BMC Biology

The brain is essential for animal survival and based on its conserved Bauplan, an impressive adaptive diversity has evolved. However, the genetic mechanisms regulating brain development and diversification remain enigmatic. The insect neural stem cells (neuroblasts, NBs) acquire different identities through the combinatorial expression of transcription factors (TFs), but this code is unknown for the brain. Here, we define the conserved core of TFs expressed in insect brain NBs by a combined analysis of single-cell expression from NBs derived from two holometabolous insects, the fly Drosophila melanogaster and the beetle Tribolium castaneum. In Tribolium, we established a Gal4 enhancer trap system to identify a line that marks NBs. From 37,137 sequenced NBs, we identified 10,425 brain NBs. In Drosophila, we sequenced 32,112 NB nuclei, identifying 12,389 brain NBs. Analysing the combined dataset strongly increased the sensitivity in specifying the core of 188 brain-specific TFs. We found two atypical clusters with some similarity to Type II NBs and identified seven transcription factors not previously associated with or confirmed in NBs (Hmx, CG15696, CG32532, dmrt99B, fD59A, TfAP-2, and Fer1). Our data reveals fundamental differences between brain and ventral nerve cord specification and paves the way to study the development and evolution of brain specific structures.

Prions, once mainly studied for their pathogenic roles, are now gaining recognition as adaptive elements in microbial physiology. Over one-third of wild yeast isolates harbor prion proteins, yet their impact on host-microbe interactions remains poorly characterized. Given the ecological dominance of yeasts in the Drosophila mycobiome, we leveraged the Drosophila melanogaster-Saccharomyces cerevisiae system to investigate how the mycobiome-derived prion, [MRPL10+], modulates host physiology. We show that flies exposed to [MRPL10+] yeast exhibit significantly enhanced cold tolerance and increased locomotor activity. This effect persists with heat-killed yeast and diluted culture, suggesting a stable, potent bioactive factor. Using the genetically diverse Drosophila Global Diversity Lines (GDL), we identified natural variation in responsiveness to [MRPL10+] yeast. Genome-wide association and functional RNAi screening revealed a gut-brain signaling axis involving genes critical for digestion, intercellular communication, transcription regulation, and neural transmission. Notably, serotonin and octopamine pathways were essential for [MRPL10+]-induced changes in cold tolerance and locomotion, implicating neuromodulatory circuits in prion-mediated microbial signaling. Our findings establish a mechanistic link between a fungal prion and host metabolic and neural adaptation. This work provides the first genetic dissection of a prion-mediated host-microbe interaction, laying the groundwork for investigating beneficial prions in complex microbial communities and highlighting a new dimension of the mycobiomes influence on animal physiology.

Nitrogenous waste excretion is essential for all developmental stages of fish. Embryonic fish excrete urea, transitioning to cutaneous and later branchial ammonia excretion. In zebrafish, ammonia excretion involves rhesus glycoproteins Rhbg and Rhcgb in keratinocytes and ionocytes, but the developmental moment they appear in the gill remains unclear. Potential redundancy between Rhbg and Rhcgb in ammonia excretion is also not fully investigated, nor is the difference in response to low pH. We hypothesized that rhesus glycoproteins are partially redundant, and that they differ in their response to low pH as ammonia excretion enables ionocytes to exchange Na+ and H+ (Rh-NHE-metabolon). We predicted that a loss of rhbg or rhcgb induces compensatory responses. We characterized the transition from urea to branchial ammonia excretion from 0 to 8 days-post fertilization (dpf) and the response to pH 5.0 on the expression and localization of rhesus glycoproteins in control zebrafish and rhbg or rhcgb-crispants. Effects of high external ammonia (HEA, 500 M NH4Cl) and 10 mM HEPES-buffering were further characterized in rhcgb-crispants. Rhag and Rhbg appeared in the gill at 5 dpf, while Rhcgb appeared at 6 dpf. A loss of rhbg or rhcgb did not impact baseline N-excretion, illustrating that zebrafish can maintain ammonia excretion without the full complement of rhesus glycoproteins. We observed no compensatory increase in rhesus glycoproteins, but expression of the transporter hippocampus-abundant transcript 1b increased. HEA-exposed rhcgb-crispants switched to urea as primary nitrogen waste. Together, these findings underline the plasticity of the larval in dealing with nitrogenous waste.

