In species belonging to the phylum Ctenophore, comb plates consisting of bundles of multiple cilia are a characteristic synapomorphy and are essential for active swimming. However, in most species of the order Platyctenida, even though pelagic larvae have comb plates, adults completely lose comb plates and exhibit a sessile lifestyle. To understand the evolution of platynectids' unique lifestyles, it is necessary to reveal how comb plates are lost during the larval stages. Therefore, in this study, to reveal the process of comb plate degeneration, histological observations on larvae of different post-hatching ages were carried out in the harp comb jelly, (Platyctenida: Lyroctenidae). The observations showed that the number of comb plates decreased along with the larval growth, and they completely disappeared before the larvae settled down. Also, it was shown that the sizes of the ribs (rows of comb plates) in larvae increased until around 30 days after hatching, while relative sizes of ribs with respect to larval body sizes continued to get smaller after hatching. This suggested that, in , although the ability to disperse away from their parents would be maintained after hatching as long as ribs develop, this ability would significantly decrease after the cessation of rib development. Therefore, in contrast to pelagic comb jellies in which ribs continue to develop throughout their lives, acquired mechanisms to cease rib development and promote rib degeneration during their post-hatching growth, which are involved in the evolution of novel sessile lifestyles.

Photoperiod and melatonin regulate reproduction in mammals. The rice rat () is reproductively photoperiodic and on a long photoperiod responds to melatonin administration with inhibited reproduction. I examined whether photoperiod, melatonin, and the removal of gonadal steroids via castration affected growth, reproduction, pelage, and swimming ability. Juvenile males were housed on 14L:10D or 11L:13D and at 68 days of age rice rats were weighed, allowed to swim for 10 minutes while being videotaped to quantify swimming and floating times, and then reweighed. One day later, these rice rats were euthanized and the testes, seminal vesicles (SV), Harderian glands (HG), and spleen were weighed. The shorter photoperiod significantly decreased body, testes, SV, and HG masses only. The pelage of rice rats absorbed more water on 14L:10D than on 11L:13D, despite no difference in pelage lengths. Melatonin implants decreased body mass, the masses of the testes, SV, and HG, and pelage water absorption, but increased pelage length. Lastly, castration decreased SV and HG masses, but increased body and spleen masses. Swimming and floating times were not affected by any treatment. Taken together, these results show that all treatments affected growth and reproduction in rice rats, but did not affect swimming ability. Thus, the physiological changes characteristic of winter are not sufficient to alter aspects of swimming ability as swimming ability appears to be independent of reproductive condition.

The Siberian weasel () is a mustelid widely distributed in Asia. Previous mitochondrial DNA (mtDNA) phylogenetic analyses showed that this species consists of two clades (the northern and southern lineages) in native populations, and that introduced populations currently expanding in western Japan could have originated from Korea. To elucidate the origin and history of expansion, genome-wide single nucleotide polymorphisms (SNPs) were obtained through double-digestion restriction site-associated DNA sequencing (ddRAD-seq) of biparentally inherited nuclear DNA in addition to the maternally inherited mtDNA. The SNPs were used to study the population genetics of Siberian weasels across the Asian continent, the Korean Peninsula, Taiwan, and the Japanese archipelago, including Tsushima and three of the four main islands: western part of Honshu, Shikoku, and Kyushu. Our results showed genetic differentiation among native populations between the continent and Taiwan. The Taiwan population differed markedly from other populations. Our phylogenetic analyses indicated that introduced founders from the continent and their offspring expanded their range from west to east in Japan, which is consistent with a previously reported mtDNA phylogeny. Our study detected no evidence of hybridization between the Siberian weasel and the related Japanese weasel (), which have overlapping habitat ranges.

