The Real World War Z: Jellyfish

We usually become aware of jellyfish when they suddenly appear in large numbers called "blooms." Such blooms are a natural part of the jellyfish lifecycle. What is of concern is the fact that these blooms are becoming more common, more intense, and are causing more problems, a sign that the ocean ecology is changing in a way that is more favorable to jellyfish populations.

Lisa-ann Gershwin has written a book that introduces the reader to the weird and frightening world of jellyfish and their actual and potential effects on the ocean environment: Stung!: On Jellyfish Blooms and the Future of the Ocean. This book should be read by those interested in jellyfish, but, more importantly, it should be read by those interested in the future of our oceans—the actual focus of the work.

Theo Tait wrote a review of Gershwin’s book in the London Review of Books. He provided this summary:

"According to Lisa-Ann Gershwin’s disturbing book, the jellyfish is an ‘angel of death’, a harbinger of ‘planetary doom’ likely to be the ‘last man standing’ in what she describes as our ‘gelatinous future’."

He also provided this assessment of the book:

"Stung! is a serious monograph, a guide to jellyfish biology and to the recent explosion in jellyfish blooms by an expert in the field…. it’s a serious monograph disguised, quite convincingly, as a monster movie. It begins with a series of horrifying vignettes of jellyfish on the rampage, such as the ‘mass fish-kill’ events suffered by salmon farms."

Continuing in the monster-movie vein, he chose to title his review Water-Borne Zombies.

Given that zombies—and vampires—appear so much in popular entertainment, one has to wonder if we are, perhaps, producing a generation that might be confused about the existence of these mythical creatures. Tait’s reference to zombies is intriguing because some of the attributes of jellyfish bear resemblance to what is commonly thought of as "the undead." Thinking of jellyfish as zombies might prove an interesting means of describing their properties. We shall see.

The best dictionary definition of a zombie is probably this one:

"a will-less and speechless human in the West Indies capable only of automatic movement who is held to have died and been supernaturally reanimated"

Being will-less, speechless, and capable of only automatic movement are jellyfish attributes, but it was startling to learn that there is at least one species that has learned to regenerate itself after death—that is more than being undead, that is being immortal.

While individual jellies don’t live forever, it seems the species, as a class, may be immortal. Jellyfish are at least a half billion years old. Prior to the Cambrian Explosion where many new species evolved, jellies seem to have ruled the oceans.

"They have been around at least 565 million years, and probably far longer….Jellyfish are among the world’s most successful organisms, having survived freezes, superheated conditions, shifting and rearranging of continents, mass extinctions, meteor strikes, predators, competitors, and even man."

The greatest, or worst, of the mass extinctions is known as The Great Dying. This occurred about 250 million years ago and is estimated to have rendered about 96% of all marine species extinct. Yet the jellyfish survived.

Gershwin prefers to think of jellyfish as weeds rather than unnatural monsters. One of the things that make a weed a weed is its ability to survive in conditions where other species fail.

"They [jellyfish] share the same weedy qualities that are the essence of weediness in dandelions and cockroaches and their other weedy brethren. They are highly tolerant of a broad range of conditions; they grow fast, breed early and often, and have a large number of young; and they will eat just about anything they can get their lips around."

Now we begin to enter the monster movie realm as Gershwin tells us some of the characteristics of jellyfish.

"Jellyfish sex is like something straight out of science fiction, except there is nothing fictional about it. The methods jellyfish use for reproduction are beyond the realms of Hollywood, and the numbers involved may seem unbelievable. Millions of moon jellyfish aggregate into a massive orgy, same time, same place, everyday. For months. Tens of thousands of eggs is not uncommon….per jellyfish. Per day. Every day. For months. Hermaphroditism. Cloning. External fertilization. Self fertilization. Courtship and copulation. Fission. Fusion. Cannibalism. You name it, jellyfish do it while they’re ‘doing it’."

Jellyfish do not spawn another jellyfish. Their offspring is another adult phase as a polyp that anchors itself to some firm object. This polyp phase can persist indefinitely and it can reproduce by cloning. When the polyp feels the time is right it goes through a process called strobilation.

"Strobilation is where the polyp undergoes a partially metamorphic process, whereby it elongates and differentiates into a stack of disks, like a stack of tiny dinner plates or a role of tiny coins, through a process of transverse fission. These disks develop into tiny, daisy-shaped larval medusae, then begin pulsating and eventually break away to become free swimming."

The number of jellyfish offspring produced in a strobilation event depends on the particular species and on the quality of conditions. Some polyps give off a single larval medusa, others give off as many as 50. This "alternation of generations" provides a powerful degree of freedom in adjusting to changing conditions. The polyp phase can simply set and continue reproducing itself until conditions improve for its potential offspring.

Gershwin provides the example of one jellyfish species that has been observed to have a zombie-like path to immortality.

"….consider the demure but fascinating Turritopsis dohrnii. When the medusa dies, the cells begin to dissociate like any normal organism—that is, it disintegrates. But then something remarkable happens. As the medusa body decomposes, the cells reaggregate and transform into new hydroid [polyp] colonies….The whole transformation from medusa to polyp takes place within a mere five days or so of the medusa’s death. This would be roughly equivalent of a dead butterfly’s cells reforming, all on their own, into a full-grown, fully-formed caterpillar. This is the first known example of true biological immortality."

The feeding habits of jellyfish are also monstrous. When food is scarce they seem quite content to eat each other. And if food is really scarce, many forms of jellyfish are able to effectively eat themselves.

