Antipredator behavior of newts (Cynops pyrrhogaster) against snakes.

Newts and salamanders show remarkable diversity in antipredator behavior, developed to enhance their chemical defenses and/or aposematism. The present study reports on the antipredator behavior of newts (Cynops pyrrhogaster) in response to snakes. Newts displayed a significant amount of tail-wagging and tail-undulation in response to a contact stimulus from the snake's tongue, which is a snake-specific predator stimulus, as compared to a control stimulus (behavioral scores: tongue, 1.05 ± 0.41; control, 0.15 ± 0.15). Newts that were kept in warm temperature conditions, 20°C (at which snakes are active in nature), performed tail displays more frequently than newts kept in low-temperature conditions, 4°C (at which snakes are inactive in nature). Our results suggest that the tail displays of C. pyrrhogaster could function as an antipredator defense; they direct a snake's attention to its tail to prevent the snake from attacking more vulnerable body parts. We also discussed the reason for inter-populational variation in the tendency of newts to perform tail displays.

Genome editing reveals fitness effects of a gene for sexual dichromatism in Sulawesian fishes.

Sexual selection drives rapid phenotypic diversification of mating traits. However, we know little about the causative genes underlying divergence in sexually selected traits. Here, we investigate the genetic basis of male mating trait diversification in the medaka fishes (genus Oryzias) from Sulawesi, Indonesia. Using linkage mapping, transcriptome analysis, and genome editing, we identify csf1 as a causative gene for red pectoral fins that are unique to male Oryzias woworae. A cis-regulatory mutation enables androgen-induced expression of csf1 in male fins. csf1-knockout males have reduced red coloration and require longer for mating, suggesting that coloration can contribute to male reproductive success. Contrary to expectations, non-red males are more attractive to a predatory fish than are red males. Our results demonstrate that integrating genomics with genome editing enables us to identify causative genes underlying sexually selected traits and provides a new avenue for testing theories of sexual selection.

Convergent evolution of body color between sympatric freshwater fishes via different visual sensory evolution.

Although there are many examples of color evolution potentially driven by sensory drive, only few studies have examined whether distinct species inhabiting the same environments evolve similar body colors via shared sensory mechanisms. In this study, we tested whether two sympatric freshwater fish taxa, halfbeaks of the genus Nomorhamphus and ricefishes of the genus Oryzias in Sulawesi Island, converge in both body color and visual sensitivity. After reconstructing the phylogeny separately for Nomorhamphus and Oryzias using transcriptome-wide sequences, we demonstrated positive correlations of body redness between these two taxa across environments, even after phylogenetic corrections, which support convergent evolution. However, substantial differences were observed in the expression profiles of opsin genes in the eyes between Nomorhamphus and Oryzias. Particularly, the expression levels of the long wavelength-sensitive genes were negatively correlated between the taxa, indicating that they have different visual sensitivities despite living in similar light environments. Thus, the convergence of body colorations between these two freshwater fish taxa was not accompanied by convergence in opsin sensitivities. This system presents a case in which body color convergence can occur between sympatric species via different mechanisms.

Behavioral responses to changes in group size and composition: a case study on grooming behavior of female Japanese macaques (Macaca fuscata yakui).

Primates flexibly change their grooming behavior depending on group size and composition to maintain social relationships among group members. However, how drastic social changes influence their grooming behavior remains unclear. We observed the grooming behavior of adult female Japanese macaques in two groups temporarily formed as one-female groups from multi-female groups and compared their behaviors between the multi-female and one-female periods. Adult females more frequently performed grooming with both their relatives and unrelated juveniles during the one-female period when other adult females were unavailable as alternatives to their absent familiar partners. The increased grooming time and diversity of grooming partners might alleviate the short-term stress caused by the loss of grooming partners and reduce social instability or mitigate the long-term stress due to disadvantages in intergroup conflicts. Our study provides rare evidence on the flexibility in grooming behavior of primates and encourages accumulating case reports for understanding behavioral responses of primates to drastic social changes.

Phylogenomics reveals habitat-associated body shape divergence in Oryzias woworae species group (Teleostei: Adrianichthyidae).