Elucidating the biological and molecular mechanisms that govern male fertility and mating behavior in mosquitoes is critical for optimizing genetic and sterile insect technique-based vector control strategies. Here, we examined age-related changes in male reproductive capacity in Anopheles culicifacies, using female egg output as an indirect indicator of male fertility. Our results demonstrated that male reproductive age follows a non-linear pattern of fertility. Morphometric analysis from emergence to day 13 post-eclosion revealed a strong correlation between seminal vesicle capacity and female fecundity, suggesting that age-dependent gonadal development directly influences reproductive potential. At the molecular level, we identified AcLITAF6 as a key regulator of male reproductive homeostasis. RNAi-mediated knockdown of AcLITAF6 impaired apoptosis-associated and phagocytic clearance, reduced sperm viability, and decreased female productive outcomes. Conclusively, we reveal a previously unrecognized role of LITAF in sperm quality control and male reproductive fitness, highlighting AcLITAF6 as a potential target for mosquito population suppression strategies.

The distribution of fat-soluble compounds (including antioxidants) in follicular fluid (FF) remains sparsely documented in relation to in vitro fertilization (IVF) outcomes and existing studies have reported diverging associations. This study aimed to describe plasma and FF concentrations of fat-soluble micronutrients in women undergoing IVF and to analyze their adjusted associations with ovarian function, embryo development and pregnancy outcomes. In 2021-2022, plasma and FF samples were collected from 82 women (first IVF cycle) at oocyte puncture, along with lifestyle data covering the three preceding months. Eleven compounds (two tocopherols, three xanthophylls, five carotenes and retinol) were quantified. All compounds were detected in both compartments (lowest in FF) except phytoene, undetectable in FF. Plasma and FF -tocopherol concentrations were positively associated with plasma estradiol levels before oocyte puncture (both p<0.01) while FF -carotene and lycopene were inversely associated with plasma progesterone concentrations (p=0.01 and 0.02, respectively). Plasma phytofluene and phytoene were positively associated with mature oocyte rate (p=0.03 and p=0.01, respectively), while FF retinol was negatively associated (p=0.03). Carotenes, tocopherols and retinol were inversely associated with later IVF outcomes: fertilization rate (p<0.001 for plasma g-tocopherol, 0.02 for FF retinol), top-quality embryo (p=0.02 for plasma phytofluene), biochemical pregnancy at day 7 post-embryo transfer (p=0.05 for plasma -tocopherol, 0.02 for plasma -carotene), clinical pregnancy (p=0.03 for plasma -tocopherol, 0.01 for plasma phytoene) and live birth (p=0.04 for plasma -tocopherol, 0.02 for plasma phytoene). Plasma and FF g-tocopherol were positively associated with embryo fragmentation (both p<0.05). Finally, among xanthophylls, only plasma {beta}-cryptoxanthin was positively associated with plasma progesterone concentrations (p=0.02). Our findings of heterogeneous associations between tocopherols, carotenes, retinol and IVF outcomes across the stages of IVF suggest a beneficial effect limited to early outcomes and support a complex and context-dependent role of these compounds in female reproduction. This manuscript has been submitted to PlosOne on August 19, 2026.

Disseminated cancer cells (DCC) in non-metastatic carcinoma patient bone marrow (BM) are predictive of metastasis. Those detected by epithelial cytokeratin or EpCAM expression have poorly-characterized transcription profiles due to their extreme rarity: 1~2 cells per two million BM cells in every third non-metastatic patient. We here characterize the transcriptomes of DCCs. Single-cell RNA-sequencing (scRNA-seq) of 864 EpCAM-positive cells (from 1,151 cancer patients) in BM or lymph nodes (LN) revealed plasma, immune, myeloid, erythroid progenitor cells and two candidate DCC populations, termed M0-DCC and M1-DCC. M0-DCC, mostly from non-metastatic M0-stage patients, displayed the highest known adult stemness scores, and were transcriptomically reminiscent of human cleavage-stage, preimplantation embryos. M1-DCC represented cancer cells undergoing the epithelial-mesenchymal transition (EMT), corresponding to later, implanting and gastrulating embryos. Detection of early-embryo-like DCC categorised patients at highest risk for metastatic progression. Furthermore, high M0-DCC scores predicted the metastatic potential of human cell lines from the Cancer Cell Line Encyclopedia. M0-DCC gene expression profiles can be reversibly induced from M1-DCC-like cells in vitro. The close correspondence between gene expression profiles in immediate early embryonic development and metastatic founder cell candidates provides strong evidence that the onset of cancer and metastasis recruits mechanisms employed in fertilization.

