Glowing

Sagittal section of a Short-Tailed Opossum (Monodelphis domestica) at 14 days after birth. One of the final steps in the visualizing process we started here and here.  Fluorescent immunostaining for muscle (red), nerve tissue (green), and cell nuclei to visualize the outlines of the animal (blue). Check out those whisker pits!  Image credit: Curious Sengi.

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Remember those Short-Tailed Opossum (Monodelphis domestica) neonates from last week?  After some chemical treatments, the specimens were frozen into a cutting compound, and then sectioned into 300 micron (0.01 inch) thick slices on the cryostat.  Here are three slices from the same animal.  The sagittal sections (parallel to the midline that divides the body into right and left halves) show all sorts of wonderful details such as the chain of the vertebral column in white, developing bones of the skull, liver, gut, eye, and tongue.  These sections look amazing, but they are not done yet!  Come back to find out what happens next.  Image credit: Curious Sengi.

Chiaroscuro

A pair of Short-Tailed Opossum (Monodelphis domestica), 14 days postnatal.  Note the presence of hairs and whiskers on the face as well as the bones ossifying in the fore and hindfeet.  Image credit: Curious Sengi.

Greetings, fellow Snurflers!

We have now entered that season during the academic year when many of us are facing great hurdles:  qualifying exams and dissertation defenses.  I will be presenting my research proposal at quals in a few weeks and I wanted to share some of the images from my work with you.

My research on the evolutionary origin and subsequent modifications of facial muscles in mammals involves a lot of comparative morphology:  looking at a wide range of animals (including non-mammals) to piece together a picture of what is old and what is novel, ancestral and derived, conserved and innovative, and what is just plain weird.  I am using techniques and ideas from developmental biology to show the spatiotemporal sequence of how facial muscles grow and differentiate in different embryos, but to also shed light on some key processes behind the question of why muscles grow over the faces of mammals, but not in animals like reptiles.

At the moment, I am working a lot with the embryos and neonates of the Brazilian Short-Tailed Opossum (Monodelphis domestica), a marsupial that is increasingly being used as a model organism in laboratories.  The images here are of young opossums, collected 14 days after birth.  Like all other marsupials, gestation time is short and the babies are born in an extremely underdeveloped state where they are essentially all just forelimbs and a mouth.  Now a few weeks after birth, these little guys are starting to look much more like recognizable animals.

These photographs were taken after the specimens were bleached into a ghostly white.  There are more steps ahead before we can visualize the development of facial muscles.  See what happens next in our following posts!

Image credit: Curious Sengi.

Happy New Year (Again)!

chicken-embryo

Happy Lunar New Year and welcome to the Year of the Rooster!  Here is a chicken embryo nestled into a pillow of yolk and surrounded by a network of blood vessels.  The eye is clearly visible as a dark circle; the developing fore- and hindlimb and tail are also visible as projections from the pink body.  At this stage, the yolk membrane is extremely fragile and will rupture when the egg is cracked.  However, this one landed perfectly intact into a petri dish.  We use a lot of chicken embryos in our line of research, so I would like to take this moment to deeply thank them for their contribution to our science and teaching.  For me, the beauty of these embryos are also a potent source of wonder.  Image credit: Curious Sengi.

Pigs Without Hams

pig_diagram

Image credit: Pinterest.

In 1833, a letter from a Briton abroad was read before the Zoological Society of London.  The contents of this rather unusual correspondence was later published in the society’s journal:

A note from Col. Hallam was read. . . . of two individuals of a race of pigs with only two legs, the hinder extremities being entirely wanting.  The latter, Col. Hallam states, were observed ‘at a town on the coast in the Tanjore country [in India], in the year 1795:  they were from a father and mother of similar make, and the pigs bred from them were the same.’

So, three successive generations of pigs missing hindlimbs. . . .  essentially, pigs lacking hams.

Pig Amelia_3

Pig born without hindlimbs in 2011 in Anhui Province, China.  Image credit: Quirky China News / Rex Features via Daily Mail.

The congenital absence of entire limbs is a relatively rare condition termed amelia.  The lack of one or more limbs at birth is merely a symptom resulting from a variety of different causes, both internal and external.  Developmental abnormalities can be genetic (internal) or they can arise from exposure to toxins, chemical substances, physical trauma, and radiation at crucial points during pregnancy (external).  In addition, amelia can occur along with a suite of other deformities, especially in the face, or it can appear by itself in an otherwise healthy, normal individual.

It is these latter cases — adorable baby animals with missing limbs yet a plucky attitude — that have been enthusiastically picked up by news media.  In 2010, an amelic piglet was born in Henan Province, China and named Zhu Jianqiang (“Strong-Willed Pig”), eventually reaching quasi-celebrity status worldwide.  The pig’s owner, Wang Xihai, is quoted as saying:  “My wife asked me to dump it but I refused as it’s a life.  I thought I should give it a chance and unexpectedly it survived healthily (Daily Mail Reporter, 1 October 2010).”  He even helped the pig learn how to walk balanced on its forelegs in a handstand, which it did with great success in about a month.  At the time of the original news report, Zhu Jianqiang was still going strong and had obtained a healthy (albeit ham-less) weight of 110 pounds (50 kilograms).

