Updates

Okay, here are the updates for the week. I've finished both iguanas, photographed them completely, and I'm now on to completing my findings for the project. As I have explained before, this involves drawing comparisons between the iguanas, pigs, and cats. Obviously these are all quadrupeds, and therefore their muscles have a certain amount of similarities, but they are all different animals. Iguanas have a sprawling posture, their legs and arms extending beyond their bodies. Pigs are ungulates; the muscles are focused on keeping their bodies supported and allowing them to move forward and backward, in a single plane. Cats are carnivores, and hence their forelimbs are involved in prey capture and require a more specialized form. 

Hopefully within the next week I will be dissecting and photographing a fetal pig, which will allow me to show direct muscle comparisons between the iguanas and the pig, including a weight difference analysis as well as how their muscles differ with response to locomotion. 

I'm working on the first slides of the slide show right now, detailing the objective (which has changed several times), and the materials and methods. I'm also going through sources looking for information I can use for comparison. This is enormously frustrating because whenever you do a lit search, you seem to never find exactly what you want. I would like to find studies that are similar to what I've done -- a dissection, followed by detailed muscle descriptions, weights, and a locomotion analysis. Unfortunately, I haven't yet stumbled upon the perfect article, so I am just pulling bits and pieces from everything. 

Really?

So this week was pretty productive. I finished dissecting, photographing, and everything else - ing on Tuesday. It's pretty exciting to be done with both specimens. For the rest of the week I worked on putting together my presentation, which right now means analyzing data. Because of how my project has changed, "data analysis" is basically taking the muscle data I have for the iguanas and comparing it to other animals, particularly cats and pigs. These two were chosen because there has been so much research done on them, information is abundant. All three of the animals also have different habitats, and differing forms of locomotion. 

At the lab meeting this week, we read a pretty cool animal about extinct porcupines. Did you know that they can climb trees, along with goats and grey foxes? Well they can, and it is presumed that their ancestors could as well, this being deducted from their fossils. This may perhaps be quite a leap though. Today when we look at a species, we analyze their behavior, relate this to their musculature and then connect this with their bones. With fossils, this processed is reversed. Bones are looked at for robustness, bony landmarks, relative length and composition as well as muscle scars and attachments. These things are used to determine where muscles were and their possible actions, and this is then used to determine locomotion, environment, as well as the phylogeny of its descendants and ancestors. But it's certainly not an exact science, and sometimes things seem just a little far fetched.

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Opposites Attract

The study for this week looked at the distal forelimb musculature of the genus of lizards Liolaemus, which includes a particular species of sand lizard Liolaemus wiegmannii (Abdala and Moro 2006). I thought it would be interesting to compare their analysis with my own of the iguana considering their two very different forms of locomotion -- digging and walking in the sand vs. climb trees and swimming. The study went through all of the muscles in what we would call the forearm -- extensor carpi radialis, extensor digitorum, extensor carpi ulnaris, flexor carpi ulnaris, flexor digitorum (palmaris longus), flexor carpi radialis, as well as the muscles of the manus, which I did not analyze in the iguana. 

The article went through and wrote up muscle descriptions similar to how I wrote up muscle descriptions, commenting on the origin, insertion, and any other features of note. As I went through, I noticed there were slight differences between the two species, but nothing of particular note. I found this a little odd, considering the differences between iguanas and sand lizards, until I got to the conclusion of the article. It basically said that the general morphology of the forelimbs in lizards remains consistent across species. That because the set up is so general, it is easily used for many different forms of locomotion, and nothing is required to specialize over much. This is interesting because often times people study the specialization of species, why their musculature is different from everyone else and why this matters. But in this case, it's really the opposite. 


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Abdala, Virginia and Silvia Moro. "Comparative Myology of the Forelimb of Liolaemus Sand Lizards (Liolaemidae)." Acta Zoologica(2006) 87.1: 1-12. Web. 19 Apr 2012. 

Time Will Tell

Alright, this week in the lab, I started Iguana 2. As expected, it was very similar to the first iguana except for the fact that it was much smaller. This is a little ... off putting. Things don't look much different, but they are much smaller and this makes things slightly more difficult to find. The muscles thus far have weighed about half as much as the first iguana, which makes sense as the lizard is about half as big. Overall, not much to say. 

