Zoological Research最新文献

Pleurostomatid ciliates, as a highly diverse and widely distributed unicellular eukaryote group, play a crucial role in the cycling of nutrients and energy in microbial food webs. However, research on pleurostomatids remains insufficient, resulting in a paucity of molecular information and substantial gaps in knowledge of their phylogenetic relationships. In recent years, we investigated pleurostomatid diversity in various Chinese habitats, including their systematic relationships and taxonomic circumscriptions, which were comprehensively analyzed using an integrative morphomolecular approach. Results revealed that: (1) pleurostomatids can be categorized into two suborders, Protolitonotina subord. nov. and Amphileptina Jankowski, 1967; (2) Protolitonotina subord. nov. represents the ancestral pleurostomatid group and includes two genera, Protolitonotus and Heterolitonotus gen. nov., characterized by right kineties progressively shortened along rightmost full kineties and absence of a left dorsolateral kinety; (3) Heterolitonotus gen. nov. represents an orphan lineage and is defined by an oral slit extending to its dorsal margin; (4) " Protolitonotus clampi" does not group with congeners but instead represents an orphan lineage, thus Novilitonotus gen. nov. is established to which P. clampi is transferred as Novilitonotus clampi comb. nov.; (5) three new species, Apoamphileptus paraclaparedii sp. nov., Heterolitonotus rex gen. nov., sp. nov., and Loxophyllum apohelus sp. nov., are described; and (6) helices 21es6a to 21es6d within the V4 region of small subunit ribosomal RNA (SSU rRNA) may serve as a useful tool for discriminating pleurostomatids. The evolutionary relationships among all main lineages of pleurostomatids are discussed and a key to the identification of pleurostomatid genera is provided.

The identification of sex chromosomes is fundamental for exploring the mechanism and evolution of sex determination. Platichthys stellatus, a species exhibiting clear sexual dimorphism and homomorphic chromosome pairs, has received limited research concerning its sex determination mechanisms. Clarifying the sex chromosome of P. stellatus will enhance our understanding of sex chromosome evolution in Pleuronectiformes. This study employed whole-genome resequencing to investigate the sex chromosome and sex determination system in P. stellatus. Notably, Chr23 was identified as the sex chromosome in P. stellatus, with the sex-determining region (SDR) occupying 48.1% of the chromosome and featuring an XX/XY system. Sex chromosome turnover was observed within Pleuronectiformes, with P. stellatus, Verasper variegatus, and Hippoglossus hippoglossus sharing a common ancestral karyotype. No inversions were detected within the SDR of P. stellatus, although chromosomal rearrangements between sex chromosomes and autosomes were identified. Additionally, a sex-specific marker for P. stellatus was ascertained, enabling genetic sex identification, with significant implications for improving breeding programs and aquaculture practices.

Bats, notable as the only flying mammals, serve as natural reservoir hosts for various highly pathogenic viruses in humans (e.g., SARS-CoV and Ebola virus). Furthermore, bats exhibit an unparalleled longevity among mammals relative to their size, particularly the Myotis bats, which can live up to 40 years. However, the mechanisms underlying these distinctive traits remain incompletely understood. In our prior research, we demonstrated that bats exhibit dampened STING-interferon activation, potentially conferring upon them the capacity to mitigate virus- or aging-induced inflammation. To substantiate this hypothesis, we established the first in vivo bat-mouse model for aging studies by integrating Myotis davidii bat STING ( MdSTING) into the mouse genome. We monitored the genotypes of these mice and performed a longitudinal comparative transcriptomic analysis on MdSTING and wild-type mice over a 3-year aging process. Blood transcriptomic analysis indicated a reduction in aging-related inflammation in female MdSTING mice, as evidenced by significantly lower levels of pro-inflammatory cytokines and chemokines, immunopathology, and neutrophil recruitment in aged female MdSTING mice compared to aged wild-type mice in vivo. These results indicated that MdSTING knock-in attenuates the aging-related inflammatory response and may also improve the healthspan in mice in a sex-dependent manner. Although the underlying mechanism awaits further study, this research has critical implications for bat longevity research, potentially contributing to our comprehension of healthy aging in humans.

