American Alligator

The Organ Lab is excited to feature alligators from the chest freezer of the newest member of the IUSM Department of Anatomy and Cell Biology, Dr. Margaret McNulty. Dr. McNulty previously served on the faculty of the Louisiana State University School of Veterinary Medicine. She is a comparative anatomist with a strong research interest in comparative anatomy, and a fascinating collection of anatomical specimens. Here is the story of some of them...

The vast majority of veterinarians (DVMs) will go into small animal, large animal, or mixed practice, treating one or all of the “Big 4” taxa (dogs, cats, horses, and cattle) or other domestic animals like poultry, pigs, and goats. However, there are some who pursue more non-traditional career paths, including exotic medicine, zoo medicine, wildlife medicine, or research, such as our friends the Gorilla Doctors of the Moutain Gorilla Veterinary Project at UC-Davis. As students, veterinarians with interests in non-traditional careers must find opportunities to get exposure to the animals that they do not encounter regularly in the traditional DVM curriculum. Therefore, many student groups organize wet labs or seminars outside of normal course hours to enhance their learning and skills necessary to practice good medicine upon graduation. A couple years ago, Dr. McNulty, in conjunction with a wildlife veterinarian and a veterinary anatomical pathologist, was invited to participate in a wet lab for professional veterinary students focusing on proper handling, routine medical procedures (e.g. blood draws), euthanasia, and necropsy procedures for alligators.

In Indiana, alligators are obviously very rare. But along the Gulf Coast, from North Carolina to Texas, alligators are almost as common as white-tail deer in the Midwest. The American alligator (Alligator mississippiensis) is the largest reptile in North America. When they hatch, they are approximately 8-12 inches in length, and they can grow between 2 and 12 inches per year. Females will usually top out at approximately 9 feet in length (200+ pounds) and males can be over 13 feet long and 500+ pounds. Alligators are found most commonly in Louisiana, and are a large part of the heritage and economy in that state. In fact, the alligator industry in Louisiana is valued at over $700 million dollars. To that end, Louisiana started an alligator ranching program in 1986; this program allows incubation and hatching of eggs as well as raising and harvesting alligators for various purposes (e.g., meat for human consumption, hides). Alligators that are not harvested are tagged and released back into the wild, to be tracked by the Louisiana Department of Wildlife and Fisheries. These released alligators provide data regarding growth, survival, and dispersal rates that are used to monitor and adjust regulations.

For a veterinarian wishing to practice any sort of wildlife or exotic medicine along the Gulf Coast, especially Louisiana, knowledge of how to handle these animals properly is critical to both the safety of the alligator as well as the veterinarian. Outside of the normal daily interaction with these animals, alligators are also commonly used in a research setting, as they have virtually remained untouched from major evolutionary change for several million years. Therefore they provide a unique opportunity to study anatomical adaptations that have persisted for long stretches of time.

3D rendering of a microcomputed tomography scan of the skull (gray), brain endocast (blue), and trigeminal nerve (yellow) of a juvenile alligator. of a juvenile alligator. From George and Holliday, 2013.

One of the most fascinating characteristics of modern crocodylians (Order Crocodylia, to which alligators belong) is their derived sense of face touch. Sensory information to the face in vertebrates is conveyed through the fifth cranial nerve (Trigeminal nerve). In crocodylians, numerous trigeminal-nerve innervated pressure receptors are present in a speckled pattern across the face and lower jaw. These dome-shaped receptors sense mechanical stimuli like splashing in water while the face is partially submerged. This is one of the mehcanisms by which alligators (and other crocodylians) can sense their prey. Interestingly, the number of axons in the trigeminal nerve is negatively correlated with body size (or skull size), indicating that smaller crocodylians have higher axon density, and presumably finer sense of touch, than larger ones.

Contributed by Margaret McNulty, PhD, and Jason Organ, PhD

Have you ever wondered about the differences between alligators and crocodiles? You can learn about those differences here.


References:
 
George, I., & Holliday, C. (2013). Trigeminal Nerve Morphology in and Its Significance for Crocodyliform Facial Sensation and Evolution The Anatomical Record, 296 (4), 670-680 DOI: 10.1002/ar.22666

Holliday, C., & Witmer, L. (2007). Archosaur adductor chamber evolution: Integration of musculoskeletal and topological criteria in jaw muscle homology Journal of Morphology, 268 (6), 457-484 DOI: 10.1002/jmor.10524

Red Kangaroo

After a blogging hiatus over the summer, The Eatles are back at it, telling the world about the fascinating animals they're consuming. Several years ago, the Organ Lab was fortunate to obtain a nearly adult, male red kangaroo (Macropus rufus) from our contacts at Grant's Farm in St. Louis, MO. After spending a considerable amount of time in a chest freezer in the Organ Lab, this summer with the help of IUSM Anatomy Education graduate students Jessica Byram and Naomi Schmalz, we began a systematic dissection and description of the lower limb musculature. Our plan is to get these descriptions published in a peer-reviewed journal. When we do, we will update this post with a link to the paper. In the meantime, it is worth pointing out a few reasons that kangaroo anatomy and biology is interesting.

