Zoological Science最新文献

The TGF-β signaling pathway plays an important role in wound healing and immune response. In this study, a TGF-β type I receptor (TGF-βRI) homolog was cloned and characterized from freshwater mussel Hyriopsis cumingii. The full-length cDNA of the TGF-β RI gene was 2017 bp, with a 1554 bp open reading frame (ORF), and encoded 517 amino acids. The predictive analysis further identified distinct regions within the TGF-βRI protein: a signal peptide, a membrane outer region, a transmembrane region, and an intracellular region. Real-time quantitative PCR results showed that the TGF-β RI gene was expressed in all tissues of healthy mussels. The transcripts of TGF-β RI in hemocytes and hepatopancreas were significantly up-regulated at different periods after stimulation with Aeromonas hydrophila and peptidoglycan (PGN) (P < 0.05). The mRNA expression of TGF-β RI progressively increased from day 1 to day 10 after trauma (P < 0.05), and it returned to the initial level by day 15. The expression levels of TGF-β , Smad5, MMP1/19, and TIMP1/2, but not Smad3/4, were significantly up-regulated at different time points after trauma. However, the expression levels of TGF-β , MMP1/19, and TIMP2 were decreased after treatment with the inhibitor SB431542. Furthermore, the recombinant TGF-βRI proteins were expressed in vitro and existed in the form of inclusion bodies. Western blotting results showed that TGF-βRI proteins were expressed constitutively in various tissues of mussels, and their expression was up-regulated after trauma, which was consistent with the mRNA expression trend. These results indicate that TGF-β RI is involved in the process of wound repair and immune response.

Extreme temperatures are a major threat to the survival of ectotherms such as amphibians. The tree frogs belonging to the genus Buergeria have accomplished a latitudinal distribution and a wide range of thermal adaptations. In particular, Buergeria japonica, referred to as the "hot spring frog", has been reported to tolerate extremely high temperatures. However, it is unclear how the heat tolerance and metamorphic strategies of this species vary among populations at different temperatures. We therefore conducted long-term heat tolerance experiments on multiple populations of B. japonica tadpoles and their congenic species to determine their survivability and development speed. We observed heat tolerance differences between B. japonica/Buergeria choui and Buergeria buergeri. Buergeria japonica exhibited the highest tolerance among all species, and the Seranma hot spring population showed the highest survival rate and accelerated development speed. However, at temperatures higher than 35°C, they could not survive until the completion of metamorphosis, contrary to previous field observations. Our behavioral experiment showed attenuation of the high temperature preference of B. japonica tadpoles associated with developmental stages, suggesting that they can tolerate extreme temperatures for a limited time window during their development until metamorphosis.

We identified two gall-inducing wasp species infesting eucalypts leaves, including an undescribed species, Ophelimus cracens sp. nov., and Epichrysocharis burwelli, which is a new record for Taiwan. The major hosts of O. cracens were Eucalyptus grandis, Eu. urophylla, and Eu. camaldulensis (Myrtaceae). We observed failed galls of O. cracens at an early stage on Eu. amplifolia and Corymbia maculata. All O. cracens adults discovered on infected leaves were females, and four parasitoid species were identified in samples collected from two cities, three counties, and four municipalities across Taiwan. Epichrysocharis burwelli was exclusively found on C. citriodora in Hsinchu, Nantou, and Tainan Cities. This marks the first record of Ep. burwelli in Asia, accompanied by the identification of one parasitoid species. The adult longevity of adults which emerged from their major hosts, when provided with honey-water solution, was 5.5 days for O. cracens and 5.7 days for Ep. burwelli. Recognizing the potential damage by these wasps on Eucalyptus production areas in the absence of parasitoids, further investigations of their biology and control are warranted.