Developmental regression is a severe but poorly understood complication of several neurodevelopmental disorders. In Kleefstra syndrome (KLEFS1), caused by EHMT1 haploinsufficiency, regression often emerges during adolescence or early adulthood and is frequently preceded by marked sleep disturbance. Experimental work implicating EHMT1/G9a in metabolic regulation and stress responses raises the possibility that impaired metabolic resilience contributes to this vulnerability. Here, we aimed to investigate whether altered glucose metabolism is a feature of KLEFS1 and whether it relates to clinical variability, including regression. Through [18F]FDG-PET/CT, individuals with KLEFS1 who had experienced regression (n=4) exhibited a hypometabolic brain profile, whereas one individual who had not experienced regression showed globally elevated metabolic activity. In parallel, G9a mutant flies exhibited increased baseline metabolic rate and neuronal ATP levels together with sleep fragmentation resembling the clinical phenotype. Providing flies with oxidative stress to model KLEFS1 regression further exacerbated sleep disruption and was associated with a reduction in metabolic output. Importantly, adult high sugar feeding in flies prevented oxidative stress-induced worsening of sleep and maintained metabolic stability under challenge. Together, these findings suggest that regression in KLEFS1 and associated sleep disturbances are linked to underlying metabolic vulnerability and impaired maintenance of energy homeostasis under stress.

The extent to which conserved neural circuit architectures depend on shared molecular specification programs remains unclear. Here, we address this question by examining the somatosensory system of the little skate, Leucoraja erinacea, an early-diverging vertebrate that retains ancestral features of both finned and limb-based body plans. We show that core features of somatosensory circuit organization, including laminar organization of the spinal cord and dorsally restricted targeting of sensory afferents, are deeply conserved. Unexpectedly, the molecular programs specifying dorsal root ganglion (DRG) sensory subtypes diverge extensively from those of mammals. Although DRG neuron subtype specification and spinal connectivity rely on target-derived cues, skates employ distinct neurotrophin receptor and transcription factor identity codes. These findings support a model in which conserved spinal circuit architectures provide a stable scaffold that leverages flexible sensory neuron specification programs, enabling the evolutionary diversification of vertebrate somatosensory systems. HighlightsO_LIIntegrated analysis of spinal cord and DRG neuronal diversity in Leucoraja erinacea C_LIO_LILaminar organization of the dorsal spinal cord is an ancestral vertebrate feature C_LIO_LIDivergent neurotrophin receptor and transcription factor codes in sensory neurons C_LIO_LIConserved target-dependent regulation of sensory identity and connectivity C_LI

THAP9 is a transposable element-derived gene which encodes a protein that is homologous to the active Drosophila P-element transposase (DmTNP). Both THAP9 and DmTNP possess a C-terminal domain (CTD) which is functionally uncharacterized. Sequence and structural analysis suggest that the THAP9-CTD has a novel fold which is only found in THAP9 homologs. To explore the evolutionary history and characteristics of this novel domain, exhaustive phylogenetic analysis (using MSA, structure prediction, MSTA-based clustering) was performed. THAP9-CTD homologs were more widely distributed throughout the animal kingdom in comparison to DmTNP-CTD homologs which were restricted to arthropods. Moreover, the THAP9-CTD homologs were more conserved, especially among mammals and birds and their average length increased in a class-specific manner. Comparison with the DmTNP-CTD homologs demonstrates that although their respective CTDs may have evolved independently, they both surprisingly share similar secondary structure elements consisting of three conserved helical regions made of hydrophobic residues that are predicted to make up a conserved core. The role of the respective CTDs were further investigated by creating truncation mutants lacking the CTD. Interestingly both THAP9 and DmTNP truncation mutants are still capable of DNA excision and integration suggesting that their respective CTDs are not essential for DNA transposition. Moreover, CTD truncation favours DNA integration in THAP9: this suggests that CTD acquisition during evolution may have led to THAP9 domestication as observed in other transposable element-derived genes like Rag1 and piggybac, which have similar terminal regulatory domains.

