Aggregation of flying insects such as gypsy moths at commercial light sources in summer not only has an aesthetically negative impact on public facilities but also permits the establishment of new insect populations there from the next year. Although energy-efficient light traps equipped with light-emitting diodes (LEDs) have recently been used for controlling pest insects in agriculture, there are very few maintenance-free light traps that are available on the market. Based on the results of field surveys, we fabricated a prototype light trap in which the preferences of insects for light irradiation angle and wavelength are implemented. Field experiments revealed that flying moths were attracted more to light with a narrow irradiation angle than to light with a wide irradiation angle. Moreover, there was a tendency for fewer moths to be collected when fluorescent paint was applied to the surface of the flight-interception board, indicating that a high contrast made by illumination and the background is preferred by flying moths. Taken together with our previous results, we found that the moth catch was influenced more by modification of the light design than by change in visible light wavelengths. A semi-portable light trap, named the “Kurihara trap” after the primary contributor to its development, is made of light-weight plastic and is driven by solar power. This light trap is omnidirectional and maintenance-free and is therefore suitable for deployment in the backyards of rest areas as well as at houses for long-term macromoth sampling.

The effects of mechanical stress on cultured muscle cells were examined with particular interest in myofibril assembly by using a cell-stretching system. We observed that formation and maintenance of cross-striated myofibrils in chick muscle cell cultures was suppressed in the media containing higher concentration of KCl, tetrodotoxin, or ML-9 (an inhibitor of myosin light chain kinase), but periodic stretching of myotubes for several days enabled formation of striated myofibrils just as in standard muscle cultures. However, ryanodine (a blocker of the Ca^{2 +} channel in sarcoplasmic reticulum) and BDM (an inhibitor of myosin-actin interaction) suppressed the stretch-induced myofibrillogenesis. We further found that stretching of myotubes causes quick and transient elevation of the intracellular Ca^{2 +} concentration and this elevation is disturbed by inhibition of Ca^{2 +} channels of sarcoplasmic reticulum and suppression of Ca^{2 +} influx from culture medium. These observations indicate that periodic stretching induces elevation of intracellular Ca^{2 +} concentration and that this elevation may be due to release of Ca^{2 +} from sarcoplasmic reticulum and Ca^{2 +} influx from outside of the cells. The increased Ca^{2 +} may activate actin-myosin interaction by interacting with troponin that is located along actin filaments and/or inducing phosphorylation of myosin light chains and thereby promote myofibril assembly.

The black kite (Milvus migrans) is widespread in the “Old World” and is a common raptor species in Japan. However, examples of regional population dynamics and genetic research are limited. To reconsider the natural history and current status of the black kite in Japan, we analyzed the genetic diversity of the Japanese black kite population. We collected 59 black kite samples from 22 locations across Japan and extracted DNA; 1585 bp sequences of the cytochrome b and control region, which form part of the mitochondrial DNA, were determined for genetic analysis of the population. Consequently, six haplotypes were detected in 59 individuals, 50 of which had the same major haplotype, namely, Mm1. Moreover, the genetic analysis indicated that the Japanese black kite population would fit the population expansion model. Phylogenetic analysis using sequences obtained in this study or from a DNA database indicated that the Japanese black kite population can be divided into two groups: (1) Mm1 and its close haplotypes and (2) Mm5. The sequence of Mm1 was exactly the same as that of black kite in Pakistan, India, and Korea, suggesting that this haplotype is generally widespread in East Eurasia, and that the ancestral haplotype of the Japanese population likely migrated from continental East Asia and expanded its distribution throughout Japan. In summary, we found that the black kite population in East Eurasia, including Japan, is composed of at least two lineages.