The selection of settlement sites by larvae is a crucial event in the life cycle of sessile animals, as they are usually unable to migrate after settlement and metamorphosis into sessile forms. For example, some species prefer hydrophilic substrates, whereas others prefer hydrophobic substrates. Understanding larval preferences for substrates will provide an essential basis for controlling biofouling. In this study, we focused on the water wettability of substrates for settlement and investigated larval substrate preference in three ascidian species, , , and (= type A), using a four-choice assay with substrates of different water wettability (contact angle of a water droplet): silicone rubber (115°), polyvinyl chloride (80°), glass (31°), and hydrophilic film SH2CLHF (14°). In some regions of the world, and are often noted as invasive species and are serious biofoulants. In all three species, larvae showed a significant preference for more hydrophobic substrates, and none settled on the most hydrophilic substrate, that is, SH2CLHF. It is difficult to explain why ascidian larvae prefer a more hydrophobic substrate, since hydrophobic materials, such as silicon, are often used as antifouling measures. This inconsistent substrate preference can be applied to mitigate biofouling.

The acanthocephalan genus Yamaguti, 1935 currently comprises 12 fish-parasitic species. Except for Yamaguti, 1935, the remaining 11 congeners have not been the subject of molecular phylogenetic studies. (Harada, 1935) has been found in brackish and marine fish in Taiwan and Japan, but its morphology remains inadequately understood. In this paper, we provide a morphological redescription and infer the phylogenetic position of within the Pomphorhynchidae. Furthermore, we summarize the morphological characteristics of to distinguish it from the morphologically similar genus Amin, Bauer, and Sidorov, 1991.

Scientific names, especially epithets (specific names in the zoological nomenclature), are derived from various factors, not only species characteristics but also cultural backgrounds, such as the names of people. They reflect how species were perceived at the time. However, several ethical issues have been raised, such as naming species after criminals and gender imbalance in eponyms (epithets named after people). Previous research has been conducted through thorough literature reviews with random sampling, which requires significant time and effort. In this study, the accuracy of the automated labeling using a large language model (LLM) was assessed, and the temporal etymological trends of 2705 species of phytophagous arthropods were investigated. LLM-based classification achieved scores above 75% and accuracy above 90% in , , , and . However, and exhibited accuracy issues. Analyses using the generalized additive model (GAM) revealed shifting naming trends, with a decrease in and an increase in and , consistent with previous research on spiders. This study demonstrates the effectiveness of LLM-based classification for epithets and provides a new perspective on the social and scientific debates surrounding scientific names based on etymological trends.

The mechanisms underlying sexual differentiation in viviparous chondrichthyans remain poorly understood, particularly regarding the impact of the maternal environment on early gonadal differentiation. In this study, we examined gonadal and reproductive duct differentiation in red stingray () embryos before and after clasper formation through detailed histological analyses. Histological observations revealed that early embryos (stage 3, before clasper formation) exhibited undifferentiated gonads with scattered primordial germ cells, whereas later embryos (stage 4, during clasper development) exhibited clear sexual dimorphism. Female gonads contained numerous germ cells localized in the dorsal region, whereas male gonads contained fewer scattered germ cells. Both the Müllerian and Wolffian ducts were present in both sexes, with the Wolffian ducts emerging from the Müllerian ducts in a segmental pattern. Stage 4 female embryos exhibited a selective enlargement of the right Müllerian duct, establishing reproductive tract asymmetry. The sex ratio of red stingray embryos was 1:1. These findings provide the first detailed histological characterization of gonadal differentiation and reproductive duct development in a viviparous chondrichthyan and establish an essential foundation for future studies on sexual development in these evolutionarily significant vertebrates.

Many animals build shelters to avoid predation, but some predators cope with these shelters to prey on them. To explore the behavioral interactions between shelter-building prey and their predators, we investigated the shelter defenses of two caterpillar species (Lepidoptera: Crambidae) and the hunting behavior of each predator species (Hymenoptera: Vespidae: Eumeninae) under laboratory conditions. Female wasps of and . were observed attacking the larvae of and (Lepidoptera: Crambidae), which construct open and closed leaf shelters, respectively. The attack behaviors differed between the two wasp species. employed two attack strategies: (I) boring holes in shelters and driving caterpillars out, and (II) invading shelters and searching for prey inside. In contrast, . utilized a single strategy: cutting the silk threads binding the leaves with their mandibles to open the shelters and search for prey inside. Approximately half of the prey caterpillars could avoid predation; the shelter morphology and behavior of each caterpillar species likely contributed to evading the wasps. Each caterpillar species may have adapted a specific anti-wasp defense, while each wasp species may have acquired offensive traits to overcome the defense of each prey.