Circadian clocks enable mosquitoes to anticipate recurring environmental variations and coordinate behaviors critical for survival and disease transmission, such as locomotion, reproduction, host-seeking, and blood-feeding, with times of day when performance is maximal. In Aedes aegypti, locomotor activity follows a robust diurnal rhythm shaped by endogenous circadian clocks and environmental cues, among which light has been shown to be the primary source of temporal information. While early studies established the role of light in regulating locomotor activity, behavior, oviposition and pupation, it remains unclear which features of a light cycle drive changes in circadian rhythms. This question is increasingly relevant as Ae. aegypti is frequently exposed to artificial and dynamic lighting conditions in urban environments. Here, we investigated how transient changes in light schedules influence circadian rhythms in locomotor activity by systematically manipulating the timing, duration, and direction of light exposure. Using a high-throughput assay, we tested over 1900 individuals, including wild-type and timeless knockout mutants, and showed that a single day of al tered lighting is sufficient to induce robust phase shifts, with no evidence of masking effects. A 6-hour light pulse was sufficient to re-entrain mosquitoes regardless of the timing of the pulse, and phase shifts were primarily driven by the offset time of the light pulse, indicating that light-offset acts as a major zeitgeber. Together, these findings challenge conventional assumptions about the timescale of circadian synchronization and highlight the remarkable plasticity of mosquito behavior in response to anthropogenic light. Eventually, these effects could explain the rapid adaptation of the species to urban environments and have potential consequences for disease transmission dynamics.

Zinc is an essential micronutrient at low concentrations, yet it becomes toxic at slightly higher ones. This is exploited by plants as an effective defensive strategy. However, the molecular components that are involved zinc-mediated immunity remain poorly defined. Here, we show that mixed-linked {beta}-1,3/1,4-glucans naturally occurring in microbial and grass cell walls and used as an agrobiological solution, trigger zinc accumulation in the Arabidopsis apoplast and upregulate the expression of the zinc transporters HMA2 and HMA4. This response occurs independently of salicylic acid, jasmonic acid and ethylene-mediated signalling pathways, but it requires the LysM receptor kinases CERK1, LYK4 and LYK5, indicating a specific pattern triggered immunity-associated mechanism. We further demonstrate that hma2hma4 mutants display constitutive activation of a broad set of defence-related genes, yet this transcriptional reprogramming is insufficient to confer resistance against the necrotrophic fungus Plectosphaerella cucumerina BMM. Moreover, metabolomic profiling highlights the contribution of specialized metabolites to this defective defence output. Altogether, our findings reveal that zinc-mediated toxicity constitutes a defence mechanism integrated into the immune response triggered by specific microbial or damage associated molecular patterns.

Genes encoding novel protein sequences are a ubiquitous feature of genomes. They fuel molecular and cellular evolutionary innovations and frequently contribute to species-specific characteristics. We are now unravelling the processes by which they originate, including de novo from noncoding sequences and through extreme divergence, yet how much and what types of novel proteins evolve through each process is still unclear Does the mechanism of origination shape the structural and functional potential of the resulting proteins? Here, we conducted a broad computational investigation of genetic and protein novelty at the scale of the entire subphylum of Saccharomycotina yeasts. We detected more than 5,000 robust de novo genes across 332 species and compared them to more than 10,000 novel genes resulting from extreme sequence divergence, revealing two distinct modes of evolution of novelty. A remarkable 40% of de novo proteins are predicted to localize to mitochondria compared to only 15% of divergent, with the latter also being substantially longer and more disordered. A detailed analysis of conservatively predicted tertiary structures of novel proteins shows that "invention" of novel folds can happen through both processes but is more likely to occur de novo. We also illustrate cases of evolutionary "re-invention" of existing protein folds from non-coding sequences. Our work deepens our understanding of the origins and importance of novel proteins opening new directions for further structural and functional characterization.

Blumeria graminis f. sp. avenae (Bga), the causal agent of oat powdery mildew, is one of the most host-specialized members of the B. graminis species complex. Despite its agricultural importance, the lack of a high-quality reference genome has limited studies of host specialization, virulence evolution and comparative genomics in this pathogen. Here, we generated the first chromosome-scale genome assembly of Bga using an integrative approach combining long- and short-read sequencing, Hi-C scaffolding and transcriptome data. The Bga genome exhibits hallmark features of powdery mildew fungi, including extensive repeat content and low gene density. Comparative analyses revealed that genome expansion is primarily associated with historical transposable element proliferation rather than recent transpositional activity. Genome organization is consistent with a functionally stratified "one-speed" model, in which genes associated with pathogenicity, including predicted effectors and infection-responsive genes, are preferentially located in transposable element-rich regions characterized by reduced synteny conservation and extended intergenic spaces. In contrast, conserved genes are concentrated in compact genomic regions and maintain strong syntenic conservation across cereal-infecting formae speciales. Hi-C analyses demonstrated a highly structured chromatin architecture and revealed genome organization patterns associated with infection-related gene expression. Comparative genomic analyses indicated that host specialization in Bga is driven by localized diversification of a relatively small subset of genes rather than large-scale genome restructuring. These results provide the first high-quality genomic resource for Bga and offer new insights into the evolutionary mechanisms underlying host specialization in powdery mildew fungi.

