Monthly Archives: June 2012

Earthling Bulletin #6

by Piter Kehoma Boll

Lonesome George, the last Pinta Island Tortoise, dies and put an end to his lineage. Photo by Rodrigo Buendia, extracted from australiangeographic.com.au

News

Blogs

Art

Scientific Articles

(If you are willing to read some of the articles but got no access to them, please contact us and we’ll send you a copy through e-mail!)

Advertisements

Leave a comment

Filed under Bulletins

Friday Fellow: ‘Abundant Yellow-Striped Flatworm’

by Piter Kehoma Boll

ResearchBlogging.org Today our Friday Fellow is an almost unknown species from an almost unknown group: Luteostriata abundans (formerly Notogynaphallia abundans) is a land planarian (a flatworm) found in southern Brazil, mainly in urban areas. It’s common to find it around in gardens and parks, hidden under leaves, stones and logs.

Two planarians Luteostriata abundans, named by me as Pierre and Marie (don’t forget they are hermaphrodites, though). Photo by Piter Kehoma Boll.

Most land planarians are very poorly known, even though they are recognized as good bio-indicators of conservation. However, there is an article published about the feeding habits of L. abundans (Prasniski & Leal-Zanchet, 2009). Currently it’s only known that it feeds on woodlice, but since it’s a very common species in disturbed areas, its diet probably includes something else. (I’m studying the predatory behavior of this and other species, but haven’t found any other prey item for it yet…)

Here at IPP (Instituto de Pesquisa de Planárias, in English “Planarian Research Institute”), we are also doing research about the regeneration of L. abundans. Everybody knows how well freshwater planarians can regenerate when cut into several pieces. Land planarians don’t seem to be so skilled, but very little is known about them on this subject too!

Another interesting fact that we noticed about L. abundans is their ability to escape from almost every container you put them into. We need to seal the lid of their plastic containers with adhesive tape and yet they sometimes manage to find a way to leave.

There is so much yet to know about these flatworms. As predators, they are essential to balance the population size of their prey in conserved areas and for those species known to live well in urban places, knowledge of their feeding habits is important to evaluate their chance to become invasive.

– – –

References:

Carbayo, F. 2010. A new genus for seven Brazilian land planarian species, split off from Notogynaphallia (Platyhelminthes, Tricladida) Belgian Journal of Zoology, 140 (Suppl.), 91-101

Prasniski, M. E. T. & Leal-Zanchet, A. M. 2009. Predatory behavior of the land flatworm Notogynaphallia abundans (Platyhelminthes: Tricladida) Zoologia, 26, 606-612 DOI: 10.1590/S1984-46702009005000011

1 Comment

Filed under Behavior, Friday Fellow

Why I Don’t Trust Jack Horner 2: Why the King deserves his crown

by Carlos Augusto Chamarelli

Hey there again. After the previous article about Jack Horner’s plan to transform chickens into dinosaurs, what’s better than go back to showing contempt for his other theories? So let’s talk about his opinions regarding that one elusive theropod nobody ever heard about: the Tyrannosaurus rex.

Most specifically, about the most heinous and debated of his claims: that T.rex was so ill-suited to be a hunter that he had to live entirely of kills from other predators and was no more than a giant vulture. Understandably not many people were happy with this, and many studies since were made to verify if Horner’s claim were true. With mixed results, but not that stopped some to agree with him.

In reality he wasn’t the first to try and discredit T.rex of his predator status; back in 1917, paleontologist Lawrence Lambe concluded Tyrannosaurus couldn’t be a predator because Albertosaurus (yeah, I don’t know either) teeth did not show any sign of wear, which soon enough was pointed out as BS because theropods constantly changed their teeth throughout their lives. So T.rex continued to enjoy his status as the supreme predator he’s cracked to be and the scavenger theory was mostly left aside.

I’m not sure when Horner first proposed T.rex was a scavenger, but his opinions were already present during the early 90’s; during the production of Jurassic Park, in which he was one of the paleontological consulters, he stated that T.rex should be depicted as such. Fortunately, everybody knew better and made him a hunter like Bakker suggested, and we could see the creature in all his glory in the first two movies of the series.

