Air-breathing behavior underlies the cell death in limbs of Rana pirica tadpoles.

Amphibians shape their limbs by differential outgrowth of digits and interdigital regions. In contrast, amniotes employ cell death, an additional developmental system, to determine the final shape of limbs. Previous work has shown that high oxygen availability is correlated with the induction of cell death in developing limbs. Given the diversity of life histories of amphibians, it is conceivable that some amphibians are exposed to a high-oxygen environment during the tadpole phase and exhibit cell death in their limbs. Here, we examined whether air-breathing behavior underlies the cell death in limbs of aquatic tadpoles of the frog species Rana pirica. Our experimental approach revealed that R. pirica tadpoles exhibit cell death in their limbs that is likely to be induced by oxidative stress associated with their frequent air-breathing behavior.

Switching of behavioral modes and their modulation by a geometrical cue in the ciliate Stentor coeruleus.

Protists ubiquitously live in nature and play key roles in the food web chain. Their habitats consist of various geometrical structures, such as porous media and rigid surfaces, affecting their motilities. A kind of protist, Stentor coeruleus, exhibits free swimming and adhering for feeding. Under environmental and culture conditions, these organisms are often found in sediments with complex geometries. The determination of anchoring location is essential for their lives. However, the factors that induce the behavioral transition from swimming to adhering are still unknown. In this study, we quantitatively characterized the behavioral transitions in S. coeruleus and observed the behavior in a chamber with dead ends made by a simple structure mimicking the environmental structures. As a result, the cell adheres and feeds in narrow spaces between the structure and the chamber wall. It may be reasonable for the organism to hide itself from predators and capture prey in these spaces. The behavioral strategy for the exploration and exploitation of spaces with a wide variety of geometries in their habitats is discussed.

Size-dependent growth tactics of a partially migratory fish before migration.

In many migratory species, smaller migrants suffer higher mortality rates during the risky migration. To minimize the size-selective mortality, migrants with smaller body sizes would need to accelerate growth rates or delay migration timing to attain a large enough body size prior to migration. To test these predictions, we investigated size-dependent patterns of growth rates and migration timing of juvenile masu salmon (Oncorhynchus masou) before their oceanic migration. We tracked uniquely marked individuals in a study population consisted of oceanic migrants and river-dwelling residents using mark-recapture surveys and PIT-tag antenna-reader system. Data supported our predictions about size-dependent growth rates and migration timing. For approximately 6 months before outmigration (i.e., between the decision of migration and the start of migration), eventual migrants grew more than residents if their initial size was smaller, but such a difference in growth rate diminished for fish with larger initial sizes. In addition, smaller eventual migrants delayed the timing of outmigration compared to larger individuals, to attain a larger body size in the river prior to migration. These results suggest that size-selective mortality during migration has shaped size-dependent patterns of the pre-migration growth in migratory masu salmon. Size-conditional changes in growth rate and duration of pre-migration period may be an adaptive tactic for the migratory animals.

Predators mitigate the destabilising effects of heatwaves on multitrophic stream communities.

Amidst the global extinction crisis, climate change will expose ecosystems to more frequent and intense extreme climatic events, such as heatwaves. Yet, whether predator species loss-a prevailing characteristic of the extinction crisis-will exacerbate the ecological consequences of extreme climatic events remains largely unknown. Here, we show that the loss of predator species can interact with heatwaves to moderate the compositional stability of ecosystems. We exposed multitrophic stream communities, with and without a dominant predator species, to realistic current and future heatwaves and found that heatwaves destabilised algal communities by homogenising them in space. However, this happened only when the predator was absent. Additional heatwave impacts on multiple aspects of stream communities, including changes to the structure of algal and macroinvertebrate communities, as well as total algal biomass and its temporal variability, were not apparent during heatwaves and emerged only after the heatwaves had passed. Taken together, our results suggest that the ecological consequences of heatwaves can amplify over time as their impacts propagate through biological interaction networks, but the presence of predators can help to buffer such impacts. These findings underscore the importance of conserving trophic structure, and highlight the potential for species extinctions to amplify the effects of climate change and extreme events.

Paedomorphosis in the Ezo salamander (Hynobius retardatus) rediscovered after almost 90 years.

