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Tough as nails

Vernal pools are unique aquatic ecosystems, fleeting and unpredictable, but rich in animal life.

Vernal pools are unique aquatic ecosystems, fleeting and unpredictable, but rich in animal life.

Last night I finally managed to see the movie “Gravity”, which proves to me incontrovertibly that humans are not meant to stick their noses outside the protective layer of Earth’s atmosphere, despite having developed all kinds of high tech space gear (which, incidentally, seemed to have been designed primarily to kill Sandra Bullock’s character.) But this unexpectedly beautiful movie also made me think of a certain creature, whose amazing survival skills had lead NASA to use it to test the limits of life’s perseverance in outer space, long before somebody finally realized that people floating aimlessly in the cosmic void make for much better television.

To photograph fairy shrimp and other inhabitants of vernal pools directly in their habitat I used a complicated underwater setup with live video feed that allowed me to see what was in front of the lens. When I turned it on I was amazed how much life was there, it was almost as if I suddenly looked at a tiny coral reef.

To photograph fairy shrimp and other inhabitants of vernal pools directly in their habitat I used a complicated underwater setup with live video feed that allowed me to see what was in front of the lens. When I turned it on I was amazed how much life was there, it was almost as if I suddenly looked at a tiny coral reef.

As the first sunny days of March begin to melt away frozen remainders of winter in the northeaster United States, members of an ancient lineage of animals are getting ready to spring back to life. Throughout most of the year their habitat was as dry as a bone, but when the last patches of snow turned into water, leaf-packed depressions on the forest floor suddenly transformed into small, ephemeral ponds. Known as vernal pools, these fleeting bodies of water will be gone again by the time summer comes, but for now they create a unique aquatic ecosystem. Soon, the water is filled with thousands of tiny animals, at first not much larger than the point at the end of this sentence, but within a few weeks reaching the length of nearly a half of a pinky finger. They are the fairy shrimp (Eubranchipus vernalis), members of a group of crustaceans known as branchiopods, animals that were already present in the Cambrian seas half a billion years ago, before any plants even considered leaving water for terrestrial habitats.

Male fairy shrimp have massive, highly modified antennae, which they use to grasp and hold the female during mating.

Male fairy shrimp (Eubranchipus vernalis) have massive, highly modified antennae, which they use to grasp and hold the female during mating.

Looking at the delicate, soft body of a fairy shrimp it is hard to imagine how a lineage of organisms so seemingly fragile could have survived for so long. Take one out of the water, and it is dead within seconds. Let the oxygen level in the pond drop, and the entire population is wiped out. Given a chance, a single fish could probably do away with them all in a day, but luckily fish don’t do well in ponds that last for only a few months of a year. But fairy shrimps’ frailty is an illusion because where it counts they are as tough as nails.

In the northeastern United States several species of salamanders, such as this Spotted salamander (Ambystoma maculatum) from Westfield MA, share vernal pools with the fairy shrimp.

In the northeastern United States several species of salamanders, such as this Spotted salamander (Ambystoma maculatum) from Westfield MA, share vernal pools with the fairy shrimp.

If you live in a place as transient as a vernal pool, here now but gone in a few months, an environment of unpredictable duration and often uncertain arrival, you better have a solid survival strategy to build your life around. First, once the right environment appears, you must develop very quickly and reach reproductive maturity before the changing conditions kill you. Second, you need a method to keep your genetic line alive, even when the only habitat in which you can survive is gone. And third, plan for the unforeseeable cataclysms, such as sudden evaporation of the pool before you are ready to produce a new generation. Because, if you fail on any of these accounts, your species will not last past the first generation. Fairy shrimp, despite their unassuming physique, are master survivalists in the most hostile and unstable of habitats, and execute the three-step action plan flawlessly.

Male fairy shrimp (Eubanchipus vernalis).

Male fairy shrimp (Eubanchipus vernalis) from Estabrook Woods, MA.