The symbiosis with photosynthetic dinoflagellate algae enables corals to build and sustain reef ecosystems. Individual coral polyps hold algal symbionts in their epithelial endoderm cells and lose them under environmental stress, leading to coral bleaching. How the host integrates symbionts into its body plan is not well understood. Here, using a combination of high-resolution imaging, quantitative analysis, and environmental perturbations in the sea anemone Exaiptasia diaphana (Aiptasia) and reef-building coral Pocillopora damicornis, we uncover a spatial organisation of symbionts along the aboral-oral axis of cnidarian polyps that emerges under the long-range translocation of symbionts between host cells through a fluid-filled cavity. The symbiont distribution becomes specifically enriched in the tentacle bud endoderm during Aiptasia polyp morphogenesis. This pattern can form in darkness and with algae-sized inert spheres, suggesting an innate host-intrinsic mechanism. Symbiont-occupied host cells are mechanically constrained within the endoderm and thus unable to rearrange; instead, they go through cycles of symbiont expulsion and re-uptake via the host gastric cavity, with regionally biased rates of these behaviours providing a route to enrich symbionts in the tentacles. Symbiont organisation is remodelled under increased light in adult coral polyps, with a characteristic pattern of reduced tentacle enrichment, lateral clustering and retention in the body column emerging over a timescale of days. Together, our findings reveal that the spatial organisation of symbionts is dynamically regulated in cnidarian host tissues, a capacity that may shape both the establishment of symbiosis and its resilience under environmental change.

Nuclear pore complexes (NPCs) are nuclear envelope (NE)-embedded protein assemblies that mediate nucleocytoplasmic exchange and interact with the genome, including binding of an NPC component Nup93 to Polycomb chromatin domains. Here, we investigated the in vivo relevance of this relationship in Drosophila, which unusually contains two distinct paralogs of Nup93. Interestingly, we identified a Nup93-2-specific tumorigenic phenotype in larval wings, where depletion of Nup93-2, but not Nup93-1, led to tumor-like overgrowth, reminiscent of Polycomb mutations. Consistently, our transcriptomic analysis revealed a wide-spread loss of gene silencing in Nup93-2-depleted wings, particularly in a Nup93-bound Polycomb domain spanning genes for activators of JAK/STAT signaling. Nup93 paralogs were not found to differ in their effect on NPC biogenesis but strikingly, showed differences in subnuclear localization patterns. While Nup93-1 co-localized exclusively with fully assembled NPCs, Nup93-2 exhibited only partial co-localization and was found at additional NE locations in a tissue-specific manner. Together, our results identify an in vivo silencing role of a Nup93 paralog and suggest that Nup93-2 may form a unique NE-associated complex that targets a subset of Polycomb domains containing growth-promoting genes.

Large language models (LLMs) are increasingly used to draft medical manuscripts, yet their citations are unreliable and clinicians lack a validated way to verify them. We evaluated three frontier LLMs, Claude Opus 4.8, GPT-5.5, and Gemini 3.5 Flash, generating 270 cardiology narrative reviews with web search enabled, and verified all 8,050 references against PubMed. Problematic references accounted for 11.5% of GPT-5.5 output, 29.2% of Claude output, and 29.6% of Gemini output (P < 0.001), with no significant gradient across topics of differing publication volume (P = 0.052). Misattribution, a valid PubMed identifier that resolves to a different article, made up 77% of errors, whereas fabrication was rare (0.6%). Against an expert-adjudicated set of 270 references, an LLM-based Chain-of-Verification (CoVe) detected 60 of 62 problematic references (sensitivity 96.8%, specificity 98.6%), including every misattribution and fabrication. LLM-generated citations require identifier-level verification, and CoVe provides it at expert-level accuracy.

