Sperm competition can theoretically affect sperm morphology; however, it remains unclear whether and how sperm morphology tracks the intensity of sperm competition in each population. The barn swallow Hirundo rustica is a model species used in the study of sexual selection, and exhibits considerable variation in extra-pair paternity (percentage extra-pair young, ca. 3-30%) among populations. In the Joetsu population of the barn swallow, extra-pair paternity is virtually absent (< 3%), providing a rare opportunity to study sperm morphology under limited sperm competition, and to compare it with those reported in populations with frequent extra-pair paternity (>15%). We found that head, midpiece, and total sperm length were significantly shorter in the Joetsu population than in populations with frequent extra-pair paternity. Moreover, the variability in total sperm length, measured as the coefficient of variation in the Joetsu population, was twice as high as that of populations with frequent extra-pair paternity. These results are consistent with a positive, directional, and stabilizing effect of sperm competition on sperm morphology. Together with previous studies in populations with frequent extra-pair paternity, the current study provides one of few sets of evidence to show a link between the intensity of sperm competition and the mean and variance of sperm morphology within a wild bird species.

The two-pore domain potassium ion (K + ) channel-related K + (TREK) channel and melatonin receptors play roles in the regulation of reproduction in zebrafish. Since reproduction is regulated by diurnal rhythms, the TREK family and melatonin receptors may exhibit diurnal rhythms in expression. In this study, we aimed to investigate diurnal variations of the gene expressions of TREK family and melatonin receptors and their associations with kisspeptin and gonadotrophin-releasing hormone (GnRH). Diurnal variations of trek1b, trek2a, trek2b, mt1, mt2, mel1a, kiss2 and gnrh3 expressions were examined by real-time PCR. For reproduction-related genes, kiss2 and gnrh3 exhibited diurnal rhythms. trek2a revealed a diurnal rhythm in the TREK family. mt2 and mel1c exhibited diurnal rhythms in the melatonin receptors. Since Trek2a regulates gnrh3 expression, the diurnal rhythm of gnrh3 expression suggests to be regulated by the diurnal rhythm of trek2a expression.

Most ascidian species settle on underwater substrates during a short free-swimming tadpole larval period. During this process, "rapid adhesion" occurs on adhesive papillae located at the anterior region of the cephalenteron. Settled and transformed ascidians subsequently expand the attachment area by "slow adhesion" with ampullae. In the present study, we attempted to identify the ultrastructures related to the adhesion process and adhesive materials in the ascidian tunic and to elucidate the biological function of vanadium in adhesion. We focused on an adhesive organ named the adhesive projection, which is newly generated by the adhered tunic to enlarge the bonding area between ascidian and substrate. Based on its structure and the presence of vanadiumcontaining blood cells, the adhesive projection was considered to be a large tunic vessel. At the adhered tunic, eosinophilic regions and migrated tunic cells were observed, but metal deposition was not detected. We speculate that the eosinophilic materials were components of the adhesive glue, and these are likey produced in epithelial cells, tunic cells, or both. Furthermore, using imaging mass spectrometry, we identified eight tunic-specific molecules as glue candidates.

Few convenient/expeditious methods for identifying the species of shed snake skins in specific areas have been developed. The scales on shed snake skins are permeable to light and can be examined by light microscopy (LM), which is of higher availability-especially for wild animal researchers and citizen scientists-than conventional approach which examines the scale microstructures by scanning electron microscopy. We collected and examined a total of 801 shed samples or scale specimens from 53 snake species in Taiwan and adjacent islands, and developed the first guide to identify the fragmented or faded shed skins of most snake species by LM. Morphological characters of scales can be examined by LM include the apical notch, apical pits, apical lobes, keels, scale symmetry, unpigmented spots (mechanoreceptor-like organs), interscale follicles, cross/longitudinal micro-ridge, oberhautchen cells, rows of spines, light/tiny dots, and other microstructures. The microstructures on the scale specimens prepared by the stripped method and the impression method were similar to those on shed skins when examined by LM. We investigated the variations of scale morphology associated with ontogeny, body region, and position on scales, discussed the character evolution of snake scale morphology, and certified that the interscale follicles and the unpigmented spots could also be useful characters for shed skin identification. The methods and results of this study could be applied to identify squamate skins/sloughs and even fecal remnants.

Abnormal embryos of Chinese giant salamander (Andrias davidianus, CGS) were observed in an imitating ecologic breeding system at 20°C. The aim of the present study was to investigate the relationship of bacterial infection on the early embryonic development of CGS. The ratio of abnormal embryos at 10 days after embryos incubated was 35.0% ± 2.1%, 35.6% ± 2.3% and 34.7% ± 3.4% in six breeding system farms of Hanzhong city in the years 2014, 2015, and 2016, respectively. However, in the standard imitating ecology breeding mesocosm, the proportion of abnormal embryos was about 5%. Six bacteria species in the egg water of the early-dead embryos and eight bacteria species in the gut of healthy CGSs were detected and identified by PCR and 16S rRNA gene sequence homology analysis. All bacteria species in the egg water were also found in the cloaca contents. Cetobacterium somerae and Hafnia alvei, which individually can cause embryo death, were first isolated from egg water and gut of CGSs. Further, the egg jelly membrane and the egg water of embryos did not inhibit bacteria survival and the bacteria could individually lead to CGS larva death. These results suggest that bacteria in the eggs of CGS may derive from the gut and that high-velocity flow of water through nest may decrease bacterial infection of egg in the imitating ecologic culture system.