As soon as the vernal pool forms, cysts containing fully formed shrimp embryos from the year before break open, and minute, swimming larvae emerge. They immediately start feeding on microscopic algae and bacteria already present in the water, and grow like crazy. During the first few days of their lives, baby fairy shrimp, known as nauplii, increase their length by a third and nearly double their weight every day. In about a month the animals are fully grown. One pair of the males’ antennae develops into giant, antler-like projections that help them catch and grasp their mating partners, while females grow big egg pouches on their abdomens. A few days later females start to lay at the bottom of the pool large clutches of cysts, eggs with embryos already developing inside, and die shortly after. Soon the water level in the pool begins to drop, and by June all traces of the once vibrant aquatic habitat are usually gone.

The body of a fairy shrimp is nearly translucent, which makes them invisible to a predator looking from above.

The body of a fairy shrimp is nearly translucent, which makes them invisible to a predator looking from above.

But inside the cysts hidden under a thin layer of soil the embryos are very much alive. They slowly continue their development, but can remain in the dormant state, out of the water, baking in the sun or being frozen in ice, for many years. Their outer shell is nearly waterproof, and quite sticky. This stickiness explains the sudden appearance of fairy shrimp in the most unexpected places, including old tires filled with water, after hitching a ride on the legs of birds and other animals. These cysts can live through being dipped in boiling water and liquid air (-194.35 °C, or -317.83°F), which is one of the reasons why these organisms are being used by NASA to test the survival of life outside of Earth’s atmosphere.
The following spring, if everything goes as planned, water of the melting snow awakens the dormant embryos, and within a few days they break the shell of their tiny survival capsules. But not all of them. Only a portion of the cysts responds to the first appearance of water, while others continue their slumber. If the pool dries prematurely, as it sometimes happens during a particularly warm spring, all early hatchlings die, and a second batch of larvae will emerge only if the pool fills up with water again. It has been shown that some cysts in a clutch will wait through eight cycles of wetting and drying before finally deciding to hatch. Fairy shrimp have evolved this ingenious strategy of hedging their reproductive bets in response to the erratic nature of their habitat, and it clearly serves them very well.

Fairy shrimp swim upside down, using 10 pairs of legs to propel themselves and collect bits of algae to feed on.

Fairy shrimp swim upside down, using 10 pairs of legs to propel themselves and collect bits of algae to feed on.

Mozambique Diary: Pardalota

Pardalota reimeri, probably the most colorful and one of the rarest katydids in the world. The individuals I observed in Quirimbas are the first record of this species in 103 years.

Pardalota reimeri, probably the most colorful and one of the rarest katydids in the world. The individuals I observed in Quirimbas are the first record of this species in 103 years.

Ever since I can remember I have been having a recurring nightmare: I am in some incredible location – usually somewhere in the tropics, there are amazing insects everywhere, often those that I have been dying to find, but I need to leave immediately and have none of my collecting gear – not a single vial, no net, no camera (not everybody can relate, I realize, but entomologists know what I am talking about). And last month I finally got to live through this bad dream.

A defensive display of Pardalota reimeri – these katydids feed on highly toxic plants and is likely that their bodies are loaded with poisonous alkaloids.

A defensive display of Pardalota reimeri – these katydids feed on highly toxic plants and is likely that their bodies are loaded with poisonous alkaloids.

Before coming to Gorongosa I flew to the northern town of Pemba where a newly opened campus of the University of Lurió trains Mozambican students in biology and engineering. It was supposed to be a strictly-business trip, meeting lecturers and students, and for this reason I did not bring with me any collecting or sound recording equipment, and only the most basic photo gear. But my friend Harith had a better idea and decided to take me on a short trip to Quirimbas National Park, famous chiefly for its spectacular marine life. Some of his students were working on insect and amphibian faunas of the park, and I said, “Why the hell not.” The seemingly easy trip turned briefly into hell after our Mitsubishi truck decided to part ways with its clutch right in the middle of nowhere. After a long while a friendly driver in a passing car went to fetch a tow truck for us, and eventually we made it to the park.

An unidentified, aposemtically-colored tiger moth found on the same plants as Pardalota.

An unidentified, aposemtically-colored tiger moth found on the same plants as Pardalota.

The first thing that I noticed was the wall of insect sound. The lush miombo forest reverberated with loud katydid calls, ones that I did not recognize. They were unusual for a couple of reasons. One, it was the middle of a hot, African day, and katydids tend not to like it, preferring to call under the cover of the night. And two, the calls were continuous, low frequency, and very complex. They were telling everybody with ears, “Here I am, come and get me.” And when you do that you better have a good trick up your sleeve to protect yourself, as katydid ladies are not the only ones listening: birds, lizards, monkeys, they all love big, juicy insects.

