Hello everyone and welcome back. Well for starters let me just say this will be my last post about the salamanders. I hope that you enjoyed and learned something from reading my blog these last few weeks. Hopefully, I inspired you to do more research on the salamander or even start your own blog on this species. But enough of that lets dive right into this week’s topic.

    This week I found a research article that focused on the limb bone stress and loco-motor forces during the movement of a Salamander. Specifically, the researchers focused on the femur of the Tiger Salamander. Before we go deeper into the article, I listed a few words below with the definition so it can be easier to read.

• Ground reaction force (GRF)- the force exerted by the ground on a body in contact with it.
• Locomotion- the movement or the ability to move from one place to another place.
• Femur- a bone of the thigh or the upper hind limb.
• Ectothermic- any cold-blooded animal or an animal that regulates its body temperature.
• MATLAB- a programming language and numerical analysis environment that include matrix calculations, and data visualizations.

    In this research, the authors had two hypotheses. One being that the salamanders exhibit low limb bone loads and high safety factors like ectothermic, non-avian replies and that torsion is a prominent loading regime in the salamander femur as in other species that use sprawling limb posture (K.M. Sheffield and R.W. Blob).

    The researchers used a total of five adult Tiger Salamanders, 3 females and 2 males, and persuaded each salamander to walk in place by gently squeezing its tail. With the help of modern technology, the researchers were able to slow down the footage of the footsteps and record the data from the plate. Several graphs were made to show the lateral and posterior view of the GRF. the mean for the femoral bending factor was also calculated the worst being at 4.5 and the best at 10.5.

    In summary, the findings using a tiger salamander confirmed the most broad patterns found in other tetrapod lineages. The safety factors were at about 10.5 in bending which is a little higher than other salamanders and suggests that salamander femora might help the variability in femoral stresses.

    This founding now helps support the broader hypotheses of limb bone stress in other tetrapods. I thought that this experiment was interesting for two reasons. First off, I have never seen anything like this before so I just thought it would be interesting to read. Secondly, I think that if I understand how something this simple (not really simple, actually very complicated) it would be easier for me to understand the different stresses and movements of the human body.

Well, guys, that’s it. We have officially come to the end of our Salamander journey. I hope you guys enjoyed my blog as much as I enjoyed writing it for you!!!

K. Megan Sheffield, Richard W. Blob

Journal of Experimental Biology 2011 214: 2603-2615; doi: 10.1242/jeb.048736

http://jeb.biologists.org/content/214/15/2603.short

Hello everyone and welcome back to another week of learning about Salamander.

Let’s just do a quick recap before we jump into this weeks discussion. In the last blog, we discussed one unique feature of the salamander. The one unique feature we discussed was salamanders being able to rearrange their cells at their wound sites so they can regrow their body parts.

But enough of that, lets dive into today’s discussion, the taxonomy of the salamander with the help of a phylogenetic tree.Why do we use phylogenetic trees you may ask? Well, we use a phylogenetic tree to demonstrate the evolutionary history of most organisms.

   In this phylogenetic tree, the author compared 36 species that fall into the Ambystoma genus. There are several sister groups, and 9 are outgroups. An example of a sister group is the Ambystoma textanum and the Ambystoma barbouri.  This phylogeny tree was constructed by comparing morphological characters. What is a morphological characteristic? It is basically the shape or size of an organism. The Ambystoma Annulatum, Ambystoma Cingulatum, Ambystoma Mabeei, Ambystoma Barbouri, and the Ambystoma Texanum were grouped here based on specific characteristics of its skull. In the group containing the Ambystoma Tigrinum, it is branched off based on its geographical location. One thing that unifies the members of this genus together is their ability to regenerate their limbs. 

 

   In the picture above, there are two different phylogenetic trees. While looking for a second phylogenetic tree to compare, I noticed that many of the articles stated that Ambystoma has a phylogenetic conflict. To solve or bring light to the situation a group of people came together and made the two trees pictured above. The first tree that is labeled “A” is separated by morphological characters like the very first tree we discussed. There were 32 morphological characters used to compare each Ambystoma. The characteristics included size, the shape of the skull, and spinal muscles. The numbers that are on the branches represent bootstrap values. A bootstrap value is when random sets of data combined with the re-run of phylogenetic analysis are reported as a percentage.

   There for the sister group between the Ambystoma texanum and Ambystoma barbouri are well supported at being labeled closely related. In the second phylogeny tree “B” were based on a different hypothesis of Ambystoma. The authors also used morphology to different group Ambystoma. This tree also included the allozyme and mitochondrial sequence-based estimates. There were a total of 26 allozyme characters and the numbers on this tree represented jackknife values. Even though the authors were trying to show the difference in the two trees both still came out very similar.

Well, that’s enough for this week. Be on the lookout for the next post about this unique animal!!!!

 

 

 

 

References:

1. https://www.semanticscholar.org/paper/Species-tree-reconstruction-of-a-poorly-resolved-of-Williams-Niedzwiecki/ff86a8cac792c3e9c672c0373794a91560da4c3c
2. http://tolweb.org/Ambystomatidae/15448
3. https://books.google.com/books?id=x-ZhDwAAQBAJ&pg=PA48&lpg=PA48&dq=Kraus,+1988;+Shaffer+et+al.,+1991&source=bl&ots=FgqQel4m_r&sig=ACfU3U31stDcvKbiqFujMlXqxH9n7qbVdA&hl=en&sa=X&ved=2ahUKEwir_YWOg7_hAhXvp1kKHYKsCboQ6AEwAXoECAkQAQ#v=onepage&q&f=false