It’s a boy! And a girl? Butterfly with rare condition emerges in Cockrell Butterfly Center

Editor’s Note: Today’s blog comes to us from Cockrell Butterfly Center Butterfly Rearing Coordinator Celeste Poorte.

The Cockrell Butterfly Center has had the privilege of witnessing a rare natural phenomenon recently. On July 10, a very unusual butterfly emerged from its chrysalis in the Museum’s greenhouses used for breeding and raising butterflies. This butterfly has a bilateral division: one side is female, while the other is male.

This condition is known as gynandromorphy. The term derives from the Greek “gyne” (female) and “andro” (male). This extraordinary butterfly is of the species known as the Great Southern White (Ascia monuste).

The Great Southern White is a cream-colored butterfly in the Pieridae family and occurs in the Southeastern United States and Central and South America. This species is sexually dimorphic, meaning the male is physically distinguishable from the female. In the case of the Great Southern White, the female has darker, greyer wings than her lighter male counterpart.

Our unique specimen’s right wing is ivory with dark scallop designs on the edges. Its left wing is a solid warm grey tone. On the right side of the abdomen you can see an anatomical protrusion not observed on the left side. This is a single clasper, a structure usually found in pairs on male individuals. Claspers are used by males to grip onto the female during mating. Our particular butterfly only has one clasper, on the same side of the body showing the male coloration and wing pattern. These observable features suggest that the entire right side of the butterfly is genetically male, while its left side is female. NEAT!

It’s a Boy! And a girl? Butterfly with rare condition emerges in Cockrell Butterfly CenterGynandromorphy is the result of a genetic mutation. It is an extremely rare condition and a topic of interest to researchers. As early as the 1700s, scientists have recorded cases of organisms that seem to be half male and half female. Recognized cases of gynandromorphy typically occur in species with sexually determined phenotypes. In the butterfly world, these specimens are prized by collectors. Cases most commonly occur in insects. Examples have also been documented in crustaceans (especially lobsters) and even birds. (Gynandromorphy has not been observed in mammals.)

It’s a Boy! And a girl? Butterfly with rare condition emerges in Cockrell Butterfly CenterCrustaceans, especially lobsters (Homarus americanus), can also display gynandromorphy. (original photo by A. R. Palmer; taken at the Bonne Bay Marine Station,)

It’s a Boy! And a girl? Butterfly with rare condition emerges in Cockrell Butterfly Center

How does this bizarre genetic anomaly occur? All sexually reproducing organisms begin as a single cell (a zygote) from the fusion of two gametes, a sperm and an egg. This single cell then undergoes division after division to produce all the cells in the body. In insects, each cell division — from the zygote on  — is determinate, meaning that cell’s fate is set. The earliest divisions will determine left from right, front from back, and top from bottom. Therefore, gynandromorphy is the result of an error during one of the very first cell divisions.

In Lepidoptera (butterflies and moths), sex is determined by a WZ/ZZ (female/male) system. We are more familiar with the human sex chromosomes X and Y, where females are XX and males are XY. In butterflies, this situation is reversed, and it is the female who has the heterogametic sex chromosomes. It is important to note that what is important in determining sex is the number of Z’s. Any individual with only one Z will be female (even if it is missing a W), and any individual with two (or more) Z’s will be male.

When cells divide (mitotically), identical copies of DNA are passed on to the resulting daughter cells. Occasionally a non-disjunction event occurs, in which the duplicated chromosomes do not correctly separate from one another, leaving one daughter cell missing chromosomes, while the other has extra copies. Gynandromorphy can happen when a non-disjunction occurs in a Z chromosome of a ZZ individual (male). In this situation, when the duplicated Z chromosomes fail to separate correctly, one daughter cell ends up with a single Z (female) and the other ends up with three Z’s (male). All the progeny of the female cell will be female, and the progeny of the male cell will be male. As a consequence, one side of the individual will have male traits, while the other side will have female traits. This is called a bilateral gynandromorph. If the non-disjunction of the Z chromosomes occurs at a later division, the butterfly will have a smaller section that is one sex while the rest of it is the opposite sex. Additionally the non-disjunction can occur several times during development resulting in a patchwork effect, yielding what is known as a mosaic.

Non–disjunction is not the only way this condition can arise. Other genetic events resulting in the spontaneous anomalous loss of a Z chromosome in a cell within the first few divisions will have similar effects.

It’s a Boy! And a girl? Butterfly with rare condition emerges in Cockrell Butterfly Center

It’s a Boy! And a girl? Butterfly with rare condition emerges in Cockrell Butterfly Center

So there you have it, gynandromorphy is a bizarre but often strikingly beautiful genetic error. The Cockrell Butterfly Center is lucky to have raised a butterfly with such a rare condition so we can all learn about the peculiarities of the natural world!