Investigating the neural mechanisms of social group interactions and other naturalistic behaviors in small animals remains limited by current technology. Tethered neural recording systems are incompatible with many of these behaviors, while existing wireless devices for small animals are constrained by weight, bandwidth, recording duration, and the lack of closed-loop modulation capabilities. To overcome these limitations, we developed a Wireless, Interactive, Lightweight Datalogger (WILD) with integrated flexible neural probes, optogenetics, an inertial measurement unit, an ultrasonic microphone, and a head-mounted camera. This platform enables simultaneous, long-term recording of neural activity, locomotor variables, vocalizations, and eye movements from groups of freely moving mice in both laboratory and outdoor settings. Model-based real-time signal processing detects specific neural events and behavioral motifs to trigger closed-loop neural interventions. By combining multimodal recordings with advanced onboard signal-processing capabilities in a compact device, WILD enables the investigation of neural mechanisms underlying a broad range of natural behaviors in small animals.

Sicyoidochytrium minutum DNA virus (SmDNAV) was isolated several years ago from a protist host of family Thraustochytriaceae of the class Labyrinthulomycetes. This virus shared little similarity to other viruses in gene content and protein sequences, albeit seemingly belonging to the phylum Nucleocytoviricota. By extensive searches in genomic and metagenomic sequence databases, we identified numerous long contigs related to the SmDNAV genome and analyzed proteins shared by these putative viruses. Phylogenetic analyses place these viruses within the class Megaviricetes, outside of all established orders, and as a sister group to the clade combining families Mamonoviridae and Manesviridae. Homologs of SmDNAV proteins were found in association (either integrated or co-sequenced) with other Labyrinthulomycetes and Rhodophyta protists from diverse marine and freshwater environments. Consequently, we propose SmDNAV as the prototype member of a new order, provisionally named Ariadnavirales, within class Megaviricetes, phylum Nucleocytoviricota. Members of Ariadnavirales have lost most of the genes encoding components of the replication and transcription systems that are otherwise conserved in nucleocytoviricots, suggestive of transition to genome replication and expression dependent on the host nucleus.

Animal mitochondrial rRNAs are commonly viewed as structurally reduced, yet sponge mt SSU rRNAs range from compact to highly expanded structures. Using nine conserved structural anchors, we compared 216 taxonomically resolved records from four classes and 22 orders, including 16 freshwater Spongillida and 200 marine sponges. Twelve homologous hypervariable substructures were coded as structural types, and their ordered combinations as composite types. We identified 38 structural types and 62 composite types across molecules ranging from 853 to 2,019 nt. Hexactinellida and freshwater Spongillida were each uniform for a distinct composite type but differed markedly in overall structure: hexactinellid mt SSU rRNAs were compact, whereas those of Spongillida were long and contained four to five candidate insertion regions. These results show that a conserved scaffold can accommodate extensive lineage-associated structural variation and provide a practical framework for comparing highly divergent mitochondrial rRNAs.

Ctenophores and placozoans arose early in metazoan evolution and are characterized by traits associated with key aspects of animal evolution. Despite the evolutionary significance of ctenophores and placozoans, their RNA viromes are poorly understood. To determine the diversity and evolution of RNA virome in these organisms, particularly whether the viruses present with these ancient host lineages similarly occupy basal phylogenetic positions, we analysed publicly available transcriptome data from the Sequence Read Archive (SRA). Accordingly, we identified 26 putative novel viruses classified into 11 virus groups, including members of the families Flaviviridae and Chuviridae. The novel viruses clustered with those previously identified in vertebrates, invertebrates, plants and fungi. Notably, some virus sequences within the Flaviviridae, Chuviridae, Lispiviridae and Marnaviridae were highly divergent, branching deeply relative to their closest known relatives or forming distinct lineages, in some cases suggesting a divergence early in metazoan evolution. In contrast, viruses within the Birnaviridae, Endornaviridae, Mymonaviridae, Narnaviridae, Phasmaviridae, Orthomyxoviridae, Orthototiviridae, and some viruses within the Picornavirales, exhibited patterns consistent with more recent diversification and host jumping. In addition, RNA viruses were detected across multiple species and tissues within the Ctenophora (including whole organisms and embryos) and Placozoa, expanding their host range and highlighting a largely uncharacterized diversity. Together, these findings expand the known diversity and host range of several virus groups, and shed light on virus evolution in early metazoans, demonstrating both host jumping within aquatic environments and virus host-associations that may span the entirety of animal evolution.