Biology subjects

Ladeveze, S.

Publications and source records attributed to Ladeveze, S..

4 recordsLinked to original sources

bioRxiv2025

Brain size reduction in dogs was already established at least by the Late Neolithic of western Europe, 5,000 years ago

The timing and causes of brain size reduction in domestic dogs remain uncertain. Using endocasts volume as a proxy for brain size, this study provides a first insight into long-term brain size evolution in the wolf-dog lineage. We compared endocranial volumes of 185 modern and 22 prehistoric wolves and dogs ranging from Western Europe to Australia, and spanning the Pleniglacial (35 Ky BP) to the Late Neolithic (5 Ky BP). Our results reveal that Pleistocene so called "protodogs" show no brain size reduction compared to coeval Pleistocene wolves. Instead, we observed a slightly larger relative endocranial volume in the 35,000-year-old protodog from Goyet, which could suggest increased behavioural flexibility in the presence of humans. This hypothesis needs to be tested further. In contrast, Late Neolithic dogs show a drastic 46% brain size reduction with an endocranial volumes comparable to modern small terrier and toy breeds. The anxious and wary temperaments of these Late Neolithic dogs, induced by the brain tissue reorganization associated with such a size reduction, could have served an alerting purpose, among the many other potential roles dogs could have played within this Late Neolithic socio-ecosystems.

zoology↗

bioRxiv2025

Anatomical description of the jaw muscles and theoretical bite force assessment in South-American opossums using manual and virtual dissection methods.

Marsupials (Marsupialia, Mammalia) represent a clade with highly varied ecologies. This is particularly true for opossums (South American marsupials), which are difficult to observe and collect. Consequently, few studies have focused on their bite force and the muscles of their masticatory apparatus, and there exists only scant information about the diet of certain species. Here we describe the masticatory muscles of several previously unstudied opossum species including Caenolestes fuliginosus, Dromiciops gliroides, and Monodelphis touan. We calculate the bite force of these species using data from both manual and virtual dissections and compare their theoretical bite forces with literature data. Additionally, we explore the differences between manual and virtual dissection to determine muscle PCSA (Physiological Cross-Sectional Area). We tried two virtual methods (VPDE: "virtual physiological data estimating method" and SM: "slicing muscle method") to calculate the PCSA, determine the differences induced by the inter-fiber void in the virtual volume, and calculate a correction post-treatment with the contrast agent. The results highlighted variation in the position of the muscular attachments of the M. zygomaticomandibularis, whose insertion area is the largest in Monodelphis touan and the smallest in Caenolestes fuliginosus. The bite forces are coherent with estimates from the literature suggesting that the biomechanical model is reliable. The comparison between manual and virtual dissection showed that while virtual dissection allows an overall description of the masticatory muscles, it is more complex to accurately describe the different subdivisions of the muscle bundles. Virtual dissection data could potentially complete manual dissection data with the association of the VPDE method, the exclusion of inter-fiber voids, and a correction for the treatment with contrast-agents.

zoology↗

bioRxiv2023

Versatile Product Detection via Coupled Assays for Ultra-high-throughput Screening of Carbohydrate-Active-Enzymes in Microfluidic Droplets

Enzyme discovery and directed evolution are the two major contemporary approaches for the improvement of industrial processes by biocatalysis in various fields. Customization of catalysts for improvement of single enzyme reactions or de novo reaction development is often complex and tedious. The success of screening campaigns relies on the fraction of sequence space that can be sampled, whether for evolving a particular enzyme or screening metagenomes. Ultrahigh-throughput screening (uHTS) based on in-vitro compartmentalization in water-in-oil emulsion of picolitre droplets generated in microfluidic systems allows screening rates >1 kHz (or >107 per day). Screening for Carbohydrate Active Enzymes (CAZymes) catalysing biotechnologically valuable reactions in this format presents an additional challenge, because the released carbohydrates are difficult to monitor in high throughput. Activated substrates with large optically active hydrophobic leaving groups provide a generic optical readout, but the molecular recognition properties of sugars will be altered by incorporation of such fluoro- or chromophores and their typically higher reactivity, as leaving groups with lowered pKa values compared to native substrates make observation of promiscuous reactions more likely. To overcome these issues, we designed microdroplet assays in which optically inactive carbohydrate products are made visible by specific cascades: the primary reaction of an unlabelled substrate leads to an optical signal downstream. Successfully implementing such assays at the picoliter droplet scale allowed us to detect glucose, xylose, glucuronic acid and arabinose as final products of complex oligosaccharide degradation by glycoside hydrolases by absorbance measurements. Enabling the use of uHTS for screening CAZyme reactions that have been thus far elusive will chart a route towards faster and easier development of specific and efficient biocatalysts for biovalorisation, directing enzyme discovery towards catalysts for their natural rather than model substrates. Graphical abstract / TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=58 SRC="FIGDIR/small/534725v1_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@13063eborg.highwire.dtl.DTLVardef@1efdcfcorg.highwire.dtl.DTLVardef@9562eeorg.highwire.dtl.DTLVardef@1923207_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2020

Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls

Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and function. Here, we characterise the shape variation among 84 marsupial cranial endocasts of 57 species including fossils, using 3D geometric morphometrics and virtual dissections. Statistical shape analysis revealed four main patterns: over half of endocast shape variation ranges between elongate and straight to globular and inclined; little allometric variation with respect to centroid size, and none for relative volume; no association between locomotion and endocast shape; limited association between endocast shape and previously published histological cortex volumes. Fossil species tend to have smaller cerebral hemispheres. We find divergent endocast shapes in closely related species and within species, and diverse morphologies superimposed over the main variation. An evolutionarily and individually malleable brain with a fundamental tendency to arrange into a spectrum of elongate-to-globular shapes - possibly mostly independent of brain function - may explain the accommodation of brains within the enormous diversity of mammalian skull form.

evolutionary biology↗