The commensal shrimp genus Athanopsis Coutière, 1897 (Alpheidae) includes nine species worldwide. Almost all congeners have been confirmed to be associated with spoon worms (Annelida: Thalassematidae). Athanopsis dentipes Miya, 1980 was originally described about 45 years ago based only on the male specimens collected along with the thalassematid spoon worm Anelassorhynchus cf. mucosus (Ikeda, 1904) in Kyushu Island, western Japan. However, it has never been collected since its original description. In this study, we rediscovered this species in the intertidal zone of the southern Kii Peninsula, Wakayama Prefecture, central Japan, and redescribed it based on both male and female specimens. Morphologically, this species is distinguished from its closest relative, Athanopsis australis Banner and Banner, 1982, by its ventrally straight rostrum, a large tooth at the cutting edge on the dactylus of major chela, and a small subacute tooth at the ventrolateral distal angle on the merus of third pereopod. All of the specimens were associated with thalassematid hosts, including two genera and four species of Thalassematini-i.e., Listriolobus cf. sorbillans (Lampert, 1883) and three species of Anelassorhynchus Annandale, 1922-substantially expanding the known host range of this shrimp species. The shrimps were observed to scuttle over the body surface of the host in the aquaria. One male-female pair was collected from the same host in February, and two ovigerous females were collected in February and April.

In animal species where dominance relationships are established through male-male competition, many subordinate males do not participate in reproduction, but some subordinate males gain reproductive opportunities through alternative tactics, such as sneaking. In medaka (Oryzias latipes), in which males flexibly change their reproductive tactics, not only the dominance relationships between males but also the courtship aggressiveness of individual males toward females may influence the selection of reproductive tactics such as pair-spawning, sneaking, and non-participation in reproduction. However, no previous studies have examined the relationship between the dominance relationship between two males and their reproductive tactics, nor the relationship between courtship behavior toward females and their reproductive tactics. In this study, two males were allowed to compete, and an ovulated female was introduced into a tank. Fighting behavior between males when only males were present, fighting behavior between males after the female was introduced, and the courtship behavior of each male toward the female were quantified, and the behavioral patterns were analyzed. The results showed that many subordinate males in male-male competition did not participate in reproduction, and that sneaker males could be classified into two different behavioral patterns: those that were subordinate to rival males and those that were dominant. These results suggest that sneaking is not a fixed tactic but rather that various behavioral patterns can be adopted depending on the aggressiveness of rival males and their courtship positivity toward females, providing important insights into the flexibility of male reproductive tactics.

Insect wings often bear dense arrays of nanoscale protrusions known as nanopillars that confer functions such as water repellency, self-cleaning, and antibacterial activity. However, how these cuticular nanostructures develop remains poorly understood. Here, I investigate the development of wing nanopillars in the dragonfly Anax parthenope and compare it with that in the cicada Hyalessa maculaticollis. Using electron microscopy, I examined the formation of the wing surface from early cuticle deposition to post-ecdysial stages. In the dragonfly, the wing surface remained smooth throughout cuticle formation and nanopillars appeared only several hours after ecdysis, indicating that they likely arise through physicochemical self-organization of wax-based lipids secreted onto the wing surface. In contrast, nanopillars were already present on pharate wings of the cicada, indicating that they form before ecdysis, although the precise timing and mechanism remain unresolved. These findings show that superficially similar nanostructures on insect wings can differ in developmental timing and may arise through different developmental routes, highlighting the diversity of mechanisms underlying cuticular surface patterning.

High-altitude environments expose poultry to low temperature, hypoxia, and strong UV radiation, but how combined environmental gradients shape plumage lightness remains insufficiently resolved. Using Qiangshan cloud chickens from Wenchuan, we analyzed 150 dorsal plumage samples collected along 900-2800 m. Plumage lightness (L-value) was measured by colorimetry, and eumelanin content was quantified by alkaline dissolution spectrophotometry. Five environmental variables (UV index, altitude, mean annual temperature, annual precipitation, and forest coverage) were integrated from field monitoring, meteorological records, and remote sensing data. We combined correlation analysis, hierarchical regression, principal component analysis (PCA), path analysis, and interaction surface modeling to partition direct, indirect, and synergistic effects. L-value was negatively associated with altitude and melanin content, and the melanin-L-value relationship remained stable across altitude strata. PCA summarized environmental variation into PC1 (UV index, altitude, temperature) and PC2 (precipitation, forest coverage), jointly explaining 88.4% of L-value variance. Path analysis showed that melanin exerted a masking effect on the PC1 pathway while partially mediating the PC2 pathway (mediation proportion 76.2%). A significant PC1 × PC2 interaction indicated non-additive control of plumage lightness under combined environmental extremes. These results support a mechanism in which high-altitude stress promotes melanin deposition and darker plumage as a photoprotective and thermoregulatory adaptation, and they highlight the importance of environmental interactions in shaping poultry phenotypic responses.

