Species of Ichthyophis, from East, Southeast, and South Asia, are difficult to identify, mainly because many species were described based only on a few specimens without examining intraspecific variation. We redescribe I. biangularis, an endemic species of Malaysian Borneo. The morphology of the newly collected topotype is consistent with the original description. The phallodeum and the larvae are first described in this study. We sequenced Cyt b of mitochondrial DNA of this topotype and genetically identify the specimens collected in adjacent areas to the type locality. Intraspecific genetic variation of the species is relatively high compared to another species in this genus. We also describe the natural history of this species, including its habitat and reproduction.
Amphibians are poorly dispersed owing to their low osmoticpressure and salt tolerance, and are rarely found on islands. However, amphibians that invade islands through anthropogenic introduction can have high population densities and enormous impact on native ecosystems. Bufo formosus, a large Japanese amphibian, was artificially introduced as a nonnative species, mainly on islands, and has had a significant impact on the native ecosystems of Hokkaido and Sado Island. However, knowledge of this introduced species on the Izu Islands is limited. Therefore, in this study, we conducted distribution and habitat-density surveys and created a species distribution model (SDM) to clarify the distribution status of introduced nonnative B. formosus on Miyake-jima Island, where approximately 20 years have passed since a volcanic eruption and species invasion. Occurrence record surveys revealed that B. formosus was found in a wide area of Miyake-jima Island. While SDM predicted that this species inhabits not only in forest but also grasslands formed after volcanic eruption, it was predicted that the potential distribution probability of this species inhabiting coastline and summit areas were low. A population density survey revealed the highest density around Tairo Pond on Miyake-jima Island, where 538 toads were found in 10 minutes. The lack of predators and competitors for this species on In the future, it will be necessary to clarify the impact of such a high-density population on the native ecosystem, especially on insect fauna.
Anuran tadpoles perceive predation risk in the environment from the types of semiochemical cues emitted by both predators and prey, and they perform various defensive responses to reduce encounter probabilities and increase the escape probability after predator attacks. While the impact of simple stimuli, such as the presence or absence of predation risk, on defensive responses has been extensively studied, the influence of quantitative gradients and the interaction of these cues on defensive responses is less understood. In this study, we reared Dryophytes leopardus tadpoles in environments with varying numbers of predatory dragonfly nymphs, Orthetrum albistylum speciosum, and tadpole prey conspecifics to examine how different levels of stimuli affect the defensive responses of tadpoles. The cue from prey consumed by nymphs triggered a decrease in tadpole activity. The two cues interact in a complex way which affects how the tadpole responded. Increased prey-borne cues result in induced increases in total length and tail length in the tadpoles when there was one predator nymph, but no effect was detected when there were two nymphs. Our results indicated that D. leopardus tadpoles perceive quantitative variations in cues of different origins and respond to varying levels of predation risk in a more complex manner than we had expected.
We briefly report the structure consisting of a claw-like phalanx with a distal bony nodule in toe tips of a fanged frog genus Limnonectes (Dicroglossidae) from Malaysian Borneo. The claw is normally covered by bony nodule under the skin, but when the frog is grasped, it comes out through the skin to scratch predators and competitors. By now, such a structure has been known only in African frogs of the family Arthroleptidae, whose remote phylogenetic position from Dicroglossidae suggests convergent origin of such a unique character in different Anuran lineages.
Reproductive processes, including spermatogenesis and vitello- genesis, have been closely associated with the migratory and behavioral patterns of sea turtles. However, whether physiological changes associated with reproduction influence behavioral adaptations, particularly swimming and feeding patterns, remains unclear. Thus, this study aimed to examine the relationship between reproductive cycles (spermatogenic and vitellogenic) and behavioral patterns (swimming and feeding) in captive loggerhead turtles, Caretta caretta. Experiments were conducted from January 2011 to December 2012 at the Okinawa Churaumi Aquarium and involved one male and two female loggerhead turtles. Monthly measurements included serum testosterone levels in the male and triglyceride and total protein concentrations in the females. Behavioral observations of swimming and feeding were recorded to calculate activity ratios. Distinct seasonal variations were observed in the male and female turtles. In the male, testosterone levels and swimming activity increased from December, peaked during the mating season (March to April), and declined thereafter. Feeding activity decreased during the peak reproductive phase (February to April) and recovered after mating in May. In the females, triglyceride and total protein levels, along with swimming activity, increased during vitellogenesis (October to February) and peaked during nesting (March to April), whereas feeding behavior declined during these periods. These findings underscore the synchronization between reproductive cycles and behavioral changes, suggesting that hypophagic behavior facilitates energy allocation for reproduction. This may make it possible to estimate the reproductive and physiological cycles of captive loggerhead turtles based on simple behavioral observations that do not cause stress to the turtles, thereby leading to the implementation of successful captive breeding programs.
