Scyphozoa, Cubozoa and Hydrozoa are classes in the phylum Cnidaria that undergo metagenesis involving a dramatic morphological transition. In Scyphozoa and Cubozoa, when exposed to species- or strain-specific transition-inducing stimuli, asexually reproducing benthic polyps transform into sexually reproducing planktonic medusae. In Hydrozoa, exposure to species- or strainspecific transition-inducing stimuli causes formation of medusa buds in the polyp's body. In Aurelia aurita (Linnaeus, 1758) (Scyphozoa, Semaeostomeae), polyp-to-jellyfish transition is induced by some simple indole compounds. However, whether indole compounds can induce polyp-to-jellyfish transition in Cubozoa and Hydrozoa remains unknown. In the present study, we show that an indole compound, 5-methoxy-2-methylindole, induces polyp-to-jellyfish transition in Scyphozoa and Cubozoa. This inducing action suggests that the downstream steps of polyp-to-jellyfish transition are regulated by the same biochemical reactions in Scyphozoa and Cubozoa, irrespective of the type of transition-inducing environmental stimuli.

The pancreas plays important roles in the regulation of blood glucose, and is a well-studied organ in mammals because its dysfunction causes serious disorders, such as diabetes mellitus. However, mammals have the limited capacity for tissue regeneration in their organs, including pancreas. Fish may be an attractive model for regeneration studies, as fish exhibit a greater capacity for regeneration than do mammals. To elucidate the regenerative capacity of pancreatic β cells in medaka, we generated transgenic lines, in which β cells can be specifically ablated using the nitroreductase (NTR)/metronidazole (Mtz) system. We examined β-cell regeneration at embryonic-larval stages after specific ablation of β cells, and found that medaka rapidly regenerate β cells. Furthermore, we found that teleost-specific secondary islet have a unique feature in that their size increases in response to β-cell ablation in principal islets.

We examined sequences of the mitochondrial control region in magpies (Pica pica) from the entire distribution range and found deep genetic splits into four major lineages: (1) group West (Europe-Siberia), (2) group East (southern Far East), (3) P. p. mauritanica (North Africa), and (4) P. p. hudsonia (North America). These lineages show a geographic pattern corresponding to known subspecies or subspecies groups. Genetic variation within the widely-distributed group West is low and neutrality tests supported a recent expansion scenario. The haplotypes from Kamchatka, representing a separated sublineage with clear affinity to the European-Siberian group, are almost identical, implying a recent bottleneck. Group East contained two subclades without clear geographic pattern, presumably due to admixing of populations that had diverged in Pleistocene refuges. The homogeneity of the Kyushu population supports historical reports of introduction of the species from Korea. In contrast, the high variation in the recently established Hokkaido population may reflect an ongoing invasion from several populations of the Far Eastern mainland. Bioacoustic data based on chatter call differentiate groups of subspecies and reflect phylogeographic patterns, i.e., mitochondrial lineages. Furthermore, we report the fast spreading of P. p. jankowskii towards the west along the upper Amur River, and a slower shifting of P. p. leucoptera in the opposite direction thus yielding a new contact zone. Overall, our data support a scenario of divergence in geographic isolation, but the ongoing expansion of distribution ranges may lead to major changes in phylogeographic patterns.

Reliable estimates of evolutionary rates of mitochondrial DNA might allow us to build realistic evolutionary scenarios covering broad time scales based on phylogenetic inferences. In the present study, we sought to obtain estimates of evolutionary rates in murine rodents using calibrations against historical biogeographic events. We first assumed that land-bridge-like structures that appeared intermittently at glacial maxima with 100,000-year intervals shaped the divergence patterns of cytochrome b (Cytb) sequences (1140 bp) of the larger Japanese wood mouse Apodemus speciosus. The comparison of sequences from peripheral remote islands that are separated from one another by deep straits allowed us to estimate mitochondrial DNA evolutionary rates (substitutions/site/million years) to be 0.027 to 0.036, with presumed calibrations from 140,000, 250,000, 350,000, and 440,000 years ago. Second, we addressed rapid expansion events inferred from analyses of the Cytb sequences of the lesser Japanese wood mouse A. argenteus. We detected five expansion signals in the dataset and established three categories based on the expansion parameter tau values: 3.9, 5.6–5.7, and 7.8–8.1. Considering that the climate became warmer 15,000, 53,000, and 115,000 years ago after preceding periods of rapid cooling, we calculated evolutionary rates to be 0.114, 0.047, and 0.031, respectively. This preliminary concept of the evolutionary rates on a time scale from 15,000 to 440,000 years ago for the wood mouse should be refined and tested in other species of murine rodents, including mice and rats.

