Male sexually-selected traits often impose an increased risk of predation on their bearers, causing male-biased predation. We investigated whether males of the sap-feeding Japanese rhinoceros beetle Trypoxylus dichotomus were more susceptible to predation than females by comparing the morphology of beetles caught in bait traps with the remains of beetles found on the ground. The males of this species are larger than the females and have a horn on the head. We found that predation pressure was greater for males than for females, and that larger individuals of both sexes were more vulnerable to predation. We identified two predators, the raccoon dog Nyctereutes procyonoides and jungle crow Corvus macrorhynchos, by monitoring sap-site trees with infrared video cameras. Raccoon dogs visited sap-site trees at night, while crows came after daybreak. The highest frequency of visits by both predators was observed in the first half of August, which matches the peak season of T. dichotomus. Raccoon dogs often left bite marks on the remains of prey, whereas crows did not. Bite marks were found on most of the remains collected at two distant localities, which suggested that predation by raccoon dogs is common. Size- and sex-dependent differences in the conspicuousness and active period of T. dichotomus probably explain these biased predation patterns. Our results suggest that having a large horn/body is costly in terms of the increased risk of predation. Predation cost may act as a stabilizing selection pressure against the further exaggeration of male sexual traits.

This study compared aggressiveness between two distinct wild populations of Japanese medaka: a Northern population, Oryzias sakaizumii, and a Southern population, O. latipes. When four males competed in intra-population contests, the social hierarchy was determined based on aggressive acts in both populations. Dominants of the Southern population showed higher aggressive acts than did dominants of the Northern population. Increased aggressiveness of Southern males compared with Northern males was also observed when a pair of Northern and Southern males were compared in inter-population contests. High expression of arginine vasotocin (AVT) in distinct preoptic regions were found in dominants and subordinates of the Southern population, but not in those of the Northern population. In contrast, neither 11-ketotestosterone nor cortisol levels in plasma differed between dominants and subordinates of either population, nor between pairs of the Northern and the Southern males. Taken together, these findings indicate that the two wild populations of medaka represent intriguing models for the study of neuroendocrinological correlates in behavioral traits underlying congeners of medaka fish.

Troponin, a Ca² -dependent regulator of striated muscle contraction, has been characterized in vertebrates, protochordates (amphioxus and ascidian), and many invertebrate animals that are categorized in protostomes, but it has not been detected in echinoderms, such as sea urchin and sea cucumber, members of subphylum Eleutherozoa. In this study, we examined the muscle of a species of isocrinid sea lilies, a member of subphylum Pelmatozoa, that constitute the most basal group of extant echinoderms to clarify whether troponin is lacking from the early evolution of echinoderms. Native thin filaments were released from the muscle homogenates in a relaxing buffer containing ATP and EGTA, a Ca² -chelator, and were collected by ultra-centrifugation. Actin and tropomyosin, but not a troponin-like protein, were detected in the filament preparation. The filaments increased Mg² -ATPase activity of rabbit skeletal muscle myosin irrespective of the presence or absence of Ca² . The results indicate that Ca² -sensitive factor, troponin, is lacking in the thin filaments of sea lily muscle as in those of the other echinoderms, sea urchin and sea cucumber. On the other hand, a paramyosin-like protein that is absent from chordates was detected in sea lily muscle as in the muscles of the other echinoderms and invertebrate animals of protostomes.

To test whether telomere length can be used in estimating the age of colonial corals, we used terminal restriction fragment (TRF) length analysis to compare the telomere lengths of the coral Acropora digitifera at three developmental stages: sperm, planula larvae, and polyps of adult colonies. We also compared the mean TRF lengths between branches at the center and periphery of tabular colonies of A. digitifera. A significant difference was observed in the mean TRF lengths in sperm, planulae, and polyps. The mean TRF length was longest in sperm and shortest in polyps from adult colonies. These results suggest that telomere length decreases during coral development and may be useful for estimating coral age. However, the mean TRF length of branches at the center of a table-form colony tended to be longer than that of peripheral branches, although this difference was not statistically significant. This suggests that both the chronological age of polyps and cell proliferation rate influence telomere length in polyps, and that estimating coral age based on telomere length is not a simple endeavor.

As with other marine ecosystems around the world, water temperature has been anomalously warm in recent years in the East China Sea. We analyzed historical data to explore the effects of climatic change on the abundance and distribution variation of Euphausia pacifica in the East China Sea (the Changjiang River estuary and adjacent areas). In 1959, the highest abundance occurred in the spring and autumn, and this krill species was still abundant in May 1974; however, its abundance was significantly reduced in 2002, markedly in spring. Euphausia pacifica was the numerically dominant euphausiid in the East China Sea in 1959. Its mean abundance was up to 1.91 ind m^-3 and 1.64 ind/m³ in 1959 and 1974, respectively; however, this figure decreased to 0.36 ind m^-3 in 2002. Since 2003, the abundances have been near zero in the most years. Both inter-annual (between November 1959 and 2002) and inter-monthly (between May and June 1959) comparisons suggest that E. pacifica has had a temperature-driven northward movement in response to rising sea surface temperature, especially the positive anomalies since 1997. However, E. pacifica did not come back to the previous habitat when temperature became relative cold. Hence additional factors affecting the E. pacifica distribution and abundance need to be investigated in the future study.