Kangaroo foot skeleton

www.gutenberg.org

Red kangaroos are the world's largest marsupial mammal. When a baby kangaroo, or joey, is born, it is not fully developed; instead, the cherry-sized newborn climbs its mothers fur until it reaches an external pouch - a marsupium - on the front of her body where it can continue to develop while nursing for the next several months. This is where we get the term "marsupial". 

Red kangaroos live in the deserts and open grasslands of Australia, and they gather in groups called mobs. They are members of the Macropodidae family, of which all genera in the family have skeletons that are highly specialized for jumping. The forelimbs are usually small and are used for slow movements on all four limbs or for handling food. The hindlimbs, however, are elongated and the foot has no big toe (hallux, digit 1). The loss of the hallux is a direct result of specialization for running or hopping, which requires more reliance on the fourth toe, which bears the largest proportion of force while in contact with the ground. Therefore, kangaroos become functionally two-toed during locomotion (digits 4 and 5 bear the load), especially during rapid (bipedal) locomotion. The running and hopping ability of large kangaroos like the red kangaroo is outstanding. On level ground, kangaroos can reach speeds of close to 70 kilometers per hour, and individual leaps can cover distances of nearly 14 meters and heights of 3.5 meters. The tail serves an important rudder function to help steer the kangaroo at high speeds.

Male red kangaroos are solidly built with strong musculature attached to their robust skeletons. When competing for mates, males often lean backward on their large tails and fight each other with their hindlimbs. Females are smaller than their male counterparts and often have a blue-tinted pelage (fur), which is why they are often referred to colloquially as "Blue Fliers".

Contributed by Jason Organ, PhD.

For information about red kangaroos, see these papers:

McCarthy, M. (1996). Red Kangaroo (Macropus rufus) Dynamics: Effects of Rainfall, Density Dependence, Harvesting and Environmental Stochasticity The Journal of Applied Ecology, 33 (1) DOI: 10.2307/2405014 

Sharman, G., Frith, H., & Calaby, J. (1964). Growth of the pouch young, tooth eruption and age determination in the Red Kangaroo, Megaleia rufa CSIRO Wildlife Research, 9 (1) DOI: 10.1071/CWR9640020 

Sonnabend, D., & Young, A. (2009). Comparative anatomy of the rotator cuff Journal of Bone and Joint Surgery - British Volume, 91-B (12), 1632-1637 DOI: 10.1302/0301-620X.91B12.22370

African Grey Parrot

African Grey Parrot, Courtesy of Animalia, Inc.

The Organ Lab is excited to partner with Animalia, Inc., to provide high quality skeletal material for public science outreach events. Animalia is a non-profit public charity dedicated to connecting people to animals and nature. Through its numerous presentations of live animals during education outreach programs in schools, libraries, etc., Animalia helps tens of thousands of children each year engage with nature, in order to foster appreciation, conservation, and responsible care for natural habitats and animals. Because Animalia is licensed by the USDA and permitted through the U.S. Fish and Wildlife Service and Indiana Department of Natural Resources for wildlife education, possession, and rehabilitation of wild and captive animals, our partnership allows us to bring a wide variety of interesting critters for The Eatles to snack on, and for you – the readers – to feed your brains!

Our first Animalia-supplied animal is an African grey parrot (Psittacus erithacus). These birds are legendary for their vocal mimicry of a diverse array of sounds and human speech. More impressive, however, is that there are anecdotes suggesting these animals are capable of basic addition and subtraction for numbers less than 8, and that they can use correct names of numbers when counting. African grey parrots can live up to 60 years. Therefore, keeping them as pets is a lifelong investment - financially and emotionally. They build strong relationships with their caretakers and that relationship needs to be nurtured and carefully managed. Their hooked beak is strong enough to crack a nut yet delicate enough to pick flowers (and eat them). They are excellent climbers, using their beak and feet like hands to grip, grab, and hold on.

The African grey parrot has, as one would suspect, grey feathers of varying shades covering its head; over its body, the grey color darkens on its wings. Its tail, however, is a distinctive bright red, making it instantly recognizable. It has a black beak and feet with bare white skin on the face around a yellow eye with a black pupil. More specific information about the cranial anatomy of this marvelous creature can be found in this dissection video from the WitmerLab at Ohio University.

