Chris Armit

*[MicroCT imaging is an exceptional tool for 3D visualisation. A [new
Data Note](https://doi.org/10.1093/gigascience/giae037) published in
]{style="font-weight: 400;"}[GigaScience]{style="font-weight: 400;"}[
reports on a unique, high-quality series of MicroCT images that covers
the lifespan of an amphibian from tadpole to froglet to mature adult
frog. The Data Note reports on a 3D anatomical atlas of an important
model organism of development, the African Clawed Toad
]{style="font-weight: 400;"}[Xenopus
laevis]{style="font-weight: 400;"}*[*.*  
]{style="font-weight: 400;"}

### **The African Clawed Toad as a Model of Development**

*[Xenopus laevis]{style="font-weight: 400;"}*[ has played an important
role in our understanding of embryonic development. In the early
twentieth century, Hans Spemann and Hilde Mangold used
]{style="font-weight: 400;"}[[transplantation
experiments]{style="font-weight: 400;"}](https://en.wikipedia.org/wiki/Spemann-Mangold_organizer)[
in ]{style="font-weight: 400;"}*[Xenopus
laevis]{style="font-weight: 400;"}*[ embryos to showcase that the fate
of cells was dependent on their location.]{style="font-weight: 400;"}

*[Xenopus laevis]{style="font-weight: 400;"}*[ was also used in the
early studies of]{style="font-weight: 400;"} [[nuclear transplantation
and
cloning]{style="font-weight: 400;"}](https://www.nature.com/articles/182064a0)[.
In 1958, John Gurdon cloned a sexually mature
]{style="font-weight: 400;"}*[Xenopus
laevis]{style="font-weight: 400;"}*[ toad by transferring a nucleus from
the somatic cells of a ]{style="font-weight: 400;"}*[Xenopus
laevis]{style="font-weight: 400;"}*[ tadpole into an unfertilised
]{style="font-weight: 400;"}*[Xenopus laevis
]{style="font-weight: 400;"}*[egg.]{style="font-weight: 400;"}

[Despite the immense understanding of
]{style="font-weight: 400;"}*[Xenopus]{style="font-weight: 400;"}*[
early development, there is a gap in our knowledge for the more advanced
stages of development from premetamorphosis tadpole to adult. As Dr.
Jakub Harnos from Masaryk University (Czech Republic), a lead scientist
of the G*igaScience* study, explained:]{style="font-weight: 400;"}

> *["Xenopus laevis, the African clawed frog, is a versatile vertebrate
> model organism in various biological disciplines, prominently in
> developmental biology to study body plan reorganization during
> metamorphosis.  However, a notable gap exists in the availability of
> comprehensive datasets encompassing Xenopus' late developmental
> stages."]{style="font-weight: 400;"}*

### **MicroCT Imaging of** ***Xenopus laevis***

[Towards this end, the authors used micro-computed tomography (MicroCT),
a non-invasive 3D imaging technique, to more accurately describe
]{style="font-weight: 400;"}*[Xenopus
laevis]{style="font-weight: 400;"}*[ development. A key advantage of
MicroCT is micrometre-scale resolution. In *GigaScience* we have
[previously published](https://doi.org/10.1093/gigascience/giac030)
similar 3D-imaging datasets of the proteus, a mysterious cave-dwelling
salamander, to reveal adaptations for life in the dark (see
[blog](http://gigasciencejournal.com/blog/proteus-imaging/)).  
]{style="font-weight: 400;"}

[X-rays used in MicroCT imaging are ideally suited for visualising
skeletal components. In addition, through the use of contrast agents,
MicroCT can also be used to visualise soft tissues, such as the brain
and alimentary system.]{style="font-weight: 400;"}

[The ]{style="font-weight: 400;"}*[Xenopus
laevis]{style="font-weight: 400;"}*[ stages of development were
carefully chosen with reference to specific morphological structures,
such as the presence and dimensions of legs and the tail, or
rearrangements of the head.]{style="font-weight: 400;"}

[By capturing development at multiple stages, the authors have created
an anatomical atlas, which is an immensely useful spatiotemporal
reference framework that enables researchers to more accurately
understand developmental dynamics.]{style="font-weight: 400;"}

::: {#attachment_5857 .wp-caption .alignnone style="width: 522px"}
![MicroCT atlas of Xenopus laevis
development](http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_01.png){.wp-image-5857
.size-full fetchpriority="high" decoding="async"
aria-describedby="caption-attachment-5857" width="512" height="172"
srcset="http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_01.png 512w, http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_01-300x101.png 300w"
sizes="(max-width: 512px) 100vw, 512px"}

MicroCT was used to generate an anatomical atlas of the African clawed
frog (*Xenopus laevis*).
:::

[To illustrate the utility of this 3D imaging resource, the authors
highlight salient changes that were observed during metamorphosis, and
during sexual differentiation.]{style="font-weight: 400;"}

