional ingestion of animal matter has ever been observed. Here, we report an unexpected trophic niche broadening for free-ranging groups of black-and-gold howlers (Alouatta caraya) living in small (≤2 ha) impoverished habitat islands in the State of Rio Grande do Sul, Brazil. We studied 3 isolated social groups (15–17, 12–14, and 5 individuals) and observed 1 of them preying on birds’ nests. We recorded 19 events of egg-eating during 2274 h of observation in 1 group and 2 suspected cases in another. Our findings highlight the dietary flexibility that characterize howlers and contrast with the widely held view that they observe a strictly vegetarian diet.     

寒露林蛙的核型和Ag-NORs研究

采用常规骨髓细胞制片法对产于湖南省双牌县的寒露林蛙的核型及NORs位点进行了观察和分析.结果表明寒露林蛙与分布于我国南方的其他林蛙相同:2n=26,NF=52,为5+8核型模式.寒露林蛙核型为14M+10SM+2ST,无次溢痕,NORs位于第11对染色体长臂的中部.通过比较分析我国2n=26的6种林蛙的核型等细胞遗传学信息,本文结果支持形态分类和分子系统发生的研究结论,认为寒露林蛙是一有效种.     

On Sympathetic Innervation of Muscle Spindles of the Frog Rana temporaria

The work is concerned with solution of a questionable problem, whether there exists a direct sympathetic innervation of muscle spindles. On the isolated total preparations of muscle spindles, with the aid of a specific histochemical fluorescent method using glyoxylic acid, revealed is the sympathetic innervation of these structures: adrenergic terminal axons were found both on the intrafusal muscular fibers and the blood vessels supplying the receptor.     

Morphological Study of Spatial Distribution of Vestibulospinal Neurons in the Frog Rana ridibunda

In the thew frog Rana ridibunda, local microphoretic injections of horseradish peroxidase into various parts of spinal cord were used for study of trajectory of retrograde enzyme-labeled fiber systems and topography of labeled neurons in vestibulospinal nuclei, the source of vestibulospinal fibers. The vestibulospinal tracts were shown to be formed by neurons of lateral vestibular nucleus, although descending vestibular nucleus also is partially involved, while medial vestibular nucleus contributes to even lesser degree. Besides, study of spatial distribution of C- and L-vestibulospinal neurons in the frog did not confirm the presence of the definite somatotopy that is characteristic of vestibular nuclei in mammals.     

Receptor-Mediated Endocytosis of Lysozyme in Renal Proximal Tubules of the Frog Rana Temporaria

The mechanism of protein reabsorption in the kidney of lower vertebrates remains insufficiently investigated in spite of raising interest to the amphibian and fish kidneys as a useful model for physiological and pathophysiological examinations. In the present study, we examined the renal tubular uptake and the internalization rote of lysozyme after its intravenous injection in the wintering frog Rana temporaria using immunohisto- and immunocytochemistry and specific markers for some endocytic compartments. The distinct expression of megalin and cubilin in the proximal tubule cells of lysozyme-injected frogs was revealed whereas kidney tissue of control animals showed no positive immunoreactivity. Lysozyme was detected in the apical endocytic compartment of the tubular cells and colocalized with clathrin 10 min after injection. After 20 min, lysozyme was located in the subapical compartment negative to clathrin (endo-somes), and intracellular trafficking of lysozyme was coincided with the distribution of megalin and cubilin. However, internalized protein was retained in the endosomes and did not reach lysosomes within 30 min after treatment that may indicate the inhibition of intra-cellular trafficking in hibernating frogs. For the first time, we provided the evidence that lysozyme is filtered through the glomeruli and absorbed by receptor-mediated clathrin-dependent endocytosis in the frog proximal tubule cells. Thus, the protein uptake in the amphibian mesonephros is mediated by megalin and cubilin that confirms a critical role of endocytic receptors in the renal reabsorption of proteins in amphibians as in mammals.Key words: Endocytic receptor, frog, kidney, lysozyme, protein uptake, proximal tubule