Zombie Birds, Astronaut Fish, and Other Weird Animals
Page 16
Once a pearlfish species from the Carapus or Encheliophis genera stumbles across a sea cucumber, it will locate its new host’s anus, or cloaca, by following the current of water that is inhaled and expelled out of it via a structure called the respiratory tree. Sea cucumbers are the only animals in the world to have respiratory trees and they are one of three sites, along with the tube feet and body wall, by which the creatures take in oxygen from the water. With the anus located, the pearlfish—which can grow up to 20 inches long—will tap the anus area a little before penetrating the sea cucumber by one of two methods: headfirst, propelling itself inside by violently thrusting its tail from side to side, or tail first, coordinating its inwards slide with the sea cucumber’s next exhale. Once inside, the pearlfish settles into the respiratory tree.
Now you know why the pearlfish is otherwise known as the assfish. They are also built to be an assfish, their anuses set in a position on the body that allows them to emerge partway out of the host to excrete waste into the ocean without having to completely exit and risk predation.
Most often, pearlfish don’t like to share their hosts with other pearlfish; however, there have been cases of some Encheliophis species living in sexual pairs inside their sea cucumbers. And in 1977, New Zealand biologist Victor Benno Meyer-Rochow from Jacobs University in Germany discovered a 16-inch-long sea cucumber into which no less than fifteen pearlfish had taken up residence. While researchers are yet to prove whether or not sea cucumbers act as a breeding site for the pearlfish, they do provide an environment in which their larvae can transform into their adult forms, which sees their eel-like bodies thicken and then shorten by up to 60 percent.
While the sea cucumber–pearlfish relationship has been well known for many years, how the pearlfish behaved toward one another when competing for a host was not clearly understood. In 2002, scientists from the University of California in Santa Cruz decided to find out. They examined two species of sea cucumber hosts: a black-skinned species called the pineapple sea cucumber (Thelenota ananas), which wears a coat of fleshy projections called papillae in the shape of sunset orange–colored stars; and the leopard sea cucumber (Bohadschia argus), a portly golden or grey sausage of an animal with a psychedelic splattering of dirty white haloes across its leathery skin. The leopard sea cucumber grows up to 20 inches long and the pineapple sea cucumber can stretch to a little over 3 feet.
Collecting a number of each sea cucumber species from their natural habitats, the team observed the relationships between the pearlfish and the sea cucumbers in the lab. They found that the pearlfish would fight to the death over a host—sometimes inside a host—and would actively check if anyone was home before entering. “Both species of carapids seemed to listen along the body of the host almost as if trying to detect the presence of another occupant inside,” the team reported.
Gross, Pearlfish. Just … I’m trying to find a redeeming feature but what do you say about an assfish? You’d better have a cool job or something because that’s honestly the only way you’re going to get anyone to talk to you. Stop laughing, I’m trying to help you! Okay, say you meet someone: a girl, a prospective boss, a friend of a friend of a friend at a party, it doesn’t matter, Pearlfish. Here’s how I see your opening conversation going.
Scenario 1
“Hi, I’m Robin.”
“Hi, I’m Pearlfish.”
“That’s a pretty name. Where do you live?”
“In an anus.”
“Oh my God. What do you do?”
“I’m a poet.”
“Hey, that’s cool.”
Scenario 2
“Hi, I’m Robin.”
“Hi, I’m Pearlfish.”
“That’s a pretty name. Where do you live?”
“In an anus.”
“Oh my god. What do you do?”
“I’m an artist.”
“Hey, that’s cool.”
Scenario 3
“Hi, I’m Robin.”
“Hi, I’m Pearlfish.”
“That’s a pretty name. Where do you live?”
“In an anus.”
“Oh my god. What do you do?”
“I’m a judge on MasterChef.”
“The nice one?”
“We’re all nice. That’s the point.”
“Yeah, true. Hey, that’s cool.”
Scenario 4
“Hi, I’m Robin.”
“Hi, I’m Pearlfish.”
“That’s a pretty name. Where do you live?”
“In an anus.”
“Oh my god. What do you do?”
“Nothing/Banker/Waiter/Mechanic.” (It doesn’t matter at this point, Pearlfish.)
“That’s so fucked.”
Houdini with an Inflatable Head
CACOXENUS INDAGATOR
“Mr. C. indagator, I’m sorry to tell you, but your wife has decided she wants half of all your assets. You didn’t sign a prenup; you slept with a Mexican stripper. Twice. There’s just no escaping this.”
“Oh yeah?” *pfft pfft pfft* “How about now?”
“You’re still ruined, Mr. C. indagator. And now your head isn’t going to fit through the door.”
WHEN YOU NEED TO get out of a tight spot, ordinarily you’d be advised to think small. Unless you’re a Cacoxenus indagator, in which case you’ve got to think big.
