Journal of Experimental Zoology Part B: Molecular and Developmental Evolution

The influences of the gut microbiome on animal physiology are well-documented, yet the developmental timing of microbial colonization and its long-term consequences remain poorly understood. In this study, we investigated how the timing of bacterial colonization during development affects transcriptional programming and phenotypic outcomes in adult Drosophila melanogaster reared on a common, rich diet. Using RNA-seq analysis on whole flies colonized either as newly hatched larvae or as newly eclosed adults, we observed minor but distinct transcriptional responses dependent on when flies were colonized. Both embryonic and adult colonization were associated with ~ 25 to ~ 200 differentially expressed genes compared to axenic controls, with the majority upregulated and enriched for immune-response genes, suggesting that colonization establishes a broader immune competence. However, only 10 genes showed persistent differential expression that was not normalized by introducing bacteria to adult axenic flies, including mitochondrial genes, the adipokinetic hormone (Adh), and a putative secreted neuropeptide. Overall, these findings suggest that Drosophila development on a rich diet is largely robust to the timing of bacterial colonization but that certain metabolic effects may occur.

The physiology of ectotherms can change substantially during acclimation to changing environmental temperature. The role of transcription in acclimation responses has been well-established, but it remains unclear whether transcriptional regulation generally reflects abrupt changes after surpassing temperature thresholds, or whether transcript abundance is a relatively monotonic, continuous function of acclimation temperature. In this study we exposed adult male Drosophila subobscura flies to four different 96-hour acclimation treatments at temperatures that were not acutely stressful but ranged from relatively cold (10{degrees}C) to relatively warm (27{degrees}C) with respect to standard rearing conditions. Transcriptome sequencing of whole-body homogenates (mRNAseq) revealed a massive, transcriptome-wide response across acclimation temperatures, with a marked overrepresentation of genes that were continuously and monotonically up- and down-regulated in response to increasing acclimation temperature. Though some genes showed more complex relationships consistent with putative threshold responses, a high percentage of the differentially expressed transcriptome (42%) showed continuous and strictly monotonic relationships. Functional enrichment suggested continuous up-regulation of spermatogenesis-related transcripts with increasing temperature and continuous up-regulation of oxidative phosphorylation-related transcripts with decreasing temperature, illustrating contrasting patterns consistent with previous studies of thermal sensitivity of male reproduction and metabolic compensation in the cold. Thus, continuous thermal sensitivity of transcription is a hallmark of acclimation in D. subobscura that likely underlies the continuous thermal sensitivity of downstream physiological processes. We also provide evidence for shared transcriptomic responses across short-term acclimation (this study) vs. published results for long-term, developmental acclimation.

Parental qualities can influence the development and fitness of their offspring via genetic and non-genetic effects. Although these effects are often linked to parental phenotypes, the effect of parental genetic variation linked with relevant phenotypes is less well understood. We performed full factorial crosses based on parental genotypes for an age-at-maturity-related gene, vgll3, to investigate how the parental genotypes influence Atlantic salmon (Salmo salar) offspring survival, growth, and development in their early life. Beyond the connection with age at maturity, the additional association between vgll3 and body condition in Atlantic salmon offers a potential pathway by which the maternal vgll3 genotype could influence offspring early life fitness. Combined with measurements of maternal phenotype and egg characteristics, the crossing design therefore allowed us to disentangle the maternal and paternal genetic and non-genetic contributions to variation in offspring survival and phenotypic traits. The phenotypic traits measured were hatching length and yolk sac area, growth, and yolk sac consumption and conversion efficiency. Parental vgll3 genotype did not influence the majority of our measured egg traits or alevin traits except for a genetic effect of paternal vgll3 genotype on offspring survival, whereby the paternal late maturation allele was associated with higher survival. Maternal effects were strongest for survival and for traits associated with hatching and weaker for alevin growth and yolk sac usage. Paternal effects on the measured alevin traits were negligible. The results from our study demonstrate that both maternal and paternal effects have the potential to influence offspring early life fitness traits.