You people, I don’t care if it’s outdated and full of inaccuracies; this is the only place where dinosaurs genuinely feel like they’re real things. Screencap of Jurassic Park. Extracted from jurassicpark.wikia.com

Until the early 2000’s that is, when Horner’s theory came in full power to the public. His TV-special “Valley of the T.rex” was entirely devoted to show the creature as a stinky scavenger, and during the production of Jurassic Park 3, Bakker knew better than participate of this train wreck, leaving the movie at the mercy of Horner as its sole consulter…

And from there, everything went downhill. Screen cap of Jurassic Park 3. Extracted from gonemovie.com.

As Wikipedia so nicely resumes for us, the main aspects that Horner uses to rationalize the idea of T.rex as a scavenger are as follow:

– Tyrannosaur arms are short when compared to other known predators. Horner argues that the arms were too short to make the necessary gripping force to hold on to prey.

– Tyrannosaurs had large olfactory bulbs and olfactory nerves (relative to their brain size). These suggest a highly developed sense of smell which could sniff out carcasses over great distances, as modern vultures do.

– Tyrannosaur teeth could crush bone, and therefore could extract as much food (bone marrow) as possible from carcass remnants, usually the least nutritious parts.

– Since at least some of Tyrannosaurus’s potential prey could move quickly, evidence that it walked instead of ran could indicate that it was a scavenger.

That said; let’s take a closer look at each of these points, shall we?

– Arms

Ah yes, T.rex arms. Those sorry excuses for limbs are the trademark of the king and his kin. Completely out of proportion and with only two fingers, it’s easily one of its most puzzling characteristics as many theories and no agreement exist about their real utility; ranging from a prosaic, moderately believable but ultimately flawed use like lifting his body when the animal was lying down, to the most reason defying such as picking his teeth or holding struggling prey.

At least it makes him easy to impersonate. Extracted from blogs.smithsonianmag.com

But I do believe the answer is in fact quite simple, but lots of people will be outraged exactly because of that.

Nothing.

T.rex most likely didn’t use them for anything because, well, it didn’t need. They were in a process of atrophy*. It’s really sad that the only mention of such occurrence is usually attributed to the outdated theory of Lamarckism, with the law of use and disuse, because, in a way, that’s kind of what happens.
To understand it better: you know that evolution work by mutations, right? They occur at random in the process of reproduction, but as the model always goes, if said mutation proves to be an advantage for that individual, he has higher chances to pass on his genes for the next generations. But sometimes, things go in a different direction.

Let’s make this one model with two different species, a caveman and a T.rex.

Why yes, MS Paint & MS Word work just fine for me. Picture by yours truly.

The caveman is like your average caveman: he has two legs, two arms, a head and a big, spiked club. The T.rex, on the other hand, is actually an ancestor form which have long arms, fictionalized for the sake of the explanation**, he’s like “cool, I can grab things with these, but my mouth already does everything I guess”.

Now say that they both at some point had offspring with mutations that affect their forelimbs, making their arms dwindle and become useless. For the cavemen, this could be fatal since he relies on his hands to grab things, make tools, maybe even socializing, so the natural conclusion is that this bad gene results in a dead caveman who never stood a chance to have children. For the T.rex, his tiny arms doesn’t affect him as much, because his jaws do all the work of killing prey and fighting rivals, which means he can survive normally and pass on his “bad” genes and create an entire dynasty of short-armed dinosaurs.

Putting a magnolia flower on her head is the way to tell she’s a female. Also, poor caveman. Picture by yours truly.

In other words, if a mutation doesn’t have a big impact in the creature’s lifestyle, it probably will carry on to next generations until the whole species has it. Among some examples where this happened we can cite snakes and other legless reptiles (which became, you guessed it, legless), primitive tetrapods (which lost fish characteristics such as fins) and even us humans (which lost our tails).

Degenerated arms are not even an exclusivity of tyrannosaurids; other dinosaurs had similar occurrences, from the small, one-fingered alvarezsaurids such as Linhenykus (whose arms were more like pointed stubs) to giant Abelisaurids, the “T.rexes of the south hemisphere”, so to speak. The latter, in fact, had much more pathetic-looking limbs than T.rex.