Amphibian skin secretions contain abundant bioactive peptides that are valuable natural resources for human beings. However, many amphibians are disappearing from the world, making relevant scientific studies even more important. In this study, 24 cDNA sequences encoding antimicrobial peptide (AMP) precursors were initially cloned by screening a cDNA library derived from the skin of the Sichuan torrent frog, Amolops mantzorum. Eighteen mature AMPs belonging to 11 different families were deduced from these cDNA clones. Biological function was confirmed in each family of these AMPs. Some of them were purified from the skin secretions, and their molecular structures were determined by Edman degradation. Liquid chromatography in conjunction with tandem mass spectrometry (LC-MS/MS)-based peptidomics was used to further confirm the actual presence and characteristics of mature AMPs in the skin secretions of A. mantzorum. Incomplete tryptic digestion and gas-phase fractionation (GPF) analysis were used to increase the peptidome coverage and reproducibility of peptide ion selection.

CRY proteins can be classified into several groups based on their phylogenetic relationships, and they function as a photoreceptor, a photolyase, and/or a transcriptional repressor of the circadian clock. In order to elucidate the expression profile and functional diversity of CRYs in vertebrates, we focused on XtCRY4, a member of the uncharacterized cryptochrome family CRY4 in Xenopus tropicalis. XtCRY4 cDNA was isolated by RT-PCR, and a phylogenetic analysis of deduced sequence of XtCRY4 suggested that the vertebrate Cry4 genes evolved at much higher evolutionary rates than mammalian-type Cry genes, such as the CRY1 and CRY2 circadian clock molecules. A transcriptional assay was performed to examine the transcriptional regulatory function as circadian repressor, and XtCRY4 had marginal effects on the transactivation of XtCLOCK/XtBMAL1 via E-box element. In situ hybridization and quantitative RT-PCR was performed to detect mRNA expression in native tissues. Quantitative RT-PCR revealed that XtCry4 mRNA was highly transcribed in the ovary. In situ hybridization showed the presence of XtCry4 transcripts in the oocytes, testis, renal tubules, the visual photoreceptors, and the retinal ganglion cells. A specific antiserum to XtCRY4 was developed to detect endogeneous expression of XtCRY4 protein in the ovary. The expression level was estimated by immunoblot analysis, and this is the first detection and estimation of endogenous expression of CRY protein in the ovary. These results suggest that X. tropicalis ovary may respond to blue-light by using XtCRY4.

Tetraophasis szechenyii and T. obscurus are endangered phasianid birds endemic to China. Historically, the question of whether T. obscurus and T. szechenyii are valid species or subspecies has been controversial. In order to clarify their phylogenetic relationship, we sequenced the complete mitochondrial genome of T. obscurus and, using the complete mitochondrial genome of T. szechenyii, which our lab had already sequenced, conducted Bayesian and maximum-likelihood phylogenetic analyses based on the sequences of 12 concatenated heavy-strand encoded protein-coding genes. Genetic distance and divergence time between the two species were also calculated. The complete mitochondrial genome of T. obscurus was 16,707 bases (accession no.: NC_018034), and its structure was similar to mitochondrial genomes reported for other phasianids. The genetic distance between T. obscurus and T. szechenyii was 0.028, and the divergence time of T. obscurus and T. szechenyii was 1.75 Myr. Considering the genetic distance and divergence time, as well as geographical distribution and morphological differences, we suggest that T. obscurus and T. szechenyii are two valid species. The Pleistocene glacial events in the Hengduan Mountains region may have played an important role in the speciation of T. obscurus and T. szechenyii.

We investigated the phylogeography of the Asian brackish water clam, Corbicula japonica, to clarify its demographic history using partial mitochondrial COII gene sequences (990 bp) from 283 individuals collected from around the Japanese archipelago and adjacent areas. Phylogenetic analyses revealed the presence of two major groups within our samples: monophyletic Group I comprising Lineages A-E of C. japonica and paraphyletic Group II consisting of Corbicula sp. Lineages A-C were distributed in Japan and Sakhalin Island, and Lineages D, E, and Corbicula sp. were distributed in the Korean Peninsula. Nested clade analysis (NCA) revealed that Lineage A—the dominant lineage in Japan—consisted of Pacific and Japan Sea lineages, the latter comprising southern and northern Japan Sea groups. Genetic diversity indices of the southern group were higher than those of the northern group, suggesting historical range expansion in the Sea of Japan from southwest to northeast. Geographical distribution of these genetic groups appears to have been influenced by major ocean currents around the Japanese archipelago. Dominant haplotypes in the star-shaped haplotype network of Lineage A were distributed throughout the entire distribution range of each genetic group, implying rapid range expansion of this species. The results of mismatch distribution analysis and molecular clock estimation suggest that expansion of lineage A occurred during the late Middle or Late Pleistocene. In contrast, restricted or past gene flow suggested by NCA and the many unique haplotypes (110/123; 89.4%) present in Lineage A suggest that gene flow among extant populations is rather limited.

The solitary ascidian Ascidiella aspersa (Müller, 1776) has sometimes been regarded as conspecific with A. scabra (Müller, 1776), although previous detailed morphological comparisons have indicated that the two are distinguishable by internal structures. Resolution of this taxonomic issue is important because A. aspersa has been known as a notoriously invasive ascidian, doing much damage to aquaculture e.g. in Hokkaido, Japan. We collected many specimens from European waters (including the Swedish coast, near the type localities of these two species) and Hokkaido, Japan (as an alien population) and made molecular phylogenetic analyses using the mitochondrial cytochrome c oxidase subunit I (COI) gene, and found that in terms of COI sequences all the analyzed specimens were clustered into two distinct groups, one of which is morphologically referable to A. aspersa and the other to A. scabra. Thus, these two species should be regarded as distinct from each other.