Biology subjects

Segall, M.

Publications and source records attributed to Segall, M..

5 recordsLinked to original sources

bioRxiv2022

Armed to the teeth: the underestimated diversity in tooth shape in snakes and its relationship to feeding constraints

Teeth are one of the most studied hard tissues in vertebrates. Their structure, composition and shape are related to dietary specialization in many species. At first glance, snake teeth all look similar; conical, sharp, curved. Yet, snakes, like other vertebrates, have very diverse diets that may have affected their shape. We compared the morphology of the teeth of 63 species that cover both the phylogenetic and dietary diversity of snakes. We predicted that prey properties play a role in shaping snakes teeth along with their feeding behavior. Limblessness combined to the peculiar feeding behavior of snakes impose strong functional constraints on their teeth, especially during arboreal or aquatic feeding. Our results show that prey hardness, foraging substrate and the main feeding constraint are drivers of tooth shape, size, and curvature. We highlight two main morphotypes: long, slender, curved with a thin layer of hard tissue for snakes that need a good grip on their prey and short, stout, less curved teeth in snakes that eat hard or long prey. Our study demonstrates the diversity of tooth morphology in snakes and the need to investigate the underlying functional implications to better understand the evolution of teeth in vertebrates.

evolutionary biology↗

bioRxiv2020

Morphological Integration and Modularity in the Hyperkinetic Feeding System of Aquatic-foraging Snakes

The kinetic skull is a key innovation that allowed snakes to capture, manipulate, and swallow prey exclusively using their heads using the coordinated movement of 8 bones. Despite these unique feeding behaviors, patterns of evolutionary integration and modularity within the feeding bones of snakes in a phylogenetic framework have yet to be addressed. Here, we use a dataset of 60 {micro}CT scanned skulls and high-density geometric morphometric methods to address the origin and patterns of variation and integration in the feeding bones of aquatic-foraging snakes. By comparing alternate superimposition protocols allowing us to analyze the entire kinetic feeding system simultaneously, we find that the feeding bones are highly integrated, driven predominantly by functional selective pressures. The most supported pattern of modularity contains four modules each associated with distinct functional roles: the mandible, the palatopterygoid arch, the maxilla, and the suspensorium. Further, the morphological disparity of each bone is not linked to its magnitude of integration, indicating that integration within the feeding system does not constrain morphological evolution and that adequate biomechanical solutions to a wide range of feeding ecologies and behaviors is readily evolvable within the constraint due to integration in the snake feeding system.

evolutionary biology↗

bioRxiv2020

Exploring the functional meaning of head shape disparity in aquatic snakes.

Phenotypic diversity, or disparity, can be explained by simple genetic drift or, if functional constraints are strong, by selection for ecologically relevant phenotypes. We here studied phenotypic disparity in head shape in aquatic snakes. We investigated whether conflicting selective pressures related to different functions have driven shape diversity and explore whether similar phenotypes may give rise to the same functional output (i.e. many-to-one mapping of form to function). We focused on the head shape of aquatically foraging snakes as they fulfil several fitness-relevant functions and show a large amount of morphological variability. We used 3D surface scanning and 3D geometric-morphometrics to compare the head shape of 62 species in a phylogenetic context. We first tested whether diet specialization and size are drivers of head shape diversification. Next, we tested for many-to-one mapping by comparing the hydrodynamic efficiency of head shapes characteristic of the main axis of variation in the dataset. We 3D printed these shapes and measured the forces at play during a frontal strike. Our results show that diet and size explain only a small amount of shape variation. Shapes did not functionally converge as more specialized aquatic species evolved a more efficient head shape than others. The shape disparity observed could thus reflect a process of niche specialization under a stabilizing selective regime.

evolutionary biology↗

bioRxiv2019

SPINT2 inhibits relevant proteases in vitro and in vivo required for activation of both influenza viruses and metapneumoviruses

Viruses possessing class I fusion proteins require proteolytic activation by host cell proteases to mediate fusion with the host cell membrane. The mammalian SPINT2 gene encodes a protease inhibitor that targets trypsin-like serine proteases. Here we show the protease inhibitor, SPINT2, restricts cleavage-activation efficiently for a range of influenza viruses and for human metapneumovirus (HMPV). SPINT2 treatment resulted in the cleavage and fusion inhibition of full-length influenza A/CA/04/09 (H1N1) HA, A/Aichi/68 (H3N2) HA, A/Shanghai/2/2013 (H7N9) HA and HMPV F when activated by trypsin, recombinant matriptase or KLK5. We also demonstrate that SPINT2 was able to reduce viral growth of influenza A/CA/04/09 H1N1 and A/X31 H3N2 in cell culture by inhibiting matriptase or TMPRSS2. Moreover, inhibition efficacy did not differ whether SPINT2 was added at the time of infection or 24 hours post-infection. Our data suggest that the SPINT2 inhibitor has a strong potential to serve as a novel broad-spectrum antiviral.

microbiology↗

bioRxiv2018

Hydrodynamics of the frontal strike in aquatic snakes: drag, added mass and the possible consequences for prey capture success.

Natural selection favors organisms that are the most successful in fitness-related behaviors such as foraging. Secondary adaptations pose the problem of re-adapting an already optimized phenotype to new constraints. When animals forage underwater, they face strong physical constraints, particularly when capturing prey. Successful prey capture requires a predator to be fast and to generate a high acceleration. This involves two main constraints due to the surrounding fluid: drag and added mass. Both constraints are related to the shape of the animal. We experimentally explore the relationship between shape and performance in the context of an aquatic snake strike. As a model, we use two different 3D- printed snake heads representing typical shapes of aquatically-foraging and non-aquatically- foraging snakes, and frontal strike kinematics based on in vivo observations. By using direct force measurements, we compare the drag and added mass faced by the aquatic and non- aquatic snake models during a strike. Our results show that both drag and added mass are optimized in aquatic snakes. Using flow field measurements with particle image velocimetry, we examine the fluid dynamical mechanisms that could be behind the reduction of hydrodynamic constraints observed for the aquatic snake head shape, which makes it well suited to capture prey under water.\n\nSummary statementThe present work explores the functional implications of head shape 15 in a group of aquatic predators using a fluid mechanics approach.

biophysics↗