Based on morphological and molecular evidence, three new earthworm species of the genera Amynthas Kinberg, 1867 and Metaphire Sims and Easton, 1972 from Leshan City of southwest China's Sichuan Province were identified in this study. They are named Amynthas agenesis sp. nov., Metaphire jinhensis sp. nov., and M. ebianensis sp. nov. All three new species have a large size (the dimensions of the adult body are more than 200 mm × 10 mm) and three pairs of spermathecal pores in 6/7–8/9. Although these three new species are morphologically somewhat similar to the other species in the same group, they are distinguishable in several morphological characteristics. Metaphire jinhensis sp. nov. has paired and bunchy ovaries that are attached to septa 12/13. Metaphire ebianensis sp. nov. has large and well-developed prostate glands, and each of its seminal vesicles has a dorsal lobe. Amynthas agenesis sp. nov. has accessory glands in spermathecae, prostate, and intestinal caeca regions. The maximum likelihood tree was constructed based on the mitochondrial cytochrome c oxidase subunit I gene, and it showed that the three new species are clustered on different branches. Besides, phylogenetic trees also suggested that the genera Amynthas and Metaphire did not evolve separately within their respective taxa and thus were not monophyletic. This study provides a detailed taxonomic characterization of three new species and helps to better understand the species diversity of earthworms, which is urgently needed to ensure the ecological stability of wild earthworms.

Phenotypic plasticity, the ability of organisms to change their phenotype depending on external stimuli, enables their survival in fluctuating environments. An extreme example is polyphenism, in which a single genotype produces discrete phenotypes in response to external cues. However, under persistent environmental conditions, natural selection would favor reduced plasticity. This study focused on the loss of reproductive polyphenism and revealed the underlying mechanism in the pea aphid Acyrthosiphon pisum. Although most populations exhibit reproductive polyphenism, known as cyclical parthenogenesis, with a seasonal shift between parthenogenesis and sexual reproduction, some exhibit obligate parthenogenesis. To investigate the potential role of changes in the environmental sensitivity of the juvenile hormone (JH) pathway during this evolutionary shift, we analyzed the expression of genes involved in JH synthesis and degradation. We found that five of seven JH-related genes exhibited photoperiodic responses in one cyclical-parthenogenetic strain, whereas none of them responded to photoperiod in the two obligate-parthenogenetic strains. Notably, CYP15A and JHEH genes, which are involved in the final step of JH synthesis and in the initiation of JH degradation, respectively, showed strong photoperiodic responses in the cyclical-parthenogenetic strain but showed no responses in the obligate-parthenogenetic strains. Acetone treatment induces male production in obligate-parthenogenetic strains, suggesting that the developmental pathway for male production remains functional in these strains. These results suggest that the loss of the photoperiodic response in both JH synthesis and degradation pathways is a key mechanism underlying the elimination of the sexual phase, resulting in the loss of reproductive polyphenism in aphids.

Cephalopods, as prey for predators of various taxa, frequently experience arm loss. Arm loss in octopods may arise not only from predation pressure but also species-specific reproductive ecology. Therefore, investigating the occurrence of arm loss may provide insights into various aspects of octopods' reproductive ecology. In this study, we explored the seasonal and sexual differences in arm loss occurrences in two small octopus species, the Japanese pygmy octopus, Octopus parvus, and the Japanese blue-lined octopus, Hapalochlaena cf. fasciata. Notably, O. parvus exhibited a higher arm loss rate compared with previously studied species, potentially attributable to its relatively small size and sublethal predation by large crabs sharing the species' intertidal habitat. Regarding H. cf. fasciata, arm loss in males and females tended to increase toward the spawning season, with males experiencing a more rapid increase. The smaller size of males and arm loss due to male–male conflict related to reproduction and sexual cannibalism during copulation are likely contributing factors. Additionally, the impact of arm loss on egg retention and protective measures may prompt females to adopt behaviors minimizing the risk of arm loss.