This study investigates the impact temperature-induced vertebral anomalies have on the C-start escape response of Astyanax mexicanus, a model species in evolutionary developmental biology. Employing three temperature treatments to induce varying degrees of skeletal anomalies, we assessed their effects on key swimming performance metrics including, C-start time, curvature coefficient, head displacement distance, and displacement velocity. Through the use of linear mixed models and generalized linear mixed models, our results reveal that specific anomalies such as vertebral fusions and anomalous haemal and neural spines affected the curving ability of C-start escape responses. However, these did not negatively impact other performance parameters, with velocity, distance, and response time showing no significant impacts from any anomaly types, when assessed individually. This suggests a complex interplay between structural deformities and compensatory physiological mechanisms that maintain functional performance. Other variables measured had a stronger and significant impact on swimming performance, including standard length, vertebral number, and temperature treatment, which influenced escape speed, curving ability, and overall locomotor performance. Our findings challenge conventional perceptions about the debilitating impact of vertebral anomalies, indicating that many affected fish can still effectively perform escape maneuvers critical for survival.

Tessellated calcified cartilage (TCC) is a hallmark of the chondrichthyan skeleton, yet its development early in ontogeny across the four major groups (batoids, galeomorphs, squalomorphs, and holocephalans) remains poorly understood. Specialised traits of TCC, such as multi-layered TCC and internal mineralised trabeculae, typically develop in response to feeding mechanics. In this study, we evaluated TCC morphology in the jaws of 12 representative taxa to observe its structure at an early ontogenetic stage to determine whether these specialised features had yet developed. Batoids consistently exhibited well-developed, homogeneous, polygonal tesserae early in ontogeny regardless of jaw morphology or feeding habit. In contrast, galeomorphs displayed high morphological heterogeneity. Notably, we document the first report of an extensive internal trabecular network in a non-batoid elasmobranch, observed in Ginglymostoma cirratum, which may serve to resist the mechanical pressures of specialised suction feeding. Furthermore, we identified voussoir tesserae in galeomorphs for the first time, extending their documented presence across all elasmobranch groups, where they display an inverted aspect ratio (wider than tall) compared to mature forms. The durophagous Mustelus mustelus exhibited surprisingly poor TCC development despite being a durophagous feeder, pointing to a pronounced ontogenetic lag. In Squatina oculata, TCC was characterised by large and thick tesserae and extensive fused tesseral regions which may relate to its explosive ambush predation mode, whereas the holocephalan Chimaera exhibited a poorly mineralized, mesh-like structure without resolvable discrete tesserae or trabeculae-matching findings from previous studies. Across all specimens, multi-layered TCC was absent, confirming that multi-layering develops later in ontogeny. These results demonstrate that generalised models of TCC development based on one group or a few taxa fail to capture the broader diversity of TCC morphology. It also opens up many exciting avenues for further study, and forms the basis for comparisons with fossil chondrichthyans, to investigate the evolution of TCC.

Phenotypic differences among populations can arise through heritable genetic divergence, phenotypic plasticity, or both, making it difficult to determine whether trait-environment correlations observed in nature reflect adaptive evolution. Within threespine stickleback (Gasterosteus aculeatus) studies, numerous document morphological differences among allopatric-, parapatric-, and even sympatric populations. These phenotypic differences among populations are often correlated with diet and lake habitat (e.g., lake size), suggesting an adaptive value to the population differences. However, many studies of ecomorphological divergence in stickleback use wild-caught stickleback, which may differ due to evolution or plasticity. Although common garden experiments have confirmed that population differences can be heritable, such experiments typically entail small numbers of populations. Consequently, we still do not know to what extent well-known trait-environment correlations in stickleback are a result of evolution. To address this gap, we reared stickleback embryos from 27 lake populations on Vancouver Island, in a laboratory environment. Morphological differences among populations persist in common-garden fish, confirming a large role for divergent evolution. These heritable differences were associated with environmental variation among lakes, implying an adaptive value. However, some well-known trait-environment relationships in stickleback did not persist in common-garden fish and may be primarily plastic.

The global expansion of Black Soldier Fly (BSF), Hermetia illucens (L.), production systems for organic waste management has increased the need to better understand its reproductive biology in order to optimize mass-rearing programs. In this study, we macroscopically characterized chronological morphological changes in the internal genitalia of adult H. illucens reared on a sustainable alternative larval diet based on coffee pulp and corn bran. Morphological assessments and dissections were conducted on female and male reproductive tracts at 3, 6, and 9 days after adult emergence. Overall, the general organization of both reproductive systems was consistent with previous descriptions. A notable observation was the presence of a tripartite fertilization chamber in females, composed of three distinct compartments apparently associated with the three spermathecae. The functional significance of this anatomical organization remains to be determined. Females showed progressively advanced ovarian development and reached the clearest morphological indicators of reproductive maturity at 9 days, while males showed the greatest testicular distention and opacity at the same age. Compared with maturation times reported in previous studies using conventional larval diets, these observations suggest a later pattern of reproductive maturation under the coffee pulp-based diet. The observed differences may be associated with the nutritional composition and carbohydrate-to-protein balance of the larval diet. These results provide chronological and iconographic information that may contribute to the optimization of laboratory rearing protocols and the use of coffee by-products in H. illucens bioconversion systems.

