Biology subjects

Godoy-Diana, R.

Publications and source records attributed to Godoy-Diana, R..

4 recordsLinked to original sources

bioRxiv2022

Measuring the 3D wake of swimming dice snakes using volumetric velocimetry

Experimental observations of the 3-dimensional wake of swimmers are scarce. This study provides the first experimental measurements of the three-dimensional vortical structures of an anguilliform swimmer. A volumetric velocimetry (DDPTV) setup was used to quantify the wake of freely swimming dice snakes (Natrix tessellata) in a tank. Multiple swimming trials were recorded with three snakes swimming at a forward swimming speed ranging from 0.2 to 0.8L.s-1. The volumetric measurements show that during swimming, Natrix tessellata sheds vortex tubes from different parts of its body with oscillating lateral undulations. The vortex tubes are then linked to form a hairpin-like structure as predicted by computational fluid dynamic analyses. Quantitative measurements show that the vortex size gradually increases over time. The vortex circulation decreases after attaining a maximum. These results provide an experimental demonstration that the 3D wake structure of an anguilliform swimmer takes well organized dynamic shapes as predicted and provide baseline data for future studies comparing the wake structure of snakes with different locomotor ecologies.

zoology↗

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

On the energetics and stability of a minimal fish school

The physical basis for fish schooling is examined using three-dimensional numerical simulations of a pair of swimming fish, with kinematics and geometry obtained from experimental data. Energy expenditure and efficiency are evaluated using a cost of transport function, while the effect of schooling on the stability of each swimmer is examined by probing the lateral force and the lateral and longitudinal force fluctuations. We construct full maps of the aforementioned quantities as functions of the spatial pattern of the swimming fish pair and show that both energy expenditure and stability can be invoked as possible reasons for the swimming patterns and tail-beat synchronization observed in real fish. Our results suggest that high cost of transport zones should be avoided by the fish. Wake capture may be energetically unfavorable in the absence of kinematic adjustment. We hereby hypothesize that fish may restrain from wake capturing and, instead, adopt side-to-side configuration as a conservative strategy, when the conditions of wake energy harvesting are not satisfied. To maintain a stable school configuration, compromise between propulsive efficiency and stability, as well as between school members, ought to be considered.

biophysics↗

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↗