Understanding population dynamics is critical for the management of animal populations. Comparatively little is known about the relative importance of endogenous (i.e., density-dependent) and exogenous (i.e., density-independent) factors in the population dynamics of amphibians with complex life cycles. A breeding population of the Japanese salamander, Hynobius tokyoensis, has been monitored at Habu in Hinode-machi, Tokyo, from 1975 to 2025. The number of breeding females was estimated annually by counting the total number of egg sacs deposited in a pond. Female abundance varied from year to year and ranged from 35 to 160 during this period. Time-series data of population abundance were analyzed using state-space modeling to estimate the strength of the effects of density dependence and climatic conditions on population dynamics, owing to the presence of plausible temporal autocorrelation. I used the exponential growth state-space model and the Ornstein-Uhlembeck state-space model as proxy models for density-independent and density-dependent population growth, selecting between them using the parametric bootstrap likelihood ratio test. The hypothesis of density independence was rejected for the study population (5,000 bootstraps, P=0.0026), and the Gompertz state-space (GSS) model, incorporating both density dependence and climate effects, was applied to the time-series data. The analysis using the GSS model also demonstrated a significant negative effect of climatic factors, such as relative humidity, in the preceding growth season. The present study shows the importance of both density-dependent and density-independent climate effects on the long-term dynamics of the breeding population of H. tokyoensis, and suggests the possibility that density dependence may buffer the salamander population against environmental stress.
Delimiting species is crucial, especially for threatened and understudied organisms, because unresolved taxonomy can result in unrecognized species diversity and misallocated conservation efforts. In this study, we used an integrative taxonomic approach, incorporating genetic, morphological, and acoustic analyses, to clarify the phylogenetic relationship of the endangered Short-legged Horned Toad (Boulenophrys brachykolos) from South China. We focused on individuals from three geographically separated regions in Hong Kong, one on the mainland (Kowloon) and two on islands (Lantau Island and Hong Kong Island). Our genetic data identified Lantau Island individuals to be an evolutionarily distinct lineage, with a minimum genetic difference of 2.1% from other populations. Acoustic analysis revealed that male B. brachykolos from Lantau Island produce calls with similar frequency, but significantly higher pulse and note rate. However, morphological comparisons did not reveal significant differences among the three regions. To conclude, the B. brachykolos population from Lantau Island may represent a case of speciation in progress, and in the interim, should be treated as a distinct conservation unit.
For tropical ectotherms invading temperate regions, cold stress imposes significant negative impacts on their activity and survival. A previous study demonstrated that the recent northward range expansion of Hemidactylus frenatus to Amamioshima Island, Japan, after 2000 was driven by climate change rather than acquisition of stronger cold tolerance: the ambient temperature on Amamioshima after 2000 has increased compared to that on Okinawajima Island prior to 1955, where H. frenatus has long persisted. Two other gecko species of tropical or subtropical origin, H. bowringii and Gehyra mutilata, established populations on Amamioshima around the 1950s-1960s, suggesting they possess stronger cold tolerance compared to H. frenatus. To test this hypothesis, we compared cold tolerance among the Amamioshima populations of these three species, representing the current northernmost limits of their distributions, through laboratory experiments. Results showed significant differences in critical thermal minimum (CTmin) among the three species: G. mutilata exhibited the highest CTmin (11.35 +/- 0.34 degrees C), whereas H. bowringii showed the lowest CTmin (8.58 +/- 0.40 degrees C) and H. frenatus exhibited intermediate values (10.36 +/- 0.55 degrees C). These findings suggest that G. mutilata persists in Amamioshima via behavioral thermoregulation, most likely relying on anthropogenic heat sources to survive the cold winter there. In contrast, H. bowringii may have stronger cold tolerance inherently or acquired locally, allowing this species to spread across Amamioshima in the 1960s. Rising ambient temperatures with climate change after 2000 enabled H. frenatus to establish a stable population on this northernmost island.