Although paedomorphosis is widespread across salamander families, only two species have ever been documented to exhibit paedomorphosis in Hynobiidae. One of these two exceptional species is Hynobius retardatus in which paedomorphosis was first reported in 1924, in specimens from Lake Kuttara in Hokkaido. This population became extinct after the last observation in 1932; since then, no paedomorphs of this species have been reported anywhere. Here, we report the rediscovery of paedomorphs of this species. Three paedomorph-like male salamanders were collected from a pond in the south Hokkaido in December 2020 and April 2021; in size, these specimens were similar to metamorphosed adults but they still displayed larval features such as external gills and a well-developed caudal fin. An artificial fertilization experiment demonstrated that they were sexually compatible with metamorphosed females, thus, confirming them to be paedomorphs. Future efforts to find additional paedomorphs in this and other populations are required to assess the prevalence of paedomorphosis in H. retardatus and to improve understanding of the ecology and evolution of paedomorphisis in Urodela.

Helicobacter pylori eradication prevents secondary gastric cancer in patients with mild-to-moderate atrophic gastritis.

BACKGROUND AND AIM: Whether Helicobacter pylori eradication prevents metachronous recurrence after endoscopic resection (ER) of early gastric cancer remains controversial. This multicenter retrospective study aimed to evaluate the long-term (> 5 years) effects of H. pylori eradication by stratifying patients' baseline degrees of atrophic gastritis. METHODS: A total of 483 H. pylori-positive patients who had undergone ER for early gastric cancer were divided into two groups-(i) those having undergone successful H. pylori eradication within 1 year after ER (eradicated group, n = 294) and (ii) those with failed or not attempted H. pylori eradication (non-eradicated group, n = 189). The cumulative incidences of metachronous gastric cancer between the two groups were compared for all patients, for patients with mild-to-moderate atrophic gastritis (n = 182), and for patients with severe atrophic gastritis (n = 301). RESULTS: During a median follow-up of 5.2 years (range 1.1-14.8), metachronous cancer developed in 52 (17.7%) patients in the eradicated group and in 35 (18.5%) patients in the non-eradicated group (P = 0.11, log-rank test). In patients with mild-to-moderate atrophic gastritis (111 and 71 in the eradicated and non-eradicated groups, respectively), the cumulative incidence of metachronous cancer was significantly lower in the eradicated group than that in the non-eradicated group (P = 0.03, log-rank test). However, no significant intergroup difference was observed in patients with severe atrophic gastritis (P = 0.69, log-rank test). CONCLUSIONS: Helicobacter pylori eradication had a preventive effect on the development of metachronous gastric cancer in patients with mild-to-moderate atrophic gastritis.

Demography and productivity during the recovery time sequence of a wild edible bamboo after large-scale anthropogenic disturbance.

Anthropogenic disturbances in forest management practices can affect wild edible plants. Soil scarification is a large-scale disturbance that may cause long-term reduction in productivity of edible dwarf bamboo, Sasa kurilensis, in northern Japan. For their effective and sustainable use, we need to understand the recovery process after such disturbances. At 14 study sites in the Teshio Experimental Forest of Hokkaido University where soil scarification had been conducted between 2 and 44 years prior, the number and stem diameter of old and young (newly emerged, edible) culms was recorded. At sites that were within 11 years of soil scarification, the proportion of old culms (<11%) was lower than in the control area where soil scarification had never been conducted. At sites where more than 15 years had passed since soil scarification, the relative number of old culms was nearly equal to that in control area. Additionally, the number of young culms increased with an increasing number of old culms. These results suggest that recovery of productivity (in term of number) of edible culms may take a few decades. In contrast, the culm diameter of young culms increased linearly with time since soil scarification, but the 95% confidence interval in this relationship suggests that dwarf bamboo can produce thick edible culms soon after soil scarification. These findings will provide useful insights into how to obtain high quality bamboo culms following anthropogenic disturbances in future.

Expression of Genes Involved in Offensive and Defensive Phenotype Induction in the Pituitary Gland of the Hokkaido Salamander (Hynobius retardatus).