The Oryzias woworae species group, composed of O. asinua, O. wolasi, and O. woworae, is widely distributed in southeastern Sulawesi, an island in the Indo-Australian Archipelago. Deep-elongated body shape divergence is evident among these three species to the extent that it is used as a species-diagnostic character. These fishes inhabit a variety of habitats, ranging from upper streams to ponds, suggesting that the body shape divergence among the three species may reflect adaptation to local environments. First, our geometric morphometrics among eight local populations of this species group revealed that the three species cannot be separated by body shape and that riverine populations had more elongated bodies and longer caudal parts than lacustrine populations. Second, their phylogenetic relationships did not support the presence of three species; phylogenies using mitochondrial DNA and genomic data obtained from RNA-Seq revealed that the eight populations could not be sorted into three different clades representing three described species. Third, phylogenetic corrections of body shape variations and ancestral state reconstruction of body shapes demonstrated that body shape divergence between riverine and lacustrine populations persisted even if the phylogenies were considered and that body shape evolved rapidly irrespective of phylogeny. Sexual dimorphism in body shape was also evident, but the degree of dimorphism did not significantly differ between riverine and lacustrine populations after phylogenetic corrections, suggesting that sexual selection may not substantially contribute to geographical variations in body shape. Overall, these results indicate that the deep-elongated body shape divergence of the O. woworae species group evolved locally in response to habitat environments, such as water currents, and that a thorough taxonomic reexamination of the O. woworae species group may be necessary.

The function of body coloration of the hai coral snake Sinomicrurus japonicus boettgeri.

BACKGROUND: Prey animals often protect themselves from visual hunting predators via their body coloration, which encompasses various visual effects. When a prey animal displays a certain color pattern on its body surface, its protective function and effect are largely dependent on how a predator would encounter and perceive the prey animal.Asian coral snakes of the genus Sinomicrurus,which are venomous, display black bands and stripes on their orange body coloration. The banded pattern has been characterized as an aposematic signal in the New World coral snakes, but the stripes generally occur in cryptic snakes. We investigated the function of this complex color pattern, which might be interpreted as aposematic and cryptic, in Sinomicrurus japonicusboettgeri. RESULTS: First, plasticine replica experiments were conducted to assess whether natural avian predators avoid the colorpattern of S.japonicus boettgeri;the results showed that they attacked the coral snake replicas and the control replicas with coloration similar to another prey snake, suggesting that the body coloration of S. japonicus boettgeri did not function aposematically in the wild. Second, we evaluated the chromatic contrast of the snake coloration with backgrounds from their natural habitats based on the avian predator visual systems. The body coloration of S. japonicus boettgeri showed the same, or lower, contrast levels with natural backgrounds than those of sympatric cryptic snakes, suggesting that the coloration was ineffective as an aposematic signal. CONCLUSIONS: These results imply that the body coloration of S. japonicus boettgeri would work as crypsis through background matching or disruptive camouflage rather than aposematism.

Sleep duration is affected by social relationships among sleeping partners in wild Japanese macaques.

Co-sleeping behaviour, such as sharing a sleeping site or bed, should play an important role in determining sleep structure in mammals by mitigating predation pressure and harsh abiotic conditions during sleep. Although environmental factors surrounding sleeping sites have been studied, there is very little information on the effects of the social environment within the site on sleep in animals other than humans. Here, we quantified the duration of nighttime sleep of wild primates during behavioural observations. Wild Japanese macaques (Macaca fuscata yakui) form clusters at sleeping sites, where they huddle with group members. Macaques slept for longer when huddled in sleeping clusters with natal members than in those with non-natal members. A high degree of synchronisation of wakefulness in pairs of macaques huddling in non-natal clusters suggested that their sleep was often interrupted by the wakefulness of huddling members at night. Our results suggest that familiarity and closeness to huddling partners influence sleep duration.

Spatial and temporal instability of local biotic community mediate a form of aposematic defense in newts, consisting of carotenoid-based coloration and tetrodotoxin.

