Research Leonard Dewaele

Abstract

Semi-aquatic mustelids have undergone a secondary transition to adapt to life in an aquatic environment. Locomotion on land and in water happen in a starkly different medium, and thus pose different locomotor requirements. This imposes an important trade-off in semi-aquatic animals. The Mustelidae are a diverse family of mammals which offers the unique opportunity of having species across many niches, including a range of aquatic specialisation; from fully terrestrial species to those specialized to operate in a semi-aquatic or almost fully aquatic niche. This range offers an insight into the trade-offs and evolution of adaptations to a semi-aquatic life. The project will use comparative functional anatomy (muscle architecture based on manual and digital dissection) and video-based locomotor kinematics to build musculoskeletal models. These models will be used to verify, in terms of muscle contraction regimes, how well the musculoskeletal system of these species is 'built' for the two different environments and thus what the functional significance of the morphological adaptations is. Starting from this data and insights of the extant species, we will use inverse modelling to build models of extinct otters to gain insight into their locomotor capabilities and which modes were likely used by these species. These distinct species, from different fossil time periods and ecologies will help elucidate which locomotive capabilities were gained or lost during otter evolution.

Researcher(s)

• Promoter: Van Wassenbergh Sam
• Co-promoter: Dewaele Leonard
• Co-promoter: Maclaren Jamie
• Fellow: De Ridder Tim

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

Pinnipedimorphs are semi-aquatic mammals that adapted secondarily to a life in water, allowing them to successfully move and capture prey underwater. The group includes all extinct and extant pinnipeds (e.g. seals, sea-lions, walruses) and stem taxa (e.g. Enaliarctos). Modern pinnipeds are still bound to land, where they rest and reproduce, but they feed almost exclusively underwater. Feeding is regarded as the main driver for their transition from land to water. However, making inferences about organismal evolution presents difficulties with a lack of a robust phylogenetic framework. The main debates about pinnipedimorph phylogeny include the monophyly of Enaliarctos and the relation of mustelid-like taxa (e.g. Puijila) to stem-pinnipedimorphs. In this project I will conduct a careful redescription of basal pinnipeds and perform a comprehensive phylogenetic analysis including all stem-pinnipedimorphs (accepted and contested taxa), later diverging pinnipedimorphs and outgroup taxa (mustelids and ursids). I will then investigate (stem-)pinnipedimorph mandibular morphology and function using geometric morphometrics and finite element analysis to better understand their feeding capabilities through time, using the updated phylogeny as the foundation for morphofunctional comparisons among pinnipedimorphs. This study will provide valuable quantitative information for understanding pinnipedimorph evolution, and will provide fundamental insights into the land-to-water transition.

Researcher(s)

• Promoter: Van Wassenbergh Sam
• Co-promoter: Dewaele Leonard
• Co-promoter: Maclaren Jamie
• Fellow: Selini Anastasia

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

Throughout the long evolutionary history of tetrapods, multiple taxa returned to life in water from a terrestrial (or aerial) environment. Notable groups are Mesozoic marine reptiles, sirenians, and whales. Among mammals, aquatic taxa within the order Carnivora, or "meat-eaters", show an 'incomplete' transition to life in the aquatic environment: pinnipeds (true seals, sea lions, fur seals and walruses), otters, polar bears, and even the fishing cat rely heavily on water for feeding, but none are exclusively aquatic and they all still return to land to rest, give birth, etc. The transition from a terrestrial to a (semi-)aquatic lifestyle is an impactful biological shift, with multiple potential drivers and requires various physiological and anatomical adaptations. As this transition occurred independently in several carnivoran groups (Pinnipedia, Mustelidae, Ursidae, Felidae), as well as in different environments (riverine, lacustrine, and marine), it asks the following questions: Which environmental and ecological changes triggered this transition for each group? How did these carnivorans functionally adapt to life in water? What are the similarities and differences between these groups, and between aquatic carnivorans and other aquatic mammals? And, more specifically, what is the extent of morphological and functional convergence between these lineages? The MEATLOAF project aims to investigate the different evolutionary aspects of this transition in carnivorans from land to water, specifically targeting adaptations for locomotion (on land and in the water) and feeding (prey sensing, prey capture, and food processing, both above and below the water surface), using a variety of well-supported proxies. Proxies will be organized along two main approaches, which will link to one another in a two-way process: (1) a comparative approach, documenting the morphological diversity and shifts in morphology, and (2) a modelling approach, focusing on performance and loading of the recorded morphologies. Comparative aspects will include anatomical, systematic and phylogenetic analyses, all gathered in a 'classical paleontology' work package, as well as geometric morphometric and microanatomical-osteohistological packages to quantify internal and external morphology. The modelling approach will encompass functional analyses, finite element analyses, computational fluid dynamics, and musculo-skeletal modelling, each within its own work package. A synthesis of the results of these different packages will ultimately result in a time-calibrated assessment of the paleoecological and paleoenvironmental frameworks in which these groups evolved to life in water, in order to better understand the biotic and abiotic drivers of such a major, iterative transition.

Researcher(s)

• Promoter: Van Wassenbergh Sam
• Co-promoter: Aerts Peter
• Co-promoter: Van Damme Raoul
• Fellow: Dewaele Leonard

Research team(s)

• Functional Morphology

Project type(s)

• Research Project