The Japanese serow, Capricornis crispus, is a species endemic to Japan, residing in the mountainous forests of Honshu, Shikoku, and Kyushu. Gunma Prefecture, situated in central Honshu, is one of its habitats. To evaluate the genetic diversity and interrelationships among local populations in Gunma Prefecture, we examined the mitochondrial DNA control region sequences of 364 individuals. Our analysis, using all accessible Japanese serow sequences, revealed that they can be broadly categorized into four clades, labeled I to VI. Within Gunma Prefecture, we identified 15 distinct haplotypes, which can be classified into three haplogroups: G1, G2, and G3. G1, included in clade I, is associated with those reported in northeastern Honshu. G2, which forms clade IV on its own, is predominantly endemic to Gunma Prefecture, with a frequency of 90% in Showa Village at the western base of Mt. Akagi. In contrast, G3, included in clade V, forms a sister group to the haplotype discovered in the Japanese Alps. The haplotype composition exhibited a stark contrast between the regions on the west and east sides of the Kanto Plain, indicating that the Kanto Plain serves as a dividing line for Japanese serow populations. In Tsumagoi Village, 134 out of 144 animals shared the same haplotype, resulting in extremely low haplotype diversity, as indicated by a significant negative value in neutrality tests. This finding aligns with the observed rapid increase in serow in Tsumagoi.

The metridioid enthemonaean sea-anemone family Gonactiniidae Carlgren, 1893 is characterized by having one of the simplest morphologies among the Actiniaria. It currently includes two monotypic genera, each consisting of a species described in the 19th century from the Atlantic, although additional specimens have also been reported from the Mediterranean and South Pacific. In this study, we discovered a new species of gonactiniid anemone from Kumano-Nada, off the Pacific coast of Japan. This is the first record of this family from the North Pacific. According to our phylogenetic analyses, this anemone is the sister group to the other two genera of Gonactiniidae, Gonactinia Sars, 1851 and Protanthea Carlgren, 1891. Accordingly, we establish a new genus for this new species. Additionally, we discuss the simplification of body form in this lineage of sea anemones based on the discovery of this new species, which exhibits an intermediate morphology between the other gonactiniids and non-gonactiniid actiniarians.

Tropical reptiles colonizing temperate regions face distinct physiological challenges due to thermal stress. Their long-term survival hinges on physiological acclimatization or adaptation to these novel thermal environments. Previous research on cold tolerance in introduced high-latitude Hemidactylus frenatus revealed that rural populations on Okinawajima Island, Japan exhibited significantly lower critical thermal minimum (CTmin) compared to their urban counterparts. However, whether this variation stems from acclimation or genetically fixed physiological differences remains unclear. To address this issue, we re-examined the cold tolerance of rural and urban populations after subjecting them to 2-week acclimation periods under high and low temperatures. Our experiments revealed that urban geckos exposed to the high-temperature treatment exhibited the highest CTmin, while rural geckos in the low-temperature treatment displayed the lowest CTmin. Urban geckos in the low-temperature treatment and rural geckos in the high-temperature treatment displayed intermediate CTmin values. These findings suggest that both acclimation and genetic differences contribute to the observed variations in cold tolerance among H. frenatus populations. The urban and rural populations are only 10 km apart, highlighting that evolutionary responses to thermal stress can occur rapidly over surprisingly small geographical scales in this species.

Mustelids are omnivorous–frugivorous and exhibit temporal dietary switching and specialism; however, the underlying mechanisms are unclear. We studied the feeding strategy of the Japanese marten (Martes melampus) in northern Japan by examining the relationship between dietary composition and abundance of main dietary items (fruits, mammals, and arthropods). The percentage of fruits in fecal samples over the study period (2020–2022) was much higher (65% in terms of the area percentage of the point-frame method) than that of arthropods (13%, with a higher proportion in spring) and mammals (11%, with a higher proportion in summer). The percentage of fruits in marten diets increased when abundance of arthropods and mammals was lower, which implies that Japanese martens are opportunistic feeders while being fruit-dependent. Different from other Martes species in boreal regions that depend more on small mammals, Japanese martens use a dietary switching strategy and prefer to eat fruits when they are seasonally available. The long-term variation in marten food habits implies that the ecological role of martens, such as controlling populations of prey animals and seed dispersal agents, can change transiently; therefore, monitoring the food environment is necessary to address inter-specific interactions in forest ecosystems.

