The first survey was conducted for helminth fauna of hybrid giant salamanders (hybrids between Andrias japonicus and other congeneric species), and introduced A. davidianus in Kyoto Prefecture, Japan. Three nematode species, Spiroxys hanzaki, Amphibiocapillaria tritonispunctati and Falcaustra sp., and one trematode species, Liolope copulans, were recovered from their alimentary canals. These results show that hybrid and introduced Andrias species are commonly infected with similar helminth species to those previously reported to infect A. japonicus. We conclude that the spillback of native parasites to introduced A. davidianus has occurred in Kyoto Prefecture. This study is also the first record of Falcaustra species parasitizing Andrias species in Japan.

Selective oviposition is widespread in anurans because it significantly affects the survivorship of their offspring, especially when environmental conditions are heterogeneous and potentially unfavorable. In the present study, we aimed to determine whether female oriental fire-bellied toads (Bombina orientalis) selectively lay eggs to increase their progeny’s survival. We studied the Jeju Island population because the streams on this island are ephemeral, so the timing and site of egg-laying can be important for the survival of their progeny. We surveyed all pools in a specific area of an ephemeral stream for two years to determine whether female B. orientalis selectively lay eggs in certain pools to increase their progeny’s survival. The characteristics of pools in our study sites varied especially in size that ranged from 0.01 to 36 m² in surface area. We found that female B. orientalis avoid laying eggs in very small pools where the risk of desiccation or over-heating of water is high. However, unexpectedly, they also avoided large pools and primarily laid eggs in the pools that are not very small or large. In terms of timing, egg-laying took place in association with the timing of rain: the number of pools with egg clutches decreased as the number of days since the last rainfall increased. Females also avoided laying eggs in pools that were already occupied by tadpoles. Field experiments demonstrated that the degree of cannibalism on eggs by conspecific tadpoles is intense in this species. These findings collectively indicate that B. orientalis that live in a fluctuating environment show complicated oviposition behavior that mediate both desiccation and cannibalism risks.

We examined predation of the forest green tree frog, Zhangixalus arboreus, as part of a two-year monitoring study of the frog’s reproductive processes at four ponds in central Japan, performed by using field censuses and sensor cameras. During the period, we confirmed predation against arboreal foam nests by the common raccoon, Procyon lotor. We also found a carcass of a female adult frog with eggs and bitten ground foam nests, the signs of which were strongly suspected to indicate predation by raccoons. These results imply that invasion of Japanese forest areas by alien raccoons is becoming an increasingly serious threat to Z. arboreus through predation at various life stages of the frog. At this study site, however, the demographics of both the raccoon and Z. arboreus have not yet been examined. We need more field data to assess the long-term effects of predation pressure on the frog.

The discrimination of developmental stages of anurans is of critical importance in understanding the morphological characteristics of each specific stage of tadpoles. Unlike most rhacophorids which construct foam nest during egg deposition, Kurixalus naso shows no foam formation during oviposition. This rhacophorid displays a unique oviposition whereby the eggs are laid in the moist soil under burrows and mixed with the loose top layer of the soil giving those eggs a seed-like appearance. The present study highlighted and documented the developmental stages of Kurixalus naso until complete metamorphosis. A normal developmental table consisting of 46 developmental stages was proposed for Kurixalus naso. Stages of development and metamorphosis of Kurixalus naso were divided into 11 major developmental terms, each consisting of a number of successive stages: fertilization (stages 1–2), cleavage-blastula (stages 3–9), gastrula (stages 10–12), neurula (stages 13–16), tail bud stages (stages 17–20), external gill stages (stages 21–22), operculum and oral disc stages (stages 23–25), hind limb bud formation (stages 26–30), toe differentiation and development (stages 31–39), well-developed hind limb (stages 40–41) and metamorphosis (stages 42–46). The embryos of this species hatched into a free-swimming tadpole at stage 25. Kurixalus naso completed the entire process of development and metamorphosis over 62 days. This investigation may contribute to future studies on evaluation of adaptive characters, comparative embryology, and other developmental studies, associated with phylogenetic inferences.