The maned wolf (Chrysocyon brachyurus) is a near-threatened canid species that suffers from gastrointestinal (GI) disease under human care. While the cause remains poorly understood, recent studies report that altered gut microbiota is linked to GI disease in the domestic dog. The goal of this study was to describe the relationship between gut bacteria and environmental factors, GI health, short chain fatty acid (SCFA) peaks, and genetic relatedness in maned wolves. Fresh fecal samples were collected twice from wolves (first collection n = 29; second collection n = 25) housed in six facilities in the United States. Fecal alpha-1 proteinase inhibitor (FA1PI), a biomarker for GI health in canids, and SCFA peaks were quantified. Information on diet, housing group and history of GI disease or inflammation was provided by the zoological facility for each wolf. We characterized gut microbiota using 16S rRNA gene amplicon sequencing with qPCR abundance corrections. We found that dietary fiber gross energy (GE), protein GE, and number of daily produce items influenced gut microbiota. Additionally, there was a negative relationship between dietary fiber GE and Fusobacterium sp. abundance, corroborating previous findings linking fiber to altered gut microbiome composition in canids. Lastly, fiber GE was negatively correlated with FA1PI, connecting fiber to GI health in the maned wolf. Findings from this study suggest that increasing dietary fiber GE changes the gut microbiome and may improve GI health in the maned wolf, highlighting important management decisions that can be considered to maintain a healthy zoo-managed maned wolf population. IMPORTANCEFindings from this study are important because gastrointestinal disease is a common health concern for maned wolves under human care, and the causes are not well understood. The current study found that diet, especially the amount of fiber gross energy, can affect gut bacteria and may support better gastrointestinal health. Diet alterations could be a practical tool for zoos to support management of gastrointestinal health issues in maned wolves. These findings also show the importance of carefully managing diets for a near-threatened species, since better gastrointestinal health may improve overall health and well-being and support reproduction. More research is needed to determine the best amount and type of fiber, but our results provide foundational information for improving care and supporting healthy zoo-managed maned wolf populations.

Zebrafish bone regeneration is a highly efficient process, enabling the complete restoration of an amputated fin within few weeks. The hallmark of this epimorphic regeneration is the formation of a blastema atop of a bony fin ray. Osteoblasts near the injury site dedifferentiate and migrate off the bone to contribute to the developing blastema. We show that an injury or a blastema alone is not sufficient to trigger off-bone migration of osteoblasts. Surprisingly, we found that blastema cells themselves possess intrinsic migratory properties. Moreover, when multiple injury sites are present, a preferential distal migration could be observed. We conclude that multiple injuries are hierarchical organized, and that injuries with the highest regenerative potential take priority.

The highly conserved body plan of nematodes makes members of this phylum excellent models to study cell type evolution. Early branching nematode lineages, mostly occupying aquatic habitats, usually contain caudal glands deployed for underwater attachment to a substrate, but have been thought to lack phasmid sensory organs, resulting in their historical classification as "Aphasmidia". With the transition to a terrestrial environment, nematodes lost caudal glands and gained phasmid sensory neurons. The supposed mutually exclusive existence of caudal glands and phasmids has led to the suggestion that phasmid neurons may have evolved from caudal glands. Here, we rule out this possibility through light and electron microscopical analysis of Mononchus aquaticus, a member of the early branching Dorylaimia lineage, showing that phasmid sensory neurons and caudal glands do coexist. This observation not only argues against a proposed cell type evolution scenario accompanying aquatic-to-terrestrial transitions but also indicates that the presence of phasmid sensory organs may have been an ancestral trait of the nematode phylum.