Amphibians exhibit phenotypic plasticity, which allows flexible adaptation to fluctuating environments. Although genes involved in expression of plastic phenotypes have been identified, the endocrine bases of plastic responses are largely unknown. Larvae of the Hokkaido salamander (Hynobius retardatus) plastically display distinct phenotypes, an "offensive phenotype" characterized as larger body with broadened gape and a "defensive phenotype" characterized as enlarged gills and tail and less active behavior, in the presence of prey larval amphibians and predatory larval dragonfly, respectively. In the presence of both prey and predators, the degree of induction of both phenotypes is reduced, suggesting cross-talk between the molecular signaling pathways of these phenotypes. We conducted a transcriptomic analysis to examine how endocrine regulation affects the phenotypic expression by focusing on the pituitary gland. We found that five endocrine genes, i.e., calcitonin related polypeptide alpha (CALCA), growth hormone (GH), neuropeptide B (NPB), parathyroid hormone 2 (PTH2), and prolactin 1 (PRL1), were involved in the expression of both phenotypes. However, we conducted only RNA-seq analysis, and no confirmation of significant up-regulation or down-regulation has been conducted. These results suggest that these genes were up-regulated for induction of the offensive phenotype and down-regulated for induction of the defensive phenotype. Phylogenetic analysis indicated that possible gene duplications of PRL and CALCA have occurred during amphibian evolution. Based on these findings, it is suggested that a trade-off of molecular signaling pathways exists between the two distinct phenotypic expressions. The results also suggest that hormonal-gene duplications might have contributed to the acquisition of phenotypic plasticity in amphibians.

Enhanced recruitment of larger predators in the presence of large prey.

Most carnivores undergo diet shift from smaller to larger prey items during ontogeny. The trophic relationship between a growing carnivore and larger prey is representative of a size-structured predator-prey interaction. The strength of this interaction is, in part, determined by the recruitment of individuals from smaller predatory size classes into larger predatory size classes. Therefore, it is interesting to investigate how larger prey alter the recruitment of smaller predator size classes into larger predator size classes, since this can affect their own future predation risk. Past empirical studies have exclusively documented that large prey reduce predator recruitment by decreasing growth and/or survival of the smaller predators. In this study, we provide empirical evidence of the contrasting pattern: large prey enhance the recruitment of smaller predators into larger predators even though they increase cannibalism mortality of the smaller predators. We have done this here by studying the trophic interaction between predatory salamander larvae Hynobius retardatus and the frog tadpoles Rana pirica that represent their large prey. In a field experiment in which salamander hatchlings were exposed to the presence or absence of large frog tadpoles, we found that more giant salamanders emerged in the presence of frog tadpoles than in their absence. Reassignment of frog tadpoles (to both treatments) in the subsequent experimental period showed that the enhanced emergence of giant salamanders in the presence of frog tadpoles leads to the intensification of salamander predation on the frog tadpoles. In an additional laboratory experiment, to better understand the underlying mechanisms, we manipulated both the presence of frog tadpoles and the occurrence of cannibalism between salamander hatchlings. This experiment revealed that frog tadpoles intensify the cannibalism of salamander larvae during their hatchling stage, thus allowing more salamander larvae to become large-sized predators. Our results suggest that frog tadpoles can inadvertently intensify their own future predation risk by intensifying cannibalistic interactions among predatory salamander hatchlings, thereby enhancing the degree of predator recruitment to a larger size class. Hence, large prey can enhance the recruitment of individuals from small predator size classes into larger predator size classes.

Classification for invasion depth of esophageal squamous cell carcinoma using a deep neural network compared with experienced endoscopists.

