Chris Broeckhoven

Chris Broeckhoven
European Space Agency | ESA · European Space Research and Technology Centre (ESTEC)

PhD

About

47
Publications
39,835
Reads
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892
Citations
Citations since 2017
39 Research Items
873 Citations
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Introduction
I'm a biologist interested in the evolution and functional morphology of body armour such as bony plates and osteoderms in vertebrates. In addition, I have great passion for bioinspired and biomimetic research, and actively contribute to the establishment of emerging fields including "paleo-bioinspiration" and "evomimetics". My most exciting research lies at the interface between these two research interests.
Additional affiliations
January 2022 - present
European Space Agency
Position
  • Fellow
October 2017 - November 2021
University of Antwerp
Position
  • PostDoc Position
March 2015 - September 2017
Stellenbosch University
Position
  • PostDoc Position
Education
February 2012 - December 2014
Stellenbosch University
Field of study
  • PhD
September 2009 - September 2011
University of Antwerp
Field of study
  • MSc
September 2005 - September 2009
University of Antwerp
Field of study
  • Biology

Publications

Publications (47)
Article
Full-text available
Nature provides an infinite source of inspiration for innovative designs that may be required to tackle the social, economic, and environmental challenges the world faces. Despite the surging popularity and prevalence, the discipline of bioinspiration is limited in unleashing its full potential by the inadequate understanding of biological and evol...
Article
Full-text available
Squamates represent a highly diverse and species-rich vertebrate group that is remarkably understudied from a genomic perspective. A scarcity of genomic data is particularly evident for scincomorph lizards, which encompass over 10% of all living squamates, and for which high-quality genomic resources are currently lacking. To address this knowledge...
Article
The functional significance of osteoderms—bony elements embedded in the dermis—remains a topic of much debate. Although many hypotheses have been put forward in the past, the idea that osteoderms can serve as calcium reservoirs has received little experimental attention thus far. In this study, we use micro-computed tomography to investigate inter-...
Article
1. Predation is widely regarded as an important selective force in the evolution and maintenance of dermal armour, yet, the basic premise that predation and armour are strongly linked to each other has proven to be difficult to assess. 2. In this concept, I put forward the fighting‐advantage hypothesis, the view that aggressive interactions with co...
Chapter
Beautiful and functional—the perfect combination of nature’s beauty and engineering functionality–best describes the synergy between biomimicry and additive manufacturing. Nature has proven to be a valuable source of inspiration for design solutions with many success stories, yet critical gaps between biological and engineering domains prevent biom...
Article
The functional significance of osteoderms-ossified bony structures in the dermis-has been a topic of discussion for many years in biological sciences. Although a protective function has received significant attention in the past, evidence is accumulating that osteoderms might play an important role during physiological activities, specifically ther...
Data
Figure S3. Graphs illustrating the mean and standard deviation for each locality with regards to shape PC3 and shape PC4. The fish outline drawings depict the variation in fish body shape for each PC axis, with the light blue line representing the average shape for all fish, while the dark blue line represents the upper and lower body shape extremi...
Data
Figure S4. PCA analyses conducted on the combined microsatellite genotypes for the seven localities (A – D, H – J). Each dot represents a genotyped individual, with colours corresponding to sampled localities.
Data
Figure S2. Variation in PCLINEAR1 among the age classes for each locality (A-J).
Data
Figure S5. STRUCTURE HARVESTER (Earl and vonHoldt, 2012) output files, implementing the Evanno method. The most probably Delta K as well as LnP(D) values for all K values (1 < K > 10).
Data
Figure S6. Mantel test indicating the significant (P =0.001) isolation-by-distance signal detected.
Data
Figure S1. Photographs capturing the variation in habitat along the Olifants River system during the summer months (December – February). Left: Locality A situated along the upper reaches of the Jan Dissels tributary; Centre: two photographs representing the middle reaches of the Olifants River (top image taken from DWA, 2006); Right: the sampling...
Article
Full-text available
Dispersal is an essential life-history trait crucial to species persistence and diversification. This is particularly important in spatiotemporal fluctuating environments such as freshwater habitats, where species movement is confined to the dendritic network and wetted boundaries. To persist in such fluctuating environments, a species can modify,...
Article
Three-dimensional concrete printing (3DCP) is an exciting new manufacturing paradigm for the construction industry. As this technology continues to grow and develop, it is revealing clear signs of progress towards industrial application with various global successes including the manufacturing of pedestrian bridges, houses, office buildings, emerge...
Preprint
Beautiful and functional – the perfect combination of nature’s beauty and engineering functionality – best describes the synergy between biomimicry and additive manufacturing. Nature has proven to be a valuable source of inspiration for design solutions with many success stories, yet critical gaps between biological and engineering domains prevent...
Preprint
Full-text available
This review article summarizes the current state-of-the-art for biomimicry in additive manufacturing. Biomimicry is the practice of learning from and emulating nature - which can be increasingly realized in engineering applications due to progress in additive manufacturing (AM). AM has grown tremendously in recent years, with improvements in techno...
Article
A striking new sandveld lizard of the Nucras tessellata group is described from the Lambert’s Bay Strandveld of the Western Cape Province, South Africa. It is sister to the clade N. livida + N. tessellata, and is phenetically most similar to N. tessellata, from which it differs in its more elongate body and possibly increased number of presacral ve...
Chapter
Animals are exposed to many threats and dangers in nature, with predation being among the most important factors. In response, prey have evolved an array of morphological defenses to protect themselves against predators, ranging from offensive weaponry to defensive armor and body size. In this article, I outline the morphological diversity in defen...
Article