Monthly sampling of freshwater shrimps infested by the corallanid ectoparasite Tachaea chinensis was conducted at an agricultural canal of the Etsura River system, Shiga Prefecture, Japan, from April 2018 through December 2019. A total of 944 Palaemon paucidens and 279 Neocaridina spp. were collected, and 203 immature T. chinensis were found attached to the carapace of these hosts. Mean prevalence was 23.1% for P. paucidens and 6.4% for Neocaridina spp. Newly hatched T. chinensis ectoparasitizing P. paucidens were detected in August 2018 (minimum body length of parasite 3.2 mm) and appeared continually until June 2019 (maximum body length of 10.3 mm) and were not observed in July. In contrast, T. chinensis on Neocaridina spp. were first detected in August of each year (with minimum body length of 2.0 mm) and were observed until September in 2018 and to November in 2019 (maximum body length of 5.8 mm). Ratios of the body length of T. chinensis to the carapace length of the host shrimp were almost constant (0.8–0.9) with the host species and parasite growth. Although infestation by early-life-stage individuals of T. chinensis was observed on both shrimp species, P. paucidens appeared to be the principal host for individuals larger than 6 mm in body length.

Whether the growth zone found in the coronal plate of echinoids can be used as a chronometer to estimate the age of individuals is controversial. In spatangoid echinoids, it is not known whether the growth zone formation occurs annually. In this study, the growth zone formation process was examined in four spatangoid species from natural conditions. In Nacospatangus alta and Brissus agassizii, the formation of a dark zone indicates the maturity of the gonad and does not necessarily correspond to the age of the individual. In Lovenia elongata, dark growth zones were formed several times per year. Unlike in the other studied species, in Metalia spatagus, the light and dark growth zones appeared to be formed radially, rather than in a ring-like manner. These results may indicate that the frequency and mode of growth zone formation differ across species. As such, it is not appropriate to use the growth zone as a chronometer in spatangoid echinoids. If the growth zone is to be used as an indicator of age, more research is needed about the phase of forming the growth zone in each echinoid species.

What environmental factors contribute to seasonal variation in immune function in striped hamsters (Cricetulus barabensis) remains unclear. How immune responses would respond to natural seasonal changes in photoperiod and temperature was investigated in the present study. Twenty-nine male and 30 female hamsters were randomly assigned to the winter, spring, summer, and autumn groups. Spleen mass was the highest in male hamsters during autumn, while it did not differ among seasons in females. Regardless of sex, bacteria killing activity (BKA) was the lowest in the spring, whereas phytohaemagglutinin (PHA) responses at 12 h, 24 h, and 48 h were all highest in the winter among the four seasons. Females had the lowest titers of immunoglobin (Ig)G5, 10, and 15 in winter, while they did not show seasonal variation in males. Compared with male hamsters, females had higher levels of IgG10 and IgG15 in the spring and autumn, but had lower BKA in autumn. Blood glucose was the lowest in the spring in both sexes. Males had higher leptin level in winter than in summer and autumn, while leptin level was higher in winter and spring than in autumn in females. Corticosterone level was higher in winter and summer than in spring and autumn in males, while it was higher in winter than in the other three seasons in females. Males had higher levels of leptin in winter, and corticosterone in summer, than females. In summary, distinct parts of the immune system respond differently to natural seasonal variations in photoperiod and temperature.

Epicatechin (EpiC) enhances long-term memory (LTM) formation in the pond snail Lymnaea stagnalis. Here we investigated at the level of a single neuron, RPeD1, which is a necessary site for LTM formation of operant conditioning of aerial respiration, how EpiC may bring about its enhancing effect on LTM formation. When snails were operantly conditioned in EpiC (15 mg/l) by a single 0.5 h training session, which typically only results in memory lasting ∼3 h, they now formed LTM lasting at least 24 h. We recorded from RPeD1 in semi-intact preparations made from snails 24 h after a single 0.5 h training session in EpiC or pond water (PW) and found that the firing and bursting rate of RPeD1 decreased significantly in the EpiC preparations compared to the PW preparations. However, the excitability (i.e., number of spikes evoked by injected depolarizing current) of RPeD1 was not different between the two preparations. We next performed “in vitro” operant training in semi-intact preparations made from naïve snails. In the training, we applied a gentle tactile stimulus to the pneumostome area every time the semi-intact preparation began to open. The preparations exposed to EpiC-saline (15 mg/l) exhibited significantly increased RPeD1 excitability compared with saline only preparations. These results suggest that EpiC can alter some electrophysiological properties of a neuron that is a necessary site for learning and memory formation.