Most animals capture light through opsins, which are light-sensitive G protein-coupled receptors (GPCRs). Recent genome analyses of anthozoans, including corals and sea anemones, have identified novel opsins that are phylogenetically classified into two groups distinct from previously known opsin groups. Despite their significance in clarifying biological functions, the specific molecular properties of these opsins remain largely unknown. In this study, we investigated the G protein activations and biochemical responses light-dependently induced by two anthozoan opsins, Antho2a and Antho2d, obtained from the reef-building coral Acropora tenuis, in mammalian cultured cells. Using jumping spider Rh1 (SpiRh1), which belongs to a known Gq-type G protein (Gq)-coupled opsin group as a control, we observed that Antho2a and Antho2d elicited light-dependent increases in Ca²+ levels in cultured cells. This response was inhibited by a Gq inhibitor, indicating that these opsins activated Gq in a light-dependent manner. Interestingly, Antho2d also activated the Gi-type G protein (Gi), similar to SpiRh1, while Antho2a showed limited or negligible Gi activation. We also found that Gi activation additionally contributed to the Ca²⁺ elevation, suggesting it enhances Gq-dependent Ca²⁺ elevation in Antho2d- and SpiRh1-expressing cells. In contrast, Antho2a demonstrated a higher specificity for Gq activation compared to SpiRh1 and was nearly equivalent to hM3Dq, a GPCR known for its strong Gq specificity and widely used as a chemogenetic tool for manipulating Gq activation. Our results suggest that this new anthozoan opsin group consists of Gq-coupled opsins with varying levels of Gi activation, demonstrating their potential for optogenetic applications.

A semi-terrestrial eumonostiliferous hoplonemertean species was discovered on the northeastern coast of the Bay of Bengal, India. Histological studies confirmed its affiliation with the genus Prosadenoporus Bürger, 1890. In this paper, it is described as a new species, Prosadenoporus indicus sp. nov. This species is distinguished from its congeners by a distinct black patch on the antero-dorsal surface of the head, a large body size, 16–18 proboscis nerves, a large frontal organ, the presence of neurochord cell, and exclusively circular muscles surrounding the rhynchodeum. A maximum-likelihood analysis of 658-bp cytochrome c oxidase subunit I (COI) gene sequences, including data from this species and five congeners available in public databases, supported the generic placement of the new species. The new species exhibited 10.3–11.1% uncorrected p-distance differences in 658-bp COI sequences compared to its congeners.

The heteronemertean genus Lineus Sowerby, 1805, currently accommodating about 100 species, is known to be non-monophyletic and is in a desperate need of taxonomic revision. In this article, we focus on a group of species including L. caputornatus Takakura, 1898, L. grubei (Hubrecht, 1879) auct., L. pictifrons Coe, 1904, and L. subcingulatus Takakura, 1898. These four morphologically similar species formed a clade to the exclusion of the type species, L. longissimus (Gunnerus, 1770), on a molecular phylogeny based on partial sequences of the 16S rRNA, 18S rRNA, 28S rRNA, cytochrome c oxidase subunit I, and histone H3 genes. For this clade we propose the name Bilucernus gen. nov. We redescribe L. grubei auct. from Japan as Bilucernus takakurai sp. nov. Bilucernus clade was nested within a larger clade that also contained members of Kulikovia Chernyshev, Polyakova, Turanov, and Kajihara, 2017, Lineopselloides Gibson, 1990, Siphonenteron Renier in Meneghini, 1847, and Tenuilineus Riser, 1993. We observed that body fragments from the intestinal region regenerated a head in B. caputornatus comb. nov. and B. subcingulatus comb. nov., but did not in B. takakurai sp. nov. The type specimen of Lineus bipunctatus Takakura, 1898 was most likely a regenerating individual of B. caputornatus comb. nov. We synonymize L. bipunctatus with L. caputornatus, giving nomenclatural priority to the latter. In addition, Lineus albifrons Coe, 1934 is herein also synonymized with L. caputornatus. We speculate that the unusually wide geographic distribution of B. caputornatus comb. nov. is related to its ability to regenerate head from fragments of body.