I mean, really, what the heck, nature? Carnotaurus skeleton mount from the Chlupáč museum in Prague. Extracted from http://commons.wikimedia.org

There were also the famous terror birds, which appeared in the Cenozoic; these too were large-sized predators with beaks as deadly as their wings where shamefully small. The logical conclusion with all of this is that arms for bipedal predator dinosaurs are overrated, and the fact T.rex had tiny arms as he did is completely irrelevant as evidence for scavenging habits.

Unless you think they were ALL scavengers, but… Why would you think that? Picture by Zdenek Burian.

– Senses

Remember that one scene in Jurassic Park where the T.rex escapes and Grant has to save Hammond’s grandchildren and they stand perfectly still because then the T.rex couldn’t see them? Of course you do, you read about it everywhere how it’s bonkers because he could have smelled them: T.rex had an exceptional sense of smell, just one more of his claims to fame.

Pictured: Bonkers. Screencap of Jurassic Park. Extracted from lost-world.com

T.rex’s sense of smell is thought to be surpassed only by the modern day turkey vulture (Cathartes aura), which is all too convenient to Horner’s theory, right? Except having a good sense of smell is just as useful for hunting animals, as proved by modern canids and felines. “But, PK, those are mammals, we’re talking about dinosaurs! They’re closer to birds!” you might say, but that’s alright, because contrary to what many might believe thanks to the super-sniffing vultures, some non-scavenger birds do have a good sense of smell.

The majority of them use it to detect predators, but there are some species that use it to hunt prey, like the kiwi birds, whose nostrils are so long they actually go all the way to the tip of the beak, excellent for sniffing worms underground.

It is fair compare it with T.rex, right? Right? Extracted from rmagibess.wordpress.com

But even more bonkerous is the fact that, never mind his extraordinary olfaction, he COULD see them!

It’s not always apparent, because most of the time you see pictures of T.rex’s skull in profile, but if you have the chance to look at one from the front, you’ll see that the hind part of the skull is actually visibly wider than the snout, causing the eyes to face forward rather than the sides as it’s more commonly seen in dinosaurs; it’s also at a higher level than the snout, giving it a clearer view and the distinctive shape.

It’s also kinda hard to find such picture, specially one that haven’t been seen around a thousand times. Sue’s skeleton mount at the Chicago Field Museum of Natural History. Extracted from wikipedia.org… Do I even need to say that?

Eyes facing forward are a characteristic of animals with good eyesight, such as primates and birds of prey, with the owls being the ultimate example of this; the binocular vision provided is essential for calculating distances better and maintain focused on targets. So that’s a tricky question: if T.rex was a purely a scavenger, then why did it had eyesight akin to predatory birds who are such efficient hunters?

– Teeth and jaws

Tyrannosaurids are an interesting lot when it comes to teeth. Usually, carnivore dinosaurs have slicing teeth shaped like steak knives, efficiently tearing the flesh out of the victim’s bone. T.rex, on the other had, had teeth at one point described as “deadly bananas”: they where thick and with very deep roots, which made them incredibly strong.

Those are medium sized, by the way. Extracted from discovery.com

In addition, their jaws were also different: the classic model has the jaws roughly the same width; while in T.rex the upper jaw was wider, giving him the characteristic overbite appearance, which allowed him to stress bones in such a way that they could easily crack them.

On top of that, T.rex is thought to have had the most powerful bite in the dinosaur world. How powerful it was? The most recent study, released this year, indicates around 30,000 and 60,000 Newtons. To puts things in perspective, the previous study pointed up to 13,000 Newtons,  enough to crush a car. That being said, I’m not surprised if someone told me that if a T.rex and a tank were in a fight, the dinosaur would’ve won.

Once again the internet proves it has everything. Extracted from nebomusic.net

But once again, this isn’t an indicative that T.rex was purely a scavenger, since powerful bites aren’t unique to such behavior. Think of the jaguar (Panthera onca), which isn’t one of the largest big cats out there, but even for its size it has an unusually strong bite that can crack even a man’s skull, and is the apex predator of its habitat.

Hypothetically speaking, if jaguars were to evolve into much larger species, then forms with even stronger bite power could appear. For a creature as big as T.rex, this could be one such scenario; their ancestors could be like the jaguar in size and potency, but things went out of hand and produced a big animal with an insanely strong bite, and being able to feed on bone marrow was just an appreciated bonus.