BACKGROUND AND AIMS: Cancer invasion depth is a critical factor affecting the choice of treatment in patients with superficial squamous cell carcinoma (SCC). However, the diagnosis of invasion depth is currently subjective and liable to interobserver variability. METHODS: We developed a deep learning-based artificial intelligence (AI) system based on Single Shot MultiBox Detector architecture for the assessment of superficial esophageal SCC. We obtained endoscopic images from patients with superficial esophageal SCC at our facility between December 2005 and December 2016. RESULTS: After excluding poor-quality images, 8660 non-magnified endoscopic (non-ME) and 5678 ME images from 804 superficial esophageal SCCs with pathologic proof of cancer invasion depth were used as the training dataset, and 405 non-ME images and 509 ME images from 155 patients were selected for the validation set. Our system showed a sensitivity of 90.1%, specificity of 95.8%, positive predictive value of 99.2%, negative predictive value of 63.9%, and an accuracy of 91.0% for differentiating pathologic mucosal and submucosal microinvasive (SM1) cancers from submucosal deep invasive (SM2/3) cancers. Cancer invasion depth was diagnosed by 16 experienced endoscopists using the same validation set, with an overall sensitivity of 89.8%, specificity of 88.3%, positive predictive value of 97.9%, negative predictive value of 65.5%, and an accuracy of 89.6%. CONCLUSIONS: This newly developed AI system showed favorable performance for diagnosing invasion depth in patients with superficial esophageal SCC, with comparable performance to experienced endoscopists.

Clinical use of molecular targeted agents for primary small bowel adenocarcinoma: A multicenter retrospective cohort study by the Osaka Gut Forum.

Primary small bowel adenocarcinoma (SBA) is a rare cancer for which effective treatment strategies have not yet been established. The results of previous retrospective studies suggest that chemotherapy contributes to a longer survival time in patients with SBA. However, there are few case reports about the efficacy of molecular targeted agent-containing chemotherapy for SBA. In the present study, the treatment and follow-up data of patients with SBA who received chemotherapy with or without molecular targeted agents were retrospectively analyzed. Each patient was treated in one of ten hospitals participating in the Osaka Gut Forum between April 2006 and March 2014. The following factors were evaluated: Age, sex, Eastern Cooperative Oncology Group performance status (PS), tumor location, tumor differentiation, chemotherapy regimen, resection of primary tumor, tumor biomarker expression, distant metastasis, best response under chemotherapy, time to disease progression, subsequent treatments, survival status and treatment toxicity. A total of 27 patients (17 males and 10 females; mean age, 63.4 years old; range, 36-83 years old) received chemotherapy due to non-curative tumor resection, unresectable tumor or post-operative recurrence. The median overall survival time was 14.8 months (range, 2-58 months). A univariate analysis revealed a PS of 0 (P=0.0228) and treatment with platinum-based chemotherapy (P=0.0048) were significant factors for an improved prognosis. An age-adjusted multivariate analysis also revealed that a platinum-based regimen was a significant positive prognostic factor (P=0.0373). Molecular targeted agents were administered to 8 patients, for whom it was their first- or second-line therapy. Among the 17 patients who received oxaliplatin-based chemotherapy as a first-line chemotherapy, a PS of 0 (P=0.0255) and treatment with bevacizumab (P=0.0121) were significant positive prognostic factors. Toxicities higher than Grade 3 occurred in 8/27 patients with SBA; however, serious side effects due to the molecular targeted agents were not experienced. The results of the present study indicate that chemotherapy containing molecular targeted agents is a well-tolerated and effective treatment option for SBA.

Environmental DNA enables detection of terrestrial mammals from forest pond water.

Terrestrial animals must have frequent contact with water to survive, implying that environmental DNA (eDNA) originating from those animals should be detectable from places containing water in terrestrial ecosystems. Aiming to detect the presence of terrestrial mammals using forest water samples, we applied a set of universal PCR primers (MiMammal, a modified version of fish universal primers) for metabarcoding mammalian eDNA. The versatility of MiMammal primers was tested in silico and by amplifying DNAs extracted from tissues. The results suggested that MiMammal primers are capable of amplifying and distinguishing a diverse group of mammalian species. In addition, analyses of water samples from zoo cages of mammals with known species composition suggested that MiMammal primers could successfully detect mammalian species from water samples in the field. Then, we performed an experiment to detect mammals from natural ecosystems by collecting five 500-ml water samples from ponds in two cool-temperate forests in Hokkaido, northern Japan. MiMammal amplicon libraries were constructed using eDNA extracted from water samples, and sequences generated by Illumina MiSeq were subjected to data processing and taxonomic assignment. We thereby detected multiple species of mammals common to the sampling areas, including deer (Cervus nippon), mouse (Mus musculus), vole (Myodes rufocanus), raccoon (Procyon lotor), rat (Rattus norvegicus) and shrew (Sorex unguiculatus). Many previous applications of the eDNA metabarcoding approach have been limited to aquatic/semiaquatic systems, but the results presented here show that the approach is also promising even for forest mammal biodiversity surveys.