The relationship between anemonefish and sea anemones is one of the most emblematic examples of mutualistic symbiosis in coral reefs. Although this is a textbook example, the major aspects of this symbiosis are still not fully understood in mechanistic terms. Moreover, since studies of this relationship have usually been focused on anemonefish, much less is known about giant sea anemones, their similarities, their phylogenetic relationships, and their differences at the molecular level. Since both partners of the symbiotic relationship are important, we decided to explore this well-known phenomenon from the perspective of giant sea anemones. Here, we report reference transcriptomes for all seven species of giant sea anemones that inhabit fringing reefs of Okinawa (Japan) and serve as hosts for six species of local anemonefish. Transcriptomes were used to investigate their phylogenetic relations, genetic differences and repertoires of nematocyte-specific proteins. Our data support the presence of three distinct groups corresponding to three genera: Entacmaea, Heteractis, and Stichodactyla. The basal position among the three groups belongs to Entacmaea, which was the first to diverge from a common ancestor. While the magnitude of genetic difference between the representatives of Entacmaea and Stichodactyla is large, intra-specific variation within Stichodactyla is much smaller and seems to result from recent speciation events. Our data reconfirms that Heteractis magnifica belongs to the genus Stichodactyla, despite an overall morphological similarity with representatives of the genus Heteractis. The availability of reference transcriptomes will facilitate further research into the fascinating relationship between sea anemones and anemonefish.

It is known that the bone matrix plays an important role in the response to physical stresses such as hypergravity and microgravity. In order to accurately analyze the response of bone to hypergravity and microgravity, a culture system under the conditions of coexistence of osteoclasts, osteoblasts, and bone matrix was earnestly desired. The teleost scale is a unique calcified organ in which osteoclasts, osteoblasts, and the two layers of bone matrix, i.e., a bony layer and a fibrillary layer, coexist. Therefore, we have developed in vitro organ culture systems of osteoclasts and osteoblasts with the intact bone matrix using goldfish scales. Using the scale culture system, we examined the effects of hypergravity with a centrifuge and simulated ground microgravity (g-µG) with a three-dimensional clinostat on osteoclasts and osteoblasts. Under 3-gravity (3G) loading for 1 day, osteoclastic marker mRNA expression levels decreased, while the mRNA expression of the osteoblastic marker increased. Upon 1 day of exposure, the simulated g-µG induced remarkable enhancement of osteoclastic marker mRNA expression, whereas the osteoblastic marker mRNA expression decreased. In response to these gravitational stimuli, osteoclasts underwent major morphological changes. By simulated g-µG treatments, morphological osteoclastic activation was induced, while osteoclastic deactivation was observed in the 3G-treated scales. In space experiments, the results that had been obtained with simulated g-µG were reproduced. RNA-sequencing analysis showed that osteoclastic activation was induced by the down-regulation of Wnt signaling under flight-microgravity. Thus, goldfish scales can be utilized as a bone model to analyze the responses of osteoclasts and osteoblasts to gravity.

The light cycle is the most powerful Zeitgeber entraining the circadian clock in most organisms. Insects use CRYPTOCHROMEs (CRYs) and/or the compound eye for the light perception necessary for photic entrainment. The molecular mechanism underlying CRY-dependent entrainment is well understood, while that of the compound eye-dependent entrainment remains to be elucidated. Using molecular and behavioral experiments, we investigated the role of timeless (tim) in the photic entrainment mechanism in the cricket Gryllus bimaculatus. RNA interference of tim (tim^RNAi) disrupted the entrainment or prolonged the transients for resynchronization to phase-delayed light–dark cycles. The treatment reduced the magnitude of phase delay caused by delayed light-off, but augmented advance shifts caused by light exposure at late night. TIM protein levels showed daily cycling with an increase during the night and reduction by light exposure at both early and late night. These results suggest that tim plays a critical role in the entrainment to delayed light cycles.