Rodents play a central role as reservoirs of zoonotic pathogens, yet the ecological and meteorological factors affecting pathogen prevalence remain unclear. In this study, a meta-analysis was used to evaluate the influence of host species and meteorological factors on the prevalence of Babesia microti in two common Japanese field mice, Apodemus speciosus and A. argenteus. The data were collected from seven published studies conducted across Japan. To examine the effects of total annual precipitation, average annual temperature, and host species, generalized linear mixed models were employed. The prevalence of the Hobetsu/Otsu-type B. microti was significantly higher in A. speciosus than in A. argenteus, indicating possible differences in reservoir competence and vector preference by Ixodes ovatus, which mainly infests terrestrial rodents. Conversely, the prevalence of the Kobe-type B. microti showed no significant differences between host species; however, it was negatively correlated with increasing precipitation. These findings suggest that meteorological factors may reflect a behavioral mismatch between the tick vectors, Haemaphysalis longicornis and Ixodes nipponensis, and their Apodemus hosts. One possible explanation for these results is that the vectors for Kobe-type B. microti, such as H. longicornis and I. nipponensis, primarily quest on vegetation, and the frequency of host-vector contact decreases when rodents remain in their burrows during heavy rain. This study provides the first quantitative evidence of host-environment interactions impacting rodent-borne babesiosis in Japan. It underscores the importance of considering meteorological and ecological perspectives when forecasting tick-borne disease risks in the context of climate change.

The biota of the southern part of the Ryukyu Archipelago (South Ryukyu) is considered to have been formed relatively recently by organisms that migrated from Taiwan Island and continental China. However, phylogeographic patterns of insect species in South Ryukyu remain largely unexplored. In this study, we elucidated the intraspecific phylogeny and divergence time of Vagitanus terminalis, a small cicada species distributed from continental China to Taiwan Island and South Ryukyu. We conducted phylogenetic analyses using two mitochondrial and two nuclear gene sequences, and genome-wide DNA sequences and SNPs obtained through MIG-seq. We found that V. terminalis populations from Sichuan in continental China and Taiwan Island were genetically closely related despite the large geographical distance between them. In contrast, in South Ryukyu substantial genetic differentiation was detected between Yaeyama Islands and Miyako Island. The Yaeyama Islands populations were estimated to have diverged from Miyako Island and Taiwan-continental China populations approximately 2.4 million years ago (confidence interval: 1.1-4.0), during Early Pleistocene when the formation of the Ryukyu Archipelago began. These results suggested that colonization to the two island areas in South Ryukyu occurred at different times and via different routes, although precise phylogenetic relationships and divergence times among these populations and Taiwan-continental China populations remain to be clarified through additional taxon sampling and sequence data. Overall, our findings revealed substantial genetic differentiation among non-endemic insect populations in South Ryukyu, including the presence of relict populations with an ancient origin.

Fissiparity, a form of asexual reproduction, involves the loss of significant body parts followed by regeneration. In echinoderms, this mode of reproduction has been documented in numerous species, particularly among holothurians, asteroids, and ophiuroids. Fissiparous brittle stars typically exhibit six-fold symmetry and restore this body plan by regenerating the missing half of the disk and three arms after fission. However, the detailed regeneration process and its dynamics in natural populations remain poorly understood. Here, we characterized post-fission regeneration in the brittle star Ophiactis savignyi by defining eight stages based on external morphology and histological features. Our observations revealed that, during early disk regeneration, the paired lateral arm primordia developed prior to the central primordium, suggesting that regenerating individuals may transiently pass through a five-armed configuration before re-establishing six-fold symmetry. We further quantified the frequency of each regeneration stage in a wild population and examined its relationships with season and body size. Early regeneration stages were less frequent from winter to spring and among large individuals, indicating that fissiparity is more active during warmer periods and in smaller individuals. In addition, swelling of interradial regions containing gonads was observed in some large individuals, suggesting a size-dependent life-history strategy in which asexual reproduction predominates in smaller individuals and sexual reproduction becomes more prominent with growth.

