While the echolocation behavior and specialized adaptive auditory system of the greater horseshoe bat (Rhinolophus ferrumequinum) are well documented, comprehensive insights into its wild ecology, especially its detailed nocturnal movements for foraging behavior, remain scarce. Therefore, our objective was to obtain information on the spatiotemporal features of the movements of the Japanese greater horseshoe bat (Rhinolophus nippon), a close relative of R. ferrumequinum, during foraging. Hence, we investigated the nightly flight paths of R. nippon using high-resolution GPS data loggers. Initially, hidden Markov modeling analysis classified bat flight paths into two behavioral patterns: commuting and area-restricted behavior, the latter primarily corresponding to foraging activities. Focusing on foraging behavior along their trajectory, we observed that R. nippon repeatedly foraged with brief stops lasting only a few minutes and an average distance of approximately 300 m between any two foraging sites. Notably, one individual covered a considerable distance (23.6 km) from its roost, possibly because of irregular social behavior during the mating season. Furthermore, for commuting, bats occasionally used forest roads, which were located along the middle of relatively steep slopes. In cases of echolocations with limited detection distances, echoes from the ground and adjacent tree lines offered crucial navigation cues, underscoring the significance of forest roads as nightly movement routes for echolocating bats. Overall, our findings highlight the importance and urgency of ongoing research on bat movement ecology in Japan.

Octopuses have well-developed sensory organs and a large brain, which allows them to use multiple senses, such as vision, touch, and taste. Most studies on the sensory abilities of octopuses have focused on a single sensory modality, particularly vision. However, octopuses are simultaneously exposed to multiple sensory stimuli. If an octopus can transfer information about its environment between two different senses, then the flexibility of its multisensory system must provide an adaptive advantage. This type of recognition system is referred to as cross-modal recognition. Here, we describe cross-modal recognition between the vision and touch of novel objects in octopuses. Octopuses were engaged in learning three geometrically identical objects that provided different sensory information: i) a soft object transforming against touch (visual-only condition), ii) a hard object being shielded (tactile-only condition), and iii) a hard object (visuo-tactile condition). In the shape discrimination test of objects (ball vs. cross), all octopuses, except those in the visual-only condition, selected the correct object. Furthermore, octopuses that first learned about an object by touch immediately recognized it solely through vision. These observations indicate that octopuses are more likely to depend on the tactile information of objects in the process of forming representations of novel objects, and that cross-modal object recognition across tactile and visual perception exists in octopuses.

Understanding bat movement patterns is essential for epidemiology and bat conservation. However, such information is lacking in East Asia, including the Japanese archipelago. It is also unclear whether the straits surrounding the Japanese archipelago affect bat movement. We conducted a population genetic analysis for the Asian parti-colored bat (Vespertilio sinensis), distributed in Far East Russia and East Asia, including Japan. Samples were collected from three colonies in Hokkaido and eight in Honshu and sequenced for a mtDNA Cytochrome-b region. The population structure of this species was examined using phylogenetic and molecular variance analyses, which revealed a genetic separation between Hokkaido and Honshu; this suggested that the Tsugaru Strait, located between Hokkaido and Honshu, is a geographic barrier. Our demographic analysis revealed that V. sinensis of Hokkaido and Honshu had different population expansion histories. The genetic divergence between Hokkaido and Honshu further suggests that two-way migration across the Tsugaru Strait did not occur with V. sinensis. However, in the Mantel test, which was restricted to the Honshu population, the response to isolation by distance differed in summer and winter. This seasonal difference in response may indicate higher fidelity to summer roost or habitat compared to wintering areas. When combined with the results of a previous banding study, which showed that females exhibited two-way movement and males exhibited one-way movement, our findings support the conclusion that V. sinensis is migratory. These results provide new insights into the movement patterns of bat species within the Japanese archipelago.

