Biology subjects

Yamanaka, T.

Publications and source records attributed to Yamanaka, T..

6 recordsLinked to original sources

bioRxiv2026

Extraocular Photoreception Controls nocturnal hatching via a neuroendocrine pathway in False Clownfish

Hatching is the transition from embryo to larva in oviparous animals. Birds, reptiles, and insects rupture the eggshell mechanically, whereas fish and amphibians digest the egg envelope using hatching enzymes. When and where larvae emerge influences their fitness. Many species regulate hatching timing using environmental cues, such as light, oxygen availability, and physical stimuli. In fish, hatching is driven by a neuroendocrine event that triggers hatching enzyme secretion; however, the mechanisms controlling this event are unknown. Using the false clownfish Amphiprion ocellaris, which hatches synchronously within 1-2 h after sunset, we showed that the role of thyrotropin-releasing hormone (TRH) as a hatching hormone, previously established in zebrafish and medaka, extended to clownfish, where TRH activated Ca2+; signaling in hatching gland cells through its receptor trhra, reinforcing the TRH-Ca2+-hatching enzyme axis as a conserved core module of teleost hatching. In clownfish, this module was additionally placed under upstream control by extraocular photoreception because dark-induced hatching persisted in eyeless embryos. This photoreceptive system was most sensitive to green light (550 nm), and several opsins with absorbance maxima in the corresponding middle- to long-wavelength range were expressed outside the eyes of pre-hatching embryos. Coupling extraocular photoreception to a conserved neuroendocrine module placed a critical life-history transition under stringent photic control, releasing larvae only in complete darkness, an adaptation that may have underpinned the success of this lineage in predator-rich coral reefs.

zoology↗

bioRxiv2026

Species traits shape the intercontinental introduction patterns of bark and ambrosia beetles

O_LIA negative consequence of international trade is the accidental transport of non-native insect species to non-native regions, but our understanding of how this risk varies among species and how it relates to species traits remains incomplete. C_LIO_LIWe conducted a multi-continental analysis of historical border interception records for bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae), integrating 13,124 interception events (353 species) from Canada, Chile, Japan, New Zealand, and the United States. We estimated an intercontinental propagule pressure index and tested how species characteristics influence transport likelihood. C_LIO_LIInterception assemblages showed low similarity among countries, with 64% of species recorded in only one nation, indicating strong geographic structuring linked to trade pathways. Interceptions were taxonomically and biogeographically non-random: species native to the Palearctic Nearctic and Indo-Malayan regions were overrepresented, whereas Neotropical, Austro-Pacific and Afrotropical taxa were underrepresented. C_LIO_LIHost tree taxa emerged as the strongest predictor of propagule pressure. Species associated with conifers--particularly Pinaceae--exhibited approximately twice the propagule pressure of species restricted to broadleaved hosts. Ambrosia beetles showed higher propagule pressure than bark and twig/seed feeders. Propagule pressure also increased with the number of regions where species have already invaded, consistent with bridgehead dynamics. C_LIO_LISynthesis and applications: Our findings demonstrate that intercontinental transport of bark and ambrosia beetles is strongly structured by host associations, feeding guild, and biogeographic origin, reflecting the composition of traded commodities and historical trade networks. Identifying taxa with consistently high propagule pressure provides a basis for prioritizing surveillance and strengthening global forest biosecurity. C_LI

ecology↗

bioRxiv2026

Changes in the microbiome of the trophosome of Lamellibrachia satsuma induced by rearing

BackgroundAdult vestimentiferan tubeworms inhabiting hydrothermal vents and cold seeps lack a mouth and anus and rely entirely on organic matter produced by sulfur -oxidizing autotrophic bacterial symbionts in their trophosomes. These symbionts, which predominantly belong to the genus Proteobacteria, are acquired horizontally from the environment. However, the effects of rearing conditions that differ from natural habitats on the microbiome composition or abundance of these bacteria remain unclear. MethodsWe conducted a metagenomic analysis of Lamellibrachia satsuma reared in an aquarium under sulfide-supplemented and sulfide-free conditions. ResultsImmediately after collection, the microbiome was dominated by known symbionts within {gamma}-Proteobacteria, exhibiting low species diversity. After 6 months of rearing, the abundance of these symbionts significantly decreased under both conditions, whereas overall bacterial diversity increased. In particular, -Proteobacteria became more abundant under sulfide-supplemented conditions, while {delta}-Proteobacteria predominated in the absence of sulfide. Despite these changes, symbionts were not entirely lost, and the hosts survived for 6 months, likely due to their low metabolic rate. These findings suggest that the microbiome of L. satsuma can respond flexibly to changes in the rearing environment. They also indicate that the hosts metabolism can be maintained even with a smaller quantity of symbiotic bacteria.