Albert Einstein once said “look deep into nature, and then you will understand everything better”. Looking deep into nature has in the last few years become much more achievable through the use of high-resolution X-ray micro-computed tomography (microCT). The non-destructive nature of microCT, combined with three-dimensional visualization and analy...
Article
Full-text available
Herpetological research, like any other (palaeo)biological science, relies heavily on accurate data collection, particularly visualisation and quantification of anatomical features. While several high-resolution imaging methods are currently available, one technique in particular, x-ray microtomography or micro-computed tomography, is on the verge...
Article
While sexual dimorphism in offensive weaponry is a well-established phenomenon, few studies have looked at sexual differences in defensive body armour. In this study, we investigate sexual dimorphism in the expression of osteoderms-bony elements embedded in the skin-in four species of cordyline lizards by using high-resolution micro-computed tomogr...
Article
To substantiate the claim of a relationship between generation gland morphology and degree of body armour in cordylid lizards, we studied the nine species in the genus Smaug. We predicted that well armoured species in this clade will have multi-layer generation glands, and lightly armoured species two-layer glands. Gland type was determined using s...
Article
Animal body armour is often considered an adaptation that protects prey against predatory attacks, yet comparative studies that link the diversification of these allegedly protective coverings to differential predation risk or pressure are scarce. Here, we examine the evolution of body armour, including spines and osteoderms, in Cordylinae, a radia...
Article
Although it is widely assumed that body armour in animals evolved to thwart predator attacks, assessing the role that predators may play in shaping defensive morphologies has proven to be difficult. Recent studies suggest that body armour might be influenced by additional factors besides predation, and/or even by sexual selection. We investigated v...
Article
Electronic supplementary material is available online at https://dx. Animal body armour is often considered an adaptation that protects prey against predatory attacks, yet comparative studies that link the diversification of these allegedly protective coverings to differential predation risk or pressure are scarce. Here, we examine the evolution of...
Article
Full-text available
This data note provides data from an experimental campaign to analyse the detailed internal and external morphology and mechanical properties of venomous snake fangs. The aim of the experimental campaign was to investigate the evolutionary development of three fang phenotypes and investigate their mechanical behaviour. The study involved the use of...
Article
Full-text available
A correction to this article has been published and is linked from the HTML version of this paper. The error has not been fixed in the paper.
Article
Full-text available
Foraging mode plays a pivotal role in traditional reconstructions of squamate evolution. Transitions between modes are said to spark concerted changes in the morphology, physiology, behaviour, and life history of lizards. With respect to their sensory systems, species that adopt a sit-and-wait strategy are thought to rely on visual cues primarily,...
Article
Full-text available
Venomous snakes—the pinnacle of snake evolution—are characterized by their possession of venom-conducting fangs ranging from grooved phenotypes characterizing multiple lineages of rear-fanged taxa to tubular phenotypes present in elapids, viperids and atractaspidines. Despite extensive research, controversy still exists on the selective pressures i...
Article
Full-text available
The functional significance of osteoderms, body plates embedded in the skin of various extinct and extant tetrapods, has been studied widely in the past, leading to the advancement of a plethora of hypotheses to explain their presence. Whereas the emphasis of most studies is on the role of osteoderms as protection against predators, alternative hyp...
Article
1. Microcomputed tomography (lCT) is a widely used tool in biomedical research, employed to investigate tissues and bone structures of small mammals in vivo. The application of in vivo lCT scanning in non-medical studies greatly lags behind the rapid advancements made in the biomedical field wherein the methodology has evolved to allow for longitud...
Article
Full-text available
Laboratory X-ray micro-computed tomography (micro-CT) is a fast growing method in scientific research applications that allows for non-destructive imaging of morphological structures. This paper provides an easily operated “how-to” guide for new potential users and describes the various steps required for successful planning of research projects th...
Article
Adaptive radiation (AR), the product of rapid diversification of an ancestral species into novel adaptive zones, has become pivotal in our understanding of biodiversity. Although it has widely been accepted that predators may drive the process of AR by creating ecological opportunity (e.g., enemy-free space), the role of predators as selective agen...
Article
Full-text available
It is generally assumed that favourable weather conditions determine the activity levels of lizards, because of their temperature-dependent behavioural performance. Inactivity, however, might have a selective advantage over activity, as it could increase survival by reducing exposure to predators. Consequently, the effects of weather conditions on...
Article
Full-text available
Predation has been proposed to be a selective agent in the evolution of morphological antipredator strategies in prey. Among vertebrates, one of the morphological traits that evolved multiple times is body armour, including carapaces, thickened keratinized scales and plates of dermal bone.It has been generally assumed that body armour provides prot...
Article
To elucidate the functional significance of the three distinct types of generation glands that have been identified among cordylid lizards, we mapped gland type to the terminal taxa in the most recent phylogenetic tree for the Cordylidae. We used the phylogenetic programme Mesquite and applied the principle of parsimony to infer character states fo...
Article
Full-text available
Rock-dwelling lizards are hypothesized to be highly constrained in the evolution of head morphology and, consequently, bite force. Because the ability to generate a high bite force might be advantageous for a species' dietary ecology, morphological changes in head configuration that allow individuals to maintain or improve their bite force under th...
Article
Full-text available
Lizards exhibit a variety of mechanisms to capture prey, including lingual prehension, jaw prehension and lingual pinning. Despite being the topic of numerous studies, the link between prehension mode and diet remains poorly understood, especially in clades where multiple prehension modes are present. We addressed this issue by comparing the feedin...