Infertility represents a significant health concern, with sperm quantity and quality being crucial determinants of male fertility. Oligoasthenoteratozoospermia (OAT) is characterized by reduced sperm motility, lower sperm concentration, and morphological abnormalities in sperm heads and flagella. Although variants in several genes have been implicated in OAT, its genetic etiologies and pathogenetic mechanisms remain inadequately understood. In this study, we identified a homozygous nonsense mutation (c.916C>T, p.Arg306*) in the coiled-coil domain containing 146 ( CCDC146) gene in an infertile male patient with OAT. This mutation resulted in the production of a truncated CCDC146 protein (amino acids 1-305), retaining only two out of five coiled-coil domains. To validate the pathogenicity of the CCDC146 mutation, we generated a mouse model ( Ccdc146 ^mut/mut ) with a similar mutation to that of the patient. Consistently, the Ccdc146 ^mut/mut mice exhibited infertility, characterized by significantly reduced sperm counts, diminished motility, and multiple defects in sperm heads and flagella. Furthermore, the levels of axonemal proteins, including DNAH17, DNAH1, and SPAG6, were significantly reduced in the sperm of Ccdc146 ^mut/mut mice. Additionally, both human and mouse CCDC146 interacted with intraflagellar transport protein 20 (IFT20), but this interaction was lost in the mutated versions, leading to the degradation of IFT20. This study identified a novel deleterious homozygous nonsense mutation in CCDC146 that causes male infertility, potentially by disrupting axonemal protein transportation. These findings offer valuable insights for genetic counseling and understanding the mechanisms underlying CCDC146 mutant-associated infertility in human males.

Type IV interferon (IFN-υ) is a recently discovered cytokine crucial for host defense against viral infections. However, the role and mechanisms of IFN-υ in bacterial infections remain unexplored. This study investigated the antibacterial and antiviral functions and mechanisms of grass carp ( Ctenopharyngodon idella) IFN-υ (CiIFN-υ) both in vivo and in vitro. The CiIFN-υ gene was first identified and characterized in grass carp. Subsequently, the immune expression of CiIFN-υ significantly increased following bacterial challenge, indicating its response to bacterial infections. The eukaryotic recombinant expression plasmid of CiIFN-υ was then constructed and transfected into fathead minnow (FHM) cells. Supernatants were collected and incubated with four bacterial strains, followed by plate spreading and colony counting. Results indicated that CiIFN-υ exhibited more potent antibacterial activity against gram-negative bacteria compared to gram-positive bacteria and aggregated gram-negative bacteria but not gram-positive bacteria. In vivo experiments further confirmed the antibacterial function, showing high survival rates, low tissue edema and damage, reduced tissue bacterial load, and elevated proinflammatory response at the early stages of bacterial infection. In addition, the antiviral function of CiIFN-υ was confirmed through in vitro and in vivo experiments, including crystal violet staining, survival rates, tissue viral burden, and RT-qPCR. This study highlights the antibacterial function and preliminary mechanism of IFN-υ, demonstrating that IFN-υ possesses dual functions against bacterial and viral infections.

In reptiles, such as the red-eared slider turtle ( Trachemys scripta elegans), gonadal sex determination is highly dependent on the environmental temperature during embryonic stages. This complex process, which leads to differentiation into either testes or ovaries, is governed by the finely tuned expression of upstream genes, notably the testis-promoting gene Dmrt1 and the ovary-promoting gene Foxl2. Recent studies have identified epigenetic regulation as a crucial factor in testis development, with the H3K27me3 demethylase KDM6B being essential for Dmrt1 expression in T. s. elegans. However, whether KDM6B alone can induce testicular differentiation remains unclear. In this study, we found that overexpression of Kdm6b in T. s. elegans embryos induced the male development pathway, accompanied by a rapid increase in the gonadal expression of Dmrt1 at 31°C, a temperature typically resulting in female development. Notably, this sex reversal could be entirely rescued by Dmrt1 knockdown. These findings demonstrate that Kdm6b is sufficient for commitment to the male pathway, underscoring its role as a critical epigenetic regulator in the sex determination of the red-eared slider turtle.

Zebrafish serve as a valuable model organism for studying germ cell biology and reproductive processes. The AB strain of zebrafish is proposed to exhibit a polygenic sex determination system, where most males initially develop juvenile ovaries before committing to male fate. In species with chromosomal sex determination, gonadal somatic cells are recognized as key determinants of germ cell fate. Notably, the loss of germ cells in zebrafish leads to masculinization, implying that germ cells harbor an intrinsic feminization signal. However, the specific signal triggering oogenesis in zebrafish remains unclear. In the present study, we identified foxl2l as an oocyte progenitor-specific gene essential for initiating oogenesis in germ cells. Results showed that foxl2l-knockout zebrafish bypassed the juvenile ovary stage and exclusively developed into fertile males. Further analysis revealed that loss of foxl2l hindered the initiation of oocyte-specific meiosis and prevented entry into oogenesis, leading to premature spermatogenesis during early gonadal development. Furthermore, while mutation of the pro-male gene dmrt1 led to fertile female differentiation, simultaneous disruption of foxl2l in dmrt1 mutants completely blocked oogenesis, with a large proportion of germ cells arrested as germline stem cells, highlighting the crucial role of foxl2l in oogenesis. Overall, this study highlights the unique function of foxl2l as a germ cell-intrinsic gatekeeper of oogenesis in zebrafish.