I'd also like to brief everyone on the changes to my project. Due to the time it took to dissect the first iguana as well as the shortness of time in general, the goals of the project have been modified. As you may have guessed, I am no longer working with anoles at all, as my original proposal suggested. The anoles are significantly smaller than the iguanas and it was easier for me to begin on a larger animal. Though I did have dissection experience prior to this project, I have never done something this in depth and hence was a little unprepared. I will also not be comparing the iguanas to any other lizards. Time just became too short, and it was only practical to dissect two lizards. I will instead be comparing the iguanas to mammals that are well documented - pigs and cats mainly. Lizard musculature differs from these mammals due to their habitat (trees and beaches), their posture (sprawling), and the fact that they are not mammals. I think it's a pretty cool comparison. 

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Means vs. Ends

Alright, the article for this week covers two subjects. The first is, you guessed it, iguanas. Specifically, general iguana ecology (was that an oxymoron?). It covers temperature preference, nesting and feeding habits. The second issue is an ethical one. 

Iguana body temperatures ranged from 34.0 degrees to 37.2 degrees Celsius (Hirth, 1963). This is 93.2 degrees to 98.96 degrees Fahrenheit, which is surprisingly not that far from human body temperatures. The air that they tended to reside in was 28 degrees C (82.4 F) to 32 C (89.6 F). Larger iguanas tended to rest in trees, while younger and smaller iguanas rested on the beach and none of the iguanas were ever far from the river or some other source of water. The scientists in the study believed this all had to do with thermoregulation. The water was a quick way for iguanas to cool down while the tree canopy offered heavy insulation, preventing loss of body heat. Remember that iguanas are cold blooded and hence cannot regulate their body temperature thus many of their adaptive behavior relates to thermoregulation.

Iguanas are herbivores, as mentioned before, surviving mainly on leaves and fruits. It has been found that young iguanas may feed on insects, however. As far as nesting goes, iguanas lay eggs in early spring, the most arid part of the year. The eggs are laid on the beach in spots that it takes the female iguanas some time to find. The scientists were not clear on what exactly the female iguanas were looking for, only that they searched for a significant amount of time to find a nesting site. 

As cool as all this iguana stuff is, the most interesting part of the article for me was the techniques used. In order to determine the body temperatures of the iguanas, the lizards were shot with .22 caliber rifle and then their temperature as well as the temperature of the surrounding area was taken as soon as possible. This seems a little ... out of line to me. The study was published in 1963, a time during which animal cruelty standards may have been different, but I'm not sure whether what was gained justified the shootings. Food for thought. 

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Hirth, Harold F. "Some Aspects of the Natural History of Iguana iguana on a Tropical Strand." Ecology (1963) 44.3: 613-615. Web. 11 Mar 2012.

Darwin Strikes Again

Integrative organismal biology (IOB). Not a term you hear everyday, but it refers to a part of biology that focuses on the ecology, behavior, and evolution of organisms. My paper for today is about the IOB of marine iguanas, a species closely related to the green iguanas I am working on (Wikelski and Romero, 2003). The study used a method of predicting evolution as the basis for its work. The idea is that if you study the performance of specific organisms you can determine which factors play a role in the selective process of evolution and then use these factors to predict how the species will evolve in the future. 

This study, "Body Size, Performance and Fitness in Galapagos Marine Iguanas," used foraging and reproductive performance as the factors to predict evolution. The reason marine iguanas were chosen as the model is because the body mass of iguanas on different islands can vary by one order of magnitude, adult iguanas really have no predators, and they don't compete with other vertebrates for food (iguanas eat the red and green algae revealed at low tide). This means that there is a ... regulated form of evolution occurring. The changes taking place are based on the iguanas alone, not on other species. 

The study found that larger marine iguanas, male or female, had better reproductive success. The females because they could produce larger babies which were more likely to survive and the males because they were able to control a larger territory and put on a better show for thefemales. However, being large comes with draw backs. The larger iguanas had far less foraging success. They had to expend more energy to move their larger masses, it takes more energy to heat a larger body (the whole cold blooded issue), and in the end, they had trouble getting enough food. When times were good, and algae abundant, the larger lizards did fine. However, when times were bad, like after a hurricane, it was the big lizards that died. 

