Ooze like an amoeba, float like a bird - wish we could still do that when stressed!

Here's another fun weird science story from NPR, about a creature that might be in the dirt in your own backyard:

20100305 Me 03 by Npr
Download now or listen on posterous

Naegleria-NPR.mp3 (1426 KB)

Courtesy of Lillian Fritz-Laylan
Naegleria gruberi grows a pair of flagella when under stress. But unlike a sperm tail, it puts these appendages out front, and swims by breast stroke. The organism is stained to emphasize its anatomy.

If you prefer to read the story rather than listen to it aloud, here's the transcript via npr.org.

While that behavioral and morphological flexibility is remarkable enough in something we might, from our lofty hominid perch, consider rather "primitive" and "simple", what graduate student Lillian Fritz-Laylan and colleagues found in its genome is perhaps even more surprising. Whle the NPR story focuses on the physical transformation of the organism, cool as that is, the full story is much richer and has far more significance for our own origins from a common eukaryotic ancestor. As they describe in their paper in the current issue of Cell, Naegleria gruberi turns out to have almost 16000 protein-coding genes, which is over two-thirds of what you and I have! A single celled organism with that many genes - no wonder it can transform itself so radically.

Here's an image from the paper illustrating that transformation, which takes a mere 90 minutes or so (far cooler special effects at half the duration of Avatar, if you ask me!):

Figure 1: Schematic of Naegleria Amoeba and Flagellate Forms. Naegleria amoebae move along a surface with a large blunt pseudopod. Changing direction (arrows) follows the eruption of a new, usually anterior, pseudopod. Naegleria maintains fluid balance using a contractile vacuole. The nucleus contains a large nucleolus. The cytoplasm has many mitochondria and food vacuoles that are excluded from pseudopods. Flagellates also contain canonical basal bodies and flagella (insets). Basal bodies are connected to the nuclear envelope via a single striated rootlet. 

Is it just me, or does that upper image, of the amoeboid form, remind you of someone? And... I just realized... that someone also has two apparent flagellae at the top of his head, which unfurl during times of stress!! What better proof do you want of our shared ancestry with Naegleria, eh? No? Oh, what - you mean citing widely published and viewed cartoons is not good enough evidence for you (even though that is a standard of evidence good enough for a third of the good people of Texas)? You want all the boring science-y stuff instead? Well, go read the paper then, which the journal Cell has graciously made freely available!

The paper (luckily for you) turns out to be far from boring. It is indeed quite fascinating because, apart from presenting the complete genome sequence of this remarkable free-living protist, Fritz-Laylan et al also describe several genetic modules for aerobic and anaerobic metabolism (for these guys can do both), amoeboid motility, and a number of other structural and functional necessities of the ecologically diverse lifestyles common to their clade. Further, comparisons with genomes of other protists allow them to predict which genes might have been present in the genome of the common ancestor to all eukaryotes. As the first representative of a fifth (out of 6) major clade of eukaryotes whose genomes have been sequenced thus far, Naegleria holds great promise of generating fresh insights into the early evolution and diversificatiion of eukaryotes. While their lineage diverged from the one we hail from about, oh, a billion or so years ago, understanding their genome brings us closer to understanding and reconstructing the genome of our shared ancestors, those early free-living eukaryotes that gave rise to us both. For it turns out that they contain over 4000 protein families that are similar to ones we have, and therefore were likely found in that common ancestor! That ancestor was presumably also quite versatile and equipped with a set of flexible modules to deal with the diverse environments of that time. And that remarkable flexibility probably underlies the extraordinary diversity of organisms that subsequently evolved from that ancestor. How fascinating and wonderful is that! (Even if some of us later lost the ability to transform ourselves and float away when under stress!)

Let me end with a video where the lead authors talk about what Nargleria's genome can tell us about our own ancestry:

Reference:

Fritz-Laylin, L., Prochnik, S., Ginger, M., Dacks, J., Carpenter, M., Field, M., Kuo, A., Paredez, A., Chapman, J., & Pham, J. (2010). The Genome of Naegleria gruberi Illuminates Early Eukaryotic Versatility Cell, 140 (5), 631-642 DOI: 10.1016/j.cell.2010.01.032

Posted via email from a leaf warbler's gleanings

Read More...

Summary only...