Mammalian ovarian cancer G protein-coupled receptor 1 (OGR1; also known as GPR68) functions as both a proton- and metal-ion-sensing receptor, activating multiple intracellular signaling pathways. Although OGR1 homologs across vertebrates are commonly activated under low pH conditions, their responsiveness to metal ions varies by species, possibly reflecting differences in physiological metal requirements. To identify the residues responsible for metal ion sensing, we analyzed human OGR1 and its homologs in zebrafish and African clawed frog. Nickel ions activated human OGR1 and one African clawed frog homolog (xLOGR1#3) but not zebrafish OGR1 and another African clawed frog homolog (xLOGR1#1), which lack a specific histidine residue in the first extracellular loop. Substituting histidine with alanine in human OGR1 reduced metal-ion-induced activation, without significantly affecting proton responsiveness. Conversely, introducing histidine at the corresponding position restored the metal ion sensitivity. This histidine-dependent activation has also been observed for cobalt and manganese ions. These findings suggest that, beyond its role as a proton sensor, OGR1 has evolved metal-ion-sensing capabilities, potentially reflecting species-specific adaptation.

Predators constitute an important source of biotic resistance influencing the establishment and population increase of non-native species, and the strength of this resistance depends on how effectively predators tolerate or overcome the defenses of non-native prey. In this study, we compared the effectiveness of defenses in the non-native leaf beetle Lema diversipes and its closely related native congener L. decempunctata (Coleoptera: Chrysomelidae) against two native predators: the Japanese tree frog, Dryophytes japonicus (Anura: Hylidae), and the Japanese skink, Plestiodon japonicus (Squamata: Scincidae). Adults of both beetle species secreted chemicals from their elytra when stimulated. To investigate defensive effectiveness, individual adults were provided to predators under laboratory conditions. All adults of both beetle species were attacked and consumed by tree frogs, whereas 93% of L. diversipes and 60% of L. decempunctata were rejected by skinks. These results indicate that the beetles' chemical defenses are more effective against skinks than against tree frogs. Consequently, native tree frogs may exert stronger biotic resistance than native skinks, and tree frogs potentially suppress the population increase of L. diversipes. Overall, our findings show that chemical defense effectiveness varies between predator groups, highlighting the importance of predator diversity in shaping invasion outcomes.

Females often choose mates using multimodal sensory signals from males. However, in many species, it is common for studies to concentrate on mate preferences for specific sensory signals. The guppy (Poecilia reticulata) is a model species used to study female mate choice. Mate preference studies in female guppies have concentrated on male visual cues, such as color spot characteristics and courtship activity. Although female chemical cues are known to affect mating preferences in male guppies, knowledge of the effects of male chemical cues on female mating preferences is limited. In this study, we examined the consistency of mating preferences for male chemical cues among female guppies. We repeatedly performed a dichotomous mate choice experiment using the chemical cues of two males for females daily for 6 successive days ("6 days' trials"). The results showed that females preferred one of the two male chemical cues throughout the 6 days' trials, indicating consistent female preference for male chemical cues in this species. In addition, the time spent by females with chemical cues decreased as the 6 days' trials progressed for both males' cues. Males with chemical cues preferred by females possessed larger orange spots than the other males. These results suggest a connection between male chemical and visual sexual signals, and female assessment of better mates using multimodal sensory signals, even in poor visual environments.

During a recent survey of tardigrades at the Cumming Nature Center (owned by the Rochester Museum & Science Center; New York, U S A), a new species of the rare and oligospecific genus Mesocrista was discovered. We provide an integrative description of this new species based on morphology and genetics (four standard DNA markers used in eutardigrade taxonomy). Mesocrista ojagwaji sp. nov. exhibits a combination of characters intermediate between those of M. spitzbergensis (Richters, 1903) and M. revelata Gąsiorek, Stec, Morek, Zawierucha, Kaczmarek, Lachowska-Cierlik, and Michalczyk, 2016, but the conducted phylogenetic analyses indicated that it is a sister species of the latter. Subtle morphological disparities with regard to M. revelata suggest a recent divergence event and deliver a new case of pseudocryptic tardigrade species.