Left-right asymmetry in paired organs is well documented across various species, including the claws of fiddler crabs and snail-eating snakes' dentition. However, the mechanisms underlying these asymmetries remain largely elusive. This study investigates Doubledaya bucculenta (Coleoptera: Erotylidae), a lizard beetle species known for pronounced left-sided asymmetry in adult female mandible and gena. Given that insect mouthparts comprise multiple functionally significant appendages, we aimed to clarify the degree of asymmetry extending beyond the mandibles and genae. Phenotypic morphology was assessed through trait measurement and asymmetry index calculations. Our detailed morphometric analyses revealed left-longer asymmetry not only in mandibles and genae but also in maxillae and labium. Notably, the degree of asymmetry in other mouthparts was generally less pronounced compared to that in outer mandibles, suggesting a potential influence of left mandible development on other mouthparts. Additionally, male mandibles exhibited region-specific asymmetry, potentially indicative of constrained evolutionary adaptations. This study enhances a comprehensive understanding of adult phenotype morphology and offers insights into the developmental basis of asymmetrical mouthparts.

Microfocus X-ray computed tomography (micro-CT) is expected to be utilized in the taxonomy of macroturbellarians that require histological technique(s) for identification, allowing nondestructive observation of the internal structures of specimens in a short time. With micro-CT, we observed a polyclad flatworm, Paraplanocera oligoglena (Schmarda, 1859), in this study. In the CT images, the main reproductive organs in the polyclad specimen were well observed, but some diagnostic characters were unclear or undetectable. We also prepared histological sections from the CT-scanned specimen. The histological sections were still observable and we could confirm the structures that were indistinct in the CT images; however, dye-affinity of tissues was slightly altered compared with those in usual sections. Integrating information from micro-CT images and subsequent histological observations, we successfully generated a 3D model of the reproductive organs of the polyclad. Our results suggest that the micro-CT imaging, as of the current resolution, would not completely replace the traditional histological technique; instead, these two techniques need to complement each other for a better understanding of the morphology that underpins the polyclad systematics.

We investigated geographic, genetic, and morphological variations in the intertidal limpet Lottia dorsuosa, a species with a broad distribution across Japan. A total of 98 specimens were obtained from 36 locations spanning the entire Japanese Archipelago, encompassing both the northern and southern regions. Examination of mitochondrial COI sequences revealed a distinct geographic genetic structure, delineating three prominent clades: (1) the Kuroshio Current, (2) the Tsushima Current, and (3) the Ryukyu-China groups. The observed geographical structuring between the Pacific and Sea of Japan side mirror patterns was noted in previously studied species, such as Turbo sazae and Batillaria attramentaria. Within L. dorsuosa, the Kuroshio Current group exhibited a substantial genetic distance, reaching a maximum of 12.35%, when compared to the more closely linked Tsushima Current and Ryukyu-China groups. Compared to other groups, the Ryukyu and China groups represented relatively recent differentiations, and the former group is currently facing a heightened risk of extinction owing to its sparse population density. The emergence of intraspecific geographic structures is likely attributable to the comparatively brief planktonic larval stage, which is a common characteristic of patellogastropod limpets.

Some anguillid eels migrate thousands of kilometers from their spawning grounds, dispersing across vast geographic areas to fresh and brackish water habitats, where they settle and grow. Japanese eels (Anguilla japonica) and giant mottled eels (A. marmorata) are both found in Japan, although their distributions differ, and their exact distributions are poorly known. We assumed that topographic distribution patterns of Japanese and giant mottled eels must differ among and within rivers along the northwest coast of Kyushu, Japan. Environmental DNA (eDNA) analysis was conducted at 87 sites in 23 rivers. Japanese eel eDNA was detected in 19 rivers (82.6%) and that of giant mottled eels was detected in eight (34.8%). We detected giant mottled eel eDNA in five rivers where they were previously unknown. eDNA for Japanese eels was detected at six of nine sites in the north (66.7%), 13 of 23 sites in Omura (56.5%), and 37 of 55 sites in the south (67.3%). In contrast, giant mottled eel eDNA was detected at one of nine sites in the north (11.1%), no sites in Omura, and 15 of 55 sites in the south (27.3%). There was no correlation between eDNA concentrations of the two species at 10 sites in the five rivers where eDNA of both species was detected. These findings suggest differences in the distribution of the two eel species and the northern distributional limit of giant mottled eels in the area facing the East China Sea.