The water mite genus Hygrobates and the newt family Salamandridae are distributed widely in the northern hemisphere. However, only in Eastern and Southeastern Asia a host-parasite association developed, with several Hygrobates species, which belong to the subgenus Lurchibates, parasitizing newts of the genera Laotriton, Pachytriton, and Paramesotriton. Presently, there is no molecular study on parasitic Hygrobates, which impedes our understanding of their phylogeny and the evolutionary history of the host-parasite association between Lurchibates and their hosts. In this study, we performed comparative phylogenetic analyses on parasitic Lurchibates mites and their newt hosts based on their respective phylogenies. Our results did not support the monophyly of parasitic species of Hygrobates, but instead, group them significantly with a free-living species, H. longiporus. Among the parasitic species, H. forcipifer, H. macrochela, H. malosimilis, and H. robustipalpis are significantly grouped together, while branching patterns of the remaining species were not supported. Distance-based approaches of cophylogeny analysis between hosts and parasites found no significant link. On the other hand, among all the cost schemes constructed by event-based cophylogeny methods, four cospeciation events, two duplication and host-switching events, one loss event, and two failure to diverge events between parasitic water mites and newts were discovered. Our findings suggested that host switching events might have played an important role in the evolution of these parasitic mites, which might have led to incompletely exclusive host-parasitic relationships at species level.

The study concentrated on the Notocomplana Faubel, 1983 species that exist in the northern regions of the Pacific Ocean. The research utilized a comprehensive methodology that combined molecular (mitochondrial COI and nuclear 28S rRNA genes) and anatomical approaches. The primary objective of this study was to gain a thorough understanding of the diversity of the genus Notocomplana in this region. This includes all possible species and their populations. The study used various analysis tools to establish the boundaries and relationships within and between species. Bayesian inference and maximum likelihood were used for kinship analysis, while bPTP, mPTP, and ABGD were used for species delimitation. Haplotype studies were conducted using TCS and MSN. The study focused on Notocomplana hagiyai Oya and Kajihara, 2017, a well-known species of the genus from Asia found along the coasts of Vladivostok in Russia, as well as Notocomplana species from the North Pacific coast of Asia and North America. The analysis revealed the degree of diversity in Notocomplana and the relationships between different species and populations, both within and between them. The diversity of species and haplotypes found on the North Pacific coasts was very motivating, particularly concerning the relationships between the Asian and American populations. Although the 28S analysis indicated that N. septentrionalis (Kato, 1937) was a sister group to the Asian species, the COI analyses did not provide any definitive resolution regarding the kinship relationships between N. septentrionalis and the other groups.

Understanding the growth of organisms is of fundamental importance in achieving the sustainable use of bioresources and/or the conservation of ecosystems. Hagfishes are oceanic scavengers that typically inhabit deep water and play an indispensable role in marine nutrient cycling. However, as the conventional methods for age determination are not applicable, the growth and lifespan of hagfishes are completely unknown. In the present study, the growth and feeding of the inshore hagfish (Eptatretus burgeri) in the laboratory were continuously monitored for an unprecedentedly long period (more than 1.4 years), with feeding once every 4–5 weeks. The animals displayed either positive/negative/zero growth across the experimental period. Eptatretus burgeri typically takes 8–10 days to digest food, and excretes all the gut contents at once as huge feces. Based on the growth, feeding and excretion data, it seems plausible that the wild populations feed at less than 2-week intervals. In addition, by adopting a recently developed technique to estimate fish age from the relative growth data, the age-size relationship in E. burgeri was explored. The generated growth curve predicted that the gonads start to develop only 4 years after hatching at the earliest. Eptatretus burgeri can live nearly 50 years, and the animals targeted in commercial hagfishery are mainly 6–9 years old. Moreover, additional insights into the oviposition cycle were obtained. The present study provides essential information for understanding the ecology of hagfishes and consequently highlights the putative vulnerability of wild hagfish populations to fishing and environmental stresses.