Sea turtle incubation temperature is an important environmental factor that can alter the hatchling phenotype and impact their survival. Turtle eggs naturally experience diurnal temperature fluctuations, but climate change is expected to intensify their impact on the eggs. Southwestern Japan encompasses the northern and southern limits of green turtle and loggerhead turtle nesting areas in the western North Pacific and is considered to be where the impacts of climate change are most evident. We investigated how the diurnal variation of fluctuating incubation temperature affects the hatching success, size and swimming performance in green and loggerhead turtle hatchlings. We collected eggs of both species from five nests each laid on beaches. Eggs from each nest were divided into three treatments based on the sand temperatures measured in natural beaches. One treatment group was held at a constant temperature of 29.0 degrees C, while the other two groups were kept at a mean 29.0 degrees C with daily fluctuations of +/- 1.0 degrees C or +/- 2.0 degrees C. For loggerhead turtles, hatching success was highest in the group with +/- 1.0 degrees C fluctuation. For both species, swimming thrusts were higher in the +/- 1.0 degrees C fluctuations and constant-temperature groups than in the +/- 2.0 degrees C fluctuations group. Our study suggests that for the traits surveyed, incubation regimes that mimic the natural daily temperature fluctuations of each species result in better hatchling outcomes. Therefore, when translocating eggs, maintaining them under conditions that reflect the natural temperature fluctuation is ideal. These findings provide valuable guidance for improving the success of hatching programs.
In Japan, countrywide spread of the red-eared slider turtle (RES; Trachemys scripta elegans) and the raccoon (Procyon lotor), both of which are invasive alien animals, has been raising concerns that they may interfere with the growth and survival of indigenous turtles, thereby altering the turtle fauna in freshwater ecosystems. Using a trap-capture method, we conducted a twoyear (2015-2016) field study to reveal transition of turtle demographics in irrigation ponds located in the southern part of Kyoto Prefecture, Japan. In a previous study conducted in 1999, when raccoons had not yet invaded in the adjacent areas, these ponds were abundant with the Japanese pond turtle (JP; Mauremys japonica, endemic to Japan) followed by Reeves' pond turtle (RP; Mauremys reevesii) and almost devoid of RES. In the present study, a total of 536 turtles were recorded and RES completely replaced JP as the dominant species. Age structure was skewed towards older age classes in the JPs but towards younger age classes in the RESs, suggesting unsuccessful recruitment of young JPs as opposed to high reproductive potentials of RESs. The sex ratio was even in the JPs and RPs but significantly biased toward female in the RESs, suggesting high fertility of the RESs. Furthermore, limb loss individuals strongly suggesting predation attacks by feral raccoons were most frequently found in the JPs followed by the RPs, but were not found in the RESs. This vulnerability of the JPs might confer relative advantages to the survival of the sympatric RESs, resulting in further growth of the RES population and an accelerating progression toward local extinction of the JPs, as symbolized by their aging population structure.
On the main islands of Japan, two closely related colubrid snake species, the Japanese rat snake (Elaphe climacophora) and the Japanese striped snake (E. quadrivirgata), coexist in sympatry. These species differ in habitat utilization: E. climacophora is semi-arboreal, while E. quadrivirgata is mostly terrestrial. Due to the differences in habitat utilization of the two species, I hypothesized that E. climacophora would exhibit superior climbing ability to E. quadrivirgata. To test this, I conducted two behavioral experiments in captivity. In Experiment 1, I compared the climbing speed of adult individuals of both species on a vertical surface formed by a 45-degree intersection of a plywood board and a wall. In Experiment 2, I tested whether hatchlings of the two species were able to climb a 90-degree corner formed by two intersecting walls. The results showed that, in adults, the hypothesis that E. climacophora climbs faster than E. quadrivirgata, independent of size differences, was only partially supported, while in juveniles, E. climacophora exhibited significantly higher climbing success rates than E. quadrivirgata. Overall, these findings suggest that E. climacophora possesses superior climbing ability across life stages. As a future direction, I briefly discussed a potential link between differences in climbing ability and differing patterns of avian prey exploitation.