Questions

Questions (18)
Question
We are conducting a number of experiments to estimate how fast (or slow) insects heat up or cool down. We are making use of a solar simulator to heat up individuals for 10 minutes starting from around 20°C and ending at about 40-45°C. Hereafter the individuals are cooled down for 30 minutes to reach the initial temperature of around 20°C.
We would like to get a reliable estimate of heating/cooling, particularly in the beginning of the experiment when they are the fastest. Towards the end of the trial, the rates start to slow down as the maximum temperature of the solar simulator is reached, so any calculations based on just the initial and maximum temperature are not very useful.
In literature, some authors have calculated the maximum change per minute, but because this is almost always the first minute it is not very accurate imo.
Are there alternative ways of getting estimates of how fast/slow heating/cooling is?
Question
I am big fan of ResearchGate and make extensive use of the Stats to see who is interested in my research and which topics are receiving the most attention. I've discovered many interesting researchers this way. Last week, I came to the discovery that this is not a free service anymore, but instead that ResearchGate now demands a monthly payment of 12 (!) Euro - something a researcher without running costs, like me, cannot afford. I understand that payments for Premium profiles can have major benefits if it increases the chances of finding a good job/position (like LinkedIn), but do not understand why we should pay to see who's interested in our research.
I hope ResearchGate reverses this at some point in time (bringing just the Stats back would be sufficient), but would like to hear the opinion of other members of the community!
Question
I'm looking for a comprehensive phylogeny/cladogram of Tetrapods, that includes extant and extinct groups preferably to Order (or Clade) level. Does anyone know if this is available online or as publication? I'm finding several useful papers, but many focus specifically on a subset of tetrapod lineages...
Question
I'm looking for datasets (or databases) in which the body mass of predator and prey are presented. I'm specifically interested in terrestrial predators (snakes, mammals, birds).
An example of is Vézina, A.F., 1985. Empirical relationships between predator and prey size among terrestrial vertebrate predators. Oecologia, 67(4), pp.555-565. (unfortunately there are no associated data as it's quite an old paper).
Any tips or suggestions are more than welcome!
Question
I would like to obtain information on the habitat use (terrestrial, arboreal, etc) and activity patterns (nocturnal, diurnal, etc) of all snake species. Does such a dataset already exist somewhere? I haven't been very successful in finding papers or databases with such comprehensive information so any suggestions are more than welcome!
Question
I would like to calculate the overlap between the distributions of two sets of data (predator & prey). The prey set has got about 250 species, the predator set approximately 5000. For each species I have a shape file in .shp format. Has anyone got any suggestions how to calculate the overlap between the pairs?
In the past I've used the function 'pairwiseRangemaps' of the fuzzySim package, but it calculates the overlap between EACH pair (so > 27 million comparisons for a 5250 x 5250 matrix), making it impossible to run on any normal computer (even splitting the data set in dozens of smaller files and taking out the upper triangle would take weeks or months). I'm not interested in the overlap between prey species or between predator species, just between each prey and each predator.
Has anyone got a suggestion how to calculate this in R? I'm thinking of two vectors (one prey, one predator) and then calculating the overlap between just these.
Question
I'm looking into the process of calcium resorption in osteoderms (i.e., bony elements embedded in the dermal layer of various vertebrates). I was wondering if there are any other mechanisms in animals that result in the resorption of calcium besides osteoclast activity. Any information or papers will be highly appreciated!
Question