In this study, we obtain and analyze the first transcriptome data for the family Thamnocephalidae, targeting Branchinella kugenumaensis (Ishikawa, 1895), an anostracan fairy shrimp primarily found in Japan and Far Eastern Eurasia. We collected a male specimen from a rice paddy in Tochigi, Japan, and performed RNA-seq analysis, obtaining an assembled transcriptome comprising a 15,157 nucleotide sequence with an 80.75% completeness score. Because the relationships among the families within Anostraca remain unclear, using both mitochondrial and nuclear genes, we constructed phylogenetic trees employing maximum likelihood and Bayesian methods. Our results indicate that Artemiidae formed a cluster with Thamnocephalidae, and together they formed a sister group to the other Anostraca. We also demonstrated that a large number of parallel or back substitutions can hinder the estimation of phylogenetic relationships. This study not only enhances our understanding of anostracan phylogeny but also highlights the significance of transcriptome data in evolutionary biology.

Oxytocin (OT)/vasopressin (VP)-like peptide has been reported in invertebrates as a single peptide with various common names. This peptide was suggested to be a primitive form of the oxytocin and vasopressin present in vertebrates. In this study, the full mRNA sequence of the OT/VP-like peptide was annotated in the central nervous system (CNS) transcriptome of the mud crab Scylla olivaceathrough the National Center for Biotechnology Information (BioProject ID: PRJNA1006859). The sequence contained 607 bp corresponding to 158 amino acids. Multiple alignment and phylogenetic tree analyses suggested that the OT/VP-like peptide of S. olivacea is most similar to that of Scylla paramamosain. Reverse transcription polymerase chain reaction (RT-PCR) analysis indicated that the mRNA was expressed in the eyestalks, brain, ventral nerve cord (VNC), ovaries, and other peripheral organs. Real-time qPCR revealed that the highest expression levels of this mRNA occurred in the CNS and ovaries of the crabs bearing stage I ovaries. Using the conserved region CFITNCPPGGKRSGGLMSTLGR to produce antibody, the OT/VP-like peptide was detected in neuronal clusters 6/7, 8, 11, and 14/15 and in neuropils of the brain, as well as the neurons and neuropils of the VNC, including the subesophageal (SEG), thoracic (TG), and abdominal (AG) ganglia. In the ovaries, immunoreactivity of this peptide occurred in the ooplasm of the oocytes of immature ovaries, and it was detected near the cell membranes of oocytes of mature ovaries. This work supports the neuro-endocrine study of an economically important mud crab species and could be helpful in aquaculture management.

A new lineid heteronemertean with a branched proboscis, Polydendrorhynchus amaleshii sp. nov., is described as the second member of the genus Polydendrorhynchus Yin and Zeng, 1986, following Polydendrorhynchus zhanjiangensis (Yin and Zeng, 1984). The description is based on specimens collected from the northeastern coastal Bay of Bengal, including the Subarnarekha Estuary and Frazerganj in the Indian Sundarbans mangrove ecosystem. The new species is distinguished from its congener by having up to 56 terminal branchlets of the proboscis and the absence of rhynchocoel compartments. In a maximum-likelihood phylogenetic analysis based on COI and 16S rRNA genes, P. amaleshii and P. zhanjiangensis formed a well-supported clade. Polydendrorhynchus amaleshii represents the ninth nemertean species recorded from India.

We report the first record of the pallenopsid pycnogonid species Bathypallenopsis californica (Schimkewitsch, 1893) from the northwestern Pacific. Based on one male specimen collected from 1987–2007 m depth off the southeastern coast of Hokkaido, Japan, we redescribe the species and present its cytochrome c oxidase subunit I (COI) sequence for use in future DNA barcoding. We found a cystidean-stage crinoid on the leg-1 femur of the sea spider, representing the first record of a cystidean found on a sea spider. BLAST searches for COI and 28S sequences revealed that the crinoid was Florometra asperrima (Clark, 1907).