The conclusion that was drawn from this data is that marine iguanas will continue to get bigger. Not only does reproductive success increase, but the world is getting warmer and that's good for the cold blooded species. However, their size will be regulated by the lack of foraging success. Bigger lizards need more food and sometimes it's just not there. Don't expect any giant iguanas anytime soon. 

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Wikelski, Martin and L. Micahael Romero. "Body Size, Performance and Fitness in Galapagos Marine Iguanas." Integrative and Comparative Biology(2003) 43.3: 376-386. Web. 4 Apr 2012. 

Uncertainty

I'm done with Iguana 1! The forelimbs of my first iguana have been completely de-muscled and now ... well they're just kind of bone that is barely attached to anything. I finally removed all of the deep muscles - the pronator teres, supinator manus, teres major, subscapularis, and the others. It was surprising that while some of the deep muscles were quite small, the majority of them were actually larger than the superficial muscles. For example, the teres major, which is a deep muscle of the back (one of the many that originates from the scapula) weighed significantly more than the trapezius and latissimus dorsi (both superficial muscles). With regards to the brachialis/brachioradialis issue I decided that there was only one muscle there and the muscle had been named differently by the different sources. The muscle itself seems to be more similar to the human brachioradialis as it has its insertion point on the radial shaft. It may be a fusion of the two muscles. 
 
Anyway, I can now start on my second iguana. The process for this one will be the same as the first, but I believe it will go much faster due to the experience I gained with the first. Skinning will hopefully only take one day, and then there is superficial identifications and separations, pictures, and then muscle removal. I already have my muscle catalogue complete, so with the second iguana I have to check with the catalogue and ensure that they agree. If they don't, I have to make a note and take further pictures of the area even though the specimen will have already been photographed. There can actually be quite a bit of difference between different samples of the same species. It is important to remember that bodies are adaptive and everything an animal does, eats, hears, sees, etc change its body chemistry and set up. There is a muscle in the human leg that 8% of humans don't have. Don't you just love the uncertainty?
 
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It's All ... Lizard to Me?

This week in the lab was ... not as productive as hoped. On Tuesday, I got a lot done. All the of the superficial muscles on my iguana were removed and weighed, revealing the deeper muscles below. Taking the muscles off was pretty simple. The hardest part was ensuring that the cut was made as close to the bone as possible. Because I am weighing the muscles for comparative purposes, it it important for the entire muscle to come off, and not just part. This was difficult because I was not familiar with the iguana skeleton. First of all, their clavicles extend all the way around their necks like a collar and they have a second interclavicle below acting like the clavicle in humans. Their sternum, instead of being a single line of bone as in humans, is almost a breastplate covering most of the chest. Some of the muscles that must be removed are attached underneath these bones, so it takes some maneuvering to get them out. 

Friday was an off day. I ended up getting sick and leaving early which means I missed out on almost an entire day of work. So next week I have to catch up and remove the deep muscles of the iguana. There really aren't that many, the problem is identifying them. For example, according to my iguana atlas (Oldham et al, 1975), iguanas have a brachialis muscle, but no brachioradialis. However, this source has been weak in identifying deep muscles. Another source on the forelimb muscles of monitor lizards (a species similar to iguanas), claims that there is only a brachioradialis and not a brachialis (Haines, 1939). However, this brachioradialis inserts and originates at almost the same place as the brachialis of the first source. Then there is the veterinary textbook I've been using (Dyce, 2002) that only references a brachialis muscle. But it uses the forelimb of carnivores for this, and iguana are not carnivores. And then there is the iguana itself. There appears to be only one muscle at the juncture of the elbow between the humerus and radius. There are several possible explanations for this. The first being that all the sources are speaking of the same muscle and have just named them differently. The second is that there are two muscles, but the sources all had different focuses and didn't mention them both. The third would be that there is a conflict in the scientific community about this particular muscle and no one really knows if there is one muscle, two muscles, a fused muscle, or some other variation. Welcome to the academic world.



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Dyce, KM, et al. Textbook of Veterinary Anatomy. St. Louis: Saunders, 2002. Print.

Oldham, Jonathan Clark and Hobart Muir Smith. Laboratory Anatomy of the Iguana. Dubuque: WC Brown,   1975. Print.

Haines, R. Wheeler. "A Revision of the Extensor Muscles of the Forearm in Tetrapods." Journal of Anatomy (1939) 73.2: 211-233. Web. 29 Mar 2012.