### **Visualising Metamorphosis using MicroCT Imaging**

[Through detailed analysis of the 3D reconstructions at the various
stages of development, the authors highlighted that it was possible to
pinpoint key changes that are occur in
]{style="font-weight: 400;"}*[Xenopus]{style="font-weight: 400;"}*
*[laevis]{style="font-weight: 400;"}*[ from premetamorphosis,
prometamorphosis, and climax metamorphosis stages, through to froglet
and mature adult stages.]{style="font-weight: 400;"}

::: {#attachment_5860 .wp-caption .alignnone style="width: 510px"}
![3D reconstructions of developing skull of Xenopus laevis from MicroCT
imaging](http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_02-300x131.png){.wp-image-5860
decoding="async" aria-describedby="caption-attachment-5860" width="500"
height="218"
srcset="http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_02-300x131.png 300w, http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_02-1024x446.png 1024w, http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_02-768x334.png 768w, http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_02.png 1186w"
sizes="(max-width: 500px) 100vw, 500px"}

3D reconstructions of developing skull of *Xenopus laevis* from MicroCT
imaging.
:::

[There were notable changes in the morphology of the head, as determined
by morphometric analysis at multiple stages of development. Most
striking was a progressive decrease in eye distance with advancing
development. As the authors explained:]{style="font-weight: 400;"}

> *["These changes actually occurred in Xenopus in two phases: a gradual
> increase in the pre-metamorphic stages followed by a peak at the onset
> of climax metamorphosis and finally, a decrease to a compact head
> configuration in froglets and adult
> frogs".]{style="font-weight: 400;"}*

[The authors additionally speculate on the evolutionary implications of
developmental trajectory:]{style="font-weight: 400;"}

> *["This adaptation aligns well with the frog's life strategy,
> transitioning from a water-dwelling tadpole with lateral eyes to an
> adult with eyes positioned on top of the head for a submerged
> lifestyle, reminiscent of crocodilians". ]{style="font-weight: 400;"}*

[There were additional changes in the morphology of the alimentary
system. As the authors state:]{style="font-weight: 400;"}

> [These observations on gut coiling morphogenesis, as captured by
> MicroCT imaging, would be very difficult to study by other
> means.]{style="font-weight: 400;"}

### **Sexual Dimorphism in** ***Xenopus laevis***

[Sexual dimorphism, which is the phenomenon where the different sexes of
a species exhibit different morphological characteristics, is
particularly prominent in adult *Xenopus laevis*, where the female is
significantly larger than the male.]{style="font-weight: 400;"}

[Through morphometric analysis of the 3D volumetric models, the authors
were able to compare growth patterns. As the authors
explained:]{style="font-weight: 400;"}

> *["Based on our micro-CT analysis, in terms of sex, we found that
> adult females can be viewed as essentially enlarged males, indicating
> a proportional growth
> pattern"]{style="font-weight: 400;"}*[.]{style="font-weight: 400;"}

 

::: {#attachment_5859 .wp-caption .alignnone style="width: 510px"}
![Sexual Dimorphism in Xenopus
laevis](http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_03.png){.wp-image-5859
loading="lazy" decoding="async"
aria-describedby="caption-attachment-5859" width="500" height="361"
srcset="http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_03.png 922w, http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_03-300x217.png 300w, http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_03-768x555.png 768w"
sizes="(max-width: 500px) 100vw, 500px"}

Sexual dimorphism is particularly prominent in adult *Xenopus laevis*,
where the female is significantly larger than the male.
:::

[The authors report that size difference is related to sex-related
differences in growth of the cartilaginous skeleton. The skeleton first
develops as cartilaginous condensations prior to calcification into
bone. As the authors explained:]{style="font-weight: 400;"}

> *["After climax metamorphosis, no proliferative ossification occurs,
> and the process is limited to the calcification of cartilage,
> irrespective of the frog's sex."]{style="font-weight: 400;"}*

### **Hidden Anatomy: Toad's Teeth**

[The authors additionally highlighted how 3D imaging was used to uncover
morphological detail in anatomical components that were otherwise quite
difficult to visualise. The authors used craniofacial development, and
specifically teeth patterning, as an illustrative example. As the
authors say on this:]{style="font-weight: 400;"}

> ["*Upon initial observation, the presence of teeth in X. laevis may
> not be readily apparent.*"]{style="font-weight: 400;"}

[The authors further explaining:]{style="font-weight: 400;"}

> ["]{style="font-weight: 400;"}*[This is due to the fact that teeth
> were exclusively found in the maxilla, referred to as maxillary teeth
> and behind the maxillary arch on the vomeral bone -- so-called vomeral
> teeth... In contrast, the mandible contains no
> teeth]{style="font-weight: 400;"}*[".]{style="font-weight: 400;"}

 