Planning husbandry tasks and experiments with Drosophila melanogaster requires converting a target date into development times that depend on the rearing temperature. This calculation needs to be done for each cross, genotype, and temperature, and the risk of error grows quickly. Available laboratory management tools let users register stocks, crosses, and track them, but they do not create schedules based on a clear, adjustable thermal model. To fill that gap, we developed DrosoTracker, a self-contained web application that works offline and predicts Drosophila development with a thermal summation model recalibrated through regression on data from Powsner (1935) (T0 = 11.78 {degrees}C, DD = 116.38 {degrees}C{middle dot}days, R{superscript 2} = 0.997). The model offers an optional two-level calibration driven by user observations. A wild-type strain first adjusts the model to the laboratorys own conditions. Then each genotype is calibrated against that reference using a random-effects shrinkage estimator that accounts for measurement error and between-batch variability. The model creates schedules for husbandry tasks, evaluates adult cohort survival with the Kaplan-Meier estimator and the log-rank test, and calculates sample size for lifespan studies using Schoenfelds formula. The quantitative components were checked against independent references, including Rs survival package and manual calculations. Ongoing work is focused on validating the calibrated model using cohorts specifically bred for this purpose. DrosoTracker runs entirely in the browser, stores data locally, and is available in English and Spanish.

Hydrozoa is a group of relatively simple animals with a well-developed nervous system. The nervous system in all hydrozoan medusae is highly conserved and includes outer and inner nerve rings at the bell margin, a neural network in the manubrium, and radial neural pathways that connect them. However, one element of the nervous system shows substantial variability among species: the subumbrella neural network. We examined the structure of the nervous and muscular systems in the subumbrella of 14 species of hydrozoan medusae. The main conclusion of this study is that the distribution of neural networks in the subumbrella strongly correlates with the distribution of smooth radial muscles. This correlation suggests that smooth radial muscles are the primary target of the subumbrella nervous system. Most species in the order Anthoathecata show a trend toward secondary loss of the neural networks and radial smooth muscle fibers in the subumbrella region, concentrating neural elements and smooth muscles only in the radial pathways along the radial canals. By contrast, all studied species in the order Leptothecata have neural networks in the subumbrella area, as well as radial smooth muscle fibers spread throughout the entire subumbrella region. The correlation between radial smooth muscles and the nervous system is also observed in the radial pathways along the radial canals. All species with thick bundles of smooth radial muscles along the radial canals have clearly defined, dense neural pathways running along or even embedded within the smooth muscle bundles.

Phenotypic plasticity, the ability of a single genotype to produce alternative phenotypes in response to environmental cues, is a key driver of evolutionary change. In the water strider Microvelia longipes, males display remarkable continuous variation in hindleg length, a sexually selected trait used as a weapon in male/male contests for access to females. To determine whether DNA methylation mediates this environmentally induced phenotypic variation, we used three inbred lines of M. longipes that differ in mean hindleg length, body size, and allometric coefficients. We performed whole-genome bisulfite sequencing on adult males and females from all lines, and tested the effect of nutritional treatment on DNA methylation patterns. Our analysis identified 12,684,876 CpG 12% of which were methylated. This global level of DNA methylation is among the highest reported in insects. DNA methylation was predominantly concentrated within or near gene bodies (77% of methylated CpGs), consistent with patterns observed in other insects. Unsupervised clustering and principal component analyses revealed that methylation patterns differed significantly between genetic lines but showed minimal differences between sexes, indicating a strong genetic influence. Most surprisingly, despite nutrition having a pronounced effect on leg length, we observed no significant changes in DNA methylation in response to dietary treatment. These results show that in M. longipes, DNA methylation patterns are largely stable across environmental conditions and primarily determined by genetic background. This challenges the common assumption that DNA methylation universally mediates environmentally induced phenotypic plasticity and suggests that other epigenetic mechanisms, such as histone modifications or non-coding RNAs, may play a more direct role in regulating continuous plastic traits. Our study underscores the complexity of epigenetic regulation and highlights the need for broader investigation of molecular pathways to fully understand the molecular basis of phenotypic variation in natural populations.

