Hammerhead Sharks: what was Mother Nature thinking?

Discovery Channel's Shark Week starts up this Sunday.  Know how I know?  Easy, just look at all the various shark news items papering the Internet today.  From the latest human/shark encounters to updates on various shark fin ban movements or legislation, sharks are stepping in to fill the void of the close of the summer Olympics.

The Mother Nature Network posted a quick look at the always curious hammerhead shark.  For most folks, great white sharks or tiger sharks can evoke fascination mixed with a little apprehension, but the hammerhead is often the one that leaves them scratching the head in bewilderment.

What was Mother Nature thinking when she drew up the plans on that one?

For me, there are two questions that come to mind with the nine species of hammerhead sharks.  The first is why?  The Mother Nature Network examines the three most common explanations and they all revolve around the shark's hunting capabilities, particularly for the larger species which like to include stingrays as one of their favorite prey.

The broad head of the hammerhead shark increases the surface area where the shark's electrical sensory organs are located.  These gel-filled pores, called Ampullae de Lorenzini, allow the shark to sense the subtle electrical fields given off by animals - as an example, stingrays camouflaged and buried under a thin layer of sand.

With eyes in each end of its head, the hammerhead is also able to increase both its stereoscopic vision (the ability to see directly forward) and its overall field of view (by swinging its head side-to-side, it is able to see above, below, and behind better than many other shark species).  The better the vision, the better the animal is able to hunt.

Finally, when hunting for stingrays, the hammerhead shark actually uses its unique shape to help shovel under a buried stingray, flip it over, and even pin it to the bottom.  This elaborate ballet that allows the shark a measure of surprise while it bites the stingray's pectoral fins, thereby eliminating the prey's ability to escape, has been documented and is quite something to see.

So, those are the three most common explanations as to why - why a hammerhead shark has evolved to have such a unique shape.  There's a purpose behind it that proves beneficial to the shark's survival.

The second question is a much challenging one to answer: How?  We can see why it has this shape and that it benefits its hunting abilities, but how did the evolutionary process start with a "conventional" shaped shark - if, indeed, that was it's original root form - and then Nature said, "Hey, I've got a whacky idea."

Evolutionary researchers have seen evidence of the adaptive radiation process, wherein plants and animals adapt to their surroundings and various requirements to ensure survival, and it takes hundreds of thousands of years for most species.  But there have been occasional jumps or sudden detours - either radical departures from the norm or greatly accelerated changes.  What was the case in the hammerhead shark?  What was happening in its surroundings that the gene pool decided to change little by little from one generation to the next, repeatedly, to where it eventually reached the iconic and unusual shape that we see today.

Evolution is no simple linear, A to B to C, process.  But its underlying motivator, that of survival (of the fittest, the most resourceful, or the smartest) has produced a staggering diversity both on land and at sea.  No better example than that of the genus Sphyma: the hammerhead shark.

Source: Mother Nature Network  

Man Evolved From Sharks!: media's hype drawn from new research

There is a new headline that is racing across the online media outlets like a Colorado forest fire: Man evolved from sharks!  Imagine the sensationalistic irony that when an unfortunate swimmer or surfer encounters a hungry shark, it is simply a case of communing with a long lost relative; some perverse form of cannibalism.

Now the facts: researchers at the University of Chicago, with funding from the National Science Foundation and published in the latest issue of Nature, have determined that one of the oldest - if not the - oldest species of fish, from which bony fish and cartilaginous fish branched off, was more similar to primitive sharks.  Vertebrates, including man, grew from that initial bony fish branch of the evolutionary tree, therefore you get today's attention-grabbing headline.

Studying what few fossil fragments exist of Acanthodes bronni, which lived over 250 million years ago, the researchers were able to determine that the brain case of this early jawed fish was more shark-like.

Professor Michael Coates, a biologist at the University of Chicago, said: "Unexpectedly, Acanthodes turns out to be the best view we have of conditions in the last common ancestor of bony fishes and sharks.  Our work is telling us the earliest bony fishes looked pretty much like sharks, and not vice versa. What we might think of as shark space is, in fact, general modern jawed vertebrate space.  For the first time, we could look inside the head of Acanthodes, and describe it within this whole new context. The more we looked at it, the more similarities we found with sharks."

For fans and diehards, like myself, of evolutionary theory, this is fascinating work in that it moves around one more puzzle piece in this enormously complex process that lead from single-cell organisms to dinosaurs, elephants, and man.  And for those who prefer a more religious-based idea of creation, I contend that the sheer complexity of the evolutionary process is evidence of a greater power.  That we have yet to have all the pieces so as to fully comprehend evolution - a process so complex with mutations, right and left turns, leaps and dead ends as to make the X-Men blush with envy - from start to finish is not grounds to dismiss it as fact.  But I digress.

