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New Collection Spotlights Current Techniques in Morphology  

Micro-CT micrographs

Synchrotron-based micro-CT micrographs showing the hind leg femoro-tibial joint of Gryllus campestris (slp=semilunar process, fem=femur, tib=tibia, HL=Heitler’s lump, GFS=genuflexor sclerite, con=femoro-tibial conjunctiva, fe-tifl=tibial flexor muscle, fe-tiex=tibial extensor muscle, lines marked with E, F show the sites of sections on figures E and F, distal to the left). Figure from paper “Universal locking mechanisms in insect legs: jumping and grasping” by Földvári et al in the “Current Techniques in Morphology” collection.

While the field of morphology—the study of the form and function of organisms—is centuries old, the last two decades have brought incredible leaps forward through the emergence of new technologies and genetic research methods. And the impact of these advances has been revolutionary for the scientists working to untangle the vast biodiversity and evolutionary paths of the world of insects.

Two prime examples are high-powered microscopy tools, giving entomologists unprecedented views of previously obscure insect anatomy, and robust genetic sequencing techniques, allowing fine-scale analysis of insect species’ relationships that is otherwise impossible with traditional physical observation. The applications of these techniques and more are showcased in a new special research collection, “Current Techniques in Morphology,” published today in the journal Insect Systematics and Diversity.

Brendon Boudinot, a Ph.D. candidate at the University of California-Davis, co-led the development of this collection with István Mikó, collections manager at the University of New Hampshire Department of Biological Sciences. Boudinot responded to some questions from Entomology Today about the collection. His answers are below.

Entomology Today: What inspired you to organize this collection?

Boudinot: Short answer: A shared love of morphology and evolution, and a desire to share fresh perspectives, novel results, and new ways of thinking about morphology to entomologists more broadly.

Long answer: I have had opportunities to meet with and talk to István about morphology at Entomological Society of America meetings over the past several years. These meetings have made a profound impact on the way that I conceive of and communicate about arthropod morphology, and so it was natural that eventually István and I would work together on the subject in some way.

This special collection arose directly out of a symposium which István and I organized for ESA 2018 in Vancouver, BC, titled “Evolutionary and Phylogenetic Morphology.” For this symposium, we wanted to bring together researchers from as many different fields as we could muster so as to catalyze synthetic thinking about morphology. Our speakers covered topics including phenotype documentation, morphological interpretation, paleontology, phylogenetic modeling, and quantitative methods for testing evolutionary hypotheses. After experiencing the energy at the symposium, we wanted to encapsulate some of the thoughts and approaches brought to us by our speakers through a special collection of articles in Insect Systematics and Diversity, which ISD editors-in-chief Sydney Cameron and Jim Whitfield so graciously facilitated.

For someone who doesn’t know much about systematic morphology, how would you describe the overall advance of the field since the turn of this century?

We believe that the turn of the century marks the beginning of the Renaissance of Morphology. Although the tide of scientific effort has strongly shifted toward genomic data over the past several decades due to the increasing ease and decreasing economic burden of generating sequence data, as well as amenability of these data to modeling, we observe that the tide is now shifting again toward morphology.

This is so for a series of reasons. First of all, many of the deep phylogenetic—hence classificatory—problems previously assailed by morphological data have become and are becoming saturated with -omic scale sequence data. As the phylogeny of the insects becomes increasingly clear, for example, we can answer questions about morphological evolution without the problem of circular inference (i.e., generating phylogeny from morphology, then using that phylogeny to interpret morphology). In effect, we can now use genomic phylogenies as objective guides for detecting organism-scale patterns of variation and evolution which were insoluble to previous generations, and which can’t be seen in strings of nucleotides or amino acids.

Moreover, the increasing availability of advanced technologies, such as micro-computed tomography and confocal laser scanning microscopy, are allowing researchers to generate models of morphology in three and four dimensions based on physical data. These models not only allow for detailed and quantitative study of anatomical systems and their biomechanical properties, but they also allow end-users to experience the richness of morphology in virtual reality, which is incredible.

To wrap up this response, I think it is important to emphasize that the theoretical foundations of morphology established during the prior century have been and are being tested, rejected, and substantiated in ways which will change the teaching, learning, and study of entomology for at least another century to come.

How are new tools and features in digital publishing further enabling these advances?

One of the major benefits of digital publishing is the ease of disseminating results, which helps specific studies reach their target audience and broadens the potential audience, thus encouraging research more generally. Free and nearly unlimited color figures in digital articles is awesome, but even better are three-dimensional models embedded in PDFs. In this way, authors may communicate a maximum amount of information, and with those embedded figures, the audience can see a visual representation of the data in a totally new and much more immersive manner than simple 2D figures. From the perspective of a morphologist, this is fantastic, as trying to understand complex 3D structures from a series of 2D projections is not a simple challenge, and is made more difficult by a learning curve. This curve is flattened for morphology when you can literally see a given structure from any angle at any magnification. Plus, cybertypes (3D scans of type specimens) enable taxonomists to not only discover new characters, but allows users of the work to see in explicit detail features which would otherwise require an expensive museum visit to view. [Editor’s note: See an example of a holotype presented as a computer generated 3D mesh model optimized for augmented reality from the paper “Ready Species One: Exploring the Use of Augmented Reality to Enhance Systematic Biology with a Revision of Fijian Strumigenys (Hymenoptera: Formicidae)” from the “Current Techniques in Morphology” collection.]

Multiple papers in the collection showcase micro-computed tomography; why has this technology become such a powerful tool for insect morphology?

Scan data are powerful because they are objective. Descriptions and character matrices of discretized characters are subjective, thus not only difficult to replicate, but are also easily biased by the researcher encoding their observations. With a scan, we can theoretically compress a terabyte of phenotype data into megabytes of data, and decompress it without loss of fidelity. We simply can’t do this with the traditional approach of scoring or describing features based on subjective observation: That matrix or those paragraphs can’t be decoded into a whole organism again.

There is a communicative benefit too, as anyone can observe a specimen in rich detail if given a rendering of a scan in 3- or 4D, without having been specially trained in the logic and language of morphology. Thus, as mentioned above, it is exceedingly easy to comprehend a complex structure, which otherwise would require dissections of fresh material, examination of vouchers (which are often lost), or an often error-prone (and often painful) exercise of the imagination. Scan data allow specimens to live on in digital perpetuity, allowing reexamination following the gain of an insight or the development of new questions. Moreover, with a µ-CT scan, one can model function, which is key for understanding structures, both simple and complex, and which also allows for the solution of biomechanical questions, linking the phenotype to the environment in ways not readily accessible to prior generations.

As a final point, there is tremendous potential to use scan data for evolutionary and phylogenetic studies—it is conceivable that one day we could visualize morphological evolution across the tree of life throughout the history of Earth not just in words, not just in 2D, but in three or more dimensions, in virtual reality nonetheless! In other words, we have the data to literally visualize the ancestors of any group we care about. It is only a matter of time before this becomes a reality.

Any additional comment?

István and I would love to organize another symposium and another special collection. If you would like to contribute to either, please don’t hesitate to get in touch with us!

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Current Techniques in Morphology

Insect Systematics and Diversity

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