::: {#attachment_5858 .wp-caption .alignnone style="width: 510px"}
![Morphometric analysis of teeth in MicroCT Imaging 3D reconstructions
of adult Xenopus
laevis](http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_04.png){.wp-image-5858
loading="lazy" decoding="async"
aria-describedby="caption-attachment-5858" width="500" height="485"
srcset="http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_04.png 806w, http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_04-300x291.png 300w, http://gigasciencejournal.com/blog/wp-content/uploads/2024/07/Xenopus_04-768x745.png 768w"
sizes="(max-width: 500px) 100vw, 500px"}

Morphometric analysis of teeth in 3D reconstructions of adult *Xenopus
laevis*.
:::

[At
]{style="font-weight: 400;"}*[GigaScience]{style="font-weight: 400;"}*[,
we wonder if citizen scientists will uncover additional hidden
anatomical components in the ]{style="font-weight: 400;"}*[Xenopus
laevis]{style="font-weight: 400;"}*[ 3D anatomical
atlas.]{style="font-weight: 400;"}

### **3D Printable Models of** ***Xenopus laevis*** {#d-printable-models-of-xenopus-laevis}

[At
]{style="font-weight: 400;"}*[GigaScience]{style="font-weight: 400;"}*[,
we see immense value in this 3D anatomical atlas as a spatiotemporal
framework to understand vertebrate development . To enable researchers,
and also the 3D modelling and 3D printing community to easily access
printable 3D models, we have generated a collection of 40
surface-rendered 3D models from the
]{style="font-weight: 400;"}*[Xenopus
laevis]{style="font-weight: 400;"}*[ anatomical atlas at multiple stages
of development. These models can be interactively explore using
SketchFab, and the set of 3D printable models are additionally available
from the 3D printing community repository
[Thingiverse](https://www.thingiverse.com/thing:6620040).]{style="font-weight: 400;"}

[There is a collection of 30 SketchFab models of
]{style="font-weight: 400;"}[*[Xenopus
laevis]{style="font-weight: 400;"}*[
development]{style="font-weight: 400;"}](https://sketchfab.com/GigaDB/collections/xenopus-laevis-development-3922d82fde27407ea1e7cc4622376178)[,
where the sex is not specified, that includes interactive models of
various anatomical components.]{style="font-weight: 400;"}

[In addition, there is a collection of 5 SketchFab models of
]{style="font-weight: 400;"}[*[Xenopus
laevis]{style="font-weight: 400;"}*[ adult
male]{style="font-weight: 400;"}](https://sketchfab.com/GigaDB/collections/xenopus-laevis-male-7eb069e65d2f49749ce4b4144dd5fc81)[,
and a collection of 5 SketchFab models of
]{style="font-weight: 400;"}[*[Xenopus
laevis]{style="font-weight: 400;"}*[ adult
female]{style="font-weight: 400;"}](https://sketchfab.com/GigaDB/collections/xenopus-laevis-female-b33299ca19604663a0cbdeb915f683e9)[,
that includes interactive models of the skeletal system, brain, and
alimentary system. With examples embedded in the
[paper](https://doi.org/10.1093/gigascience/giae037) using our
[Sketchfab
integration.](http://gigasciencejournal.com/blog/interact-with-the-crabs-in-your-computer-new-gigadb-imaging-widgets/)]{style="font-weight: 400;"}

[For a step-by-step guide on how to 3D print the data from a scientific
publication such as this see our previous
[Blog ](http://gigasciencejournal.com/blog/a-step-by-step-guide-to-3d-print-a-scientific-publication/)and
[video](https://youtu.be/EHSbeDFN_k8?si=l5UuRmYL6_VDlQZp).  
]{style="font-weight: 400;"}

[The MicroCT data (8-bit TIFF format) 3D reconstructions (STL format)
are available for download from
]{style="font-weight: 400;"}[[Zenodo]{style="font-weight: 400;"}](https://doi.org/10.5281/zenodo.10951411)[.
Supporting metadata and movie files are additionally available from
]{style="font-weight: 400;"}[[GigaDB]{style="font-weight: 400;"}](https://doi.org/10.5524/102534)[. ]{style="font-weight: 400;"}

### **References**

Laznovsky J; Kavkova M; Reis A; Robovska-Havelkova P; Maia LA; Krivanek
J; Zikmund T; Kaiser J; Buchtova M; Harnos J (2024). Unveiling
Vertebrate Development Dynamics in Frog *Xenopus laevis* using Micro-CT
Imaging. *GigaScience* giae037
<https://doi.org/10.1093/gigascience/giae037>

 

The post [MicroCT Imaging of Metamorphosis in the African Clawed
Toad](http://gigasciencejournal.com/blog/3d-models-of-metamorphosis-microct-imaging-african-clawed-toad/){rel="nofollow"}
appeared first on
[GigaBlog](http://gigasciencejournal.com/blog){rel="nofollow"}.


<em>
 MicroCT imaging is an exceptional tool for 3D visualisation. A new Data Note published in GigaScience reports on a unique, high-quality series of MicroCT images that covers the lifespan of an amphibian from tadpole to froglet to mature adult frog.
</em>

Messaggi di Rogue Scholar

MicroCT Imaging of Metamorphosis in the African Clawed Toad