So anyways, remember that scene in Jurassic Park 3? Yes, THAT scene…

So many bad words were uttered directed at this. Screencap of Jurassic Park 3. Extracted from djgomasar.blogspot.com.b

IT WAS TOTAL BS!

The first bite to the neck would’ve been enough to kill the Spinosaurus. See, that’s one reason that makes T.rex lives up to its title: it doesn’t matter if Spinosaurus or Giganotosaurus or any other theropod was larger than him, his absurdly powerful bite would be more than able to overpower them.

But no, Horner had to have things his way and cheated by okaying them into making a Spinosaurus on steroids not care about fish and fight a sub-adult T.rex and survive a bone-crushing bite to the neck. Sorry about that little rant, but it’s all just too unnerving to see such gratuitous mockery of paleontology in one place.

SO MANY. Screepcap of Jurassic Park 3. Extracted from villains.wikia.com

– Legs and body build

Paleontologists have divergent opinions about the overall build of Tyrannosaurus; two body models commonly followed are the bulky type and the athletic type. The bulky body implies a slow-moving creature with a more limited ability to run, some might say one that would be unable to chase its prey, while the athletic body implies an active running creature.

Paleontologists who support the athletic type suggest that, despite it’s size, the overall proportion of the legs of the T.rex are more characteristic of a running animal, in other words, T.rex was very much able to catch up with its prey in a chase. So naturally this is what makes the most sense if you want to show T.rex as a hunter.

“Look, a Velociraptor!”. Sue’s skeleton again. Extracted from cmnh.org

My opinion? He was a bulky type.

“Say what?”

In reality, nobody is quite sure of how fast Tyrannosaurus was, but from analysis and calculations an estimative can be made, but even those don’t really support the image of T.rex running at overly high speeds as usually shown.

In a optimistic scenario, the top speed for T.rex is somewhere around 30 km/h (18 mph) at best, which isn’t terribly fast. I’ve read about some estimatives being over twice this value, but that seems more like an exaggeration to argue with Horner’s theory in the wrong direction.

Because the larger the creature becomes, the more heavily built it has to be in order to support its own weight, there’s a limit on how light the creature can be until it become too big and heavy to support itself, so a large bipedal creature like T.rex probably needed to have a solid build in order to stand in their feet. Not to mention that, in order to be able to run at the suggested exaggerated speeds, much of its body mass would have to be in their legs muscles.

Whoever, being slow doesn’t rule out the possibility of Tyrannosaurus being a hunter; he maybe just had a different approach. Instead of focusing in speed, Tyrannosaurus could be a robust creature built primarily for strength. Why would did he need to be so? Well, what manner of prey did he had available in his domain?

Spikes, spikes everywhere. Pictures by John Sibbick. Extracted from http://fineartamerica.com

Why, just the most dangerous herbivores ever to appear in the Mesozoic era.

Nobody can attribute speed as a quality of ankylosaurids; they had a solid build, covered in heavy armor and short legs for better standing their ground.

Ceratopsians, despite what most reconstructions tend to show, were probably very poor runners: their forelimbs weren’t even appropriate to run, (I intend to talk about this in a future post) so they probably relied more in numbers and their own weaponry for survival than making a dash for it. So if being fast wasn’t needed to catch its prey, the best option would build up endurance, and the apparent running legs of T.rex would be more like a way to trade speed for strength without being completely handicapped.

Meaning the T.rex wasn’t a creature made to pursue its prey. No sir. He was juggernaut made to stay there and fight them, and win. Somehow pure raw strength could prove to be a better strategy than speed to overcome a well armed opponent.

Suddenly this setup makes a lot of sense. Picture by Charles Knight.

While the T.rex could be injured or even killed by his prey, he could also finish it just as easily: biting the head or the backs would have shattered their bones and leave the prey paralyzed in the best of hypothesis, while just ripping a chunk could leave a fatal wound. In this scenario, T.rex’s eyes would then be an invaluable asset to focus on their prey during the fight, rather than be used during a chase. And if he ever needed to run, it would be more like walking real fast.

In a way, one can think that ceratopsians and ankylosaurus where in a mutual armed race with tyrannosaurids, each developing even more powerful weapons against each other: they seemed to be found primary where those types of herbivores thrived (i.e. North America and Asia), and their evolution is somewhat consistent with the appearance and ascension of those herbivores. Now consider this: despite the duckbilled dinosaur’s fame as widespread, they were actually outnumbered by ceratopsians, which means something must have been preying on them to keep their numbers, right?