A Pinky’s Promise

In the summer of 2008, a multi-national team of Russian, European and American researchers found a small bone at a remote cave site in Siberia. At the time of discovery researchers had been working at the Denisova cave, located in the Altai Mountains in southern Siberia for several years already. Moreover, the cave was open to visitors as early as 2000, when it was listed on the program of The Second International Conference on Bioinformatics of Genome Regulation and Structure, held in Novosibirsk.

Initially, the discovery of a bone did not raise eyebrows, as the presence of Neanderthal people in the area between 48,000 and 30,000 years ago was a well-established fact. Interesting thus far, but nothing out of the ordinary.

As it turns out the small bone, identified as one of the bones in one’s pinky, held some surprises. Scientists at the Max Planck Institute in Leipzig extracted DNA – specifically mitochondrial DNA — and concluded that this type of DNA represented “a hitherto unknown type of hominin mtDNA that shares a common ancestor with anatomically modern human and Neanderthal mtDNAs about 1.0 million years ago.”  [For those scratching their head over the term “hominin,” this refers to extinct members of the human lineage.] So we are looking at one bone of a previously unknown hominin? Possibly. Or maybe not. 

The notion that we had several hominins living side by side, modern humans, Neanderthalers, and possibly this third species, should not come as a surprise. This happened quite frequently in our past; our existence today as the sole representatives of the human lineage is seen as an exception rather than the rule. What would be remarkable is that we have evidence of a human ancestor or close relative whom we did not know existed.

The latter realization has created a lot of buzz among those interested in human evolution. As is always the case with this type of endeavor, we need to be cautious and outline what we know, what the limits of our understanding are and where we shift from scientifically supportable reconstructions to pure speculation. A number of topics need further clarification here.

First, where does the owner of the bone fit in on the family tree, especially compared to us and to Neanderthals?

 Location of Denisova Cave and presumed place
on the family tree of the Denisova Cave specimen.

Researchers compared the Denisova mitochondrial DNA to complete mitochondrial sequences from 54 modern humans as well as a human who lived in Siberia about 30,000 years ago, six Neanderthals from more than 40,000 years ago, a modern pygmy chimpanzee and a modern common chimp. The results indicated that there are about 400 differences between us and the DNA in the pinky. This is twice as many differences as exist between modern human and Neanderthal DNA. This has led researchers to suggest that our last common ancestor lived about 1 million years ago, about twice as long ago as the common ancestor to us and Neanderthalers.

A second question that begs an answer is:  “what creature does this DNA belong to?” Various scenarios have been suggested here. It is possible, that we are dealing with a new species, neither modern human nor Neanderthal. Secondly, it could be a Neanderthal child, resulting from a union between a Neanderthal and an unknown species. Lastly it could be a Neanderthal individual, carrying variations in genetic make up thus far not identified in predominantly European samples.

The possibility that we are dealing with a completely new species is the most exciting. It is also one that most people caution us against. “Too soon,” “not enough material,” are some of the more common reactions. Others disagree and support the notion that this is a different species. This argument between those who see few species in the archaeological record (“lumpers”) and those who prefer a larger number of species (“splitters”) is one that has been described in a previous blog.

Skeleton of an alleged
Homo sapiens – Neanderthal
hybrid child found in Portugal.
Image courtesy of donsmaps

The scenario raising the possibility of an interspecies affair (between Neanderthal and another species) is favored by some, who see parallels with an alleged Neanderthal – modern human hybrid child found in Portugal. In this case, however, we would be looking at a child of a Neanderthal and a yet unknown species. This still implies that we had an unknown creature wandering the Siberian wilds, one whose genetics were inherited by a mixed offspring. In other words, this scenario still requires acceptance of the existence of an unknown species.

Finally it is conceivable that the breath of Neanderthal genetic variation is such that we have not mapped all of it. Given that most research on Neanderthals has concentrated on European materials, rather than Siberian, perhaps these Eastern Neanderthals carried in them a number of genetic variations that hark back to the original population in Africa. This would support the third option, one which identifies this pinky bone as belonging to a Neanderthal individual, albeit it with genetic markers not encountered in European samples. If identified as such, then this bone would reinforce the notion that Neanderthals occupied a much larger territory than originally assumed.

This discovery is meaningful in several ways. It illustrates that science marches on, providing answers to questions and, in the process, raises additional questions. It also shows how meticulous one has to work as an archaeologist or paleoanthropologist. One small pinky bone has provided us with a “what-in-the-world-is-this?” moment. The decision to perform a DNA test warns us not to be complacent. Up until recently, the party line about who was around some 40,000 years ago would have been answered with Homo sapiens or Neanderthalers, and nobody else. We are now forced to entertain the possibility of a hitherto unknown species living side by side with the other two. That is the promise this one tiny pinky bone holds.