The Coleoptera Cerambycidae (longicorn beetles) use wood under different states (living healthy, freshly snapped, completely rot, etc.) in a species-specific manner for their larval diet. Larvae of some Cerambycidae groups have mycetomes, accessory organs associated with the midgut that harbor fungal symbiont cells. The symbionts are thought to improve nutrient conditions; however, this has yet to be shown experimentally. To deduce the evolutionary history of this symbiosis, we investigated the characteristics of the mycetomes in the larvae of longicorn beetles collected in Japan. Lepturinae, Necydalinae, and Spondylidinae are the only groups that possess mycetomes, and these three groups' mycetomes and corresponding fungal cells exhibit different characteristics between the groups. However, the phylogenetic relationship of symbiont yeasts does not coincide with that of the corresponding longicorn beetle species, suggesting they have not co-speciated. The imperfect vertical transmission of symbiont yeasts from female to offspring is a mechanism that could accommodate the host-symbiont phylogenetic incongruence. Some Lepturinae species secondarily lost mycetomes. The loss is associated with their diet choice, suggesting that different conditions between feeding habits could have allowed species to discard this organ. We found that symbiont fungi encapsulated in the mycetomes are dispensable for larval growth if sufficient nutrients are given, suggesting that the role of symbiotic fungi could be compensated by the food larvae take. Aegosoma sinicum is a longicorn beetle classified to the subfamily Prioninae, which does not possess mycetomes. However, this species contains a restricted selection of yeast species in the larval gut, suggesting that the symbiosis between longicorn beetles and yeasts emerged before acquiring the mycetomes.

Praesagittifera naikaiensis is an acoel flatworm that inhabits the sandy beaches in the intertidal zone of the Seto Inland Sea. This species carries Tetraselmis sp., a green unicellular chlorophyte, as a symbiont in its body, and depends on algal photosynthetic products to survive. However, the eggs of P. naikaiensis contain no symbiotic algae, and juvenile P. naikaiensis acquire symbionts from the surrounding environment through horizontal transfer after hatching, thereby establishing new symbiotic relationships in each generation. Other acoel species, Symsagittifera spp., also inhabit the Seto Inland Sea shores and acquire symbiotic green algae via horizontal transfers. To characterize their symbionts, these acoels were collected from a wide area of the Seto Inland Sea and partial nucleotide sequences of the chloroplast ribulose diphosphate carboxylase large subunit (rbcL) of the symbiotic algae were determined and used for molecular phylogenetic analysis. Symbionts of both P. naikaiensis and Symsagittifera spp. belonged to the genus Tetraselmis but were phylogenetically distant, and both species established symbiotic relationships with different symbionts even when they were sympatric. To test whether each species selects specific algae in the environment for symbiosis, we established algal strains from P. naikaiensis and Symsagittifera sp. symbionts and conducted uptake experiments on aposymbiotic juveniles of P. naikaiensis. The results suggest that symbiotic algae from Symsagittifera could be taken up by P. naikaiensis juveniles, but were unable to establish a normal symbiotic relationship with the juveniles.

A thorough understanding of the development of complex plumages in birds necessitates the acquisition of genetic data pertaining to the mechanism underlying this phenomenon from various avian species. The oriental honey-buzzard (Pernis ptilorhynchus orientalis), a tropical summer migrant to Northeast Asia, including Japan, exemplifies this aspect owing to the diversity of its ventral coloration and intra-feather barring patterns. However, genetic polymorphism responsible for this diversity has not been identified yet. This study aimed to investigate the link between dark-plumed phenotypes of this subspecies and haplotypes of the melanocortin-1-receptor (MC1R) gene. A draft sequence of MC1R was constructed using next generation sequencing and subsequently amplified using designed polymerase chain reaction (PCR) primers. The genome sequences of 32 honey-buzzard individuals were determined using PCR, and 12 MC1R haplotype sequences were obtained. Among these haplotypes, we found that unique haplotypes with nine non-synonymous substitutions and four or five synonymous substitutions in the coding region had a perfect correlation with the dark-plumed phenotype. The lack of correlation between the genotype of ASIP coding region and plumage phenotype reiterated that the dark morph is attributable to specific MC1R haplotypes. The absence of a correlation between genetic polymorphisms of MC1R and the intra-feather barring patterns, as well as the diversity observed within lighter ground color classes (pale and intermediate), implies the involvement of alternative molecular mechanisms in the manifestation of the aforementioned phenotypes.