Oc course, that’s my personal opinion, I might be wrong: there’s no evidence of ankylosaurids with signs of predation yet, but I’m not convinced absolutely nothing would attack them if given the chance, specially something with a bite like T.rex.

And to think for the longest time museums didn’t like those kind of findings because they were “no good for exhibition”. Triceratops sacrum with T.rex bite marks. Extracted from palaeocritti.com

While there’s evidence that T.rex preyed on both hadrosaurids and ceratopsians (i.e. some show teeth perforations while others healed bite marks in bones that could only be possible if the dinosaur was alive), it’s safe to assume that the horned dinosaurs were his chief prey, at least to the fully mature individuals.

While there’s no official estimative on how fast hadrosaurids could run, it’s certain that they were faster than an adult T.rex, but if it’s true that they could also hunt in packs to a degree, then it could be an explanation for this finding. Alternatively, younger individuals could have preyed on hadrosaurids if they were light built. But even more impressive seem to be the fact that something actually could survive an T-rex attack.

-Anything else?

Actually yes, there’s one more point beyond the ones listed: Energy efficiency.

Modern scavengers like vultures and jackals are allowed the luxury having this lifestyle because they’re small and can cover a large area without wasting too much energy (i.e. vultures are soaring birds, meaning they are able to maintain flight without flapping their wings).

A large creature like T.rex would be doomed to extinction if it was an obliged scavenger because he would probably run out of energy trying to locate the next meal, and even then he has to hope there’s enough left to eat and no other T.rex claimed it already, not to mention this unviable lifestyle would make their population be massively reduced in order to be able to support just a handful of these dinosaurs

So there you have it. Tyrannosaurus might not have been the largest carnivore to ever exist, but he certainly was the most powerful. Despite all those evidences, there’s a consensus among those who support the hunting behavior of T.rex that he was an opportunistic hunter. That is, while he could very well kill his own prey, he wasn’t above stealing or eating carcasses. It’s a free meal after all.

In the end, this is what the whole problem is about: Horner didn’t take in account that the evidence he used to support his theory also had explanations that indicated the opposite. Just to make things clear with the “Why I Don’t Trust Jack Horner” series: while I don’t think he’s a bad paleontologist, I do believe he’s a little misguided about his recent theories. And quite frankly, I’m pretty sure that if Horner went back in time and was face-to-face with the creature he’s sure was a scavenger, he would NOT just stand there calmly.

Thanks for reading!

* Because once the first degeneration took place, nothing would stop it from being further degenerated by a subsequent mutation.

** Early tyrannosaurids did have longer arms, but in the model the dinosaur is already in its later form to illustrate that even a sudden mutation, as opposed to a gradual one, still wouldn’t affect it.
– – –
References & Further Reading:
Erickson, Gregory M. 2005. ‘Um Sopro de Vida no Tyrannosaurus rex’. Scientific American Brasil – Edição Especial: Dinossauros e Outros Monstros.

Wikipedia. Tyrannosaurus. Available on-line in: <en.wikipedia.org/wiki/Tyrannosaurus>. Acess on May 15th, 2012

BBC – T. rex bite was world’s strongest. Avaiable online at: <http://www.bbc.co.uk/nature/17159086&gt;

Science Daily- Birds Can Detect Predators Using Smell. Avaiable online in: <http://www.sciencedaily.com/releases/2008/04/080427233813.htm&gt;

19 Comments

Filed under Evolution, Paleontology

If you like flowers, you should love insects

by Piter Kehoma Boll

ResearchBlogging.orgEverybody likes flowers, right? They are so colorful and beautiful and usually have a wonderful scent. People love to have them in their gardens and women love to receive a nice flower bouquet from their boyfriends.

Some flowering plants, from left to right: Rosa ‘Hybrid Tea’, Pachystachys lutea and Zinnia elegans. All photos by Piter K. Boll (i.e. myself!)*

But why are flowers so beautiful? Of course the flowers seen above are derived from varieties artificially selected by humans to increase their beauty, but flowers in nature are wonderful too!