Copper is an essential micronutrient in most organisms that becomes toxic in large quantities. Repeated or prolonged sub-lethal exposure can lead to evolved resistance to copper toxicity over many generations, which may result in trade-offs between energetically expensive detoxification mechanisms and fitness. Alternatively, evolved resistance to chemical stressors may lead to correlated changes in other traits. This study focuses on a population of flies for which artificial selection for copper resistance led to an increase in both copper resistance and longevity. The apparent off-target benefit of copper selection on one component of fitness led us to investigate differences in fecundity and developmental viability in copper resistant and copper sensitive, non-selected populations. We assessed the effect of copper selection and copper exposure on multiple aspects of fecundity over the lifespans of females from the non-selected and copper-selected populations. Our study corroborated previously observed increased longevity in copper-selected flies. Controlling for variation in lifespan, copper-resistant females had comparable age-matched fecundity to copper-sensitive females and benefitted from increased longevity with higher lifetime fecundity. Overall, copper exposure negatively affected egg quality, but we found no difference in this trait between the copper-resistant and sensitive populations. Further, we found developmental viability under copper stress was significantly higher for eggs laid by copper-resistant females. Overall, we determined that copper resistant flies experienced a fitness benefit through both lifespan and fecundity. Costs of maintaining copper resistance may be associated with energetic costs, but these trade-offs may not always manifest in reproductive or lifespan fitness costs.

The human bony labyrinth has attracted increasing interest because of its taxonomic, evolutionary, and functional significance. Although sexual dimorphism has been reported in several aspects of the temporal bone, the extent to which sex, age, size, and allometry contribute to labyrinth shape variation remains poorly understood. Here, we investigated patterns of sexual shape variation in the human bony labyrinth using three-dimensional geometric morphometrics in a sample of 98 archaeological individuals from South America with known genomic sex. Centroid size and allometric effects were assessed in a subset of 90 individuals with comparable metric scaling. In addition to analysing the complete labyrinth, the cochlea and semicircular canals were examined separately to evaluate region-specific patterns of sexual shape variation. Principal Component Analysis showed extensive overlap between females and males, and overall labyrinth shape did not differ significantly between sexes. Males exhibited significantly larger labyrinths than females, and centroid size explained a small but significant proportion of overall shape variation. Regional analyses showed no evidence of significant sexual shape differences in the cochlea or in any individual semicircular canal when analysed separately. In contrast, the combined semicircular canal system exhibited subtle but significant sexual shape variation independent of centroid size, whereas morphological disparity did not differ between sexes. The geometric comparison of the female and male consensus configurations further showed that sexual shape variation was regionally heterogeneous. Whereas the cochlea exhibited a pattern of localized changes with low directional coherence, the semicircular canals displayed more coordinated regional shape changes. The male consensus also exhibited slightly higher canal circularity across all three semicircular canals, particularly the posterior canal, while differences in canal-plane orientation remained minimal. These findings demonstrate that sexual shape variation in the human bony labyrinth is subtle and anatomically partitioned among its components. Although significant sex differences in centroid size were detected across most anatomical regions, overall labyrinth shape and cochlear morphology were primarily influenced by allometry, whereas significant sex-related shape differences were detected only when the semicircular canals were considered as an integrated anatomical system. These findings demonstrate that sexual dimorphism in the human bony labyrinth is subtle but regionally heterogeneous, with the cochlea and semicircular canals exhibiting distinct patterns of shape variation, suggesting that these structures are influenced by different developmental, functional, and evolutionary processes.

Global change is driving rapid ocean warming, exposing organisms to both chronic temperature increases and acute marine heatwaves. Understanding how species cope with thermal stress is critical for predicting ecosystem resilience. Echinoderms are globally distributed and often function as foundational species, yet comparative assessments of upper thermal tolerance among species occupying contrasting thermal environments remain limited. Here, we address this gap by comparing upper thermal tolerance across three sea urchins with distinct biogeographic distributions: the latitudinally broad purple sea urchin (Strongylocentrotus purpuratus), the circumpolar green sea urchin (S. droebachiensis), and the tropical variegated sea urchin (Lytechinus variegatus). We quantified thermal limits after two acclimation treatments: ambient temperatures approximating native habitat conditions for each species and an elevated temperature (+6 C). We developed a novel assay to measure critical thermal maximum (CTmax), comparing variability and inconsistencies associated among multiple assays. Upper thermal tolerance increased with acclimation to elevated temperatures in all three species, but acclimatory capacity differed markedly, with S. droebachiensis showing the strongest response and S. purpuratus the weakest. Conversely, S. purpuratus had the highest thermal safety margin and thus the lowest proximity to its thermal ceiling. Our adhesion based CTmax method was more reproducible and the most precise compared to other metrics tested, providing an improved framework for quantifying physiological thermal limits of sea urchins. Together, these findings reveal substantial but unevenly distributed thermal resilience in ecologically diverse sea urchins, advancing our understanding of how foundational marine species may respond to future global change.

