Publications

Pigments not only contribute to the extraordinary diversity of animal coloration but also play vital physiological roles. Riboflavin, or vitamin B2, is a macronutrient essential for cellular metabolism and growth, and is a well-known yellow pigment produced industrially for a wide range of applications, both as a colourant and dietary supplement. Remarkably, however, its role in animal skin coloration has been largely overlooked. Using quantitative mass spectrometry, we show that high riboflavin concentrations correspond to yellow hues in the skin of two species of lizard and one snake species. The comparison of riboflavin concentrations in different skin colours within individuals provides compelling evidence that riboflavin can contribute to skin pigmentation in reptiles beyond its general role in cellular metabolism. The role of riboflavin was further corroborated by high concentrations of riboflavin in yellow blotches of the Snow morph of the corn snake. In this mutant, xanthophore pigment cells, which in wild-type corn snakes contain pteridine pigments, are heavily impacted, and the overall amount of yellow pteridines is low. Like carotenoids, riboflavin must be acquired through diet and has powerful antioxidant properties. Thus, its use in coloration may have unrecognized ecological and evolutionary implications.

The macroanatomy of the digestive tract is typically interpreted in relation to trophic biology, potentially overlooking other determinants of digestive system design. Here, we investigate how digestive tract morphology reflects the interaction between anatomy, molecular makeup, taxon-specific physiology, and ecological context. We show that several taxa occupying similar trophic niches, tenrecs (Setifer setosus and Echinops telfairi), African hedgehogs (Atelerix and Paraechinus spp.), and the European hedgehog (Erinaceus europaeus), have similar gastrointestinal morphology (a simple stomach and an intestinal tube of largely homogeneous diameter without a cecum) yet differ markedly in total intestinal length, mainly due to differences in small intestine length. S. setosus has a comparable relative length of the intestinal regions to E. europaeus, while Atelerix albiventris has a slightly elongated large intestine. Although S. setosus exhibits enhanced absorptive capacity at the microanatomical level, reflected in higher serosal surface area enlargement factors, its shorter absolute intestinal length constrains total absorptive surface. Thus, E. europaeus possesses approximately 2.5 times the absorptive surface of A. albiventris and five times that of S. setosus. We suggest that these differences are related to differences in metabolic intensity, namely, energetic turnover and food-processing rates. This is determined by both the taxon-specific (Afrotheria vs. Laurasiatheria) pace of life and the extrinsic challenges of seasonal habitats with periods of resource scarcity and abundance, during which reproduction and adipose reserve accretion for the next winter occur. This supports the view that digestive tract morphology is shaped by the interaction of dietary, ecological, and phylogeny-related physiological constraints.

Monothalamous foraminifera are a highly diverse, paraphyletic assemblage of single-chambered lineages characterized by an organic or agglutinated test or lacking any external covering. Traditional morphology-based taxonomy divides them into the organic-walled Allogromiida and agglutinated Astrorhizida. Molecular systematics showed that this division is not justified as different wall types occur within the same lineages. Twenty years ago, based on molecular phylogenetic data, the monothalamids were classified into 13 lineages, called clades. Since then, the diversity of monothalamids from different habitats and regions has been extensively studied both genetically and morphologically, and many new species and genera have been described. Here, we analyzed 70 sequences of the 18S rRNA gene, representing 66 described species. We also analyzed 23 sequences of the COI gene for selected taxa. Based on molecular phylogenetic analyses and available morphological data, we establish a new formal higher-level taxonomy of monothalamous foraminifera. We introduce 5 new orders and distinguish 1 suborder and 34 families, of which 20 families are new. Our classification establishes a new taxonomic system that we hope will provide the foundation for organizing the vast diversity of monothalamous foraminifera revealed by recent studies.