zoology↗

bioRxiv2024

Extracellular disposal of nuclear waste by APP: a protective mechanism impaired in Alzheimer's disease

Although the amyloid beta (A{beta}) hypothesis1 has long been central to Alzheimers disease (AD) research, effective therapeutic strategies remain elusive2,3. Here we re-evaluate the functions of amyloid precursor protein (APP) and reveal its critical function in protecting against nuclear impairment-induced cell death and inflammation4,5. Overexpression of APP mitigated etoposide or lamin A knockdown-induced nuclear damage, while APP removal or mutations exacerbated these effects. Interestingly, neurons differentiated from induced pluripotent stem cells (iPSCs) exhibited similar patterns, and notably, familial AD-associated mutant APP failed to confer protection against nuclear impairment. We identify APPs interaction with a cytoplasmic structure of nuclear origin, termed "nuclear waste", and propose its role in extracellular waste disposal. Intriguingly, cells lacking APP showed impaired nuclear waste clearance, leading to abnormal cytoplasmic accumulation of the nuclear waste. Similarly, neuron-specific APP overexpression using adeno-associated virus (AAV) in mice reduced neuronal death and inflammation caused by nuclear damage. Conversely, shRNA-mediated APP exacerbated these effects, and mutant APP associated with familial AD lacked protective effects. Moreover, postmortem analysis of AD brains revealed accumulation of abnormal nuclear waste in the neurocytoplasm, irregular nuclear morphology, and reduced APP levels per neuron. Our data underscore APPs crucial role in disposing of nuclear waste, maintaining cellular homeostasis, and suggest its dysregulation as a potential contributor to AD pathogenesis. Restoring APP waste clearance in AD could be a promising target for disease-modifying therapies.

neuroscience↗

bioRxiv2024

Testosterone-Induced Metabolic Changes in Seminal Vesicle Epithelial cells Alter Plasma Components to Enhance Sperm Fertility

Male factors account for almost half of the causes of infertility. In rodents and humans, most of the components of semen are supplied by the seminal vesicles, and they support male reproductive ability, but there are many unknown details. In this study, the metabolic changes in the seminal vesicle epithelial cells were focused on, and the mechanisms by which testosterone affected the seminal plasma composition were investigated. A factor improving the linear motility of sperm was secreted from the seminal vesicles, and it was produced in an androgen-dependent manner. Bioassays, gene expression, and flux analysis studies demonstrated that testosterone promotes glucose uptake in seminal vesicle epithelial cells via GLUT4, resulting in fatty acid synthesis. ACLY was a critical factor in this metabolic change, which produced fatty acid, especially oleic acid. In conclusion, the critical role of testosterone-induced metabolic changes in the seminal vesicles is to ensure the synthesis of fatty acid. These findings suggest that testosterone-dependent lipid remodeling may contribute to sperm straight-line motility, and further functional verification is required. One Sentence Summary Testosterone promotes the conversion of glucose to fatty acid by increasing the expression of ACLY in seminal vesicle epithelial cells, thereby regulating the seminal plasma components.

cell biology↗

bioRxiv2023

Drivers of asymmetrical insect invasions between three world regions

The geographical exchange of non-native insects can be highly asymmetrical, with some world regions exporting or importing more species than others. Several hypotheses have been proposed to explain such asymmetries, including differences in propagule pressure, environmental features in recipient regions, or biological traits of invaders. We tested aspects of these hypotheses in the context of the exchange of non-native insects between North America, Europe, and Australasia. Europe was the dominant exporter of non-native insect species between the three regions, with most of this asymmetry arising prior to 1950. The European dominance could not be explained by differences in import value, source species pool sizes, or native plant richness in the recipient regions. We identified that the introduction of non-native plants, driven in part by European colonization, best explains the asymmetrical exchange of non-native insects between our focal regions.

ecology↗