Weird-cool bubble-headed Barreleyes like only evolution can come up with

Now here's a wonderful, bizarre discovery from scientists at our neighboring Monterey Bay Aquarium Research Institute:

Researchers at the Monterey Bay Aquarium Research Institute recently solved the half-century-old mystery of a fish with tubular eyes and a transparent head. Ever since the "barreleye" fish Macropinna microstoma was first described in 1939, marine biologists have known that its tubular eyes are very good at collecting light. However, the eyes were believed to be fixed in place and seemed to provide only a "tunnel-vision" view of whatever was directly above the fish's head. A new paper by Bruce Robison and Kim Reisenbichler shows that these unusual eyes can rotate within a transparent shield that covers the fish's head. This allows the barreleye to peer up at potential prey or focus forward to see what it is eating.

The barreleye (Macropinna microstoma) has extremely light-sensitive eyes that can rotate within a transparent, fluid-filled shield on its head. The fish's tubular eyes are capped by bright green lenses. The eyes point upward (as shown here) when the fish is looking for food overhead. They point forward when the fish is feeding. The two spots above the fish's mouth are are olfactory organs called nares, which are analogous to human nostrils. Image: © 2004 MBARI

Deep-sea fish have adapted to their pitch-black environment in a variety of amazing ways. Several species of deep-water fishes in the family Opisthoproctidae are called "barreleyes" because their eyes are tubular in shape. Barreleyes typically live near the depth where sunlight from the surface fades to complete blackness. They use their ultra-sensitive tubular eyes to search for the faint silhouettes of prey overhead.

Although such tubular eyes are very good at collecting light, they have a very narrow field of view. Furthermore, until now, most marine biologists believed that barreleye's eyes were fixed in their heads, which would allow them to only look upward. This would make it impossible for the fishes to see what was directly in front of them, and very difficult for them to capture prey with their small, pointed mouths.

And what's more, the researchers got them on video too - look below the fold:

Robison and Reisenbichler used video from MBARI's remotely operated vehicles (ROVs) to study barreleyes in the deep waters just offshore of Central California. At depths of 600 to 800 meters (2,000 to 2,600 feet) below the surface, the ROV cameras typically showed these fish hanging motionless in the water, their eyes glowing a vivid green in the ROV's bright lights. The ROV video also revealed a previously undescribed feature of these fish--its eyes are surrounded by a transparent, fluid-filled shield that covers the top of the fish's head.

Most existing descriptions and illustrations of this fish do not show its fluid-filled shield, probably because this fragile structure was destroyed when the fish were brought up from the deep in nets. However, Robison and Reisenbichler were extremely fortunate--they were able to bring a net-caught barreleye to the surface alive, where it survived for several hours in a ship-board aquarium. Within this controlled environment, the researchers were able to confirm what they had seen in the ROV video--the fish rotated its tubular eyes as it turned its body from a horizontal to a vertical position.

In addition to their amazing "headgear," barreleyes have a variety of other interesting adaptations to deep-sea life. Their large, flat fins allow them to remain nearly motionless in the water, and to maneuver very precisely (much like MBARI's ROVs). Their small mouths suggest that they can be very precise and selective in capturing small prey. On the other hand, their digestive systems are very large, which suggests that they can eat a variety of small drifting animals as well as jellies. In fact, the stomachs of the two net-caught fish contained fragments of jellies.

After documenting and studying the barreleye's unique adaptations, Robison and Reisenbichler developed a working hypothesis about how this animal makes a living. Most of the time, the fish hangs motionless in the water, with its body in a horizontal position and its eyes looking upward. The green pigments in its eyes may filter out sunlight coming directly from the sea surface, helping the barreleye spot the bioluminescent glow of jellies or other animals directly overhead. When it spots prey (such as a drifting jelly), the fish rotates its eyes forward and swims upward, in feeding mode.

Barreleyes share their deep-sea environment with many different types of jellies. Some of the most common are siphonophores (colonial jellies) in the genus Apolemia. These siphonophores grow to over 10 meters (33 feet) long. Like living drift nets, they trail thousands of stinging tentacles, which capture copepods and other small animals. The researchers speculate that barreleyes may maneuver carefully among the siphonophore's tentacles, picking off the captured organisms. The fish's eyes would rotate to help the fish keep its "eyes on the prize," while its transparent shield would protect the fish's eyes from the siphonophore's stinging cells.

Read More...

Summary only...

Samurai Crab

Submitted by Nasir Sadeghi.

Heikegani crabs of Japan have markings on their carapace that resemble a human face, the face of a medieval samurai to be exact. It is locally believed that these crabs are reincarnations of the spirits of the Heike warriors defeated at the Battle of Dan-no-ura as told in the >Heike Monogatari ("The Tale of the Heike"). It is believed that when caught, these crabs are not eaten, but are thrown back into the water because if they're resemblance to a human face. This raises a question: how could the face of a samurai end up on the carapace of a Japanese crab?