Most described Mesozoic ants belong to stem groups that existed only during the Cretaceous period. Previously, the earliest known crown ants were dated to the Turonian (Late Cretaceous, ca. 94-90 million years ago (Ma)) deposits found in the USA, Kazakhstan, and Botswana. However, the recent discovery of an alate male ant in Kachin amber from the earliest Cenomanian (ca. 99 Ma), representing a new genus and species, Antiquiformica alata, revises the narrative on ant diversification. Antiquiformica can be distinctly differentiated from all known male stem ants by its geniculate antennae with elongated scape, extending far beyond the occipital margin of the head and half the length of the funiculus, as well as its partly reduced forewing venation. Furthermore, the combination of a one-segmented waist with a well-developed node, elongated scape extending beyond the occipital margin, and reduced forewing venation, particularly the completely reduced m-cu and rs-m crossveins and absence of rm and mcu closed cells, firmly places the fossil within the extant subfamily Formicinae. Fourier transform infrared spectroscopy (FTIR) confirmed that the amber containing Antiquiformica alata originated from the Kachin mines in Myanmar. This discovery significantly revises our understanding of the early evolution of Formicinae. The presence of Antiquiformica in Cenomanian amber indicates that the subfamily Formicinae emerged at least by the start of the Late Cretaceous, with crown ants likely originating earlier during the earliest Cretaceous or possibly the Late Jurassic, although paleontological evidence is lacking to support the latter hypothesis.

Glass catfish ( Kryptopterus vitreolus) are notable in the aquarium trade for their highly transparent body pattern. This transparency is due to the loss of most reflective iridophores and light-absorbing melanophores in the main body, although certain black and silver pigments remain in the face and head. To date, however, the molecular mechanisms underlying this transparent phenotype remain largely unknown. To explore the genetic basis of this transparency, we constructed a chromosome-level haplotypic genome assembly for the glass catfish, encompassing 32 chromosomes and 23 344 protein-coding genes, using PacBio and Hi-C sequencing technologies and standard assembly and annotation pipelines. Analysis revealed a premature stop codon in the putative albinism-related tyrp1b gene, encoding tyrosinase-related protein 1, rendering it a nonfunctional pseudogene. Notably, a synteny comparison with over 30 other fish species identified the loss of the endothelin-3 ( edn3b) gene in the glass catfish genome. To investigate the role of edn3b, we generated edn3b ^-/- mutant zebrafish, which exhibited a remarkable reduction in black pigments in body surface stripes compared to wild-type zebrafish. These findings indicate that edn3b loss contributes to the transparent phenotype of the glass catfish. Our high-quality chromosome-scale genome assembly and identification of key genes provide important molecular insights into the transparent phenotype of glass catfish. These findings not only enhance our understanding of the molecular mechanisms underlying transparency in glass catfish, but also offer a valuable genetic resource for further research on pigmentation in various animal species.

DNA methylation plays a crucial role in environmental adaptations. Here, using whole-genome bisulfite sequencing, we generated comprehensive genome-wide DNA methylation profiles for the high-altitude Yunnan snub-nosed monkey ( Rhinopithecus bieti) and the closely related golden snub-nosed monkey ( R. roxellana). Our findings indicated a slight increase in overall DNA methylation levels in golden snub-nosed monkeys compared to Yunnan snub-nosed monkeys, suggesting a higher prevalence of hypermethylated genomic regions in the former. Comparative genomic methylation analysis demonstrated that genes associated with differentially methylated regions were involved in membrane fusion, vesicular formation and trafficking, hemoglobin function, cell cycle regulation, and neuronal differentiation. These results suggest that the high-altitude-related epigenetic modifications are extensive, involving a complete adaptation process from the inhibition of single Ca ²⁺ channel proteins to multiple proteins collaboratively enhancing vesicular function or inhibiting cell differentiation and proliferation. Functional assays demonstrated that overexpression or down-regulation of candidate genes, such as SNX10, TIMELESS, and CACYBP, influenced cell viability under stress conditions. Overall, this research suggests that comparing DNA methylation across closely related species can identify novel candidate genomic regions and genes associated with local adaptations, thereby deepening our understanding of the mechanisms underlying environmental adaptations.