Naturally occuring flowers. From left to right: Oxalis sp., Ipomoea fimbriosepala and Zephyranthes robusta. All photos again by myself (Piter K. Boll)*

Surely that beauty is not intended to please people or whatever. That’s totally nonsense and just some religious people could have such a wrong idea. If plants have nice flowers, it must give them some advantage.

As everybody knows (at least I hope so), plants usually cannot move like animals, so they are condemned to stay still on their spot. That can mean a lot of trouble when you are looking for resources like water, light or basic elements like nitrogen. So evolution leads to the rising of amazing structures to make plants survive, like getting a hard stem to become taller or developing smaller or larger leaves, thorns, tendrils or even becoming carnivorous. But plants also need to reproduce and for that they need a mate, but since they are attached to the substrate, they have to find alternative ways to join their gametes.

Most primitive plants manage to do that through water or wind, just letting their reproductive structures go and hoping that they will reach their destination. As you can see, this method is not the best one, since fertilization occurs totally by chance. Besides that, these ways are limited regarding to the places where they are successful. A plant fertilized through water needs to be inside water or live close to the ground on places where it eventually get submersed; the same way, a plant which relies on the winds needs, of course, to be where the wind blows.

Moss (left) relies on water to reproduce, while conifers (right) need wind. Once more, photos by Piter K. Boll. *

Those methods, though limited, worked well enough for millions of years until sometime in the Cretaceous period, when a group of animals started to diverse astonishingly: the insects.

Insects are small and prolific. They have a hard outer skeleton of chitin, which prevents dehydration and injuries, and many of them learned to fly, so being able to cross large distances and colonize new habitats.

Insects existed, of course, at least since the Carboniferous. The most famous of them is the giant dragonfly Meganeura. But during the Cretaceous those groups that today are the most diverse started to appear in fossils: ants, bees, termites, butterflies, moths, aphids and grasshoppers. Beetles, the most diverse group of insects today (containing more species than all other arthropods together) are found in fossils since the Carboniferous, but almost went extinct during the Permian-Triassic boundary that marks the most terrible mass extinction on Earth. After this tragic event, they stayed more discrete until a boom in diversification in Cretaceous together with the already mentioned insects.

Well, all those insects needed to eat like anything else and started to feed on plants, including their pollen. That could have been a serious trouble, but plants managed to deal with it by modifying themselves in a way that the insects now became something useful to them. If insects were attracted to their pollen, why couldn’t they carry it to other plants, so assuring a more secure fertilization?
That’s exactly what plants made, but in order to attract insects even more to their reproductive organs, those started to increase in size and get nice colors. It all happened through natural selection of random mutations, of course. No one is assuming that plants or insects actually chose to change, that’s nonsense. What I’m trying to say (through a simpler way) is that those plants that were able to attach some of their pollen grains to insects, so that it reached other plants that the insect visited, were more successful to reproduce. The same way, those plants with more beautiful flowers attracted more insects and were also more successful to reproduce.

Anyway, that’s why we should thank insects for existing, since without them we wouldn’t have so nice flowers to decorate our lives. And if you like flowers but hate insects, well, you are being extremely unfair to nature.

I know that some may say “but I like butterflies. They are beautiful and cool and cute and they pollinate everything, so I just need to like these insects and not all those disgusting things.”
Oh, really? So you like butterflies? I’m sure you like this one:

Caterpillar of Agraulis vanillae. Photo by Bill Frank extracted from jaxshells.org

Most people like butterflies and hate caterpillars, but they are exactly the same thing. And actually these insects spend most of their life as a larva. Now just to satiate your curiosity, this is what that caterpillar looks like as an adult:

An adult of Agraulis vanillae on a head of Zinnia elegans. Photo by Piter K. Boll.*

But butterflies are not the only pollinators and not even the most common ones. Bees, as you know, are also very important and the main pollinators of many economically important plants, especially fructiferous ones. Wasps, flies, mosquitos, scorpionflies and moths are also important, but we cannot forget beetles.

Most basal and primitive angiosperms are pollinated by beetles, so that its more likely that these were the guys behind the appearance and diversification of flowering plants. There are many evidences for that, like an increasing diversity of angiosperms in fossil records being contemporaneous to an increase of beetle species.

Recently, some fossil flowers from the Turonian age (about 90 million years old) were found in Sayreville, New Jersey. Those were called Microvictoria svitkoana due to their astonishing similarity to the giant Amazon water lily, Victoria amazonica, even though much smaller in size.

