Zoological Science最新文献

Due to limited spawning seasons, embryogenesis of corals has not fully been studied and the embryonic origin of gastrodermis remains uncertain in Acropora. We herein examined how embryonic endodermal cells develop into the gastrodermis and mesentery of polyps in Acropora tenuis. In juvenile polyps, the gastrodermis invaginates to form mesenteries, both of which were stained with rhodamine-phalloidin, an anti-myocyte-specific enhancer factor 2 (anti-AtMef2) antibody, and an anti-lipoxygenase homology domain-containing protein 1 (anti-AtLoxhd1) antibody. Rhoda-mine-phalloidin staining was traced back to the endodermal cells of 60-85 hpf 'pear'-stage embryos through the larval stage. AtMef2 appeared in the blastomeres of a 12-hpf 'prawnchip'-stage embryo that was a variant U-shaped blastula with a narrow blastocoel. AtMef2 temporarily disappeared from the nuclei of 28-hpf 'donut'-stage embryos and reappeared in the endodermal cells of 40-hpf early 'pear'-stage embryos, suggesting a transition from maternal to zygotic expression of Mef2. The blastopore closed without the invagination of blastomeres. The gastrocoel collapsed and the Mef2-positive endoderm was dissociated into single cells in the well-developed blastocoel filled with yolk cells. The mesoglea appeared in the yolk cell layer. AtLoxhd1 was traced back to the endodermal cells of 'pear'-stage embryos. In 11-dpf larvae, Loxhd1-positive endodermal cells elongated in the vicinity of the mesoglea to adhere to each other and form the gastroderm epithelium in larvae. Therefore, in this coral, the inner wall of U-shaped early embryos is the cellular origin of the gastrodermis. Inner wall-derived endodermal cells move independently toward the mesoglea, where cell-cell adhesion occurs to establish the gastrodermis.

Recent studies have suggested that, in some bird species, predator-elicited vocalizations of males may function as an advertisement to conspecific females, but the evidence remains scarce. Male Japanese bush warblers, Horornis diphone, are known for producing long, conspicuous songs (continuous songs), in response to both predators and conspecific females. In this work, I investigated the temporal and spatial associations of continuous songs with the presence of females. In seven surveys throughout a breeding season, male singing activity of continuous songs was low before females arrived at the breeding ground but increased thereafter. Singing activity was higher in territories where the presence of females was confirmed than in those where it was not. Over multiple days, I observed a single male from sunrise to sunset and observed that the locations where the male sang continuous songs were concentrated at the locations where the females were observed. These temporal and spatial associations of the continuous song with the presence of conspecific females support the hypothesis that the continuous song is an advertisement to females. Additional observations showed that females did not fly away or enter the bushes in response to the continuous songs as they did when they encountered danger, and that the male sang continuous songs even towards females that were not considered their mating partner. These findings are inconsistent with the hypothesis that the continuous song is an alarm to alert their mates of danger. This study shows the possibility that male Japanese bush warblers advertise their quality to potential mates by singing continuous songs under dangerous situations.

Most true predators are generalists, and it is difficult to examine their actual diets in the wild. In many cases, the prey that experience a large impact are also not well known. Amphibians are generalist predators that prey mainly on insects, and amphibian species active beginning in spring are considered to prey on food resources other than insects in this season due to the low number of insects. The Japanese red-bellied newt (Cynops pyrrhogaster) is a generalist predator widely distributed in Japan and is known to frequently prey on amphibian eggs. Here, we showed that amphibian eggs are a precious food resource for C. pyrrhogaster in spring. The total weights of stomach contents were compared among seasons and we found that the total weights of stomach contents in spring were the same as those in summer. Also, we examined whether C. pyrrhogaster preys on amphibian eggs instead of insects in spring. The composition of the taxonomic groups in their stomach contents was compared among the seasons, and the indicator groups in their stomach contents were identified in each season. We found that they preyed not only upon insects but also upon amphibian eggs in spring, while they preyed mainly upon insects in summer and autumn. Our results suggest that C. pyrrhogaster preys on amphibian eggs to compensate for the shortage of food in spring when the number of insects is low.

Sexual differences are commonly described as male-biased sexual dimorphism, female-biased dimorphism, and monomorphism. Nevertheless, detailed patterns of sexual dimorphism have only been explored in a few rodent species. We used geometric morphometrics to investigate patterns of sexual dimorphism, static allometry, and modularity in the skull of the Ethiopian white-footed mouse (Stenocephalemys albipes). Procrustes analysis of variance showed nonsignificant sexual dimorphism for the size and shape of the cranium. Significant sexual differences were detected in the mandibular size but not in the mandibular shape. Discriminant analysis indicated nonsignificant differences between sexes in the Procrustes distance of the cranium and mandible. Additionally, scatter allometric plots demonstrated similar patterns of allometry in both sexes. Allometric variation showed an elongation of the rostrum, widening of the zygomatic bones, and narrowing of the braincase. We also observed an expanding of the ascending ramus and shortening of the alveolar part for the mandible. These may indicate the existence of modularity in the skull, which was supported by modularity analysis. Although these trends have been thought to be a growth-related phenomenon of the mammalian skull, functional requirements may also have an effect. In conclusion, our results indicate sexual monomorphism in the skull of S. albipes, which may have no effect on allometric variation and modularity patterns.

Melampus "sincaporensis," Auriculastra "duplicata", and Ellobium chinense are Red-Listed snail species of the family Ellobiidae that co-occur on salt marshes in mainland Japan. Here, we report the genetic diversity and population structures of the former two taxa in comparison with our previous data on E. chinense for the evaluation of connectivity and conservation values of their local populations. Analyses of 655-bp or 652-bp sequences of the mitochondrial cytochrome c oxidase subunit I gene showed the highest genetic diversity and panmictic structure for M. sp. cf. sincaporensis throughout its geographic range in Japan, whereas they showed the highest level of genetic subdivision for A. sp. cf. duplicata. Our laboratory observation of egg masses and planktotrophic larvae of A. "duplicata" and reference to previous ontogenetic data for the species of Melampus suggested differences in their fecundity and pelagic larval duration, which apparently have led to the contrasting levels of population differentiation in the study species. Particular need of conservation efforts was identified for the isolated population of A. "duplicata" in the Ise-Mikawa Bay area to avoid local extinction and shrinking of the species' geographic range. In addition, we present molecular and morphological evidence that individuals of A. "duplicata" from mangrove swamps in the northern part of Okinawa Island represent an independent, surviving lineage of a different species.

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.