And so the media is having a field day making the same kind of leap-frog assumption that was branded on Charles Darwin with the first publication of the Origin of the Species.  "Man came from monkeys" is now being modified to "Man comes from sharks," the only difference being that the former was meant to ridicule the scientific theory behind Darwin's work whereas today's headline is meant to grab the reader in an attention-deficient age, perhaps with a little chuckle under our breath.  Sigh. . .

Paleontologists study evolution - this vast, incredibly complex process of biological progress - to better understand the world of today.  It is the foundation from which grew all of the present intricate and inter-related ecosystems.  By deciphering the past, we better understand the present and can best protect the future.

And the next time I'm in the water with a great white, I'll look close to see if it resembles my Uncle Ed.

Source: The Telegraph
Source: The Daily Mail
Source: Huffington Post UK
Source: Science Daily
Source: Futurity
Source: Mother Nature Network

Nature's Indomitable Spirit: New Zealand wilding pines, a reminder about the will to survive

Was just finishing a short opinion piece by Brian Taylor for New Zealand's Otago Daily Times about how best to deal with the wilding pines that spread throughout both the north and south islands. Wilding pines, also referred to as wilding conifers, are invasive species of pine trees, the result of a combination of early settlers stripping indigenous scrubland for agriculture and cattle grazing which provided a fertile base for various imported pine tree species to explode across the valleys and hillsides.

With New Zealand spending millions of dollars annually to try to stem the tide of the ever-expanding wilding pines, Taylor was questioning the wisdom of current strategies. Yes, the pines are an invasive species that is altering the natural landscape and the result is both an economic and environmental threat, but it's a result due in part to man providing the trees with the initial foothold. Taylor questioned whether current land management use - grazing and burning techniques to maintain economically important grasslands - would forever be at odds with wilding pines and whether there could be other natural buffers developed to help manage the pines' growth and expansion, rather than the felling of mature trees and removal of seedlings which has not yielded hoped for results.

Interesting article but what caught my attention most of all was Taylor's description of nature's tenacity, as it is applicable to all environments - land or sea, plant or animal.

"Mother Nature can be a rather intractable old matriarch, and no matter how strenuously Man tries to thwart her advances, she will invariably be the clear winner in a marathon. After all, she has been around far longer than mankind and has not survived millions of years by simply taking a back seat when threatened. She is a formidable contestant, smart, very smart in fact, versatile, highly adaptable, and loves a challenge. When the chips are down, she will always be one jump ahead, ever ready to override our mistaken endeavours by taking control of regeneration her way.

She abhors nudity and will make sure that all of her domain remains well covered. There will be no bare spots for her, no sir. Pull out a weed and see what she does, she will plant another one straight back and will continue to do so as long as we constantly annoy her by perpetuating our misguided attempts at laying the ground bare."

Taylor is describing nature's will to survive. Despite all that can be heaped upon it, whether through natural occurrences or man-made interference, nature will do what it can, do whatever is necessary to carry on. It will adjust; it will adapt. But what we must keep in mind is that to evolve and continue its existence, nature can make some cold, harsh decisions - such as extinctions if that's what it takes. And that can involve the loss of the smallest insect all the way up to the largest mammals in the sea. And it can include us just as easily. For all our accomplishments and all our self-importance, if we push nature too far, it can shake us off like a bad case of fleas.

After pondering whether New Zealand could adopt land management policies that work with nature rather than continually fighting it, Taylor closes with a thoughtful reminder about ecological perspective - in whose playground we are briefly being allowed to roam.

"We live in a mere moment of time in the history of the planet. It has constantly evolved throughout the ages, and will continue to do so long after we have gone. We are able to exist on earth only because nature provides us with all our needs for survival. Yet in this modern world of rapidly diminishing forest cover, some are still prepared to promote the age-old slash and burn mentality - in this case, 'for the good of the view, rather than for the good of the planet'.

Maybe it is time we reconfigured our response strategies and embraced greater biodiversity, which is, after all, the key to a balanced and healthy ecosystem."

Here, here.

Source: Otago Daily Times

Zebra Shark Survival: could "virgin births" be a sign of nature's resilience?

Nature will find a way.

It's an amazing component of nature's dedication to survival that, when faced with conditions that impede propagation of a species, nature may choose another course other than to watch a population dwindle towards extinction. Parthenogenesis, or virgin birth, is just one such avenue. This is when an animal is able to produce viable offspring without the need for a traditionally fertilized egg, also known as asexual reproduction. No males around to breed with? Well, why wait?

Parthenogenesis is a somewhat rare occurrence, limited to a few reported cases, but one zebra shark that resides in the Burj Al Arab Hotel's aquarium in Dubai, has successfully produced eggs that brought forth healthy juvenile sharks. And she has done it each year for the past four years. The aquarium can verify that the shark has not had any contact with a male in all that time.

