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This 'Living Fossil' Fish Has a Lung

Fish physiology is a little more complicated than you learned in grade school. Some fish are warm-blooded—and some fish have lungs. 

A recent study in Nature Communications confirmed that a rare order of deep water fish called coelacanths have a lung, though the respiratory organ is no longer functional. The ancient species of fish, dating back about 410 million years, was long thought to be extinct until a living species was found near South Africa in 1938. 

Although scientists have known that coelacanth fossils show a large calcified organ, it was previously thought to be a bladder or some other type of tissue. But researchers, led by a zoologist from Rio de Janeiro State University, recently dissected several of these living fossils from the species Latimeria chalumnae, to confirm that the organ in question is a lung—at least in the living fish. Using X-ray imaging, the experts also reconstructed five different developmental stages of the fish, showing how the organ grows. 

Reconstructions of the fish lung at different developmental stages. Image Credit: Brito et al., Nature Communications (2015)

While early-stage embryos have a well-developed lung that might be functional, by the time the fish is fully grown, the organ isn't operating (the species breathes through its gills). In fact, as the fish becomes a juvenile and an adult, the lung ceases to grow and eventually becomes useless. 

The researchers also found small, hard, flexible plates surrounding the fish’s lung, which might be analogous to the calcified lung in the fossils. These hard plates might have once helped regulate lung volume millions of years ago when the fish lived in shallow, muddy waters, and potentially breathed air (compared to breathing through its gills, as it now does in deep-water environments). 

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Animals
Where Do Birds Get Their Songs?
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Birds display some of the most impressive vocal abilities in the animal kingdom. They can be heard across great distances, mimic human speech, and even sing using distinct dialects and syntax. The most complex songs take some practice to learn, but as TED-Ed explains, the urge to sing is woven into songbirds' DNA.

Like humans, baby birds learn to communicate from their parents. Adult zebra finches will even speak in the equivalent of "baby talk" when teaching chicks their songs. After hearing the same expressions repeated so many times and trying them out firsthand, the offspring are able to use the same songs as adults.

But nurture isn't the only factor driving this behavior. Even when they grow up without any parents teaching them how to vocalize, birds will start singing on their own. These innate songs are less refined than the ones that are taught, but when they're passed down through multiple generations and shaped over time, they start to sound similar to the learned songs sung by other members of their species.

This suggests that the drive to sing as well as the specific structures of the songs themselves have been ingrained in the animals' genetic code by evolution. You can watch the full story from TED-Ed below, then head over here for a sample of the diverse songs produced by birds.

[h/t TED-Ed]

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Animals
Watch the First-Ever Footage of a Baby Dumbo Octopus
NOAA, Wikimedia Commons // Public Domain
NOAA, Wikimedia Commons // Public Domain

Dumbo octopuses are named for the elephant-ear-like fins they use to navigate the deep sea, but until recently, when and how they developed those floppy appendages were a mystery. Now, for the first time, researchers have caught a newborn Dumbo octopus on tape. As reported in the journal Current Biology, they discovered that the creatures are equipped with the fins from the moment they hatch.

Study co-author Tim Shank, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, spotted the octopus in 2005. During a research expedition in the North Atlantic, one of the remotely operated vehicles he was working with collected several coral branches with something strange attached to them. It looked like a bunch of sandy-colored golf balls at first, but then he realized it was an egg sac.

He and his fellow researchers eventually classified the hatchling that emerged as a member of the genus Grimpoteuthis. In other words, it was a Dumbo octopus, though they couldn't determine the exact species. But you wouldn't need a biology degree to spot its resemblance to Disney's famous elephant, as you can see in the video below.

The octopus hatched with a set of functional fins that allowed it to swim around and hunt right away, and an MRI scan revealed fully-developed internal organs and a complex nervous system. As the researchers wrote in their study, Dumbo octopuses enter the world as "competent juveniles" ready to jump straight into adult life.

Grimpoteuthis spends its life in the deep ocean, which makes it difficult to study. Scientists hope the newly-reported findings will make it easier to identify Grimpoteuthis eggs and hatchlings for future research.

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