We conducted field observations of spawning sites of the Japanese forest green tree frog (Zhangixalus arboreus: Rhacophoridae) at four ponds for two years. In 2019, a total of 50 foam nests were made on trees (77%), whereas 15 foam nests were made on the ground (23%). In 2020, 65 nests were arboreal (97%) and there were only two ground nests (3%). About 70% of all ground nests deteriorated or disappeared without their eggs hatching, mostly because of predation. In contrast, only about 4% of all arboreal nests died because of desiccation and 27% died mainly of outside spawning and disappearance before egg hatching for any reason. The relative proportions of arboreal versus ground spawning sites differed significantly between 2019 and 2020. Ground spawning was scarcely observed in 2020; in that year the amount of precipitation during the reproductive period was about 1.5 times that in 2019. Our field experiment using paper-clay models confirmed that arboreal nests were more susceptible to desiccation than ground nests. These results suggest that ground spawning may be of some advantage in resistance to desiccation, whereas arboreal spawning may be less susceptible to predation of foam nests.

The green bamboo pit viper, Trimeresurus stejnegeri, is a sit-and-wait predator that forages mainly on frogs in Taiwan. We predicted that T. stejnegeri is able to identify prey at the species level to locate appropriate ambushing sites. We conducted a chemical preference test among frog species and compared its result with the natural diet of T. stejnegeri. The test suggested that T. stejnegeri can discriminate prey species even within the same family. The three highest tongue flick ambush scores (TFAM) were obtained in Odorrana swinhoana, Polypedates braueri, and Zhangixalus moltrechti, which corresponded to the dominant prey items found in stomach contents. Some frog species, however, did not show coincidence between TFAM and the snake’s natural diet. Abundance, active period, and defensive mechanisms of frogs are potential factors affecting the realized diet of T. stejnegeri in the field. We also propose that ambushing behavior exhibited during the chemical preference test should be considered an important indicator of interest in potential prey for sit-and-wait species of snakes.

The family Rhacophoridae, including Buergeria japonica, shows a great diversity of reproductive patterns, but the knowledge of developmental processes is still limited. The genus Buergeria is a sister group to all other rhacophorids and shows a conservative, probably primitive, reproductive mode for this family. Thus, it is valuable to clarify the developmental process in this genus for understanding the evolution and diversification history of reproductive modes and developmental processes across the broader family members. In this study, we describe the normal development of B. japonica by rearing eggs and larvae under ambient temperatures of 27±1°C. The developmental speed of B. japonica from fertilization to gill elongation (stage 20), corresponding to their hatching period, was faster than most of other anuran species, when comparison was made using relative age, which is independent of temperature. The rapid embryonic development may be advantageous in their highly fluctuating breeding environment.

The morphological and ecological characteristics are studied for the population of Plestiodon japonicus of the Danjo Islands, a group of small islands in the East China Sea, on the basis of field observations and data from museum specimens. The population density of the lizards in this island group was estimated to be higher than those in conspecific mainland populations. Also, P. japonicus of the Danjo islands were differentiated from the latter by the following combination of characters: larger number of mid-body scale rows and subdigital scales, blackish juvenile coloration with different stripe pattern, faded tail color, and delayed sexual maturity in males. The evolutionary implications of these findings are briefly discussed.

Hydrophis stokesii was collected in the coastal water of Okinawajima Island on 30 March 2021. This is the first record of the species from Japanese waters, extending its known range of occurrence toward east-northeast by more than 900 km. The snake was an adult female, 1,545 mm in snout-vent length, 203 mm in tail length, and 3,360 g in body mass. It had 11 well-developed yolked follicles in ovaries and a half-digested spiny puffer fish (Diodon sp.) in its stomach. This individual may possibly represent a stable population of H. stokesii in the Okinawan waters.