The red-crowned crane (Grus japonensis) is recognized internationally as an endangered species. Migratory populations breed in eastern Russia and northeastern China, whereas the resident population inhabits the island of Hokkaido, Japan. Although the population inhabiting Hokkaido had experienced a severe bottleneck by the end of the 19th century, the population size has recovered to about 1500 and continues to increase now thanks to conservation efforts. A previous study reported that no marked genetic differences were seen in the island population, and that the genetic variation of the whole population on Hokkaido was lower than that of the continental population. However, the precise genetic structure of the island population in the past or near present remains unclear. To better understand the spatiotemporal changes in the genetic structure of the island population, we performed mitochondrial DNA (mtDNA) analyses using stuffed specimens (years 1878–2001) and tissue or blood samples (years 1970–2014). We found three haplotypes in the island population, one of which was a novel mtDNA haplotype in 1997 and 2007 samples. In addition, there was no clear difference in the haplotype frequency through the time span. These results suggest that the low genetic variation of the island population persisted for the last hundred years. It is thus nearly impossible for the island population to recover its genetic variation in isolation. Conservation plans for this species should therefore include the promotion of genetic exchanges between the continental and island populations, such as through artificial introduction to Hokkaido.

Bell-shaped ciliates of the subclass Peritrichia, such as Vorticella, Carchesium and Epistylis, are commonly found in freshwater and other aquatic environments, either solitary or colonial. Peritrichs attach to a substratum via a contractile or non-motile stalk, and collect food particles by water current using ciliary rows around the edge of the bell, called the peristome. Some peritrichs are epibiotic and ectocommensalistic associates of aquatic insects and other animals, settling on the surface of their specific hosts. Only a few peritrichs are known to establish a more internal association with their hosts, locating within the preoral cavity or esophagus of water beetles and presumably subsisting on food materials chewed and ingested by the insects. To date, no endoparasitic or endocommensalistic peritrichs have been reported from insects. Host insects reported to date have all been aquatic, and given the aquatic lifestyle of peritrichs, terrestrial hosts have been considered unlikely. In the present study, we report a dense population of bizarre microbes within the gut of a terrestrial insect, and histological, ultrastructural and molecular phylogenetic analyses identified it as a peritrich ciliate. The highly-developed hindgut of the stag beetle Aegus currani contained oval colonial peritrichs connected by branched stalks resembling grape clusters. Each zooid exhibited a reduced peristome without disc, a vestibulum with active ciliary movement inside, and an elongated macronucleus. These features are morphologically reminiscent of but distinct in some respects from those in Operculariella parasitica, known from the esophagus of dysticid diving beetles. Taxonomic, ecological and functional aspects of this gut-dwelling peritrich warrant future study.

Polymesoda spp., which represent bivalves in the mangrove ecosystem, inhabit the mangrove forests of the Indo-Pacific region. They tend not to be broadly distributed across zones within the mangrove forest, but are instead typically encountered in the mesozone. We conducted field rearing experiments on four plots which were set across a mangrove forest along the Urauchi River of Iriomote Island, from the seaward to landward sides, over a period of 10 months. We compared the survival rates of clams at these plots with different environment for four months. Salinity was also measured during the study period, and we established a correlation between survival rate and change in salinity of each plot. The survival rate of the plot in the mesozone was 90%, that of two plots which were positioned in the seaward zone of the mesozone was 40%, and that of the plot on the landward side was 0%. In plot 4, the ambient water of the bivalves was fresh water. The salinity of the seaward zone changed rapidly in one day, or the salinity of the ambient water surrounding the bivalves was high for a long period of time. In Plot 3, salinity change was gradual, and the average salinity was lower than in Plots 1 and 2. This study indicates that salinity level affects bivalve survival rate and that area similar the mesozone, where gradual salinity change and average salinity were neither too high nor too low, are suitable for these species.

To understand geographic body size variation in an insect species, various factors including habitat temperature, correlation between life history traits, and food availability must be examined. Carabus (Ohomopterus) japonicus is univoltine, feeds exclusively on earthworms during its larval stage, and shows a clinal body size variation along the habitat temperature gradient in northern Kyushu, Japan. Carabus japonicus occurs at both high and low altitudes; at high altitudes it coexists with a larger species, C. (O.) dehaanii. At low altitudes, C. japonicus shows larger body sizes. We sought to determine whether this increase in body size is only an adaptation to high habitat temperatures in the absence of C. dehaanii, and examined the life history of C. japonicus and seasonal trends in prey earthworms at six sites between altitudes of 30 and 980 m. While high-altitude populations used the entire warm season for reproduction and larval development, low-altitude populations showed shorter periods of reproductive activity and larval incidence coincided with seasonal trends in earthworm abundance. Thus, C. japonicus attained larger body sizes at lower altitudes without a notable extension of their juvenile period. At lower altitudes, earthworms grew faster and reached sizes, which may be too large for predation by small carabid larvae. Large females had higher fecundity, and laid larger eggs, from which larger first instar larvae hatch. The large body size of C. japonicus in warm habitats may thus be an adaptation not only for high fecundity, but also for producing large first instar larvae to more efficiently prey on large earthworms.