During a faunal survey in Baños del Inca hot spring (40-50°C), Cajamarca, Peru, we collected a cyprinotine ostracod species, the sixth example of a thermophilic ostracod inhabiting freshwater in temperatures above 40°C. Because this could not be assigned to any of nine genera in Cyprinotinae, we established the new genus for it and described it as gen. et sp. nov., defined by the following combination of characters: (1) no dorsal hump on carapace, (2) no tubercles on either valve, (3) left valve slightly overlapping right valve along all margins, (4) no selvage on anterior part of right valve, (5) only seta d1 on first podomere of 6th limb, (6) only two shields (medial and lateral) on hemipenis, and (7) medial shield unilobed and lateral shield tooth-shaped. We determined partial sequences for the mitochondrial cytochrome oxidase subunit I (COI) and nuclear 18S and 28S rRNA genes from a specimen of the new species. In a maximum likelihood tree based on 18S + 28S, was the sister taxon to (Yoo, Cohuo, Macario-Gonzalez, and Karanovic, 2017), with high branchial support. A clade including Cyprinotinae ( Brady, 1868 + Claus, 1892 + ) and Eucypridinae ( Vavra, 1891) was fully supported; our phylogeny showed not to be monophyletic.

We describe a new species of loach, sp. nov. from Guangxi Daguishan Crocodile Lizard National Reserve in Hezhou City, Guangxi Zhuang Autonomous Region, China. Morphologically, the new species can be distinguished from congeneric species by the following combination of characters: dorsal-fin origin posterior to pelvic-fin origin; pectoral fins short, not reaching pelvic-fin base; pelvic-fin tip does not exceed anus; body width 10.2%-13.6% of standard length; eye diameter 15.5%-19.3% of head length; posterior chamber of swim bladder degenerated. Phylogenetic analysis of the mitochondrial cytochrome oxidase subunit I and cytochrome gene markers supports its species-level distinctiveness, with uncorrected -distances ranging from 7.4% to 9.7% from closest relatives.

Three non-encysted digenean metacercariae were found parasitic in the mesoglea of two of 13 individuals of the staurozoan cnidarian Kishinouye, 1910 from Yoichi, Hokkaido, Japan. The metacercariae comprised two morphospecies (one oval, the other elongate), for which the gross morphology is described. Partial sequences of the 18S and 28S rRNA genes and the internal transcribed spacer 2 region were determined for both species, and a partial sequence of the cytochrome oxidase subunit I gene was determined for the oval species. Molecular phylogenetic analyses revealed both digeneans to be in the family Lepocreadiidae, a taxon not previously reported from staurozoans. The oval species was a member of the " Clade." The elongate species was identified as (Layman, 1930), known to use marine fishes in the genus Linnaeus, 1758 as definitive hosts. Second intermediate hosts of known around Australia include five hydrozoan, one scyphozoan (Cnidaria), and one ctenophoran species. This is the first information on a second intermediate host from Japan; however, we cannot rule out the possibility that staurozoans may also be dead-end hosts. Including an opecoelid species previously reported, three digenean species in two families are now known from a single staurozoan species in the small region comprising the northwestern coast of Hokkaido. Future surveys for parasites in other staurozoan species and regions will likely detect additional digeneans and other parasite groups utilizing staurozoans.

Using mitochondrial DNA and genome-wide SNP, phylogenetic relationships in were investigated. Phylogenetic analyses based on subregions of mtDNA found possible lineages of several cryptic species, but did not support the phylogenetic relationships of some groups. Phylogenetic analyses based on SNP resulted in the same topology as mtDNA, with some exceptions, and clarified the phylogenetic relationships among all lineages. Genome-wide analyses successfully estimated taxonomic positions of several lineages that could not be resolved in mtDNA analyses.