Flower of Victoria amazonica, one of the most primitive angiosperms. It’s easy to notice that it still resembles somewhat a conifer cone. Photo by Frank Wouters, extracted from commons.wikimedia.org.

Despite primitive, it’s certainly a very beautiful flower, and it can only exist thanks to beetles of the genus Cyclocephala, like this one.

Cyclocephala hardyi, a beetle that pollinates Victoria amazonica. Photo extracted from ssaft.com/Blog/dotclear/

What do you think about it? It’s actually a cool pal, isn’t it? If you look closer, you may see that every insect is amazing in it own way, even cockroaches!

– – –

References:

Béthoux, O. 2009. The Earliest Beetle Identified. Journal of Paleontology, 83 (6), 931-937 DOI: 10.1666/08-158.1

Crepet, W. L. 1996. Timing in the evolution of derived floral characters: Upper Cretaceous (Turonian) taxa with tricolpate and tricolpate-derived pollen. Review of Palaeobotany and Palynology, 90, 339-359 DOI: 10.1016/0034-6667(95)00091-7

Gandolfo, M. A., Nixon, K. C. and Crepet, W. L. 2004. Cretaceous flowers of Nymphaeaceae and implications for complex insect entrapment pollination mechanisms in early Angiosperms. PNAS, 101 (21), 8056-8060 DOI: 10.1073/pnas.0402473101

Seymour, R. S. and Matthews, P. G. D. 2006. The Role of Thermogenesis in the Pollination Biology of the Amazon Waterlily Victoria amazonicaAnnals of Botany, 98 (6), 1129-1135 DOI: 10.1093/aob/mcl201

Creative Commons License
These works are licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Leave a comment

Filed under Botany, Ecology, Entomology, Evolution, Extinction, Paleontology

Friday Fellow: Heartworm

by Piter Kehoma Boll

Life is not composed only by beautiful and cute creatures. Parasites form a big part of life. In fact, it is likely that there are more parasitic species than non-parasitic ones.

The heartworm (Dirofilaria immitis) is one of these not-so-cute species. A species of roundworm, it infects small mammals, especially dogs, and is spread by mosquitoes.

The name heartworm comes from the fact that this worm lives in the heart and pulmonary arteries of dogs during its adult stage. The result of the infection may be heart failure and damage on the heart and the arteries, but some infections may pass completely unnoticed, especially in sedentary dogs.

Not a pleasant view. Heartworms in a dog's heart. Photo by Alan R Walker*.

Not a pleasant view. Heartworms in a dog’s heart. Photo by Alan R Walker*.

After males and females mate in the heart of the dog, females give birth to live larvae called microfilariae. These are released in the bloodstream and await for being transfered to a bloodsucking mosquito during a bite. Over 60 species of mosquitoes are known to serve as intermediate hosts of microfilariae.

Inside the mosquito, the microfilariae grow from the larval stage L1 to the larval stage L3 and then migrate to the mosquito’s salivary glands and, once it bites another dog, they are transferred to it and develop under the skin at the site of the bite to the stage L4. Now the L4 larve migrate to the dog’s muscles and develop into the stage L5. Finally, they start to migrate through the bloodstream until they reach the heart and the pulmonary artery, where they mold into adults and the cycle is complete.

We may find such worms disgusting, but we must admit that they have a complex and amazing life.

– – –

References:

Wikimedia. Dirofilaria immitis. Available at: < https://en.wikipedia.org/wiki/Dirofilaria_immitis >. Access on June 7, 2012.

Ludlam, K. W.; Jachowski, L. A.; Otto, G. G. 1970. Potential vectors of Dirofilaria imiitis. Journal of the American Veterinary Medical Association, 157: 1354-1359.

– – –

*Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Leave a comment

Filed under Friday Fellow, Parasites, worms

What’s a species 2: Vertical species concepts

by Piter Kehoma Boll

Hello, guys!

I finally decided to go on and write the second part of my article about species concepts. You can see the first part here, where I talked about horizontal species concepts. Today I’m going to talk about the other perspective, the vertical species concepts, which are based on lineages, i.e., how species happen through time.