"If food supply gets really scarce, many jellyfish have a backup plan. In times of famine, jellyfish can go without food for a very long time, switching into a process called ‘degrowth.’ Starving jellyfish consume their own body mass very slowly, becoming smaller and smaller, until food is once again available. When they start eating again, they rapidly recover to their normal size—with no ill effects. Throughout the degrowth period, they remain reproductively active and look and act like normal jellyfish, despite becoming progressively smaller."

Any true monster must be capable of frightening those it comes into contact with. Jellyfish are quite capable of that. Jellies are of two varieties; one stings its prey with special cells loaded into tentacles, and the other entangles prey in merely slimy tentacles. The most common form stings. Wikipedia provides this note:

"Jellyfish sting their prey using nematocysts, also called cnidocysts, stinging structures located in specialized cells called cnidocytes….When a nematocyst is triggered by contact by predator or prey, pressure builds up rapidly inside it up to 2,000 pounds per square inch (14,000　kPa) until it bursts. A lance inside the nematocyst pierces the victim's skin, and poison flows through into the victim."

Luckily, not all stings cause serious effects in humans, but some species can cause extreme illness and even death. The truly monstrous part is that these stinging cells seem to have a life of their own, maintaining their threat even after the host specimen has died. Again, from Wikipedia:

"In 2010, at a New Hampshire beach, pieces of a single dead lion's mane jellyfish stung between 125 and 150 people."

Gershwin provides some examples of the nastiest specimens.

The box jellyfish, native to the waters around Australia, are referred to as "the world’s deadliest animals."

"They can kill a healthy adult in as little as 2 minutes—the average time to death is 4 minutes….Death is merely a consequence of ‘enough’ jellyfish tentacle coming into contact with unprotected skin—for an adult this is about 3-5 meters (9-15 feet), for a child it is 1-2 meters (3-6 feet)—not much, considering that a mature jellyfish has 120-180 meters (350-550 feet) of combined tentacle length in its arsenal."

And then there is the nasty little jellyfish known as Irukandji, an Aboriginal word.

"Its sting causes Irukandji syndrome, a constellation of seemingly unrelated symptoms. The sting itself is often not even felt, or is so minor that it is dismissed. After a characteristic delay of about 20-30 minutes, the lower back begins to ache, then rapidly escalates to fully debilitating, cramping, or pounding pain. Patients often describe it as akin to being hit in the kidneys with a wooden bat again and again and again, or feeling as if an electric drill is drilling into the back. Then nausea begins along with relentless vomiting—every 1-2 minutes for up to 12 hours. The syndrome rapidly develops into full-body cramps comparable to the bends with shooting spasms in the arms and legs and behind the eyes; difficulty breathing; profuse, drenching sweating; coughing; and muscular restlessness. Many patients feel a creepy skin sensation, often described as feeling like spiders crawling on or worms burrowing into the skin. Many patients feel an ‘impending doom,’ believing they are going to die. Some go as far as to beg their doctor to put them out of their misery."

One of the "benefits" of globalization is that we have enormous ships that suck water up into ballast tanks in one port and deposit it into the waters of another port across the ocean, thus contaminating one ecosystem with specimens from another. The Irukandji was thought to be limited to the area around Australia.

"….we now know of some remarkably distant cases that have occurred in Florida; Hawaii; Thailand; Goa; India; Perth; Western Australia; Cape Town, South Africa; and even North Wales in the UK….In fact, it seems that Irukandjis (as a group of species producing similar syndromes) are distributed from about 55 degrees N to 38 degrees S latitude, that is, most of the recreationally usable oceans and seas of the world."

Jellyfish blooms can create densities of specimens where they are literally cheek to jowl. This density of matter has caused enormous difficulties just by getting in the way. Jellyfish are notorious for clogging cooling vents on everything from aircraft carriers to nuclear reactors. In true zombie-like fashion, they cannot be stopped.

"Chemical repellants don’t work, because jellyfish drift on the current and can’t respond. Electric shocks don’t work for the same reason. Acoustic shocks don’t work, because jellyfish, not having a brain, aren’t afraid of noise. Bubble curtains don’t work because the bubbles kill them and, alive or dead, they block the flow of water all the same. Biocides don’t work for the same reason."

There are occasions where jellies clogging nets are more than a nuisance. Jellyfish can make short work of fish farms if allowed to make contact. Gershwin described one salmon kill that occurred in New Zealand in 1998 when 56,000 3-kilogram salmon were killed within 30 minutes.

"The salmon all swim in one direction inside the circular pens, creating a fairly strong vortex that sucks water from the surrounding area. The Aurelia, being passive drifters, became entrained in the vortex. Too large to pass through the mesh, the jellyfish were pinned against the netting. As the jellyfish struggled against the current and the netting, their mucus, which is profuse and packed with stinging cells, was sucked into the cages. It appears that as the salmon inhaled the mucus, it blocked the oxygen-exchange surfaces of their gills, causing them to suffocate. The stinging cells exacerbated the problem by alarming the salmon, causing them to breathe faster, thereby serving to suffocate them faster."

Not only do they sting with their tentacles, but they emit slime filled with stinging cells that can be sent out, kind of like a calling card announcing "Watch out, I have been here and I will be back."

In the last chapter of her book Gershwin summarizes all the damage we have done to our oceans by pollution and overfishing and reminds us that degrading ocean ecology almost always leads to more favorable conditions for jellyfish blooms. She chose to call that chapter "The Rise of Slime."

Perhaps one day an enterprising author will produce the screenplay for World War S (or World War J).