Spawning activity of the Japanese red-bellied newt, Cynops pyrrhogaster, was surveyed in Minami-ohsawa, Hachioji-shi, Tokyo, using artificial egg strips. The number, size, and mortality of the deposited eggs were monitored daily from April to July in 2017. Spawning activity was observed mainly over three months from April to June, and a total of 5,339 eggs were successfully detected using artificial egg strips, which was estimated to be approximately 40% of the total number of eggs deposited in the study population. Time-series data were analyzed using state-space modeling to estimate the impact of water temperature on spawning parameters owing to the presence of plausible temporal autocorrelation. The survey quantitatively showed seasonal changes in spawning activity and demonstrated a significant effect of water temperature as females laid more eggs on warmer days. The average daily mean egg size was 2.19 mm (SD=0.05, N=86), and average daily egg mortality was 0.169 (SD=0.148, N=84), with clear seasonal trends: a convex trend for egg size and a concave trend for egg mortality. We did not detect any significant effects of water temperature on egg size or mortality. Currently, there are no data on the factors affecting seasonal changes in egg size and mortality in this species. Newt eggs are difficult to find in natural ponds, but the present study demonstrated that newt surveying using artificial egg strips is an effective way to monitor newt spawning activity.
Japan has a high diversity of amphibians; however, there are concerns that native species may become extinct due to habitat degradation and invasive species. Raccoons, which prefer wetland habitats, have caused population declines in amphibians, even those with short breeding periods. We evaluated the hypothesis that raccoons appear in wetlands and predation events increase according to the timing of amphibian breeding. In particular, we evaluated differences in the presence of raccoons in wetlands depending on the breeding status of various frog species, accounting for spatiotemporal autocorrelation. From May to July 2022, January to July 2023, and January to February 2024, we monitored animal and frog calling levels using camera traps at 28 sites in Aina Satoyama Park, Hyogo Prefecture. We constructed a generalized linear mixed model with the number of raccoon appearance events and average estimated staying time as objective variables and presence or absence of breeding frogs of each species on the day and previous day, number of egg masses, and month as explanatory variables, using a poisson distribution and tweedie distribution accounting for spatiotemporal autocorrelation. The both best models based on Akaike's information criterion values included the breeding of Rana japonica on the day, breeding of Zhangixalus schlegelii on the previous day, egg masses of R. japonica, and month. Our results suggest that raccoons form an association between frog calls or breeding days and prey resources.
Several recent studies have highlighted that climate change is a major driver of biodiversity loss. In particular, amphibians, including the genus Philautus (small rhacophorid frogs), are seriously vulnerable due to their permeable skin and biphasic life cycle. This study used ecological niche modeling to predict the current and future distributions of three common Philautus species from Sumatra (P. larutensis, P. polymorphus, and P. thamyridion) under climate scenarios SSP2-4.5 and SSP5-8.5 for 2050 and 2090. The model results aligned well with field records of the examined species, showing that P. larutensis occupies a large area from north to south along the Bukit Barisan Mountain Range, while P. polymorphus and P. thamyridion are mainly distributed in the mountainous areas of southern Sumatra. Projections under future climate scenarios indicate that the suitable habitats of the three species could decline by 44% to 96%, with shifts toward higher altitudes. Alarmingly, only 8.6% to 12.5% of the suitable habitats of these tree frogs overlap with current protected areas. These findings highlight the urgent need for conservation measures to mitigate the effects of climate change on Philautus species on Sumatra.