The larval trematode taxon Monilicaecum ventricosum Yamaguti, 1942 (Didymozoidae) was redescribed from its type host, the Pacific saury Cololabis saira (Brevoort, 1856), collected from the North Pacific off Eastern Hokkaido, Japan. Because didymozoid larvae and adults differ markedly in morphology, linking these two stages using morphological data alone has traditionally been difficult. Consequently, the monotypic genus Monilicaecum Yamaguti, 1942 is currently regarded as a collective group, similar to genera established solely on larval forms of other trematodes. However, recent advances in molecular studies have enabled researchers to link larval and adult stages, clarify life cycles, and undertake more robust taxonomic evaluations. In this study, newly collected larval specimens were examined morphologically, and DNA barcodes (28S, ITS, and cox1) were generated to confirm their identity as M. ventricosum through morphological comparisons with type materials. These sequences were compared with those available in public databases to determine the corresponding adult stages and definitive hosts. Although no identical adult sequences were detected, M. ventricosum showed a close genetic relationship with four didymozoid species parasitizing the Australian yellowfin tuna, Thunnus albacares (Bonnaterre, 1788), suggesting that its definitive host is likely a species of Thunnus South, 1845. These findings provide essential molecular data for M. ventricosum, contribute to the taxonomic stability of Didymozoidae, and offer a foundation for future studies aimed at elucidating species boundaries and life-cycle connections within this group.

Cerebratulus sardonyx sp. nov. is described from a single specimen collected at Kita-Koho Seamount on the Kyushu-Palau Ridge, a major submarine arc extending from southern Japan into the Philippine Sea. The specimen was obtained at a depth of 454 m using the remotely operated vehicle KM-ROV during cruise KM24-03C of the R/V Kaimei. An integrative taxonomic approach-combining external morphology of the living specimen, histology, and molecular phylogenetic analyses-was used to characterize the species. The new species is readily distinguished from all congeners by its vivid reddish-brown body crossed by numerous sharply defined opaque white transverse rings, together with a uniquely patterned head bearing orangish patches and alternating white and brown transverse bands. Phylogenetic analysis places the species within a clade referred to as Lineage J in a previous study, corresponding to the Cerebratulus clade. This discovery represents the first record of Cerebratulus Renier, 1804 from Japanese seamounts and the first described nemertean from the Kyushu-Palau Ridge.

The Zoological Collection at the Stazione Zoologica Anton Dohrn di Napoli has been accumulating since research activities began in 1872. Following the opening of the collection room, known as "Museo", after 1906, the former collections were gathered there and Reinhard Gast became the first curator. Between 1910 and 1914, he left behind an accession record of 1098 preparations. We have found that at least 624 of these preparations remain in the current collection. These preparations bear at least five distinct types of labels applied by successive curators over the last 110 years. One hundred preparations still retain Gast's original labels and containers, and clearly exhibit his characteristic showcase-style arrangements. They are often displayed vertically on glass plates with fine threads and placed in rectangular or cylindrical glass jars with black backgrounds, with some specimens arranged to evoke their natural habitat at the bottom of the sea. Gast also produced species reference cards describing the biological and ecological characteristics of each species. Taken together, these features suggest that Gast intended the collection not only as a taxonomic reference, but also as a visual and ecological representation of the marine fauna of the Gulf of Naples-an early form of a biodiversity information resource.

This study examines how testosterone levels and kisspeptin gene expression are affected in male Syrian hamsters following pinealectomy and photoperiod modification. By examining the rhythmic changes in these parameters under long (16L: 8D) and short (8L: 16D) photoperiods, we aim to elucidate the role of melatonin and photoperiod in regulating seasonal reproductive physiology. One hundred and ninety-two male Syrian hamsters were equally divided into four groups (n = 48/group). Two groups were pinealectomized (pinx) and the other two groups were sham-operated (control). Treatment and control groups were then exposed to either a long photoperiod (LP) of 16 hours light/8 hours dark or a short photoperiod (SP) of 8 hours light/16 hours dark for 30 days and then sampled at specific temporal intervals (ZT0, ZT4, ZT8, ZT12, ZT16, and ZT20) at which hypothalamic tissues and serum samples were collected. Kiss1 mRNA expression and protein levels were measured using qPCR and Western blotting, while testosterone and melatonin levels were determined via ELISA. Under a long photoperiod, Kiss1 mRNA expression and protein levels exhibited significant diurnal variation, peaking during the light phase (P < 0.05). Pinealectomy disrupted these rhythms, leading to altered testosterone levels. Under a short photoperiod, a marked change in Kiss1 expression and testosterone was also observed, emphasizing photoperiod and melatonin's role in synchronizing reproductive rhythms. These findings highlight the central role of melatonin not just in modulating levels, but also in synchronizing the daily reproductive rhythms necessary for seasonal adaptation.