Nereidid polychaete Perinereis wilsoni is a homonomous metameric worm with a complete septum between each segment. Each segment has germ cells localized in the distal area of the parapodia. Perinereis wilsoni is also known to have high abilities of tissue regeneration; however, it is still unclear whether germ cells can regenerate in the healing tissue. To address this, we surgically operated the parapodia of an adult worm to remove germ cells from the segments and observed the germ cell regeneration using the germ cell genetic marker Pw-piwi. At day 20 post-surgical operation of the parapodia in one side of the segment, we found that Pw-piwi was expressed in the regenerating parapodia. We surgically operated the parapodia on both sides of the segment to remove the germ cells completely and it gave a similar result. However, before the expression of this gene marker in the regenerating parapodia, we observed that Pw-piwi was expressed in cells in the skin layer of the worm just after surgical operations. These Pw-piwi-positive cells were not observed in the un-operated worm. Our observations showed that germ cells of Perinereis wilsoni can regenerate even after the complete removal of germ cells from the defined habitat. The Pw-piwipositive cells that appeared in the skin layer after the disappearance of germ cells may be involved in the regeneration of new germ cells.

Fauna of the Central Ryukyus includes a high percentage of endemic species, and Hallowell's tree frog Hyla hallowellii Thompson, 1912 is one of such elements, occurring in a total of eight islands in the Amami and Okinawa Island groups. Using samples representing all of these eight island populations, we studied variations in morphology, karyotype, allozyme, and mtDNA, to clarify the pattern of geographic differentiation of H. hallowellii and consider factors for its formation. We could not clearly discriminate one population from another in morphology, nor could we find any interpopulation difference in karyotype. From genetic analyses, using allozymes and cyt b, we found low overall differentiations among populations. However, the southern populations from Okinawajima and Yoronjima were genetically nearly identical with the northern Amamioshima population. From that group the geographically intermediate Tokunoshima and Kakeromajima populations showed prominent differentiations. These patterns of geographical differentiation greatly differ from those known in other amphibian species of the Central Ryukyus, and suggest that H. hallowellii has evolutionary history unique to the species.

We focused on Meloe beetles that have lost all flight ability, and conducted molecular phylogeographic analyses based on their mitochondrial DNA COI and nuclear DNA EF1-α regions. Meloe beetles infiltrate bumblebee nests by attaching to bumblebees as they pollinate flowers and thereafter have a unique and specific life history as they complete their life-cycle within the host nest; flight-based dispersal is achieved by piggybacking on bumblebees. In fact, Meloe beetles, which cannot fly, even inhabit remote islands (i.e., “Oceanic Islands”). Regarding four species, i.e., Meloe coarctatus, Meloe proscarabaeus, Meloe violaceus and Meloe corvinus, the conventional morphological classification system based on morphological characteristics was strongly supported by the molecular markers. On the other hand, for two species, Meloe menoko and Meloe auriculatus, it was found that M. menoko may be evaluated as having a paraphyletic relationship with M. auriculatus. Furthermore, two other cryptic, undescribed species were also discovered in this study. One was collected in the Nikko Highland, and inhabited the area sympatrically with M. coarctatus. The other was collected from Hachijo-jima Island. These cryptic species were highly differentiated, independent lineages in terms of mitochondrial and nuclear gene regions. That is to say, a new level of species diversity was revealed among the Meloe beetle species, known for their unique and strange ecological and ethological characteristics.

Symbiotic associations with beneficial microorganisms endow a variety of host animals with adaptability to the environment. Stable transmission of symbionts across host generations is a key event in the maintenance of symbiotic associations through evolutionary time. However, our understanding of the mechanisms of symbiont transmission remains fragmentary. The deep-sea clam Phreagena okutanii harbors chemoautotrophic intracellular symbiotic bacteria in gill epithelial cells, and depends on these symbionts for nutrition. In this study, we focused on the association of these maternally transmitted symbionts with ovarian germ cells in juvenile female clams. First, we established a sex identification method for small P. okutanii individuals, and morphologically classified female germ cells observed in the ovary. Then, we investigated the association of the endosymbiotic bacteria with germ cells. We found that the symbionts were localized on the outer surface of the cell membrane of primary oocytes and not within the cluster of oogonia. Based on our findings, we discuss the processes and mechanisms of symbiont vertical transmission in P. okutanii.