Pig Amelia_1

Pig Amelia_2

Zhu Jianqiang, “Strong-Willed Pig”, has learned to move around by balancing on forelimbs alone.  It is unknown what caused this developmental anomaly, especially given the health and normal anatomy of the pig’s parents and siblings.  There are some reports of amelia occurring if the pregnant sow consumes tobacco stalks (Nicotiana tabacum), but that is not confirmed in this case here.  Image credit:  Quirky China News / Rex Features via Daily Mail.

The absence of hindlimbs has been popularly reported not only in pigs, but also in other domesticated animals.  A Florida kitten named Anakin was found in 2012 without pelvis or hind legs and yet “. . . . he plays and scurries around by balancing on his forelegs, which he positions under his middle, and balancing with his tail (Hartwell).”  An English Bulldog was born to a Arkansas breeder in 2015 with a truncated spine, no pelvis, and only vestigial hindlimbs.  This pup, Bonsai, became a Facebook darling and a crowdfunding campaign raised over $24,000 to support medical expenses.

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Bonsai the bulldog puppy.  Image credit: Daily Mail.

Like the pigs in Colonel Hallam’s 1833 report, existence without hindlimbs did not prevent these animals from living out their lives well into adulthood.  At least in the case presented by Hallam, this included the somewhat mentally inconceivable act of breeding between two limb-less pigs.  However, this carnival of cute oddities should not draw us into comfortable complacency.  The congenital loss of limbs is the result of catastrophic disturbances in development.  Many times, the results are fatal, if not outright cruel.  For an amelic calf, veterinarians decided to euthanize the otherwise healthy animal because it could only drag itself around on its belly, causing raw skin abrasions.  Bonsai the puppy was born with vestigial remnants of hindlimbs that had to be surgically removed.  Also, Bonsai’s unsupported posture was putting pressure on internal organs — hardly good news for a bulldog, a breed already highly compromised with respiratory and other health problems.  Needless to say, animals like Bonsai, Anakin, and Zhu Jianqiang will need extensive human care.

Bulldog Amelia_1

X-ray of Bonsai after surgical removal of his vestigial hindlimbs.  Image credit: Daily Mail.

There is a sense of renewal at the delivery of a newborn.  What we expect to find is something tiny, yet utterly new and perfect in every way.  This is the body before the hard knocks of life, before battle wounds, poorly considered tattoos, run-ins with power tools.  Congenital deformities can feel like a betrayal of these expectations.  The birth of “monstrous” animals and babies were once seen as ominous signs that something was terribly amiss in the world.  Such fearful portents may no longer signal religious heresies or political upheaval, but we must still think carefully about what they mean.  We must be able to understand the difference between something so deep and hidden within our cells it is beyond our control, and warnings from an environment under siege.  We must reconsider what is “normal”, what constitutes a meaningful life, and realize how our immediate culture defines those terms for us.

References

Daily Mail Reporter.  “Hogging the limelight:  Meet Zhu Jianqiang, the two-legged pig who’s become a celebrity in China.”  Daily Mail 1 October 2010.  Accessed 2 August 2016.

—–.  “Hamstand:  ‘Gymnast’ piglet born without hind legs learns to walk on two front trotters.” Daily Mail 28 November 2011.  Accessed 2 August 2016.

Hallam.  1833.  “Letter on a singular Race of Pigs.”  Proceedings of the Zoological Society of London:  16.

Hartwell, Sarah.  “Feline Medical Curiosities:  The Limbs.”  Messybeast Cats:  Curious Cats and Medical Anomalies.  Accessed 2 August 2016.

Hiraga, Takeo et al.  1991.  “Anatomical Findings of Apodia in a Calf.”  Journal of Veterinary Medical Science 53 (6):  112 – 1127.

MacFarlan, Tim.  “Cute bulldog puppy born with genetic conditions that mean he has no bottom half.”  Daily Mail 10 July 2015.  Accessed 2 August 2016.

Merck Sharp & Dohme Corporation.  “Overview of Congenital and Inherited Anomalies.”  The Merck Veterinary Manual.  Accessed 2 August 2016.

Mosbah, E. et al.  2012.  “Congenital Limb Deformities in Some Farm Animals.”  Proceedings of the 5th Animal Wealth Research Conference in the Middle East  North Africa.  Pp. 23 – 38.

Szczerbal, I. et al.  2006.  “Chromosome Instability in a Calf with Amelia of Thoracic Limbs.”  Veterinary Pathology 43 (5):  789 – 792.