The cane toad, Rhinella marina, is invasive on several islands in Japan, including Ishigaki Island which lacks native bufonid species. Cane toads possess toxins in the aquatic and terrestrial life stages, and thus pose a risk to native predators, especially predators that have evolved in the absence of bufonids. We tested tadpoles of three anuran species native to Ishigaki for responses to cane toad hatchlings as potential prey. All three species showed high propensity to consume toad hatchlings. However, the species differed in sensitivity to hatchling toxins: consumption of toad hatchlings was always fatal to M. kuramotoi and Z. owstoni, whereas toxic effects on F. sakishimensis were variable (approximately 40% mortality) independent of tadpole size, developmental stage or the number of hatchlings consumed. Our results are the first to highlight the potential for toxic impacts of invasive cane toads on native anurans in Japan.
This study investigates arboreal behavior in the scincid lizard, Plestiodon japonicus, focusing on populations in mainland Japan. Previous research suggested that the population on the Danjo Islands uses trees for basking, but whether this behavior is widespread or a specific adaptation to the islands remained unclear. To explore this, camera traps were set up in a forest in Kumamoto Prefecture from June 2022 to October 2023, recording lizard behaviors. Climbing behaviors were observed at two sites, with five climbing events recorded over 9,570 camera-days. The lizards moved smoothly along tree trunks, with speeds comparable to arboreal lizards like Anolis. The current findings may provide a reliable record of a specific aspect of the species' broader habitat use.
Climate change is a major factor contributing to the loss of habitat and decline of amphibian populations, posing a threat to biodiversity conservation. Bufonidae species are particularly sensitive to changes in their environment and vulnerable to climate change due to their strong homing instinct and frequent group behavior (mating and migration of juveniles). We identified the major distribution areas and habitat characteristics of two toad species found in Korea, toad, Bufo gargarizans, and water toad, B. stejnegeri, based on observation points and species distribution modeling. Distributional changes due to climate change were predicted. The toads used low altitudinal ranges and agricultural land, whereas the water toads used forested areas. The average model test area under the curve (AUC) value for toads was 0.695 +/- 0.007, while the average test AUC value for water toads was 0.883 +/- 0.015. Toad distribution was most affected by temperature and altitude. By the 2100s, the number of occupied grid cells for toads and water toads is predicted to decrease by 99.57% and 100.00%, respectively, compared to the present number of occurred grid cells under the SSP 5-8.5 scenario. These critical data inform conservation measures for amphibians affected by global climate change.
A genetic sex identification method was applied to the Japanese Giant Salamander and its hybrids with the introduced Chinese Giant Salamander. This method detects female-specific sequences on the W chromosome by PCR, using specific primers originally designed for the Chinese Giant Salamander. We improved the method for application to the Japanese Giant Salamander and the hybrids. We then applied our new technique to examine the sex ratio of hybrid larvae collected from one breeding nest in the wild. The sex ratio was equal between sexes at this site, suggesting that their sex is determined by chromosomal combination.
A Bornean megophryid, Leptobrachella gracilis (G & uuml;nther, 1872), the type species of now synonymized genus Leptolalax, proved to contain two different call types that differ in various aspects of advertisement calls including pulse repetition rate and dominant frequency. Genetic analyses of mtDNA and nuDNA of these two types (slow- and fast-call) co-occurring at the type locality, Matang, Sarawak, revealed them to be heterospecific with no evidence of gene exchange. The female holotype of L. gracilis is estimated to belong to the slow-call type based on morphological similarities. We therefore describe the fast-call type as a new species, Leptolalax sarawakensis sp. nov.
Sexual size dimorphism (SSD) in body size and head size can vary among species in the lizard genus Sceloporus. We studied the SSD in body and head size of two closely related species, Sceloporus nelsoni from Chihuahua and two populations of S. pyrocephalus, one from Michoac & aacute;n and the other from Guerrero. Males had larger bodies than females in both species. However, SSD in head size was only found in the two populations of S. pyrocephalus, with males having relatively longer and wider heads than females. Our results suggest that these two species share SSD in body size, but vary in SSD in head size. This species pair might therefore be an interesting system in which to further explore the underlying causes of SSD in body and head size.