Contacts with large, active individuals intensify the predation risk of small conspecifics.

Size variation within a population can influence the structure of ecosystem interactions, because ecological performance differs between individuals of different sizes. Although the impact of size variation in a predator species on the structure of interactions is well understood, our knowledge about how size variation in a prey species might modify the interactions between predators and prey is very limited. Here, by examining the interactions between predatory Hynobius retardatus salamander larvae and their prey, Rana pirica frog tadpoles, we investigated how large prey individuals affect the predation mortality of small prey conspecifics. First, in an experiment conducted in a field pond in which we manipulated the presence of salamanders and large tadpoles (i.e., large enough to protect them against salamander predation) with small tadpoles, we showed that in the presence of large tadpoles the mortality of small tadpoles from salamander predation was increased. On the basis of our observations of the activity of individuals, we hypothesized that active large tadpoles caused physical disturbances, which in turn caused the small tadpoles to move, and thus increased their encounter frequency with the predatory salamanders. To test this hypothesis, we conducted a laboratory experiment in small tanks with three players (i.e., one salamander as predator, one small tadpole as focal prey, and either a small or a large tadpole as the prospective movement inducer). In each tank, we manipulated the presence or absence of a movement inducer, and, when present, its size (large or small) and access (caged or uncaged) to the focal prey. In the presence of a large, uncaged movement inducer, the focal prey was more active and suffered from higher predation mortality compared with the other treatments, because the large movement inducer (unlike a small movement inducer) moved actively and, when uncaged, could stimulate movement of the focal prey through direct contact. The results indicated that high activity of large prey individuals and the resulting behavioral interactions with small conspecifics via direct contact indirectly increased the mortality of the small prey.

Networks Depicting the Fine-Scale Co-Occurrences of Fungi in Soil Horizons.

Fungi in soil play pivotal roles in nutrient cycling, pest controls, and plant community succession in terrestrial ecosystems. Despite the ecosystem functions provided by soil fungi, our knowledge of the assembly processes of belowground fungi has been limited. In particular, we still have limited knowledge of how diverse functional groups of fungi interact with each other in facilitative and competitive ways in soil. Based on the high-throughput sequencing data of fungi in a cool-temperate forest in northern Japan, we analyzed how taxonomically and functionally diverse fungi showed correlated fine-scale distributions in soil. By uncovering pairs of fungi that frequently co-occurred in the same soil samples, networks depicting fine-scale co-occurrences of fungi were inferred at the O (organic matter) and A (surface soil) horizons. The results then led to the working hypothesis that mycorrhizal, endophytic, saprotrophic, and pathogenic fungi could form compartmentalized (modular) networks of facilitative, antagonistic, and/or competitive interactions in belowground ecosystems. Overall, this study provides a research basis for further understanding how interspecific interactions, along with sharing of niches among fungi, drive the dynamics of poorly explored biospheres in soil.

An aquatic vertebrate can use amino acids from environmental water.

Conventional food-web theory assumes that nutrients from dissolved organic matter are transferred to aquatic vertebrates via long nutrient pathways involving multiple eukaryotic species as intermediary nutrient transporters. Here, using larvae of the salamander Hynobius retardatus as a model system, we provide experimental evidence of a shortcut nutrient pathway by showing that H. retardatus larvae can use dissolved amino acids for their growth without eukaryotic mediation. First, to explore which amino acids can promote larval growth, we kept individual salamander larvae in one of eight different high-concentration amino acid solutions, or in control water from which all other eukaryotic organisms had been removed. We thus identified five amino acids (lysine, threonine, serine, phenylalanine, and tyrosine) as having the potential to promote larval growth. Next, using 15N-labelled amino acid solutions, we demonstrated that nitrogen from dissolved amino acids was found in larval tissues. These results suggest that salamander larvae can take up dissolved amino acids from environmental water to use as an energy source or a growth-promoting factor. Thus, aquatic vertebrates as well as aquatic invertebrates may be able to use dissolved organic matter as a nutrient source.