We investigated the geographic diversification of Plestiodon finitimus, which occurs in the central to northern parts of the Japanese Islands, based on a time-calibrated mitochondrial DNA (mtDNA) phylogeny and external morphological characters. The mtDNA phylogeny suggests that P. finitimus diverged from its sister species Plestiodon japonicus in western Japan 2.82–4.63 million years ago (MYA), which can be explained by geographic isolation due to the spread of sedimentary basins in the Pliocene. The primary intraspecific divergence was that between P. finitimus lineages in central and northeastern Japan 1.58–2.76 MYA, which could have been caused by the upliftings of major mountain ranges. In the northeastern lineage, mtDNA and morphological characters suggest a geographic differentiation between sub-lineages of the northwestern Tohoku District (α) and other areas (β). Although the sub-lineage β occurs in a disjunct geographic range, consisting of Hokkaido and the central to south of Tohoku, these areas are bridged by populations with intermediate characteristics along the Pacific side of northern Tohoku. Overall, the geographic variation in P. finitimus in northern Japan can be explained by an initial allopatric divergence of the sub-lineages α and β at 0.71–1.39 MYA, a recent northward expansion of the sub-lineage β, and subsequent secondary introgressive hybridization between the sub-lineages.

Pesticide use is known to have a negative impact on the habitat use of birds. The decomposition of residual pesticides causes a drastic decrease in the biomass of wildlife food sources, indirectly affecting the ecosystem. In this study, we investigated the effects of pesticide use on the distributions of grey herons (Ardea cinerea) and great egrets (Ardea alba) in rice fields in the Republic of Korea. From early May to mid-June in 2015 and 2016, we recorded the abundance of these birds and their prey (loaches, other fish, tadpoles, and benthic invertebrates) and investigated their dependence on rice agricultural practices (eco-friendly vs conventional) and field types (harrowed, plowed, or transplanted). We found that both grey herons and great egrets preferentially used transplanted fields. Grey herons were observed more in conventional rice fields, while great egrets were observed more in eco-friendly rice fields. This may be driven by the distribution of their preferred prey types; we observed a higher density of tadpoles (the prey type favored by grey herons) in conventional fields and a higher density of loaches (the preferred prey of great egrets) in eco-friendly fields. Pesticides drive these patterns both directly and indirectly; pesticide use in conventional rice fields directly suppresses the abundance of loaches, which frees the tadpole population from predation pressures and indirectly boosts their abundance in conventional rice fields. Our findings suggest that the distributions of grey herons and great egrets vary depending on food availability and are directly and indirectly influenced by pesticide use.

The exumbrellar surfaces of six pelagic cnidarians from three classes were ultra-structurally compared to reveal their structural diversity in relation to their gelatinous, transparent bodies. We examined two hydrozoans (Diphyes chamissonis and Colobonema sericeum), a cubozoan (Chironex yamaguchii), and three scyphozoans (Atolla vanhöffeni, Aurelia coerulea, and Mastigias papua). The exumbrellar surfaces of the mesoglea in D. chamissonis, Ch. yamaguchii, Au. coerulea, and M. papua were covered with a simple epidermis; the shapes of the epidermal cells were remarkably different among the species. The epidermal cells of Ch. yamaguchii and M. papua possessed an array of microvilli on the apical side. The array possibly reduced light reflectance and provided some other surface properties, as seen for the cuticular nipple array in tunicates, considering the length, width, and pitch of the microvilli. The reduction of light reflectance on the array of microvilli was supported by the simulation with rigorous coupled wave analysis (RCWA). Microvilli were sparse and did not form an array in metephyrae of Au. coerulea. The mesoglea matrix beneath the basal side of the epidermis was loose in all of the species. The exumbrellar side of the mesoglea was exposed only in the mesopelagic species, At. vanhöffeni and Co. sericeum, and electron-dense layer(s) covered the surface of the mesoglea. It is uncertain whether the exumbrellar epidermis is absent in these species or the epidermal cells are completely exfoliated during the sampling and handling processes. In the latter case, the electron-dense layer(s) on the mesoglea surface might originally underlie the epidermis.