The self-organised morphogenesis of multicellular organisms emerges not only from biochemical but also from mechanical processes operating across spatial scales. Yet, computational tools for simulating tissue-scale mechanics have largely been released as restricted, study-specific codes. Here, we present NewtonBioMorphX, a GPU-accelerated, open-access comprehensive framework for simulating tissue-scale mechanical morphogenesis. Built on a finite-strain finite-element formulation on tetrahedral meshes, the software implements an unusually broad set of mechanical ingredients: isotropic and anisotropic (direction-specific) growth; multi-layer tissue mechanics; neo-Hookean hyperelasticity combined with stretch-based plasticity; Kelvin–Voigt viscoelasticity; passive anisotropic fibres emulating 3D collagen networks; anisotropic active contractile filaments emulating actin; Hertzian contact forces; and multiple orthonormal coordinate bases (Cartesian, normal–tangent, cylindrical, spherical, cone-adapted, and toroidal). Equally central is an extensive, user-friendly graphical interface spanning the entire workflow — mesh generation from geometric primitives or arbitrary mesh input, per-layer material and growth specification (including analytical functions of space and time compiled at runtime), boundary-condition assignment, real-time colour-mapped and glyph-based visualisation of scalar and tensor fields, and structured data export — allowing intricate mechanical modelling of morphogenetic processes without editing or recompiling source code. The NewtonBioMorphX framework is validated using a benchmark implementing the well-known Cook’s membrane problem, and its versatility is illustrated through parameter gradient plots, as well as twelve ready-to-run preset examples spanning diverse morphologies.

Working memory (WM) enables the temporary maintenance and manipulation of sensory information to guide behavior, yet the neural circuits supporting this process remain incompletely defined. The claustrum is a highly interconnected brain structure positioned to integrate distributed cortical activity, but its contribution to WM has remained unclear. Here, we combined microendoscopic calcium imaging, chemogenetic and optogenetic manipulations in mice performing sensory-guided WM tasks to examine the role of the claustrum in WM. Claustrum neurons exhibited cue-evoked activity that persisted across delay periods and evolved dynamically over time, with population states retaining information about cue identity on single trials. Reducing claustrum excitability during encoding, delay maintenance, or target comparison similarly impaired WM performance across sensory modalities, without affecting sensory processing, motor output, arousal or inhibitory control. Together, these findings reveal an important causal contribution of the claustrum to WM maintenance.

In this study, we investigated the feeding behavior of deformed and normal benthic foraminifera (Protista, Rhizaria) of the species Ammonia veneta. The degree of deformation was visualized by scanning electron and light microscopy. Food uptake and assimilation were quantified in undeformed, slight deformed (1–3 abnormal chambers), and heavy deformed (irregular coiling) individuals using isotopic labeling and confocal microscopy. Specimens were collected from the Belle Isle Marsh (Boston, USA) and maintained under controlled laboratory conditions. After a three-day incubation, slight deformed individuals showed food uptake and isotopic enrichment comparable to undeformed specimens. In contrast, heavy deformed foraminifera exhibited significantly reduced carbon and nitrogen assimilation, as well as a lower number of ingested food particles. Confocal observations further indicated reduced food processing in heavy deformed individuals. These results demonstrate that pronounced morphological deformities are associated with impaired feeding and assimilation performance. Our findings highlight that severe test deformation can substantially affect physiological functioning and should be carefully considered when selecting specimens for laboratory experiments or observing them in polluted areas.

Despite the progress in understanding the circadian pacemaker, the specific mechanism by which it regulates sleep remains incompletely understood. We have previously demonstrated that a substantial number of genes are rhythmically expressed in the mushroom body (MB) Kenyon cells (KCs), including Pka-C1, which encodes the catalytic subunit of protein kinase A (PKA). PKA-C1 plays a crucial role in promoting daytime wakefulness; however, the underlying mechanism remains elusive. Here, using a newly developed in vivo luciferase reporter, we show that the γ lobe is the primary site of rhythmic Pka-C1 expression. Through a combination of in silico analysis, CRISPR mutagenesis, and chromatin immunoprecipitation, we identify the transcription factor Onecut as a regulator of Pka-C1 transcriptional rhythms in γ-KCs. Furthermore, genetic trans-synaptic connectivity mapping and neuronal activity imaging reveal that the dorsal lateral clock neurons (LNds) provide inhibitory input to a subset of dopaminergic (DA) neurons in the protocerebral anterior medial (PAM) cluster, PAM-γ5, rhythmically modulating their activity. This, in turn, rhythmically activates MB γ-KCs via excitatory Dop1R signaling. Resulting γ-neuron activity rhythms drive Pka-C1 transcriptional rhythms through Onecut. Furthermore, these PKA-C1 rhythms reinforce neuronal activity rhythms, creating a feedback cycle between transcriptional and neural activity rhythms that promotes daytime wakefulness. Our findings highlight the conserved role of DA in promoting wakefulness and offer mechanistic insights into its complex regulation. More generally, this work provides a mechanistic framework for how circadian rhythms are translated into neural activity to orchestrate complex behaviors such as sleep.