Interestingly, the juvenile sharks are all female - but not just clones of the female; their gene structure shows distinct differences. Could this also be another way that nature is trying to improve the odds, by generating more females? Scientists are not sure; the rarity of the event makes it a difficult subject to study.

David Robinson, the aquarium's operations manager, explained how the aquarium staff originally made the discovery, "We were actually moving the eggs and one of the guys felt something move inside the egg. And we checked the eggs with light and there were babies inside. So, it was actually quite, I don't know...we went looking for it, but I don't think we were ever expecting to find it. So we're just awestruck."

Zebra sharks - which get their name because of the striking zebra pattern on the juvenile, which later gives way to a more leopard-like spotted pattern - will continually lay eggs several times throughout the year, fertilized or not. When I was a dive team leader at the Aquarium of the Pacific in Long Beach, CA, part of my team's responsibilities was to round up zebra shark eggs strewn about the Tropical Reef exhibit, deposited by either of the two large female zebra sharks in the exhibit.

Stuck to the artificial rocks and corals with mucus-like strands that could probably be bottled and sold as the next super glue - or at least that was what we thought as we would spend considerable effort getting the gunk off of our fingers - the eggs would be collected and set aside for disposal. With Dubai's reproductive zebra shark, named Zebedee, as an inspiration, the aquarists in Long Beach are probably now taking a long look at those eggs that the divers find.

BBC News reported on Zebedee's egg-laying abilities recently and the report includes an interesting video. Click here to view the video.

Nature has many fascinating ways of dealing with the natural or organic challenges it has had to contend with for eons. Evolution can be both an organized progression and an abrupt reaction to environmental changes. Unfortunately, man-made impacts seem to exceed even nature's formidable skills in perseverance and resiliency. But if we give it a break, nature can do wonders.

Sources: i09.com, BBC News.

Evolution: study finds commonality in fish and mammal development

Evolution can appear to be a very complex process. How biodiversity developed over millions of years, producing thousands of various animal and plant species, is continually being studied and surprises seem to crop up with every new study. Whether piecing together the many branches and various dead ends that ultimately resulted in homo sapiens or deciphering the genetic code that determines who has a tail or who has wings, scientists are, piece by piece, assembling the puzzle that makes up nature's grand experiment in life on Earth.

And yet, from time to time, they discover within the puzzle a point of commonality - a puzzle piece that is being used over and over again - and the end result in diversity becomes simply a matter of timing. A recent study, published in the Proceedings of the National Academy of Sciences, highlights a genetic process that determines gill structures in elephant fish and sharks and its similarities with the development of limbs in lizards and mammals.

The elephant fish is a distant relative to sharks and rays, sharing the same type of cartilage-based skeletal system and also an outgrowth called a branchial ray - an appendage that extends from the skeleton and forms a supporting structure for the gills. Somewhere in the development process, the elephant develops one set of branchial ray while sharks develop several. To determine how or when this takes place requires studying things at the embryonic level. And for the scientists involved in the study, from Cambridge and the University of Chicago, this was a challenge as elephant fish embryos are difficult to find. Elephant fish lay their eggs in cold, muddy ocean bottoms, so the researchers spent months diving and searching possible breeding sites in Australia and New Zealand, gathering the needed embryos.

The researchers traced the impact of a genetic factor called Shh - the sonic hedgehog gene. It is common to both the elephant fish and sharks but when it expresses itself in the early developmental process determines whether there's one branchial ray set or more. This same process appears in the development of lizards and mammals, helping to determine outgrowths like limbs and number of toes for different species.

"The research highlights how evolution is extremely efficient, taking advantage of preexisting mechanisms, rather than inventing new ones," said Dr. Andrew Gillis of Cambridge University. "By simply tinkering with the timing of when or where a gene is expressed in an embryo, you can get very different anatomical outcomes in adults."

"It's basically showing that the limb story is part of a much more general narrative, which is the story of outgrowths," said Dr. Neil Shubin, University of Chicago. "There's a common development toolkit for all the outgrowths that we know in the body; they're all versions of one another in a developmental sense."

While analyzing all of the minute components found within the evolutionary process might seem a little esoteric or obscure to some, one of the advantages in understanding species development is to then be able to consider how or what might change that process. What environmental factors might come into play to alter or disrupt embryonic development, producing an evolutionary course correction or a tragic mutation? How easily can an evolutionary process, millions of years in the making, be altered by pollution, climate change, or other shifts in the norm?

As we study and learn more about both the complexity and the commonality or simplicity of evolutionary development, we can begin to see nature's wondrous puzzle of life and how the pieces can possibly be rearranged for better or for worse.

Read about the study in EurekAlert!
Read more in a Cambridge University press release.
Read the entire report published in Proceedings of the National Academy of Sciences.