Predator cannibalism can intensify negative impacts on heterospecific prey.

Although natural populations consist of individuals with different traits, and the degree of phenotypic variation varies among populations, the impact of phenotypic variation on ecological interactions has received little attention, because traditional approaches to community ecology assume homogeneity of individuals within a population. Stage structure, which is a common way of generating size and developmental variation within predator populations, can drive cannibalistic interactions, which can affect the strength of predatory effects on the predator's heterospecific prey. Studies have shown that predator cannibalism weakens predatory effects on heterospecific prey by reducing the size of the predator population and by inducing less feeding activity of noncannibal predators. We predict, however, that predator cannibalism, by promoting rapid growth of the cannibals, can also intensify predation pressure on heterospecific prey, because large predators have large resource requirements and may utilize a wider variety of prey species. To test this hypothesis, we conducted an experiment in which we created carnivorous salamander (Hynobius retardatus) populations with different stage structures by manipulating the salamander's hatch timing (i.e., populations with large or small variation in the timing of hatching), and explored the resultant impacts on the abundance, behavior, morphology, and life history of the salamander's large heterospecific prey, Rana pirica frog tadpoles. Cannibalism was rare in salamander populations having small hatch-timing variation, but was frequent in those having large hatch-timing variation. Thus, giant salamander cannibals occurred only in the latter. We clearly showed that salamander giants exerted strong predation pressure on frog tadpoles, which induced large behavioral and morphological defenses in the tadpoles and caused them to metamorphose late at large size. Hence, predator cannibalism arising from large variation in the timing of hatching can strengthen predatory effects on heterospecific prey and can have impacts on various, traits of both predator and prey. Because animals commonly broaden their diet as they grow, such negative impacts of predator cannibalism on the heterospecific prey may be common in interactions between predators and prey species of similar size.

Transcriptome analysis of predator- and prey-induced phenotypic plasticity in the Hokkaido salamander (Hynobius retardatus).

Predator- and prey-induced phenotypic plasticity is widely observed among amphibian species. Although ecological factors inducing diverse phenotypic responses have been extensively characterized, we know little about the molecular bases of variation in phenotypic plasticity. Larvae of the Hokkaido salamander, Hynobius retardatus, exhibit two distinct morphs: the presence of their prey, Rana pirica tadpoles, induces a broad-headed attack morph, and the presence of predatory dragonfly nymphs (Aeshna nigroflava) induces a defence morph with enlarged external gills and a high tail. To compare the genes involved in predator- and prey-induced phenotypic plasticity, we carried out a de novo transcriptome analysis of Hokkaido salamander larvae exposed to either prey or predator individuals. First, we found that the number of genes involved in the expression of the defence morph was approximately five times the number involved in the expression of the attack morph. This result is consistent with the fact that the predator-induced plasticity involves more drastic morphological changes than the prey-induced plasticity. Second, we found that particular sets of genes were upregulated during the induction of both the attack and defence morphs, but others were specific to the expression of one or the other morph. Because both shared and unique molecular mechanisms were used in the expression of each morph, the evolution of a new plastic phenotype might involve both the co-option of pre-existing molecular mechanisms and the acquisition of novel regulatory mechanisms.

Gene expression profiles in Rana pirica tadpoles following exposure to a predation threat.