Splanchnotrophidae Norman and Scott, 1906 is a family of parasitic copepods that infest nudibranchian and sacoglossan sea slugs. In this study, a new species of splanchnotrophid copepod, Lomanoticola nishiharai n. sp., is described based on specimens of both sexes collected from the facelinid nudibranch, Sakuraeolis enosimensis (Baba, 1930), in the Seto Inland Sea off Hiroshima, central Japan. It represents the third species of Lomanoticola Scott and Scott, 1895 and is characterized by the following female characters: the cephalosome distinctly protruded; the second and third lateral processes on the body originated from same bases; the caudal rami bears a seta V which almost same as long as the rami. Ultrastructural observations revealed that the cuticular surface of the lateral process on the female body is covered with numerous protuberances that may have protective functions against the cellular immune system of the host.

The evolutionary history of eight-barbel loaches of the genus Lefua was investigated to resolve the faunal formation and evolutionary history of Japanese and East Asian freshwater fishes. In the present study, we found that seven Lefua specimens obtained from western Japan could not be assigned genetically to any population recognized so far, although they were morphologically and ecologically indistinguishable from Lefua sp 1. We tentatively designated the specimens as the Nihonkai population. Sequencing of the mitochondrial D-loop region showed that five specimens of the Nihonkai population were allied with the Kinki and Tokai populations of L. echigonia and other two with Lefua sp. 2, indicating a discrepancy between morphological-ecological and genetic traits. In order to determine whether the population experienced parallel evolution or introgression of mitochondrial DNA, we sequenced the nuclear ribosomal S7 subunit, and demonstrated that the Nihonkai population is included within Lefua sp. 1. These results indicate that the Nihonkai population can be identified as Lefua sp. 1, possessing introgressive mitochondrial DNA, and suggest that the evolutionary history and faunal formation of Japanese and East Asian freshwater fishes are more complicated than previously thought.

A new species in a new genus of sea anemone, Tempuractis rinkai gen. et sp. nov., was discovered at several localities along the temperate rocky shores of Japan. The new species is approximately 4 mm in length and has been assigned to family Edwardsiidae, because it has eight macrocnemes, lacks sphincter and basal muscles, and possesses rounded aboral end. The sea anemone, however, also has a peculiar body shape unlike that of any other known taxa. This new species resembles some genera, especially Drillactis and Nematostella, in smooth column surface without nemathybomes or tenaculi, but is distinguishable from them by several morphological features: the presence of holotrichs and absence of nematosomes. Furthermore, this edwardsiid species exhibits a peculiar symbiotic ecology with sponges. Therefore, a new genus, Tempuractis, is proposed for this species. In the field, T. rinkai sp. nov. was always found living inside homosclerophorid sponge of the genus Oscarella, which suggests a possible obligate symbiosis between Porifera and Actiniaria. The benefit of this symbiosis is discussed on the basis of observations of live specimens, both in the aquarium and field. This is the first report of symbiosis between a sea anemone and a homoscleromorph sponge.

Human, mouse, and zebrafish ovarian cancer G protein-coupled receptors (OGR1s) are activated by both metals and extracellular protons. In the present study, we examined whether pig, rat, chicken, and Xenopus OGR1 homologs could sense and be activated by protons and metals. We found that all homologs stimulated serum response element (SRE)-driven promoter activities when they are stimulated by protons. On the other hand, metals differentially activated the homologs. The results using chimeric receptors of human and zebrafish OGR1s indicate that the specificity of the metal-induced activation lies in the extracellular region. These results suggest that protons are an evolutionally conserved agonist of OGR1. However, the types of metals that activated the receptor differed among the homologs.

Without the establishment of effective culturing systems, little can be known about the late developmental stages of polyclad flatworms. Here, we report a laboratory culturing system for three polyclad species: Comoplana pusilla, Notocomplana koreana, and Pseudostylochus obscurus, and we describe changes in their morphology from hatching to reproductive maturity. These species hatch out as lobe-less larvae with four eyespots, but the number of eyespots increases in later development. Cross-like and triangularly shaped larvae are observed in N. koreana and P. obscurus, respectively. After settlement, a pale area appears on the body of juveniles and then develops into the copulatory complexes. All three species could be successfully reared on brine shrimp, but only C. pusilla and N. koreana achieved reproductive maturation in such a culturing system. In P. obscurus, switching the food to the gastropod Monodonta labio induced sexual maturation.