Originally from the lowland forests of West Africa, throughout the dense forests of the Congo in Central Africa, and into the wooded savannah of East Africa, this species is listed as Vulnerable by IUCN due to trapping hundreds of thousands of wild birds for export for the pet trade. Sadly, up to 90% of these birds die before reaching their destination. Even with trade limits and quotas placed by international agencies, many African nations lack the capacity to manage these limitations and illegal trade persists. Before purchasing a parrot as a pet, find out its origin and determine if you have the ability to care for the animal for the next 60 years. To protect wild populations, only consider those that were bred in captivity.

Contributed by: Joel Vanderbush and Jason Organ, PhD.

References:
http://animaldiversity.org/accounts/Psittacus_erithacus/

Pepperberg IM (2006). Grey parrot numerical competence: a review. Animal cognition, 9 (4), 377-91 PMID: 16909236

White's Tree Frog

The Eatles have been busy munching away for the first time on a non-mammal vertebrate! Specifically, they are devouring the soft tissue remains of a White's Tree Frog (Litoria caerulea) from Grant's Farm in St. Louis, MO, named Nona.

White's Tree Frog. Photo from Animal Diversity Web.

Also known as the Smiling Frog, and the Dumpy Frog, this animal is fascinating. It belongs to the Hylidae family of frogs, which is an interesting group because it is united by a single morhpological character shared by all of its members (well, almost all...): claw-shaped terminal phalanges (bones of the fingers and toes). White's tree frogs are native to Australia, Indonesia, and New Guinea, and they live mostly in rainforests and coastal areas. They are usually bright green in color (before The Eatles get ahold of 'em), although the color of their skin can range from brown to light blue and even gray. These frogs are arboreal, as their name implies, and therefore their diet consists largely of insects like moths, locusts, and roaches. But that's not all! They also are known to eat other animals like spiders, worms, and even small mammals (rodents). Because their diet is varied, it is not surprising that they have multiple modes of prey capture. To capture small prey like insects, these frogs extend their sticky tongues and reel in the catch; but to capture larger prey like mice, they will pounce on their victim and force it into their mouth with their hands - much like college students devouring a pizza after a long night at the bar or Buddy the Elf...
 

One of the most interesting aspects of these animals, however, is their skin. Like all amphibians, they have thin, moist skin that can be easily penetrated by gasses and liquids. This allows them to breathe underwater through gas exchange, without aspirating fluid into their lungs. But the skin of the White's tree frog also possesses a waxy cuticle that prevents water evaporation, which enables it to live in areas farther from a water source, like arid regions or even inside someone's house (they are frequent house "guests" in Australia). The waxy cuticle is interspersed with skin glands that also help to keep it moist. Even more interesting than the waxy cuticle is the fact that the skin secretes a protein that is effective in killing the bacteria Staphylococcus aureus and also in lowering human blood pressure.

We hope you've enjoyed this little diversion into the amphibian world. We are excited to be fostering new relationships with local animal advocacy groups that will lead to more interesting animals being fed to The Eatles. More to come soon, we promise!

Contributed by: Jason Organ, PhD

If you want to read more about White's tree frogs, these papers are a good place to start: 

Boland MP, & Separovic F (2006). Membrane interactions of antimicrobial peptides from Australian tree frogs. Biochimica et biophysica acta, 1758 (9), 1178-83 PMID: 16580625  

Campbell CR, Voyles J, Cook DI, & Dinudom A (2012). Frog skin epithelium: electrolyte transport and chytridiomycosis. The international journal of biochemistry & cell biology, 44 (3), 431-4 PMID: 22182598  

Manzano AS, Abdala V, & Herrel A (2008). Morphology and function of the forelimb in arboreal frogs: specializations for grasping ability? Journal of anatomy, 213 (3), 296-307 PMID: 18565111

Domestic Dog - Osteoporosis Research

The evolutionary origin of the domestic dog (Canis lupus familiaris) is not well understood. DNA evidence suggests that the domestic dog diverged from its closest relative, the grey wolf (Canis lupus), sometime between 11,000 and 16,000 years ago, although a recent report pushes this date back to at least 27,000 years ago, which is in closer accord to the archaeological evidence that suggests a divergence around 36,000 years ago. And of course, once we humans assert our dominance over another species, we begin to tinker with it, in order to improve it. Today, the World Canine Organization (Federation Cynologique Internationale) recognizes over 340 breeds of domestic dog.