C. indagator is a species of fly that lives in Western Europe, with ruby red eyes bulging out of a dusty black body. It belongs to the Drosophilidae family of flies, which is a large, diverse group that includes the well-known common fruit fly (Drosophila melanogaster). And just like the fruit fly, C. indagator has a particular penchant for sweet substances and has evolved an extraordinary mechanism for acquiring them as larvae.
The object of C. indagator’s desire is the pollen and nectar mixture that the red mason bee (Osmia bicornis) stores in its tube-shaped nest. The red mason bee, which is a fuzzy black and copper-colored species from all over Europe, North America, Turkey, and Iran, is what’s known as a solitary bee. This means that rather than living in a nest built by the entire colony, as honeybees do, the red mason bee will move into any thin tunnels or cavities they come across, whether holes burrowed into a tree trunk by a beetle or cracks in crumbling masonry around populated areas. Every spring, the female red mason bee drops her mixture of pollen and nectar into the farthest end of the tube, attaches a single egg to the wall, and closes the two of them in by constructing a 0.08–0.24-inch-thick wall of mud that quickly dries hard. She will repeat the process all the way up the tube nest, filling each brood cavity with an egg and a package of sweet nutrients.
Over the following months, the egg will hatch into a larva that will spin itself into a cocoon when old enough, and eventually emerge as an adult. At this point it will have mandibles strong enough to nibble its way through its mother’s mud wall, which it will do to release itself from the tube nest. Of course, a package of nutrients is the perfect food resource for a parasitic species, but many do not have mandibles strong enough to break their way through the mud walls, such as the flies that raid dauber wasp cavities—around 12 percent won’t make it out alive. But C. indagator has figured out a way around this, as Erhard Strohm, an entomologist from the Institute of Zoology at Germany’s University of Regensburg, discovered in late 2010.
“We observed Cacoxenus that were freshly enclosed from their cocoons for a project with the aim to analyze how they orientate to emerge from the brood cells of their hosts and we had the working hypothesis that the flies use the same cues as the bees themselves,” says Strohm.
Under a stereomicroscope, I saw that the young flies touched the walls with their forelegs, probably in order to detect the side that is convex, since this is the side that points to the entrance of the nest. Surprisingly, they then started to press their heads into small crevices at this side of the nest partition and their head blisters began to pulse and were eventually fully inflated.
So C. indagator hides itself inside a b
rood cell, eats another species’ offspring and then inflates it own head to break itself free. But how does one inflate one’s own head without damaging oneself? By filming them, Strohm was able to figure out that they pump hemolymph, which is the fluid in the circulatory system of some arthropods that acts like blood, into their ptilinum—a pouch on the head above the base of the antenna that can be turned outward or inside out. Publishing in Physiological Entomology, Strohm described the closed-in fly as being able to locate small crevices in the mud walls, against which it would press its body and abruptly expand its head, breaking pieces of the partition away using hydraulic pressure.
This process would only take from 5–30 seconds, and because the fly is still young at this stage, it is able to squeeze its soft, developing body through the small hole it has created and escape. “Interestingly, the cuticle is still very soft, so that they can ‘distort’ their bodies to a large extent. I actually do not know whether C. indagator can inflate their head blisters more than when breaking down the walls of their cocoons,” says Strohm. He found that if multiple flies are trapped in a brood cell together, they will work in the same area to create a single exit hole. About a third of the flies observed in the study escaped by inflating their heads, the rest waited for the mother red mason bee to return and unwittingly break them out.
C. indagator presents a huge problem for the red mason bee, in some cases parasitizing more than 40 percent of its brood cells. And according to Strohm, in most cases the bee larvae will die from starvation in the cell. “In most places Cacoxenus is by far the most important parasite of Osmia bicornis,” he says. But it’s not like the bees haven’t figured out what’s going on, he said, adding:
I once observed a nest where a Cacoxenus was actually beginning to oviposit [lay eggs] into a brood cell when the female unexpectedly returned. The Cacoxenus immediately “understood” and quickly ran towards the entrance of the nest, thus passing the incoming female in the nest tube. The female startled and appeared to search for an intruder and it seemed to check the brood cell (possibly for eggs). I had thought that the Cacoxenus had left the nest, however, the stupid fly returned, the bee turned around then the fly also turned around and tried to escape. The bee was faster, and it grasped the fly with its comparatively large mandibles and within a second, chewed it and then threw it out of the nest.
The Toughest Fish in Outer Space
KILLIFISH
(Fundulus heteroclitus)
AT NO MORE THAN 6 inches long, the blunt-nosed, stout-bodied killifish is about as unassuming as a fish can get. But don’t be fooled—this could well be the toughest fish on Earth.