Symbiont-bearing benthic foraminifera, like corals, rely on endosymbionts for growth and nutrition and experience bleaching under heat stress. , found in tropical and subtropical waters, hosts a diverse range of endosymbionts belonging to Symbiodiniaceae. We examined the thermal tolerance of the Red Sea population, which is the source of an established, invasive population of in the Eastern Mediterranean. The Red Sea population is expected to exhibit enhanced thermotolerance, potentially due to its greater variety of endosymbionts. We conducted temperature-manipulation experiments, measuring calcification rates and net photosynthesis, evaluating the thermotolerance of and its endosymbionts. We also analyzed the diversity of Symbiodiniaceae by sequencing the internal transcribed spacer 2 (ITS2). Our results show that exposure to 35°C initially induced stress in the endosymbionts during the first week; however, net photosynthesis gradually recovered in subsequent weeks. In contrast, host calcification rates remained low at 35°C, though not completely inhibited. Amplicon sequencing revealed that by the end of the experiment, a single ITS2 type, belonging to Symbiodiniaceae and initially present in field-collected specimens, became dominant in cultured individuals. Because this type became dominant across all temperature treatments, the observed shift likely reflects a response to laboratory conditions rather than direct thermal selection. Consequently, although the recovery at 35°C is consistent with acclimatory physiological responses, it does not provide direct evidence for symbiont-specific acclimation. Our findings suggest that holobiont physiological recovery and symbiont shuffling under laboratory conditions may contribute to the resilience of in warming oceans.

The mechanisms by which novel differentiation pathways evolve to produce new cell types are still not fully understood. Chromatophores, the pigmented cells in the skin, offer an ideal paradigm because each type independently develops from neural crest cells to produce a distinct colour using well-characterised biosynthetic pathways. Here we show, using single-cell gene expression analyses, that canonical chromatophores develop in the embryonic skin of corn snakes and bearded dragon lizards. Yet, we identify previously undescribed chromatophore subtypes in the bearded dragon. These populations co-express progenitor and mature markers and possibly contribute to embryonic skin patterning, as revealed by whole-mount in situ hybridisation. Comparative analyses uncover that while mature chromatophores show cross-species similarity reflecting shared pigmentary function, progenitor states differ in transcription factor usage, including species-specific deployment of MITF, PAX7, and TFEC. Integration with teleost and amphibian datasets confirms that diversification of pigmentation arises through distinct progenitor trajectories converging on similar mature states.

The spatial patterning of mammalian hair follicle precursors in embryonic skin is most commonly studied in the laboratory mouse (), where new follicles form equidistantly from preexisting ones in successive waves. This simple geometric rule has been effectively described as emerging from an expansion-induction process. However, such a description is incompatible with more recent developmental data indicating instead that scale, feather, and hair placodes self-organize through reaction-diffusion-chemotaxis cell interactions involving epidermal and dermal signaling. Here, we suggest that the chemotactic component of this framework suffices to describe the dynamics of placode insertion in two mammalian species that exhibit drastically different patterns. More specifically, we investigate a continuum dynamical model capturing interactions between motile dermal mesenchymal cells and an epidermal chemoattractant, embedded in a two-dimensional, isotropically expanding domain representing the growing embryonic skin. Through numerical simulations, mathematical analysis, and comparison to experimental developmental data, we first show that the chemotaxis model gives rise to the effective geometric rule that initially justified the development of the expansion-induction model in the laboratory mouse. Second, we show that the strikingly regular hair placode pattern in the spiny mouse ()-with long-range order, specific orientation and anisotropies-is not generated by an expansion-induction mechanism, but is recapitulated by an anisotropic chemotaxis model combined with experimentally observed anisotropic growth. Overall, our findings reveal that variation in the chemotactic component of the corresponding self-organizational system might be a key determinant of interspecific differences in hair placode patterning dynamics and resulting spatial organizations.