Little is comprehensively known or understood about giant panda fecal and serum metabolites, which could serve as important indicators of the physiological metabolism of giant pandas. Therefore, we determined the contents of fecal and serum metabolites of giant pandas based on an untargeted metabolome. Four hundred and 955 metabolites were detected in the feces and serum of giant panda, respectively. Glycerophospholipid and choline metabolism were the main metabolic pathways in feces and serum. A significant correlation between the gut microbiota and fecal metabolites was found (P < 0.01). Fecal metabolites were not greatly affected by the age or gender of giant pandas, but serum metabolites were significantly affected by age and gender. The majority of different metabolites caused by age were higher in serum of younger giant pandas, including fatty acids, lipids, metabolites of bile acids, and intermediate products of vitamin D3. The majority of different metabolites caused by gender included fatty acids, phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylethanolamine (PE). A separate feeding diet should be considered according to different ages and genders of giant panda. Therefore, our results could provide helpful suggestions to further protect captive giant pandas.

The ultrastructural features of axoneme organization within the cytoplasm and exflagellation were investigated in detail in microgametes of a malaria parasite, Plasmodium berghei, by electron and fluorescence microscopy. The kinetosomes (basal bodies) of the microgamete were characterized by an electron dense mass in which singlet microtubules (MTs) were embedded. Around the kinetosomes, several singlet and doublet MTs were recognized in transverse sections. Incomplete doublets with growing B-tubule were also observed. As precursors of the axoneme, arrays of over three doublets showed a tendency to encircle the central pair MTs. Some of the doublet MTs were already equipped with inner and outer dynein arms. In the microgamete, which lacks an intraflagellar transport (IFT) system, self-assembly of microtubular and associated components appeared to proceed stepwise from singlet MTs through arrays of one to nine doublet MTs, surrounding the central pair, to form the complete axoneme in a quite short time. At exflagellation, some extra doublets were occasionally included between the axoneme and the flagellar membrane. At high magnification, the outer dynein arm of the Plasmodium microgamete had a pistol-like shape representing a three-headed dynein molecule like that of other Alveolata.

The heteronemertean Kulikovia alborostrata (Takakura, 1898) was originally described as Lineus alborostratus based on material from Misaki, Japan. Although this species was regarded as consisting of two color variants, purple and brown-yellow, the identity of these variants has never been examined based on topotypes. In this study, we performed a multi-locus phylogeny reconstruction, species delimitation analyses, and cross-fertilization experiments to examine the species status of Takakura's original taxon concept consisting of these color variants. Our results suggest that the purple type is identical to Lineus alborostratus Takakura, 1898 auct. (currently Kulikovia alborostrata), whereas the brown-yellow type is conspecific with Lineus fulvus Iwata, 1954, originally established from Hokkaido. These two species appear to have a sister-taxon relationship and are reproductively isolated from each other by prezygotic mechanisms involving gamete incompatibility, minimally separated with 2.8% (16S rRNA) and 14.4% (COI) uncorrected p-distances. We propose that the purple type be considered as representing the true identity of the nominal species Lineus alborostratus (currently assigned to the genus Kulikovia) to maintain the common usage of the name. Although Takakura's type material is not extant, we consider that neotypification is unnecessary in this case because no taxonomic/nomenclatural confusion persists. We also propose to transfer Lineus fulvus to yield Kulikovia fulva comb. nov.