Anemonefish have a characteristic vertical white barred color pattern on an orange background made by a specific distribution of three types of pigment cells: melanophores, xanthophores, and iridophores. This color pattern is an interesting alternative model to zebrafish to understand the cellular and molecular basis of complex color pattern formation. Using transmission electron microscopic observations, we have investigated the pigment cell composition in the skin of the anemonefish and found that: 1) white skin comprises iridophores and isolated melanophores; 2) orange skin contains xanthophores and scattered melanophores; and 3) black skin encompasses melanophores only. All three pigment cells can be found in the dermis. Iridophores are also present in the hypodermis, but general cell morphology differs depending on the dermal layer, distinguishing them into S-type and L-type iridophores. While melanophores can mix with xanthophores and iridophores, xanthophores and iridophores are not in direct physical contact, always being separated by melanophores. Anemonefish with differing color patterns than , either color mutants or other anemonefish species, possess different pigment cell distribution and organization reflecting their respective colors. Our analysis provides key data to inform on the mechanism generating the diversity of color patterns present in anemonefishes.

Snails of the family Eulimidae are parasites of echinoderms in all five extant classes. Despite long years of taxonomic research on Eulimidae in Japan, their local species richness remains to be investigated, and few studies have focused on a eulimid fauna of a certain echinoderm taxon, even if it is a common species. Here, we conducted a comprehensive sampling of species parasitizing the black sea cucumber in Shirahama, Wakayama, central Japan. The data used in this study were partly obtained during a summer education program of the Seto Marine Biological Laboratory, Kyoto University. and parasitized the external surface, and two unidentified species were found inside the host's body cavity. This study represents the first record of in Japanese waters and eulimids exploiting the internal habitat of . Morphological and molecular comparisons between the present four species and other Japanese specimens suggested that they generally exhibit wide geographic distributions and low host specificity. Additionally, the two species from the body cavity were probably seldom observed in central Japan, as inferred from the accumulated results of the dissection of through a long-running, annual education program at Shirahama.

Copy number variation (CNV) in gene loci in animals can be driven by adaption to the environment. The relationship between CNV in genes for amylase (), which hydrolyzes starch, and dietary adaptation has been well studied. Copy number (CN) of is higher in human populations with high-starch diets, compared with those with low-starch diets. Although CNV in has been reported in humans and some domestic animals, there have been few studies of animals in the wild. The brown bear (), widespread in the Northern Hemisphere, shows large dietary variation among individuals and groups. Brown bear population genetic structures are associated with the dispersal history due to climate change over the past few tens of thousands of years, and this together with dietary variation should have led to CNV in . In this study, we investigated CNV in in brown bears worldwide by using whole genome sequencing data. We detected CNV among regional groups. CN was similar among brown bears in geographically proximate populations, such as between Hokkaido (Japan) and East Asia, and between the North America mainland and the ABC islands. CNs were smaller in bears from East Asia, including Hokkaido, compared to those from other regions across brown bears' distribution. Our results suggest that CNs of reflect the population demographic history of brown bears after the Last Glacial Maximum.

Symbiosis is a key driver of evolution in life-history traits and reproductive strategies. Some symbiotic microorganisms manipulate host reproduction to enhance their own transmission, a phenomenon well studied in insects but less understood in crustaceans. Among these microorganisms, manipulates host reproductive systems, such as parthenogenesis, cytoplasmic incompatibility, and male killing in arthropods. However, its role in ostracods, small bivalve-shelled crustaceans, remains unclear. Some ostracod species reproduce via parthenogenesis, and high infection rates in these lineages suggest a potential link between the symbiont and asexual reproduction. To investigate this relationship, we examined localization in the parthenogenetic ostracod from Japan. Using tissue clearing and fluorescence in situ hybridization (FISH), we visualized within the ovaries. FISH observations revealed a widespread infection across the germarium, nurse cells, and oocytes. In early-stage oocytes, bacteria were evenly dispersed throughout the cytoplasm, whereas in more-developed oocytes, they clustered around the nucleus. Additionally, was also detected in the hepatopancreas, indicating infection of both the reproductive and digestive systems. The presence of in host reproductive structures, particularly the germarium, nurse cells, and developing oocytes, suggests its role in reproductive manipulation. To our knowledge, this study provides the first detailed localization of in ostracods, reinforcing its potential influence on reproduction. Future research using antibiotics and genomic analysis will be crucial to confirm 's role in parthenogenesis induction.