Vertical concepts are hardly used to actually define a species, since they do not represent the current situation of living beings and it’s hard to know the real history of a population to determine its status through all his existence. However these concepts are useful in phylogenetic reconstructions and to understand how new species arrive from others through time.

Well, let’s see the two main vertical species concepts.

1. Cladistic species concept

Proposed by Ridley in 1989, it defines a species as a set of organisms between two speciation events, or between one speciation event and one extinction event. According to this, a species comes to exist when a lineage of organisms is split in two. There are no paraphyletic species in this concept, since when a speciation event occur, the ancestral species becomes extinct, giving rise to two new species.

Cladistic concept: every time a speciation event occur, two new species are created and the ancestral species becomes extinct.

2. Evolutionary species concept

An evolutionary species is defined as a set of organisms from a single lineage that has its own evolutionary tendencies and historical fate. Differently from the cladistic species, the evolutionary species does not necessarily become extinct when another lineage split from it, so being able to be paraphyletic, i.e., if a population is divided in two, the one that continues to have the same general features and the same evolutionary path is considered the same species as the ancestral one.

Evolutionary concept: a species does not necessarily become extinct during a speciation event. Species 1 is paraphyletic after split from species 2.

Since there is no record of the evolutionary history of organisms, there is no way to determine it for any species. Some ideas may be proposed and highly supported by genetic analyses, but we can never know for sure how things really happened, so that vertical concepts cannot be applied practically and are more useful to infer genetic relationships between different populations and so guide their correct management in conservation efforts.

Another point is that by vertical concepts, two organisms are considered separate species as soon as they move on in different lineages, in different populations that will not come in touch again, so that even two cousins would be different species, even though genetically, morphologically and ecologically very similar.

So vertical concepts are more useful to determine phylogeny and help in population genetics, but not to actually define species in any ecosystem, since in this case the situation is characterized by the present status of organisms and so better supported by horizontal approaches.

– – –

References:

Mayden, R. L. 1997. A hierarchy of species concepts: the denoument in the saga of the species problem, in M. F. Claridge, H. A. Dawah and M. R. Wilson (eds.), Species: The units of diversity, London: Chapman and Hall, 381-423

Ridley, M. 2004. Evolution. Blackwell Publishing. ISBN 1-4051-0345-0.

Stamos, D. N. 2002. Species, languages, and the horizontal/vertical distinction. Biology and Phylosophy, 17, 171-198.

1 Comment

Filed under Ecology, Evolution, Systematics

Friday Fellow: Mauritius Fruit Bat

by Piter Kehoma Boll

So I decided to start a new category of posts here called “Friday Fellow” (yeah, kind of a silly name, but I couldn’t figure anything better!). Every friday I’ll try to bring you one interesting species among our earthling “biosiblings” and talk a bit about it.

The first one to be presented is a nice and cute guy from Mauritius, the so called Mauritius fruit bat or Mauritius flying fox (Pteropus niger).

Mauritius fruit bat (Pteropus niger). Photo extracted from batconservacy.org

However, despite its cuteness, it is the last survivor of the Mascarene-endemic fruit bats and is facing a high risk of extinction. The country has a law to protect them, but (guess what?) fruit growers from the Islands are pressing the Mauritian government to amend that law so that it would allow “culling quotas” to control the bat’s population size, reducing so the “depredation caused to fruit crops”.

Pteropus niger is already listed as an endangered species by IUCN and if its protection is not enforced instead of amended it can in fact became extinct. It’s sad to watch people concerned only about their own problems, trying to fix them in the easiest way, without looking at the aftermath that comes from it. The Mauritius fruit bat its the largest surviving frugivore in the island, having a central role to disperse seeds. Instead of simply hunting it down, the government and fruit growers should realize that protecting the bat’s natural environment (the forests) would let it have plenty of food to consume without looking for it in fruit crops.

Let’s hope that this story will have a happy ending.

– – –

References:

Florens, F. B. V. 2012. Going to Bat for an Endangered Species. Science, 336 (6085), 1102 DOI: 10.1126/science.336.6085.1102-a

IUCN Red List:Pteropus niger. Available at <http://www.iucnredlist.org/apps/redlist/details/18743/0 >

Lubee Bat Conservacy: Africa Projects. Availabe online at <http://www.batconservancy.org/africa-projects-bat-conservation.php >

Leave a comment

Filed under Friday Fellow