It is thought that from the first crab that had a carapace shaped remotely like a human face, it was thrown back into the water, and thus humans were applying artificial selection on the crabs. Fishermen were probably reluctant to eat a crab with a human face, and because of this, these crabs were selected for, and thus this phenotype was passed down the hereditary line. Over the generation of interaction between humans and these crabs, the crabs with patterns resembling the samurai face preferentially survived. None of this involves the crab making a conscious decision about its carapace pattern (Lamarkian Evolution), but it is the artificial selection being imposed on the crabs from the outside that is responsible for this phenomena.

Read More...

Summary only...

The trouble with eating things with claws

... is that they can get you even after you've killed them! If you need another reason to stay away from eating chicken-feet, check out this photo: they might be kinda hard to swallow!

Note, however, that this is not a case of a bird trying to fight its way out of they hawk's gullet - more an accident when you try to swallow sharp objects that can rupture your crop and burst through your skin! This poor little Sharp-shinned Hawk had properly killed the small bird it was trying to eat, but appears to have bitten off more than it could swallow, resulting in a rather bizarre death. Can we nominate this hawk for a Darwin Award?

[From Dead Hawk's Last Meal Claws Partway Out]

Read More...

Summary only...

Weird Ways to Pick Your Mate

Student post submitted by Stephanie Chow.

Can you imagine picking your soul mate merely by their scent? It has been shown that people can show a preference to certain people of the opposite sex based on how they smell (Wedekind et al 1995; click on photo for another such study). In the experiment, participants were asked to wear a t-shirt for two consecutive nights, and remain as odor-neutral as possible during this period (use fragrance-free detergent and soap, refrain from exercising and eating smelly foods). Participants also had their MHC (major histocompatibility complex) typed. The shirts were then collected and given to members of the opposite sex to sniff and rate how pleasant the odors were to them. The more pleasant the odor, the “sexier” that person was considered. These results were compared to the degree of closeness of the male’s and female’s MHC. The males and females that had more difference between their MHCs found each other’s scents more attractive than those who had similar MHCs. Essentially, people’s preference towards different MHCs ensures a greater chance for variation in this important factor of the immune system. This is an important selection aid to avoid inbreeding. By nature, people tend to show preferences towards people that are more like them. If there were not selection guides, like the scent preference linked to MHCs, there would be a much higher incidence of inbreeding. As a result, there would be less genetic variation and a higher incidence of accumulation of deleterious mutations or rare genetic diseases in the inbred population.

A more recent study showed human males’ innate ability to detect higher probability for mating success at strip clubs (Miller et al 2007).

Lap dancers were asked to report their tip earning for each shift they worked, and to also record their ovulatory cycle for 60 days. The results showed that men were most responsive to women approximately one week after their menstruation had ceased. This implies that the men found the women most attractive (indicated by a higher tip amount) when they were the most fertile—just before ovulation. Part of this study also asked men to rate the attractiveness of each woman’s body (the faces were covered) in photographs of women during their peak fertile period compared to other times during their cycle. The picture taken during ovulation was deemed the most attractive. This is due to the slight physical changes in women during ovulation: increased facial attractiveness, decreased hip-to-waist ratio, and increased body symmetry—all traits that men perceive as more attractive in a woman. This heightened sensitivity to women’s ovulatory cycle is comparable to other animals—such as dogs—being in estrous or “heat”.

References:

Wedekind, C., Seebeck, T., Bettens, F., Paepke, A.J. (1995). MHC-Dependent Mate Preferences in Humans. Proceedings of the Royal Society B: Biological Sciences, 260(1359), 245-249. DOI: 10.1098/rspb.1995.0087

Miller, G., Tybur, J., Jordan, B. (2007). Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus? Evolution and Human Behavior, 28(6), 375-381. DOI: 10.1016/j.evolhumbehav.2007.06.002

Read More...

Summary only...

Ages of Rocks or Rocks of Ages

Hat-tip to Pharyngula for this wonderful video. As I pondered what those sage rocks would think of our ephemeral evolution-creation culture wars, and scratched my head (and keyboard) for a title for this blog post, I stumbled upon this. Some added context to the show coming into town next week, I suppose!

Read More...

Summary only...

And now, a frog with no lungs!

Such a biological wonder has indeed now been discovered lurking in the rainforests of Borneo, as you may have read in the science blogosphere and even mainstream news channels already!