Animals reproduce across a spectrum from oviparity to viviparity. Internal gestation and live birth have inherent advantages despite their costs. However, comparative analyses of key drivers, such as resilience to dehydration, lack taxonomic breadth. In this study, we assessed whether live birth improves the ability to proliferate in environments with limited access to water. To do so, we used the viviparous cockroach, Diploptera punctata, as a model of viviparity to assess dehydration-induced damage during extended periods of water deprivation. During pregnancy, maternal survival did not decline during dry periods compared with non-pregnant individuals, suggesting that pregnancy has minimal impact on resistance to dehydration stress. When mothers are deprived of water for 2 weeks, they show an increase in osmolality after one week, while their embryos show no change in osmolality until after two weeks, at which point abortions occur. Periods of dehydration increased the duration of pregnancy, likely due to a slower production of in utero milk, but there was no change in the size of progeny. After birth, viviparous D. punctata newborns showed increased survival under dry conditions compared to two other ovoviviparous species, which are much smaller and dehydrate more quickly. The combined impact of increased dehydration resistance during pregnancy and during the first independent phase indicates a benefit of prolonged viviparity in Diploptera punctata. This study provides evidence that viviparity in animal systems could enable progeny survival during drought.

Allee effects are positive relationships between components of individual fitness and the number or density of individuals in a population. Negative density effects are well documented in Drosophila melanogaster across life stages, while Allee effects are rare and largely confined to the larval stages. However, despite the costs of high density, adult flies are found to exhibit attraction to same-sex conspecifics, suggesting some fitness value to the presence of conspecifics. We measured fitness related traits of singly mated-females housed at same-sex densities of 1, 2, or 10 and found clear reductions in lifetime reproductive output at low densities. Additionally, these females concentrated reproductive effort within early adulthood, albeit without improving estimates of fitness. When housed at variable densities, females altered their reproductive output in response to immediate densities, but were unable to improve it unless remating was possible, indicating an interaction between mating and density. Overall, our findings suggest that reproductive plasticity in response to the presence of conspecifics mediates positive effects of density on fitness in female Drosophila melanogaster. Understanding the physiological and ecological bases of such plasticity may help explain the evolution of social tendency in the fly.

Webspinners (Insecta: Embioptera) are an unusual insect order that are known for their subsocial behavior and prolific silk-production. Due to their unique foreleg silk glands, and spider-like ability to produce silk throughout their entire life cycle, webspinners are hypothesized to have evolved silk independently from other arthropod lineages. To date, there are no reference-quality genomes available for the order, preventing the study of their silk gene origination and diversification. Here, we assembled PacBio HiFi reference genomes and characterized the silk genes present in two webspinner species, Aposthonia ceylonica and Oligotoma nigra. The genomes reveal multiple full-length copies of the primary Embioptera silk gene, e-fibroin, that have undergone both ancestral and recent gene duplications within the group. For both species, all e-fibroin paralogs show the presence of complex repeat units consisting of multiple exons and introns that are remarkably homogenized across each gene. We also used CT-scanning of the internal silk glands to provide details concerning the localization of silk production in foreleg tarsi, and interspecific morphology. Article summaryThis study introduces the first high-quality genomes for webspinners, enabling new research on silk for evolutionary biologists and materials scientists alike. The authors sequenced two embiopteran species, Aposthonia ceylonica and Oligotoma nigra, to compare silk genes and gland structure using micro-computed tomography, an imaging method that shows internal anatomy in detail. They found multiple copies of the primary silk gene in both species that likely arose from multiple duplication events at different evolutionary times. These silk genes exhibit unusual gene structure with hierarchically organized repeat units that are highly homogenized within a gene. The findings show that silk genes have a complex evolutionary history in webspinners and provide a foundation for studying silk diversity within the order, and in the broader context of insect silk.

Previously, we have demonstrated that certain ferric salts common in Archean waters, such as iron trichloride and ferric ammonium citrate, can protect liposomes from destruction by short-wavelength UVC light. In this study, we investigate the propagation of 254 nm UV radiation through aqueous FeCl3 solutions and its interactions with liposomes. We then consider these findings in the context of early Earth UV environment, discuss their implications for our hypothesis of the Darwinian evolution of liposomes, and integrate them with our previous experimental results.