Found off the coast of North America and in the Gulf of St. Lawrence—the world’s largest estuary, encapsulated by the coasts of Newfoundland, Quebec, Nova Scotia, and New Brunswick in Canada—the killifish is famous for its ability to live in a range of water salinities, ranging from fresh to heavily salty water. There are a number of species, known as euryhaline organisms, which carry this ability, such as the bull shark, the herring, the puffer fish, and the barramundi, but none can compete with the killifish’s tremendous level of adaptability. They can live quite happily in any muddy pool, creek, or ditch, any salty marsh, polluted harbor, or brackish estuary you throw at them; they are unfazed by a severe lack of oxygen, high levels of carbon dioxide, or foul substances in their water, and even if their habitat dries up completely, they can survive in the surrounding mud, flopping overland until they reach the nearest body of water.
How this little fish can survive the kinds of environments that would kill just about any other species is what biologist Andrew Whitehead from Louisiana State University in Baton Rouge set out to discover, publishing his findings in mid-2010. “In Louisiana, these fish are well known among fishermen, who often use them for live bait,” says Whitehead. “When curious Louisiana fishermen see me knocking around in marshes … I tell them that the reason I study them is that I’m interested in the evolution of physical toughness. Then they instantly get it, and usually launch into a series of stories often having to do with some extraordinary survival tale of killifish.”
Whitehead collected six fish from the coastal waters of New Hampshire and kept them for three months in artificial seawater with a salinity level of 32 parts per thousand (ppt). The average level for ocean water is between 32 and 37 ppt. They were then transferred to freshwater and were tested for their bodies’ reactions to the change in environment after 6, 24, 72, 168, and 336 hours at a time. Whitehead found the killifish to be extremely resilient, exhibiting changes in their blood plasma sodium levels at the 24-hour mark, but this was balanced out again by the 72-hour mark. “This is what I find most impressive of killifish, in that they can adjust their physiology and gill morphology to enable tolerance to freshwater all the way up to four times the salinity of seawater,” says Whitehead. “The salt starts falling out of solution before you can kill them. If there were an Olympic event for osmotic tolerance, killifish would stand (swim?) alone on the podium.”
When there is a sudden change in the solute concentration around an organism’s cell, caused by high concentrations of salts, for example, water is drawn out of the cell in a process called osmosis which can severely damage the cell. Alternatively, if a cell is suddenly exposed to low concentrations of salts, an increased amount of water will enter the cell, causing it to swell and sometimes burst. Ordinarily, if you suddenly transport fish acclimatized to salt water to fresh water, they will likely experience osmotic shock, and if too many of their gill cells burst they will suffocate. The secret to the killifish’s extreme osmotic tolerance, according to Whitehead’s research, is that they are able to change the entire morphology of their gill structure to either retain ions in their blood when they end up in fresh water, or to actively pump out ions when in sea water to regulate the amount of water in their cells. This involves a dramatic transformation of the gill tissues and, according to Whitehead, certain populations of killifish can achieve this in a single day.
Whitehead puts the killifish’s physiological flexibility down to the way it has adapted to its natural habitat—the estuary. Estuaries are shallow, partly enclosed coastal bodies of water that have freshwater rivers flowing into them, so their residents need to be able to cope with wild fluctuations of salinity, oxygen availability, temperature, and nutrient availabilities. These fluctuations can occur periodically with the tides or seasons, or randomly, such as when a storm hits, which will decrease the salinity of the water. “Estuaries are among the most dynamic habitats on the planet and impose severe physiological challenges on resident species,” says Whitehead, who published his team’s findings in the Journal of Heredity.
Also characteristic to the killifish is its ability to thrive in foul water that would kill any other fish, and the nature of this changes across individual populations, depending on what chemicals they are exposed to in their environment. Whitehead and his team examined three populations to discover their different survival mechanisms. One group lives in Newark Bay, an estuary in New Jersey where one of the biggest container shipping facilities in the United States, the Port Newark–Elizabeth Marine Terminal, is situated. The second population lives in New Bedford Harbor in Massachusetts, and the third is in the Elizabeth River in Virginia. All three environments contain different levels of highly toxic, manmade carcinogenic chemicals, heavy metals, and pesticides, which make the water extremely difficult to live in.
The researchers compared the genetic make-up of these three populations of killifish to populations from clean estuaries. The New Bedford Harbor comparison found 16 percent of the genes were significantly different from the clean reference sites, the Newark Bay comparison found 32 percent of genes were different, and the Elizabeth River comparison found 8 percent of total genes were different. Further, they found very little overlap in the gene sets of the three populations, suggesting that the different chemical pollutants they grow up around brought about different evolutionary solutions.
“This is fucking miserable, this is,” declared Zden Lowy, the cook aboard the Starship Compromise. “We’ve been going around in circles for days and I’m this close to running out of potatoes.”