Fins to Limbs: study identifies possible gene trigger

In the complex web of evolution, one of the pivotal moments occurred with the transition from aquatic animals to land animals - an event marked by the change from fins to limbs. While fossils have shown us evidence of this transition, the actually biological processes, what accomplished this change, has not been clear.

In a report recently published in Nature, a research team from the University of Ottawa conducted experiments that could shed some light on evolutionary change. Their studies identified a group of genes responsible for the supportive fibers found in fish fins, not found in tetrapods (land animals). These genes, known as actinodins, were found in both the researchers' primary laboratory specimen, the zebrafish, and in the elephant shark - an example of an ancient fish that has changed very little from its millions year old ancestors.

By chemically suppressing the actinodin genes in zebrafish embryos or in adults that were regenerating new fins, the resulting fins lacked the supporting fibers. What could not be tested is the causal event that might have triggered the gene change millions of years ago or whether the gene loss occurred as the instigator of change or as a reaction to some other evolutionary biological process.

"It's a very nice example of how changes in one or two genes can be responsible for a huge evolutionary transition," says Axel Meyer, a evolutionary biologist at the University of Konstanz. "We tend to think that new genes bring new functions, but this study shows that the presence of genes constrains or directs development in certain directions. Gene loss is actually a creative force in evolution."

Evolution is an incredibly complex process that not only provides historical insight but has the potential for unlocking secrets into the processes that impact species today in their ability to alter or adapt to changing circumstances. While some people do not subscribe to theories of evolution for religious reasons, I find that, if there is a higher power, there is no clearer evidence than in the intricacies of evolution, from single-celled organisms eons ago to the diversity of life that graces this planet today - a diversity that is being threatened by one of its most successful species.

Read more about the study in Scientific American.

World Population: guess who is in the room?

When discussing conservation, the environment, or any number of global issues, there lurks in the background the 800-lb. gorilla that no one wants to talk about: human population. Not just populations in 3rd world countries, but global numbers and that includes industrialized countries as well.

If we look at this matter-of-factly, nature has over thousands of years developed methods of equilibrium, checks and balances as it were, all designed to maintain a healthy ecosystem. Whether through predation, disease, or life cycle, all plants and animals are given a chance to flourish within the boundaries of that system or face possible extinction. And humans are part of that equation. However, because of our intelligence (some cynics would say our self-importance) we have exceeded the boundaries of that natural system and are now facing many unintended consequences.

It's a touchy subject to be sure. Who wants to turn to a young child or a close family relative stricken with serious disease and say, "Sorry, it's nature's way." And who wants to consider an Orwellian future where governments control reproduction - regulations like China's one-child policy run amok like some futuristic sci-fi movie. But as long as populations increase, as long as life expectancies are increased, and mortality rates are lowered, then we have a responsibility to consider the consequences in terms of the demands we are putting on the planet as a whole.

There was a time when our ability to feed, clothe and house a growing population was accomplished through our intelligence and our ingenuity. But we are fast approaching the point where we are exceeding what the planet can provide us with in terms of food, resources, and clean air. We must act decisively to control the problems that we have brought upon ourselves and also find the compassionate means to manage a world population of 6.76 billion that has been predicted to increase by another 2+ billion in less than fifty years.

Or we can wait for nature to take care of it . . . coldly but effectively.

(Read press release from Center of Biological Diversity.)

Moray Eels: feeding science fiction-style

For those of you who don't read National Geographic, here's an interesting "fun fact" from the latest March issue. . . You think the slimy villain from the Alien movies is the only creature with a second set of jaws? Well, how about the Moray Eel?

Many divers are familiar with the moray's threatening display of sharp teeth - a pose that comes about from the eel's breathing, as it doesn't have large flapping gill structures like bony fishes - and that these rear-facing teeth are designed to hold fast to its prey. But did you know that it has a second set of jaws that spring forward and assist in pulling the prey down its esophagus? This all takes place deep in the eel's throat and though it seems like something right out of a sci-fi thriller, it's actually a very efficient method of food transport for an animal that doesn't have the ability to gulp food down - like the vacuum motion you see with many other fish.

National Geographic reported that researchers from the University of California at Davis have studied this ability using x-ray and high-speed video (see photo) and it is apparently the first known mechanism of its kind in a vertebrate. Snakes get close, with hinged jaws that can slowly ratchet their prey down the gullet, and it's an example of evolutionary convergence - the development of a similar solution between animals facing the same problem.

As a volunteer diver at the Aquarium of the Pacific, me and my fellow team mates would feed the aquarium's eels and watch how they would grab a large sardine or squid perpendicular, turn it towards their throat and then down it would go without any help from the front teeth. A second set of jaws . . . who knew? Well, obviously somebody in Hollywood did!

Article also on online National Geographic.