I would like to extract a number of bioclimatic variables (mainly from the Worldclim database) from the distribution ranges of several animal species. These distribution ranges are presented as shape files (.shp). Has anyone got some insightful links or info how to perform these analyses in an effective way using R? Unfortunately, I am only familiar with extracting variables from coordinates directly. Thanks!
Question
I'm trying to obtain equal absorption rates of silica gel along a temperature gradient (20 - 40 °C) by adjusting the weight of the silica granules. Is there any literature on the relationship between temperature and absorption capacity (or a formula) of silica gel that can help me calculate this? The silica that will be used are 'shop-grade' pellets.
Question
I am looking into Spatial Neighbors to address autocorrelation in my dataset, but I find it difficult to find arguments as to which method to prefer. I am using the R package "spdep" and functions dnearneigh and knearneigh to determine the distance-based neighbors and k-nearest neighbors, respectively. However, could someone advise me on the main differences between the two methods, as well as on how to determine d2 (upper distance bound) and k (number of nearest neighbors).
Question
I have gene sequences (ND2, mtDNA) for 59 samples belonging to 6 populations. I would like to find out if there is a program that can easily calculate the genetic distance between the populations. I can calculate the genetic distance between the individuals, but that is not what I am looking for. I would like to build a matrix with the population average genetic distances to compare them to morphological differences.
Question
I would like to calculate the Aridity Index for a number of GPS coordinates. I have downloaded the files required to calculate Aridity Index from http://www.cgiar-csi.org/data/global-aridity-and-pet-database. These files come in .adf format. Is there a way to convert these into GeoTiffs or similar? I would like to obtain the values in R since I'm unfamiliar with ArcGIS.
Question
I am struggling finding the appropriate test for a data set I would like to analyse. I have the following parameters:
Dependent variable: X (i.e. log-transformed measurement)
Factor: A (=SEX)
Factor: B (=SPECIES)
Co-variate: Y (i.e. log-transformed SIZE measurement)
I would like to test whether variable X differs the species and between the sexes.
Problems:
1) The residuals are not-normally distributed so an  AN(C)OVA seems not appropriate. 
2) Ignoring the non-normality, an ANCOVA shows a strong interaction effect between the co-variate and the species (SIZE*SPECIES), no interaction between the factors (SEX*SPECIES) or between the co-variate and sex (SIZE*SEX)
3) Trait X is correlated with SIZE, but only in SPECIES 1, not SPECIES 2.
I am a bit confused how to proceed as this statistical issue goes beyond my knowledge. I've been reading up on RANCOVA: some websites suggest to rank both variable X and co-variate Y, regress X on Y (not sure how this is affected by Problem 3) and conduct an ANOVA using the residuals. 
Any help will be more than appreciated!
Question
I am trying to determine whether trait A follows an allometric or isometric growth trajectory. The dependent variable Y is a trait expressed in mm³, while the independent variable X is a trait expressed in mm. 
I have log-transformed both variables and conducted a reduced major axis regression. 
I know that for two traits on the same scale (e.g. mm) the null hypothesis of isometry is a slope of 1.0 so that the trait scales isometrically if the confidence interval includes 1.0. Positive allometry is present when the slope is > 1.0 and negative allometry when the slope is < 1.0 (same for confidence intervals).
In my case, given the scale of variable Y (i.e. mm³), is it correct to assume that the trait scales isometrically if the confidence interval includes 3? 
The results from the RMA regression show a slope of 11.78 with a confidence interval of 7.98-17.38. This seems a bit odd to me. 
Any help will be greatly appreciated!

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Projects

Projects (5)
Project
This research involves the learning of design guidelines and rules from natural systems, mostly using high resolution 3D imaging of internal structures of interesting model systems. Reverse-engineering nature has many potential applications, especially when using additive manufacturing to realize those designs.