Rhabdocoel flatworms of the family Typhloplanidae are predominantly found in freshwater and limnoterrestrial environments, with only a few species inhabiting marine and brackish water ecosystems. In this study, a flatworm was discovered in moist soil containing nematodes in the Guizhou plateau of southwest China for the first time. A new species, Zuo, gen. et sp. nov., belonging to a newly established genus, was described through morphological and phylogenetic analyses. The main distinguishing features of this new species include a rosette-shaped pharynx located at 1/2 of the body length, paired testes embedded in the vitellaria on either side of the pharynx, an independent copulatory bursa, and a short rod-like ascus. Additionally, a single gonopore is situated in the posterior 1/4 to 1/5 of the body length, with a distinct genito-bursal duct leading to the dorsal intestine. The new species was observed to prey on the soil nematode (Kofoid and White, 1919). Experiments demonstrated that the flatworms could reproduce normally over an extended period when fed on . Isolated cultured flatworms can produce offspring, indicating their capability of self-fertilization. The findings of this study are anticipated to offer a novel solution for the biological control of agricultural soil nematodes.

Many cnidarian animals possess multiple opsins, including a type known as cnidopsin, which is found throughout the phylum Cnidaria and is divided into several subgroups. Previous studies have suggested that cnidopsins from jellyfish and coral can light-dependently elevate intracellular cAMP levels, likely via activation of Gs-type G protein in cultured cells. However, their spectroscopic properties remain largely unclear, with the exception of jellyfish opsins. We recently identified eight cnidopsins from the reef-building coral and showed that they phylogenetically belong to different cnidopsin subgroups. Here, we spectroscopically analyzed one cnidopsin from each subgroup as a representative. We successfully obtained the absorption spectrum of one purified cnidopsin and found that it was blue-sensitive, with an absorption maximum at ∼460 nm. Blue light irradiation (460 nm) resulted in a red-shifted absorption spectrum, while subsequent irradiation with orange light (> 560 nm) caused a blue-shift. The difference spectra of after versus before repeated irradiation with alternating blue and orange light produced mirror images, indicating a bistable nature. We also successfully observed the absorption spectra of one of two other cnidopsins belonging to the same subgroup as the blue-sensitive cnidopsin. The spectral changes suggested that it was also a bistable opsin. These results suggest that these two coral cnidopsins, which belong to the same cnidopsin subgroup, are bistable-unlike jellyfish opsins, which belong to a different cnidopsin subgroup.

To elucidate the control mechanism of tail resorption during metamorphosis, the expression of , a macrophage-apoptotic cell bridging molecule that promotes phagocytosis in mammals, was examined. In both and , the expression in the tail increased significantly during metamorphosis, reaching its peak at the metamorphic climax, when the tail shortens rapidly. This finding suggests that the up-regulation of at metamorphic climax is involved in the clearance of apoptotic tail muscles. To investigate the significance of up-regulation, -deficient tadpoles were generated using the CRISPR/Cas9 method, and the effects of -deletion were examined. Delayed tail resorption process was observed in the -deficient mutants (from 9.8 days [wild type] to 13.2 days [F2 mutant]), suggesting that elevated expression during the metamorphic climax contributes to the tail resorption.

An understanding of the food web in forest ecosystems is essential to ensuring that society lives in harmony with nature; however, this can be challenging in areas mainly composed of forest environments, such as in the Japanese Archipelago. Examining fecal samples collected from the forest edge can aid in determining the ecological roles of host species. In this study, a DNA barcoding method using original primers was applied to identify the carnivoran host species from fecal samples. DNA metabarcoding using and markers was then conducted to elucidate the plant and invertebrate diets of the Japanese marten, (Carnivora, Mustelidae). The dietary analyses revealed that consumed a diverse array of plants and animals. Most of the consumed plant species were fresh fruits, reflecting the fruiting season of the detected plants. This implies a role for in seed dispersal and thus in forest maintenance. Considering the activity seasons, we also found that various adult-stage insects (beetles, cicadas, sphinx moths, and grasshoppers) contributed to the marten's diet, together with invertebrates (earthworms, etc.), which are easily digested and therefore difficult to detect through traditional methods. Although the marker used was designed for invertebrate species, one bird species, the brown-eared bulbul, , was found to make up a small part of the winter to early spring diet. These results show that, while mainly consumes seasonal fruits, it can adapt its diet in response to environmental changes, such as by including invertebrates and small vertebrates.

We report the first record of the pallenopsid pycnogonid species (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 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 (Clark, 1907).