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Marbled Lungfish (Protopterus aethiopicus)

Also known as the Leopard Lungfish, the marbled lungfish is a species of lobe-finned fish found throughout Northeast Africa. Like other lungfish the marbled lungfish can breath air using a special lung like appendage. Using their ‘lungs’ these fish can live in streams and swamps that are dry for long periods of time, emerging when the water returns. Marbled lungfish usually inhabit rivers, swamps and floodplains where they feed on molluscs, fish and insects. The marbled lungfish is also one of the few animals that have had their genome’s sequenced it also has one of the largest genomes of all vertebrates at an outstanding 133 billion base pairs long!

Phylogeny

Animalia-Chordata-Sarcopterygii-Dipnoi-Lepidosireniformes-Protopteridae-Protopterus-aethiopicus

Image Source(s)

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So I recently had the opportunity to purchase a West African Lungfish (Protopterus annectens). These are ancient sarcopterygians that grow very large and are pretty unique animals. They possess many traits that early tetrapods had and many odd characteristics for fish such as a four chambered heart and primitive lung structures. These are traits more commonly found in amphibians (some of the first tetrapods) rather than most fish.

After talking it over with my SO, whom obviously has a say in whether or not we could house this fish as an adult, we came to the conclusion that we can make the space for him if he ends up growing 3ft+. With lungfish living 20 years, and quite often more in captivity, they are definitely a long term commitment. In fact there is a Queensland lungfish at the Shedd Aquarium in Chicago that has been in their collection since 1933. (That’s 81 years!) Visually lungfish look so reminiscent of a salamander or axolotl, it’s hard to believe they’re a fish at all. There are only six extant species of lungfish with the largest species reaching over 6ft in length.

Almost all lungfish species are wild caught so I want to give this little guy a nice environment that allows him to behave as he would naturally. Right now I have him set up in a 20gal with some sand and plants while he adjusts. He is already roughly 6-7in in length so he’ll need to go into a 29 gal or 40b as soon as he settles in and I’m certain he’s healthy. He was a rather unexpected purchase and so I have to hunt down a stand for the bigger tank since I used to keep them on a large dresser which I no longer own.

Behaviorally hes a pretty sedentary critter except for when food is around or when he goes up for air. The rest of the time is spent napping among the plants, under the driftwood, or sifting through sand for food he may have missed. I also didn’t have a net large enough to for him but I was pleasantly surprised to find he doesn’t mind being handled gently. Right now he’s being fed NLS large fish formula 3mm sinking pellets and frozen bloodworms. Once I’ve had him for a while I’ll likely write a caresheet on P. annectens. I’m open to name suggestions as well!

Evolutionary history of air-breathing vertebrates. Relative abundance and diversity of each group is roughly proportional to the band width.

The groups indicated in horizontal type & bars on the right side relate to the phylogeny of mudskippers, amphibious fish of the Indian and Pacific oceans, and the Atlantic coast of Africa.

[Nelson (ed), 1994 – Fishes of the World – 3rd edition. John Wiley & Sons] [Redrawn from Graham (1997 (ed) – Air–breathing Fishes. Evolution, Diversity and Adaptation

(source)

How We Got On Land, Bone by Bone

The bones that Shubin and his colleagues described in 2006 came from the front half of Tiktaalik. Only now, eight years later, have Shubin and his colleagues unveiled the other half of this remarkable beast. And they’ve now stretched out the transition from fish to tetrapod even more….

The two rocks made it safely back to Chicago. The scientists began work on the rock that contained the skull and other bones from the front half of Tiktaalik. By the time they were done, they had isolated bones from three different individuals in the rock. Once they had analyzed the bones and written up detailed descriptions of Tiktaalik’s anatomy, they turned their attention in 2008 to the other rock, which had been sitting untouched for four years.

Chipping away, they started to come across bones. Some were fin rays from the pelvic fin. Some were ribs from the back half of the animal. And nestled in the rock was an especially valuable bone: a pelvis.

It was not what Shubin and his colleagues were expecting. The closest lobe-fin relatives of tetrapods had tiny pelvises, which only served to attach muscles that controlled the pelvic fin during swimming. Tiktaalik had a massive pelvis–as big as those of the earliest true tetrapods with legs and digits. And like us, it also had a massive scoop carved out of the side, where the ball of the femur could fit….

All those hip bones have brought Tiktaalik into sharper focus. For one thing, they show that the creature could get big. The largest pelvis bones they’ve found suggest that Tiktaalik could grow up to nine feet long. Our ancient relatives, in other words, were the size of alligators.

Not only was its pelvis big, but its pelvic fin was big, too. Shubin and his colleagues envision Tiktaalik using massive muscles anchored to its pelvis to power its hind fins–not just to swim, but to walk underwater or push its way across muddy flats.

While Tiktaalik had hips that were tetrapod-like in size, they were still fish-like in anatomy. Our own hips are tightly fused to our spine. It would be catastrophic for them to be floating free in our bodies, because we wouldn’t be able to hold up our torsos against the force of gravity, nor could we transmit much of the force generated by our legs to the rest of our body. That is true of most other tetrapods, all of which are adapted for moving on dry land rather than being supported by water. By 360 million years ago, early tetrapods had evolved attachments from the pelvis to the spine.

But their forerunner Tiktaalik still had free-floating hips. IN other words, Tiktaalik shows that 370 million years ago the tetrapod body plan was still very much a work in progress–from head to tail.

(Read more at Phenomena: The Loom)

Diplurus

The Late Triassic / Early Jurassic freshwater coelacanth fish from eastern North America, Diplurus. Some coprolites have been found from the right geological strata, and due to their size and chemical composition scientists believe these fossil fish feces can be attributed to a large predator like Diplurus.