A few final comments and thoughts.

What most articles I have read do not elaborate on is the fact that research is now happening in Siberia. This is a huge territory, difficult to access for all kinds of reasons. When discoveries like these are made, we should not be surprised that they generate questions we cannot answer yet, as researchers are accessing a territory close to the size of the US (a fact appreciated more than a century ago). I hope this discovery will result in greater support for research in the region. One day I am sure we will have a much clearer picture of what it is we are dealing with here.

Pinky promise.

The Eyes Have It: Evolutionary Development and DNA

Today’s guest blogger is Neal Immega. He has a Ph.D. in Paleontology and is a Master Docent here at HMNS. In his post below – originally printed in the Museum’s volunteer newsletter – Neal discusses Evolution Development and DNA.

Popular media crime shows, like CSI: Crime Scene Investigation, show amazing applications of DNA technology. For example, a person can be traced to a specific location by means of cells he left on a door knob.

A new science called “Evo-Devo,” shorthand for Evolutionary Development, can tell us even more amazing information. Evo-Devo techniques probe deeply into the structures of DNA to look at how DNA actually codes for the growth of body parts, telling us more about the animal kingdom than we ever dreamed possible. It shows genetic similarities between very different organisms and lets us understand how two organisms, like mice and men, can have DNA that is 85% similar and, yet, code for very different organisms.

We all know the basics of DNA molecules, where the genetic code is stored by a very long sequence of four proteins strung together in various arrangements. That is the easy part! What we need to
worry about is how these genes blueprint a living being. Geneticists, like Sean Carroll (whose popular books are listed in the references box), have discovered that the DNA code is made up of some large master programs that control things, such as eyes, and lots of very small programs (they call them switches) that control what kind of eye will be displayed.

Normal Fruit Fly
Image courtesy of The Exploratorium

Let’s confine ourselves to understanding and experimenting on simple life forms, such as fruit flies. To figure out which specific piece of DNA causes some feature to appear in a developing embryo, geneticists experimentally inactivate a segment of DNA, transplant the complete strand (including the inactivated segment) back into the egg, fertilize that egg, and then see what turns up missing. If that missing part is not vital for survival, the egg might even grow into an adult fly. Compare the drawings of a normal fly with the one below it where the master program for eyes has been deleted.

Eyeless Fruit Fly 
Image courtesy of The Exploratorium

Such experiments have found that the master program for making eyes can cause an eye to grow on a fly’s leg, body, antenna, or inside the body, depending on where it is placed on the DNA strand. Check out the drawing showing the results of moving the master program for legs to the site of the antenna. Note that the extra legs are fully formed but lack the neuron connections to the brain and so are not functional. (In the references box is a link to an electron microscope image of a real fruit fly that shows a mutation in which eyes replace antennae.)

Various mollusks (like clams, snails, and octopuses) grow eyes that vary in complexity from very simple sensitive pits to complex eyes that would compete well with human eyes. The EXACT SAME eye master program from a fruit fly can replace the eye master program for a squid, and it will grow a perfectly functional squid eye. You might be tempted to say that fruit flies and squids are cousins.

Fruit fly with extra legs
replacing the antennae 
Image courtesy of The Exploratorium

That is an amazing statement, but to take it even further, the same experiment with a mouse eye master program will grow fly eyes on flies and squid eyes on squids. They only differ by the small switch segments. These experiments establish a link between vertebrates and invertebrates that paleontologists are unlikely to find in the rock record. This also helps explain the amazing degree of structural similarity between mice and men—although many of the master programs are similar, the really critical parts of the DNA are the small switches that control the details.

Mollusks have just one master program that is controlled by different switches. Pectens, for example, have the most complex vision arrangement of any animal with three different types of eyes on its body. The DNA can be experimentally adjusted to grow any of these eyes anywhere on the body. Random mutations could thus cause novel arrangements, and survival would judge their fitness—evolution in action.

The switch concept explains how mice, chimps, and humans can have a similar number of genes. The switches control the result of the master programs. You can pick up any modern textbook and read that men and chimps have nearly identical genes. It is the switches that make us different and that provide the evolutionary means for dramatic changes, good and bad.

The fossil record is full of cases where a dramatic new species just appears. Paleontologists have often wondered if this was caused by a missing rock interval, by migration, or by rapid evolution. The concept of rapid evolution has often been discounted because it seemed to violate the incremental nature of evolution. We now can see how rapid evolution may just be a single point mutation in a switch. There are numerous biological examples where altering one protein is lethal, as in Tay-Sachs disease, or altering another might bear strongly on survival, as in changing
the color of hair from white to black.