BACKGROUND: Rana pirica tadpoles show morphological changes in response to a predation threat: larvae of the dragonfly Aeshna nigroflava induce heightened tail depth, whereas larval salamander Hynobius retardatus induce a bulgy morphology with heightened tail depth. Although both predators induce similar tail morphologies, it is possible that there are functional differences between these tail morphs. RESULTS: Here, we performed a discriminant microarray analysis using Xenopus laevis genome arrays to compare tail tissues of control and predator-exposed tadpoles. We identified 9 genes showing large-scale changes in their expression profile: ELAV-like1, methyltransferase like 7A, dolichyl-phosphate mannosyltransferase, laminin subunit beta-1, gremlin 1, BCL6 corepressor-like 1, and three genes of unknown identity. A further 80 genes showed greater than 5 fold differences in expression after exposure to dragonfly larvae and 81 genes showed altered expression after exposure to larval salamanders. Predation-threat responsive genes were identified by selecting genes that reverted to control levels of expression following removal of the predator. Thirteen genes were induced specifically by dragonfly larvae, nine others were salamander-specific, and sixteen were induced by both. Functional analyses indicated that some of the genes induced by dragonfly larvae caused an increase in laminins necessary for cell adhesion in the extracellular matrix. The higher expression of gremlin 1 and HIF1a genes after exposure to dragonfly larvae indicated an in vivo hypoxic reaction, while down-regulation of syndecan-2 may indicate impairment of angiogenesis. Exposure to larval salamanders caused down-regulation of XCIRP-1, which is known to inhibit expression of adhesion molecules; the tadpoles showed reduced expression of cα(E)-catenin, small muscle protein, dystrophin, and myosin light chain genes. CONCLUSION: The connective tissue of tadpoles exposed to larval salamanders may be looser. The differences in gene expression profiles induced by the two predators suggest that there are functional differences between the altered tail tissues of the two groups of tadpoles.

Nonadditive impacts of temperature and basal resource availability on predator-prey interactions and phenotypes.

Predicting the impacts of climate change on communities requires understanding how temperature affects predator-prey interactions under different biotic conditions. In cases of size-specific predation, environmental influences on the growth rate of one or both species can determine predation rates. For example, warming increases top-down control of food webs, although this depends on resource availability for prey, as increased resources may allow prey to reach a size refuge. Moreover, because the magnitude of inducible defenses depends on predation rates and resource availability for prey, temperature and resource levels also affect phenotypic plasticity. To examine these issues, we manipulated the presence/absence of predatory Hynobius retardatus salamander larvae and herbivorous Rana pirica tadpoles at two temperatures and three basal resource levels. and measured their morphology, behavior, growth and survival. Prior work has shown that both species express antagonistic plasticity against one another in which salamanders enlarge their gape width and tadpoles increase their body width to reach a size-refuge. We found that increased temperatures increased predation rates, although this was counteracted by high basal resource availability, which further decreased salamander growth. Surprisingly, salamanders caused tadpoles to grow larger and express more extreme defensive phenotypes as resource levels decreased under warming, most likely due to their increased risk of predation. Thus, temperature and resources influenced defensive phenotype expression and its impacts on predator and prey growth by affecting their interaction strength. Our results indicate that basal resource levels can modify the impacts of increased temperatures on predator-prey interactions and its consequences for food webs.

Response of a Wild Edible Plant to Human Disturbance: Harvesting Can Enhance the Subsequent Yield of Bamboo Shoots.

Wild edible plants, ecological foodstuffs obtained from forest ecosystems, grow in natural fields, and their productivity depends on their response to harvesting by humans. Addressing exactly how wild edible plants respond to harvesting is critical because this knowledge will provide insights into how to obtain effective and sustainable ecosystem services from these plants. We focused on bamboo shoots of Sasa kurilensis, a popular wild edible plant in Japan. We examined the effects of harvesting on bamboo shoot productivity by conducting an experimental manipulation of bamboo shoot harvesting. Twenty experimental plots were prepared in the Teshio Experimental Forest of Hokkaido University and were assigned into two groups: a harvest treatment, in which newly emerged edible bamboo shoots were harvested (n = 10); and a control treatment, in which bamboo shoots were maintained without harvesting (n = 10). In the first year of harvesting (2013), bamboo shoot productivities were examined twice; i.e., the productivity one day after harvesting and the subsequent post-harvest productivity (2-46 days after harvesting), and we observed no difference in productivity between treatments. This means that there was no difference in original bamboo shoot productivity between treatments, and that harvesting did not influence productivity in the initial year. In contrast, in the following year (2014), the number of bamboo shoots in the harvested plots was 2.4-fold greater than in the control plots. These results indicate that over-compensatory growth occurred in the harvested plots in the year following harvesting. Whereas previous research has emphasized the negative impact of harvesting, this study provides the first experimental evidence that harvesting can enhance the productivity of a wild edible plant. This suggests that exploiting compensatory growth, which really amounts to less of a decline in productivity, may be s a key for the effective use of wild edible plants.