Nutrient availability differs among habitats and can promote evolutionary divergence in metabolic traits. For example, freshwater habitats are typically deficient in polyunsaturated fatty acids, such as docosahexaenoic acid (DHA), and freshwater fishes often exhibit a higher capacity for DHA biosynthesis from precursor fatty acids than marine fishes. However, it remains unknown whether freshwater and marine fishes differ in the patterns of lipid deposition or in the utilization of fatty acids such as DHA. In this study, we tested whether marine and stream ecotypes of the threespined stickleback (Gasterosteus aculeatus) have diverged in lipid deposition strategies and DHA utilization. Fish were reared under nutritionally and energetically poor or rich conditions, and body growth, visceral fat deposition, blood cholesterol levels, and whole-body lipid composition were analyzed. We found that the rich diet promoted growth in both ecotypes, but visceral fat deposition diverged with stream fish accumulating more visceral fat and marine fish showing variable responses. Blood cholesterol levels were unaffected by diet and did not differ significantly between ecotypes. Lipidomic analyses revealed that the rich diet increased the abundance of phosphatidylethanolamine and phosphatidylserine, and the proportion of DHA in several lipid classes, including membrane lipids, in both ecotypes. In conclusion, stream sticklebacks tended to accumulate more visceral fat under a lipid- and energy-rich diet than marine sticklebacks, whereas lipidomic responses were largely conserved between ecotypes. These results indicate that divergence between marine and stream sticklebacks may primarily involve differences in energy storage strategies, with less pronounced divergence in core lipid metabolic pathways.
Leaf beetles of the tribe Haemoniini (Chrysomelidae: Donaciinae) comprise two genera, Macroplea in the Palearctic region and Neohaemonia in the Nearctic region. These beetles are exceptional among aquatic insects in that they complete their entire life cycle underwater, obtaining oxygen either directly from the water or from the tissues of aquatic plants. Because they depend on clear, unpolluted water, their populations are considered highly vulnerable to decline and local extinction in habitats affected by human disturbance. In this study, we generated short-read genomic sequencing data for 11 specimens representing seven haemoniine species (four Macroplea and three Neohaemonia) and assembled mitochondrial genome (mitogenome) sequences and nuclear 18S ribosomal RNA gene sequences. These data were used to investigate phylogenetic relationships within the tribe and to provide reference sequences for DNA barcoding. Phylogenetic analyses based on mitogenome, 18S rRNA, and previously published 28S rRNA gene sequences were performed using maximum-likelihood methods. The analyses supported the monophyly of Macroplea and Neohaemonia and resolved most interspecific relationships within each genus. In addition, our divergence-time estimates suggest that the Japanese and continental East Asian populations of M. japana and M. mutica diverged around the transition from the Last Glacial Period to the early Holocene.
The Mediterranean house gecko, Hemidactylus turcicus (Linnaeus, 1758), is a widespread alien reptile that was recently designated as an “Alert Alien Species” in South Korea. This study documents the first stable established population of H. turcicus in Pyeongtaek, South Korea, and assesses its ecological adaptation through longitudinal field surveys and fecal metagenomic analysis. From September 2024 to September 2025, 105 individuals, including juveniles and gravid females, were observed utilizing anthropogenic structures for overwintering, indicating successful demographic establishment and thermal adaptation. Molecular identification based on the mitochondrial COI gene confirmed species identity with > 97% similarity to the known sequences. Fecal metagenomic analysis revealed a predominantly insectivorous diet composed mainly of Coleoptera, Blattodea, and Hemiptera, with 62% of the families matching the local native fauna. Notably, the detection of Trichinellidae nematode DNA in fecal samples highlights a potential zoonotic risk associated with this alien population. Although the population is currently in the lag phase of invasion, its exploitation of local prey resources and artificial habitats necessitates immediate management and monitoring to prevent range expansion and reduce predation pressure on native prey species.
Although taxonomic studies have been increasingly conducted on deep-sea chemosynthesis-based ecosystems, the diversity of sipunculans in these habitats remains insufficiently characterized. To investigate their diversity around the Japanese Archipelago, a taxonomic survey was conducted on deep-sea sipunculan specimens collected from southern Japanese waters during JAMSTEC cruises from 1999 to 2011, spanning hydrothermal vents, hydrocarbon seeps, and whale falls. Morphological and molecular analyses (based on 16S, 18S, and 28S rRNA, COI, H3, and H4 genes) revealed three distinct species of Phascolosoma (subgenus Phascolosoma), two being new to science and possessing introvert hooks serrated along the posterior margin, but morphologically distinguishable by the presence or absence of pigmented eyespots; one was found at hydrothermal vents and whale falls, while the other occurred at vents and hydrocarbon seeps. The third species, occurring across the three habitat types and bearing pigmented eyespots, closely resembled P. turnerae Rice, 1985 from the western Atlantic and Mediterranean, but showed clear genetic divergence, and was therefore identified as P. turnerae complex. The molecular phylogenetic analyses, including divergence time estimation, suggested a single monophyletic origin of Phascolosoma species inhabiting deep-sea chemosynthesis-based ecosystems during the Cretaceous Period. Ancestral character reconstruction indicated that organic-fall ecosystems, such as wood falls, served as evolutionary stepping stones, facilitating the colonization of chemosynthesis-based habitats by sipunculans.
The genetic structure of Hynobius kimurae and H. fossigenus, lotic-breeding salamanders widespread throughout montane regions of central and western Honshu of Japan, was surveyed. A mitochondrial DNA analysis to explore intraspecific genetic variation and infer the evolutionary population history of the two species was performed. Complete gene sequences of cytochrome b (Cyt b, 1141 bp) and cytochrome c oxidase subunit I (CO1, 1551 bp) were studied for 58 samples from 31 localities of H. kimurae and 22 samples from 12 localities of H. fossigenus, both encompassing the known range of the species. The two species proved to be monophyletic and H. kimurae included six clades grouped in four major clades (Clades West-1 from Northern Kinki, West-2 and West-3 from Hokuriku and Northern Chubu, West-5 and West-6 from Southwestern Kinki to Chugoku, and West-4 from Chubu to Kinki). Hynobius fossigenus consisted of two clades. In addition to East-1 from Kanto to easternmost Aichi, East-2 from eastern Aichi was herein first identified. Hynobius fossigenus occurs in the northernmost region among the lotic-breeding Hynobius species, whose range does not extend to the Tohoku District of northeast Japan. Our estimates indicate that H. fossigenus could not enter the region because of the presence of Paleo–Tokyo Bay and also of the hindrance through the ecological niche occupation by H. lichenatus, originally a lentic breeder but actually utilizing lotic water for breeding.
