Random Marine Life Generator

What the random marine life generator does

You need something from the sea. A creature for a report, an animal for a game, a starting point for finding out what actually lives down there.

Press the button and you get one.

What follows starts with a question that sounds too simple to be interesting. What do a blue whale, a jellyfish, and a strand of kelp have in common? The answer is almost nothing, and the almost-nothing turns out to be the most powerful force in the ocean.

How to use it

1. Choose how many you want. One if you are deciding, more if you are browsing.
2. Press Generate. A fresh draw every time.
3. Press Copy to take the set with you.

The only thing this list has in common

Pull a handful and look at what comes out. A blue whale. A great white shark. A jellyfish. A giant clam. A strand of kelp. A sea urchin. A dolphin.

Now try to say what connects them, and watch it fall apart in your hands.

The whale and the dolphin are mammals. They breathe air, they nurse their young, they are warm-blooded, and their nearest relatives on land are hoofed animals. A whale is closer kin to a cow than to the shark swimming beside it.

The shark is a fish, but an old and unusual kind, built from cartilage rather than bone, on a branch that split off before most of the fish you could name existed.

The clam and the sea urchin are invertebrates, and they are not even close to each other. A clam is a mollusc, in the same broad company as snails and octopuses. A sea urchin is an echinoderm, and its closest relatives, strange as it sounds, are on the branch that eventually leads to us.

The jellyfish is something older and simpler than all of them, an animal with no bones, no blood, and no brain.

And the kelp is not an animal at all. It is not even a plant, in the strict sense. It is an alga, on a branch of life so far from the whale that the two of them are less closely related than you are to a mushroom.

So what unites this list? Genuinely one thing. The water. They all live in the sea. That is the entire connection. There is no family here, no shared ancestor that makes them a group, nothing tying them together except the fact that they are all wet. "Marine life" is not a branch of the tree of life. It is a postcode.

And that would just be a tidy fact, except for what the water does to everything that moves into it.

The ocean keeps building the same animal

Picture a fast-swimming hunter of the open sea. A smooth torpedo body. A pointed snout. A tall, stiff fin on the back. A crescent tail beating side to side, or up and down. Fins for steering. The whole thing built to hold a straight line at speed through deep water.

You are picturing a tuna. You are also picturing a dolphin. You are also picturing a shark. And you are picturing an ichthyosaur, a sea reptile that has been extinct for ninety million years.

Four animals. A fish, a mammal, a shark, and a reptile. Four completely separate branches of the tree of life, four ancestors that had nothing to do with each other, and they all arrived at the same body.

This is called convergent evolution, and it is the ocean's signature move. The water does not care what you used to be. If you are going to make a living chasing prey at speed through open sea, the physics of moving through water permits only so many good answers, and that torpedo shape is the best one. So every lineage that takes up that life gets pushed toward the same form, no matter where it started.

The dolphin's ancestors were four-legged animals that walked on land and went back into the sea. Over millions of years the water reshaped them. The legs became flippers. The body lengthened and smoothed. A fin rose on the back, a fin that is not built like a fish's fin at all on the inside, made of completely different stuff, arrived at completely separately, and yet from the outside almost identical, because the water asked the same question and there was only one good answer.

You can see the water's hand everywhere in the list once you know to look for it. The flattened bodies of things that lie on the bottom. The gulping mouths of ambush hunters. The transparency of animals drifting in open water, trying not to be seen. Again and again, unrelated creatures wearing the same solution, because the sea set them all the same problem.

The list is not a family. It is a collection of separate answers to the same set of questions, and the questions were asked by the water.

The one in here with no brain at all

Go back to the jellyfish, because it is the strangest thing in the list and it has been quietly getting on with life for longer than almost anything else in it.

A jellyfish has no brain. Not a small brain. None. There is no central place where thinking happens, because there is nothing doing anything we would call thinking. Instead it has a net of nerves spread through its body, and that net is enough. It can sense light, sense which way is up, feel a touch, and fire its stinging cells and its swimming pulse without anything we would recognise as a decision being made anywhere.

It has no blood and no heart either. It does not need them, because it is thin enough everywhere that the sea can supply every cell directly. It is mostly water, held in a shape, drifting and pulsing, doing everything an animal needs to do to survive with almost none of the equipment we assume an animal requires.

And this design is ancient. Jellyfish, or things very like them, were in the ocean before there were fish, before there were plants on land, before almost anything you could name. They are one of the oldest animal body plans still running, and they are still running because the design works: it is cheap, it is simple, and it has outlasted an enormous number of cleverer-looking things.

The Portuguese man o' war, which is in this list, pushes the strangeness further still. It looks like a single jellyfish, but it is not one animal at all. It is a colony of many small organisms, living together so completely that they function as one creature, with different members doing different jobs, some for stinging, some for feeding, some for floating. A thing you would point at as one animal is a committee.

All of which is worth holding onto the next time this hands you something from the sea. Whatever it is, it is not related to most of the other things in the list. It just lives in the same water, and the water has been shaping it, and everything else down there, into whatever the sea will allow.

Where these come from

The animals are drawn from a list our team researched and checked by hand, so the names are real species rather than approximations. Your browser picks from them at random. Nothing you do here leaves your device.

Questions people ask

Why is a whale not a fish?

Because it is a mammal, and the resemblance to a fish is the water's doing, not a family tie. A whale breathes air, is warm-blooded, and nurses its young on milk, and its ancestors walked on land before returning to the sea. The shark shape and the whale shape match because the ocean imposed the same form on two unrelated animals, which is the whole point of the piece above.

Is kelp really not a plant?

Not in the strict sense. It is a large brown alga, on a branch of life separate from true plants, and it reaches its size without the roots, stems and internal plumbing that define a plant. It anchors rather than roots, and it takes what it needs directly from the water around it. It looks plant-like for the same reason so much in the sea looks like something else: the environment shapes the form.

How does a jellyfish survive with no brain?

With a nerve net rather than a central brain, which is enough to sense light and gravity and touch and to coordinate stinging and swimming. It is one of the oldest animal designs still in the ocean, and its longevity is the strongest possible argument that a brain is one solution to staying alive rather than a requirement for it.

Are sharks really older than trees?

The shark lineage is genuinely ancient, older than many of the landmarks people assume came first, including trees. Sharks have been refining the same broad body plan for a very long time, which is a large part of why it works so well: it has had more time to be tested than almost anything else swimming.

What is convergent evolution, simply?

It is unrelated creatures arriving at the same solution because they face the same problem. The torpedo body of the tuna, dolphin, shark and extinct ichthyosaur is the classic example: four separate branches of life, one shared shape, because the physics of moving fast through water permits only so many good answers.

Can the same animal come up twice?

Not within a single draw. Ask for ten and you get ten different ones. Press again and everything is back in play.

References

1. A multi-gene phylogeny of Cephalopoda supports convergent morphological evolution in association with multiple habitat shifts in the marine environment. BMC Evolutionary Biology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3733422/
2. Convergent evolution in toothed whale cochleae. BMC Evolutionary Biology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6813997/
3. Convergent evolution in fish morphology. United States Fish and Wildlife Service. https://www.fws.gov/story/convergent-evolution-fish-morphology