The katydids were calling from high in the trees and I was afraid that I would not be able to catch, or even see them. But then one flew down from the canopy and landed right in front of me. When I saw what it was, my heart skipped a beat – it was Pardalota reimeri, the Holy Grail for katydid aficionados (there are a few of us out there). This species had been known only from the original type series, described in 1911 and preserved in a museum in Berlin. What is special about this species is that even those old, dried husks retained vivid, crazy colors, unlike those of any other known katydid species. And colors as awesome as this indicate an equally awesome biology.

I caught the katydid and he immediately went into a defensive mode: he opened his bright purple, black and white wings, and exposed his neon-orange abdomen and cervical membrane; he lifted his hind legs that had yellow and black markings, remarkably similar to those of toxic chrysomelid beetles. This was either a daring bluff, or this thing was seriously poisonous. All around me other males continued to sing.

A video of a P. reimeri nymph – although the insect is not feeding it gives the perfect illusion of the front end of a fuzzy caterpillar chewing on a leaf.

What to do? Here I was, surrounded by a remarkable entomological discovery, but with no way to collect, preserve, or record it. I decided to exploit Harith’s students and we fanned out looking for the insects. Soon we discovered where they sang – they were only calling from, and feeding on, two species of trees, both known to produce potent chemical defenses, including some powerful psychoactive alkaloids. This almost certainly explained their aposematic coloration. We also found nymphs of this species, which turned out to be incredibly hairy. In fact, when I first saw one I thought I was looking at a fuzzy caterpillar feeding on a toxic plant – its movements were an uncanny imitation of the front end of a caterpillar chewing on a leaf, even though I was looking at at the katydid’s butt. It wasn’t shocking then when a minute later I noticed very similar looking caterpillars feeding on the same plant and, also on the same plant, tiger moths (well known to be toxic) wearing colors very similar to those of the katydids’. Having nothing else at my disposal I pointed my Canon 6D at the canopy and used its video recording feature to record the sound of the singing males. I collected as many individuals as I could, stuffing them into Ziplock bags, hoping to be able to get decent photos and proper sound recordings later on.

In the end I managed to collect enough material and data to write a short note about the biology of this species. But not being able to do a very good job at data and specimen collecting in the field was not a pleasant experience. I have already learned never to go anywhere without my headlamp, a GPS, and a camera, and now I am adding to this list an ultrasonic sound recorder and a large set of vials with 96% ethanol. On the second thought, maybe also an extra clutch for a Mitsubishi and a satellite phone. And some beer, for emergencies.
Two nights later I had a nightmare about Quirimbas.

A female P. reimeri cleaning her foot.

A female P. reimeri cleaning her foot.

Mozambique Diary: Victims of our deficiencies

Am I the only person who thinks that the White-headed vulture (Trigonoceps occipitalis) looks like Billy Idol's doppelgänger?

Am I the only person who thinks that the White-headed vulture (Trigonoceps occipitalis) looks like Billy Idol’s doppelgänger?

I had a very short and uneventful tenure as a boy scout – I simply could not stand having my activities organized for me, and the idea of wearing a uniform fills me with dread to this day. But I did learn a valuable lesson at one of my camping trips: if a can of meat appears bulgy, throw it away. Botulism, a deadly disease caused by the bacterium Clostridium botulinum, is something that our immune system cannot cope with, and thus it is not surprising that our species has evolved an innate repulsion to things that are dead or putrid. This aversion protects us from getting in contact with other harmful microorganisms that cause such diseases as salmonellosis, anthrax, or cholera. Unfortunately, the same revulsion also makes us consider creatures that are resistant to the deadly effect of these pathogens with disdain. We tend to treat animals that feed on carrion or dung as the lowest possible forms of life, oblivious to the fact that necrovores and coprophages’ immune system and  their efficiency in procuring nourishments  are far superior to ours.