Ain't evolution cool! Its never about "progress" in a certain direction, or increasing complexity, or any other "upward" trajectory we may think of. Its always about what works best for a given organism in its particular environmental circumstance: if a trait (such as lungs or skin to breathe through) works well enough to let you survive and make lots of babies, it may prevail and become the norm in your lineage; OTOH, if an existing trait (such as your newly evolved lungs) get in the way of surviving and procreating, natural selection might well get rid of it! Sometimes, your entire lineage goes with the trait - natural selection isn't really all that particular in that way. But if, like this frog, you have one troublesome big trait that is chafing against the filter of selection, and also have a backup system to perform the same physiological function, you may get away with losing the big new innovation!

These frogs apparently live in fast, cold, mountain streams rich enough in oxygen that they can get enough through their skins. Of course all amphibians can breathe through their skin to some extent, but the big innovation that allowed them to plant the tetrapod flag in the terrestrial realm in the first place, was of course lungs! Yet these little guys have given up on lungs, and, unable to re-invent more ancestral gills, reverted to the skin - and it'll be fascinating now to study how that skin has evolved in this species.

Meanwhile, the serendipitous discovery of this wonder must give pause to my friends who are against vivisection (for many good reasons, and some poor ones), and even against collecting specimens at all for museum collections or scientific study. And it becomes harder to argue with activists of that persuasion when it comes to rare new species. Yet, this amazing discovery would not have been possible if someone hadn't thought to look inside the body of the frog! Contrary to what the romantic Wordsworth wrote, I have to contend that we biologists do not always "murder to dissect"!

Read More...

Summary only...

Grey-Faced Sengi - in action

And if you want to communicate directly with the discoverer Francesco Rovero, tune in to Conservation International's live chat today (@ 1:00 PM EST).

Read More...

Summary only...

Now I know why the sun sometimes makes me go ACHOO!

Do you find that your nose gets ticklish when you step out into the sun suddenly sometimes? If so, you just might have the Autosomal-dominant Compelling Helio-Ophthalmic Outburst syndrome (ACHOO!) - a phenomenon noted even by Aristotle in his Book of Problems, but thought obscure enough by scientists to bother giving it its own above syndrome name/acronym until 1978! More simply called the Photic Sneeze Reflex (PSR), it may result from a neural crosswiring in one's face - a current leakage between the optic (which controls pupil contraction due to sudden sunlight exposure) and trigeminal (senses nasal irritation and causes sneezing) nerves!

Aristotle mused about why one sneezes more after looking at the sun in The Book of Problems: "Why does the heat of the sun provoke sneezing?" He surmised that the heat of the sun on the nose was probably responsible.

Some 2 ,000 years later, in the early 17th century, English philosopher Francis Bacon neatly refuted that idea by stepping into the sun with his eyes closed—the heat was still there, but the sneeze was not (a compact demonstration of the fledgling scientific method). Bacon's best guess was that the sun's light made the eyes water, and then that moisture ("braine humour," literally) seeped into and irritated the nose.

Humours aside, Bacon's moisture hypothesis seemed quite reasonable until our modern understanding of physiology made it clear that the sneeze happens too quickly after light exposure to be the result of the comparatively sluggish tear ducts. So neurology steps in: Most experts now agree that crossed wires in the brain are probably responsible for the photic sneeze reflex.

A sneeze is usually triggered by an irritation in the nose, which is sensed by the trigeminal nerve, a cranial nerve responsible for facial sensation and motor control. This nerve is in close proximity to the optic nerve, which senses, for example, a sudden flood of light entering the retina. As the optic nerve fires to signal the brain to constrict the pupils, the theory goes, some of the electrical signal is sensed by the trigeminal nerve and mistaken by the brain as an irritant in the nose. Hence, a sneeze.

Yet another example of our not-so-intelligently-designed but marvelously quirky evolved bodies, eh?

[Hat-tip to Mark Hoofnagle of Denialism Blog]

Read More...

Summary only...

Kinky? Gross? But they're just beetles...

(Fleur Champion de Crespigny)

You know, those little creatures that any mythical "creator" must have an inordinate fondness for, because there are so many of them! So what's kinky/gross about them? Well, you just have to read this really sexy new paper by Martin Edvardsson in the latest Animal Behaviour:

Female Callosobruchus maculatus mate when they are thirsty: resource-rich ejaculates as mating effort in a beetle

Don't tell me you would pass up that tantalizing title if you found it on the newsstand! But if you still find it dry and academic, you can always turn to some friendly science blogger to pre-digest it for you: Jake Young adds good background with a video so you can see what bruchid beetles are, while Mo the Neurophilosopher offers the truly scary photo of male genitalia in these beetles.

Its all "about nuptial gifts (basically, females will trade sex for drinks)" as pondering pikaia puts it, although it seems to me these females have a rather rougher bargain than that - just look at that penis!

Ain't evolution cool?

Read More...

Summary only...