Most animals advertise their unprofitability to potential predators via conspicuous signals. Whether the strength of this aposematic signal indicates the quality and quantity of chemical defenses in animals is controversial. Here, we investigated the relationship between the conspicuousness of an aposematic signal and toxicity, which likely depends, at least in part, on dietary sources, in the newt Cynops pyrrhogaster. Our results indicate that the magnitude of the aposematic signal was not correlated with the amount of tetrodotoxin (TTX) and 6-epi TTX of wild individuals among populations. Using atoxic newts, reared from eggs, we compared the ability to accumulate TTX from diets between mainland and island populations. Newts of a mainland population that exhibited a less conspicuous signal accumulated more TTX than did equivalent newts of an insular population that displayed a more conspicuous signal; this was unrelated to variation in the toxicity of wild individuals of these two populations. We also found toxicity of wild newts changed over approximately one generation (10 years) in both populations. These results indirectly suggest that environmental variance, such as fluctuations in TTX resources in nature, may obscure differences in the ability of wild newts to accumulate TTX, and that this variation may be responsible for a lack of correlation between the strength of a newt's signal and its toxicity in the wild. These results imply that toxicity of wild individuals likely is a phenotypic trait largely dependent on environmental conditions.

Temperature-dependent aposematic behavior in the newt Cynops pyrrhogaster.

Aposematic animals advertise their unprofitability to potential predators via morphological and behavioral signals. Strong signals are detectable and memorable for the predators, and such signals would therefore be expected to be most effective. However, many apparently well-defended animals do not have very conspicuous signals. To better understand this paradoxical phenomenon, I compared intra-individual variation in an immobile aposematic behavior of the newt Cynops pyrrhogaster under different thermal gradients, using 40 animals from four populations. I found a negative relationship between ambient temperature and the frequency of performing this behavior, independent of body size. Newts kept in low temperature conditions showed a stronger tendency to display the immobile aposematic behavior than those in high temperature conditions, indicating that this behavior in the newt is temperature-dependent. However, interpopulational comparison of thermal thresholds governing the decision to flee or remain immobile as an antipredator strategy suggested that the effect of temperature might not be responsible for interpopulational variation in the immobile aposematic behavior of the newt.

Coprophagy-related interspecific nocturnal interactions between Japanese macaques (Macaca fuscata yakui) and sika deer (Cervus nippon yakushimae).

The influence of sympatric large animals on the sleeping behavior of primates in the wild is still largely unknown. In this study, we observed behaviors of wild Japanese macaques (Macaca fuscata yakui) at their sleeping sites, using a highly sensitive video camera. We found evidence of nocturnal interspecific interactions, such as agonistic interactions, between Japanese macaques and sika deer (Cervus nippon yakushimae). Deer approached sleeping clusters of macaques, which slept on the ground, to eat their feces or unidentified materials near the sleeping clusters, and as a result, the macaques were often quickly displaced from their sleeping site. There was a significant difference in the occurrence of macaque-deer agonistic interactions between seasons. Our results suggested that the size of the sleeping cluster, the number of adult macaques in the cluster, and the existence of adult males in the cluster did not influence the occurrence of the agonistic interactions. Finally, we discuss the influence of this interaction on macaques and speculate on the influential factors leading to nocturnal coprophagy of macaques' feces by deer.

Food habit of the juvenile of the Japanese newt Cynops pyrrhogaster.

The previous study showed that the red coloration of the ventral skin of the Japanese newt Cynops pyrrhogaster was associated with the number of carotenoid vesicles and the content of carotenoid in the pigment cell of the skin. To elucidate the mechanism for the red coloration of the skin of the newt, we studied the food habit of the juvenile from the Japanese newt Cynops pyrrhogaster. Sixty-two juveniles were collected in Fukue Island in Nagasaki Prefecture from November 2000 to May 2002 and divided into 2 groups according to the snout-vent length (SVL). Over 400 prey animals were obtained from the juveniles by stomach flushing. In the larger group (SVL>30.0mm), Collembola (45.4%) and Acari (12.6%), which are very common species of soil animals, were the prey animals dominant in number. In the group with the smaller SVL (<29.9mm), Collembola (30.4%) and Acari (25.4%) were in number as well. We also studied the food habit of the Japanese clouded salamander, Hynobius nebulosus. In the salamander, Doratodesmidae (56.5%) and Amphipoda (13%) were the prey animals dominant in number. Our results, taken together, suggest that the Japanese juvenile C. pyrrhogaster does not change its food habit as it grows, and that it eats soil animals common in its habitat. Moreover, the food habit of juvenile C. pyrrhogaster differs from that of H. nebulosus, although the juveniles of both species live in the same area.