Two events in 2013 made me think about the legions of these underappreciated, but critically important, members of animal communities. The first one was the biological survey of the Cheringoma Plateau in Gorongosa National Park, which I lead in April and May. Among many groups of organisms that we surveyed were dung beetles, heroically sampled by Bruno de Medeiros, who had to withstand countless, painfully repetitive jokes about his “bait.” But in the end Bruno proved not only that Gorongosa had a surprisingly rich fauna of these insects, indicative of a rich and diverse fauna of vertebrates, but also that some of the beetles were both beautiful and had fascinating behaviors. An earlier post on this blog mentions some of these findings.

After following a radio-collared lion, Gorongosa veterinarian Rui Branco (right) lead us to a freshly killed sable antelope.

After following a radio-collared lion, Gorongosa veterinarian Rui Branco (right) lead us to a freshly killed sable antelope.

I went back to Gorongosa in September and this time I was privileged to witness another remarkable, yet blatantly underappreciated animal in action, the vulture. Seeing them feeding on a carcass of an antelope killed by lions was for me the highlight of 2013. Which is saying a lot, considering that this year I have also seen centipedes with feathers, the cat mantis, frog-eating spiders, bomb-sniffing rats, and ants that cannot walk. Vultures are birds, I know, but I feel that they deserve being considered honorary members of the Smaller Majority on account of the low esteem in which they are generally held – just like most things that look or behave in a way that is unlike us, mighty humans.

Once the lions had left about fifty White-backed vultures (Gyps africanus) descended onto the carcass.

Once the lions had left about fifty White-backed vultures (Gyps africanus) descended onto the carcass.

But vultures, two unrelated groups of birds that have converged on similar appearance and behavior, are both fascinating and remarkably beautiful. In the New World members of the family Catharitidae and in the Old World some members of Accipitridae have evolved the ability to locate and feed on carcasses of large vertebrates. In order to do this they had to acquire the ability to sniff them out from many miles away, a feat that they were able to achieve through extremely well developed olfactory tubercles in their nasal cavities, scrolled and lined with epithelium innervated by the olfactory nerve. Interestingly, early naturalists speculated that vultures’ ability to find carrion was due to the possession of a mysterious “occult sense.” More pragmatic and rational scientists realized that vultures’ incredible sense of smell can be put to a good use, and in late 1930s the Union Oil Company began to inject mercaptan, a compound produced by rotting flesh, into gas lines in order to patrol them for Turkey vultures attracted to leakages from damaged pipes.

Thirty minutes later all meat has been stripped from the antelope's carcass, leaving only bones, pieces of skin, and the stomach content.

Thirty minutes later all meat has been stripped from the antelope’s carcass, leaving only bones, pieces of skin, and the stomach content.

Even more impressive is the vultures’ ability to resist the toxins produced by C. botulinum, Salmonella, Bacillus anthracis, Vibrio cholerae, and other deadly pathogens. Their first line of defense is, surprisingly, avoidance of rotten meat. Contrary to popular belief vultures prefer meat of freshly killed animals, and will eat old, decaying flesh only if absolutely desperate. But even if they consume meat infected with these bacteria, the extremely high acidity of their stomachs kills almost anything that might have been alive in the carrion. Gastric fluids in vultures have pH levels of 0.2-0.8 – essentially equivalent to pure hydrochloric acid (in humans it usually ranges between 2.0 to 3.5.) This high acidity also allows them to digest bones, and the Bearded vulture (Gypaetus barbatus) is the only vertebrate feeding exclusively on bones (even spotted hyenas eat bones only occasionally). But on top of this vultures have incredibly efficient immune response to pathogens, making them virtually impervious to infections and diseases. This fact is not lost on some, and in Colombia drinking vulture blood is considered an effective cure for cancer (albeit the efficacy of such a treatment has yet to be evaluated by the medical community).

Like cruel children who mock those among them who are different and often more talented, our entire species picks on those organisms that don’t conform to our notions of normalcy. We tell ourselves that dung beetles and vultures are disgusting, but I think that deep down we are just jealous.

We tell ourselves that vultures are ugly and disgusting, but I think we are just jealous of their superior abilities and survival skills.

We tell ourselves that vultures are ugly and disgusting, but I think we are just jealous of their superior abilities and survival skills.

Happy 2014!