Nuclear receptor (NR) interacting proteins, such as coactivators and corepressors, play a crucial role in specifying the transcriptional activity of the receptor. However, little is known about the functional features of the NR coregulators in marine invertebrates. Using the yeast two-hybrid screening method, a sea urchin oocyte cDNA library was screened for proteins that interact with the ligand-binding domain of human RXRα (hRXRα) as the bait protein in the presence of 9-cis retinoic acid. Here, we describe IQ motif containing protein D (IQCD) as an RXR-interacting coactivator. The open reading frame of Strongylocentrotus nudus IQCD (SnIQCD) cDNA contains 1464 bp encoding a protein of 487 amino acids. SnIQCD and the vertebrate IQCDs contain well-conserved C-terminal IQ motifs and coiled-coil domains. The interactions between RXRα and IQCD were confirmed by an immunoprecipitation assay and a mammal two-hybrid assay. RXRα preferentially interacted with the C-terminal half including IQ motif than the N-terminal half of SnIQCD. The coactivator interacting LXXLL motif in SnIQCD is not directly involved in the interaction with RXRα. SnIQCD overexpression increased the basal RXR transactivation of a RXR-responsive reporter gene. Furthermore, SnIQCD enhanced the transcriptional activity of RXR heterodimeric partners such as RAR, PPAR, and the steroid hormone receptor family members from mammals, teleost fish, and sea urchin. Taken together, we suggest that IQCD orthologs are able to function as transcriptional coactivators cooperating with NRs.

Mushroom corals are reef corals of the family Fungiidae, which live in the tropical and subtropical Indo-Pacific region. Recently, most species of this family have been revised taxonomically based on morphological and molecular analyses. However, the phylogenetic position of Cycloseris hexagonalis (Milne Edwards and Haime, 1848) has not been analyzed and remains unclear. This species is believed to show allometric growth by changing its corallum shape from hexagonal in juveniles to irregularly circular with an undulated corallum margin in mature individuals. However, these morphological changes have not been monitored and their genetic basis has not been confirmed. In the present study morphological and molecular phylogenetic analyses were performed to evaluate the identity of the morpho-types in C. hexagonalis and to clarify the phylogenetic and taxonomic position of the species. In the morphological analysis, we used 20 specimens of C. hexagonalis collected from around Iriomote Island, Okinawa, Japan, and identified four morphotypes. Moreover, the molecular phylogenetic analyses using mitochondrial COI and nuclear ITS markers showed that all morpho-types of C. hexagonalis together form an independent clade, indicating that they are all conspecific. Molecular phylogenetic comparison between this species and other fungiids revealed that the clade of C. hexagonalis is clearly distant from the Cycloseris clade as well as from clades representing other genera in the Fungiidae. Considering these data, we establish a monotypic new genus, Sinuorota, to accommodate C. hexagonalis.

An Asian species of Perinereis, which has been regarded as a local population of a cosmopolitan species P. cultrifera (Grube, 1840) (type locality: Italy), is described as a new species, P. euiini., based on Korean specimens. This new species is distinguishable from P. cultrifera and other similar species such as P. floridana (Ehlers, 1868) (type locality: USA), P. anderssoni Kinberg, 1866 (type locality: Brazil), and P. helleri (Grube, 1878) (type locality: Philippines) by the character combination of the absence of lateral group of paragnaths in area III on the proboscis, the presence of small notopodial prechaetal lobe in anterior parapodia, and the greatly expanded dorsal ligule in posterior parapodia. All previous records of “P. cultrifera” from eastern Asia (Taiwan, China, Japan, and Korea) are judged to belong to P. euiini sp. nov., leading to the conclusion that P. cultrifera is not a cosmopolitan species. Specimens previously identified as P. cultrifera var. floridana (or P. cultrifera floridana) in eastern Asia are also judged to belong to P. euiini sp. nov., although they have different paragnath number in area V (one instead of three). Their aberrant paragnath number was regarded as an intraspecific variation of P. euiini sp. nov. The comparison of DNA sequences of the mitochondrial cytochrome c oxidase subunit I (COI) between P. euiini sp. nov. and “P. cultrifera” from China and Portugal also supports the erection of the new species.