The most common breed of dog used in biomedical research is the beagle, and our laboratory is no exception. The Organ Laboratory does not take animal research lightly. Like every other laboratory at Indiana University School of Medicine, before we begin a study we are required to submit an animal protocol for review by the Institutional Animal Care and Use Committee (IACUC). The IACUC is comprised of university leaders, other researchers, veterinarians, and members of the general public. Every single procedure we wish to perform in an experiment must be approved by the IACUC prior to the initiation of the experiment. THIS. IS. CRITICAL. It is critical because animals, unlike people, are not able to give their informed consent to a procedure. Therefore, the IACUC assures that these animals will experience the least amount of discomfort and stress during any procedure. In fact, it is not uncommon to have more difficulty getting an animal study approved than it is to get a study approved for humans. Again, this is because humans can refuse to participate in a study, whereas a laboratory animal cannot. Because we study the mechanical properties of bone and muscle in a biomedical context, our work could not proceed without the use of vertebrate animals. Typically, our studies are carried out using laboratory rodents such as mice and rats because a whole lot is known about the genetic makeup of these animals, and we can control more variables because we can measure them with species-specific tools like biomarkers and DNA. Unfortunately, and perhaps due in part to size constraints, mouse and rat bone are inferior models of human bone. Why is that? Allow us to digress for just a moment…

Bones are dynamic tissues, and they are constantly remodeling out the numerous micro-cracks that materialize from normal wear and tear. This remodeling occurs when osteoclast cells resorb the bone matrix and osteoblast cells synthesize and lay down new bone where the old bone was removed. There are multiple places (envelopes) on any given bone where this type of activity occurs. One of the most important areas in human bone is the cortical shell surrounding the marrow cavity. Human cortical bone experiences a lot of intra-cortical remodeling, activity within the middle of the cortex.  Contrast this with rats and mice which typically only remodel on the inner and outer surfaces of cortical bone. Therefore, rodents make a poor research model if the question to be answered focuses on intracortical remodeling. Beagles, and dogs in general, do experience intracortical remodeling, and thus they are suitable animal models of human cortical bone.

The ultimate goal of the research described here utilizing a dog model is to improve treatment of osteoporosis by treating the underlying mechanisms that lead to fracture. Our most recent studies have investigated whether combining different types of anti-osteoporosis drugs might be more beneficial than using either one of the drugs alone. In particular, we combined two different classes of anti-catabolic drugs, meaning that these drugs prevent the loss of bone. There are two different classes of anti-catabolic agents used to treat metabolic bone diseases: bisphosphonates and selective estrogen receptor modulators (SERMs). Through our experiments, we have made several significant findings. Below, we highlight two of them.

First, we showed that 6 months of daily raloxifene treatment improves bone material mechanical properties as measured with reference point indentation (RPI). RPI is a novel tool used to assess mechanical properties of bone in vivo and has shown some ability to distinguish between fracture and non-fracture patients when used clinically. We were very excited to discover that raloxifene was effective in enhancing skeletal mechanical properties because we know the drug has little effect on bone mineral density. Subsequent studies utilized the same set of dogs to demonstrate that raloxifene increases cortical bone matrix-bound water, essentially increasing the hydration of the bone, and therefore increasing its material toughness. We hypothesize that this altered hydration is related to the known anti-fracture efficacy of raloxifene. Voila! A mechanism of action!

Some of the skulls in our outreach collection.

Once The Eatles are finished cleaning this skull, we will add it to our growing collection of animal skulls that we use for outreach programming. Over the years we have developed a number of initiatives that bring skeletal biology and functional anatomy to the classroom, and we can aim our programs for any grade level from preschool to high school. If you are in central Indiana and are interested in having one of us visit your classroom, please get in touch on twitter: @eatlemania

Contributed by: Neil Jain, Kelly Biro, and Jason Organ, PhD

References:

Allen MR, Territo PR, Lin C, Persohn S, Jiang L, Riley AA, McCarthy BP, Newman CL, Burr DB, & Hutchins GD (2015). In Vivo UTE-MRI Reveals Positive Effects of Raloxifene on Skeletal-Bound Water in Skeletally Mature Beagle Dogs. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research, 30 (8), 1441-4 PMID: 25644867

Allen MR, McNerny EM, Organ JM, & Wallace JM (2015). True Gold or Pyrite: A Review of Reference Point Indentation for Assessing Bone Mechanical Properties In Vivo. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research, 30 (9), 1539-50 PMID: 26235703 

Aref M, Gallant MA, Organ JM, Wallace JM, Newman CL, Burr DB, Brown DM, & Allen MR (2013). In vivo reference point indentation reveals positive effects of raloxifene on mechanical properties following 6 months of treatment in skeletally mature beagle dogs. Bone, 56 (2), 449-53 PMID: 23871851

Skoglund P, Ersmark E, Palkopoulou E, & Dalén L (2015). Ancient wolf genome reveals an early divergence of domestic dog ancestors and admixture into high-latitude breeds. Current biology : CB, 25 (11), 1515-9 PMID: 26004765