Geneticists can now explain things in a way that profoundly affects how we think about evolution. Biologists and paleontologists have always wondered if evolution had to generate complex structures like eyes from scratch for each phylum. The reuse of master programs from very simple life forms through complex ones means that evolution can build on what went on
before. Critics of evolution often claim that eyes are too complex to have evolved. (The “half-an-eye-is-nogood” argument is derived from the first sentence of the Darwin quote in the box below.) Now, with Evo-Devo tools, we can see commonalities between the genetics of simple life forms and complex life forms– between clams and people.

The possibilities just became more complex.

REFERENCES:
Wyoming Dinosaur Center: http://www.wyodino.org/

Sean B. Carroll:
Endless Forms Most Beautiful: The New Science of Evo-Devo, (paperback) 2006
The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution,
(paperback) 2007
Remarkable Creatures: Epic Adventures in the Search for the Origins of Species, 2009

Lynn Helena Caporale:
Darwin in the Genome: Molecular Strategies in Biological Evolution, 2002

SEM (scanning electron microscope) photograph of eyes replacing antenna in a fruit fly by Naoum
Salame. http://1tv4.sl.pt

Fly Eye Genetics:
http://www.pbs.org/wgbh/evolution/library/04/4/text_pop/l_044_01.html
Renowned scientist Dr. Walter Gehring discusses master control genes and the evolution 
of the eye.

Darwin, 1859, The Origin of Species, http://darwin-online.org.uk/contents.html. In most editions, the quote appears on pp143-4.

Explore Evolution with Lucy’s Legacy

lucy-model-face

Lucy’s Legacy, an exhibition featuring the world’s most famous fossil, recently opened at Discovery Times Square Exposition in Times Square, New York. The exhibit will remain on display until October 25, 2009.

The Lucy exhibit has been an exciting catalyst for discovery, discussion, and debate within the scientific community. In this series of blogs, Dirk presents all sides of the controversy surrounding Lucy’s existence and significance while skillfully separating fact from fiction with supporting evidence and research.
  
Do you enjoy debate about scientific theories or issues? If so, prepare yourself for a great read while perusing the following blogs by Dirk. In addition to his perspective and logic, Dirk also provides links to research and evidence that will leave you on the edge of your seat…and excited about evolution!

-In fide constans… Always loyal [Lucy's Legacy]     
-Neanderthal Controversy
-A Letter From Lucy: Making no bones about it. (Pun intended)
-Lucy loves Houston – and she’s not leaving. Yet.
-If Humans came from monkeys, than why are monkeys still around?
-Evolution
 
 Neanderthals—most people know what they were, but do we know who they were or how they lived? Join Dirk as he discusses these unique people and their lifestyle.

-Neanderthal Controversy 
-Neanderthals on the move
-Neanderthals Speak Out

Why are genetics important in the development of humans? More than just appearance, genetics play a role in where we live and even how we survive. In the following blogs, Dirk explores where genetics has contributed to history and evolution. 

-Neanderthals on the move
-We are all mutants
-10,000 BC: The story behind the date
-A major step forward – 40,000 years ago

s-legacy-exhibitSure, they’re adorable and entertaining to observe but chimps and monkeys offer far more than that! They provide valuable information about human behavior and progress. Follow-up with these blogs and read Dirk’s presentation of our connection to these magnificent animals.

-Chimps using tools: Archaeology’s most fascinating discovery of 2007
-The Apple Doesn’t Fall Too Far from the Tree
-Monkey business
-If Humans came from monkeys, than why are monkeys still around?
  
The study of fossilized remains (like Lucy and other hominids) offers an exciting opportunity to draw parallels on our own existence and physicality. What did they look like and how did they live? Dirk has explored these questions in the following blogs:

-Discovering behavior: a step-by-step process
-Reconstructing ancient hominid behavior
-Lucy’s kitties
-Paleoanthropology: making the past come alive.
-Extinction doesn’t mean failure

If you ask a fossil to share the secrets it holds, it will provide invaluable information and insight into the past. But how can we piece the puzzle together? Dirk explains the wisdom of what happens when fossils meet modern technology…and dating begins (pun intended).

-How do we know: dating techniques
-Meet Lucy, Australopithecus afarensis. (What’s in a name?)
-Teeth Tell Tales
 
Want to find out more about Lucy’s home, Ethiopia? Click below and discover a wealth of history, culture and tradition.

-Timkat, an Ethiopian Epiphany celebration
-The Ark of the Covenant and Aksum