I created this image for a new exhibit at Dinosaur State Park in Connecticut.

The West African lungfish (Protopterus annectens) is the largest of the four lungfish species found in Africa, reaching lengths of up to 2 m. Rather than gills, it has a pair of lungs that it uses to obtain oxygen. When the dry season comes, this fish makes a mucous-filled cocoon for itself and burrows into the mud to keep its skin hydrated.

Photo by Jibran Shariff

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The many stages of Linnaeus begging for food. He loves to be hand fed algae wafers! For those of you unfamiliar with Linnaeus he is a West African Lungfish (Protopterus annectens). Unlike most modern fish which are in the class Actinopterygii (this includes 99% of fish spp), lungfish and their distant cousins the coelocanths belong to the class Sarcopterygii. This is the class that gave rise to the first tetrapods, so lungfish have some very odd physical characteristics for a fish. This includes teeth coated in true enamel, lungs homologous to tetrapod lungs, and a four chambered heart.

The Indonesian coelacanth (Latimeria menadoensis) was discovered very recently (late 1990s), and as such there is not a lot of information regarding its behavior or ecology. However, because it is physically extremely similar to the coelacanth (Latimeria chalumnae) found off the coast of South Africa (discovered in the 1938), scientists can assume the two fish have similar life habits. Genetic analysis has revealed that the two species diverged from one another around 5 million years ago, effectively making both species of coelacanth living fossils.

(Source)

What It Means to Be a Fish

The word “fish” is a very touchy subject for biologists.  It actually has zero scientific meaning today, and is an archaic word that is well past its expiration date only because the general public keep using it and scientists have to use it to make any sense to the general public (“reptile” and “amphibian” both also have that problem, by the way).  I could go on a long, passionate rant about how horrible and ucky the word “fish” is, but I will spare humanity this time.


There is actually a scientific meaning for “fish,” but it isn’t what you may expect.  “Fish” is now synonymous with “vertebrate,” which means that a fish is basically any animal with a backbone (in biology we are trying to stamp out defining life via physical traits, but I won’t go into the technical stuff).  This means that you are a fish.  Birds are one of the most common types of fish on Earth.  There are herds of fish roaming the African savannah.  To argue that this isn’t true—that these animals are not fish—is to argue that it is completely logical for a branch growing on the left side of a tree to suddenly switch to growing from the right side of the tree.  It is the exact same argument.


But when I say that I am a “fish” (horrible word), don’t be fooled.  I am not saying that I am something like a tuna, and nor are you (unless you are a tuna reading this).  It is true that both humans and tuna are “fish,” but I am not descended from anything like a tuna, nor a salmon, nor a sturgeon.  Usually when we think of the word “fish,” we think of one of those animals—they are a type of creature known as actinopterygians (we also call them “ray-finned fish”).  They are fish (as in, vertebrates) that have fins right up against their torsos.  Most of them actually evolved after the dinosaurs.


Humans are not ray-finned fish.  We are “lobe-finned fish.”  Throw out any idea you may have of what a “fish” is like, and allow me to describe what your typical lobe-finned fish looks like.  Most lobe-finned fish have beaks.  They have very complicated respiratory systems that can extract a lot of oxygen from the air.  They have feathers, and can fly.  What’s that, you say?  It sounds like I’m describing a bird?  I am—by far, the most common lobe-finned fish on our planet are birds.  When you picture the average lobe-finned fish, you should be picturing them.  The next most common type of lobe-finned fish has hair and feeds its children with nutrient-rich sweat—mammals.  Frogs, salamanders, lizards, turtles, snakes, and crocodiles are all lobe-finned fish too.  Several lobe-finned fish swim in the water—most of them we call “whales,” “dolphins,” or “seals.”


Lobe-finned fish used to be the dominant group of aquatic animals, well before sharks, rays, and most ray-finned fish evolved (although their ancestors were certainly around back then, trying to swim away from a ferocious lobe-finned fish’s open jaws).  They have since lost the marine throne to the ray-finned fish, although lobe-finned fish such as orcas remain at the top of the aquatic food chain.  There are only two lobe-finned fish alive today that look anything like the lobe-finned fish back in their aquatic hayday before the dinosaurs.  They are the coelacanth and the lungfish.  How are they like you?  Just like you, the coelacanth and lungfish do not have fins pressed tightly up against their bodies.  Although they do not have fingers and toes, coelacanths and lungfish have arms, legs, hands, and feet just like you do (these limbs are the “lobes” that we get the name “lobe-finned fish” from).  Just like you, a coelacanth or lungfish has a humerus, a radius and ulna, and carpal and metacarpal bones; just like you, a coelacanth or lungfish has a femur, a tibia and fibula, and tarsal and metatarsal bones.  Lungfish, like most lobe-finned fish today, can even breathe air.


Now, certainly, ray-finned fish and lobe-finned fish have a common ancestor.  But the ray-finned fish (what you typically think of when you think “fish”) are our cousins, not our siblings or ancestors.  We are fish, yes; we are even bony fish (sharks, rays, ratfish, lampreys, and hagfish are not).  But we are not anything like a tuna, nor were we ever anything like a tuna.  The problem with saying that humans are “fish” is that people hear that and think “ray-finned fish” instead of thinking “lobe-finned fish” and then are incredulous that anybody could say we are one and the same.  The word “fish” in general needs to be deleted from our vocabulary, but until the general public catch on that it is meaningless and misleading, scientists will have to continue to use it when speaking to the general public.

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^ The above picture is a picture I took from Wikipedia of a lungfish.  Notice how the fins of the lungfish are at the tips of arms and legs—these are lobe-finned fish.

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