At the surface, blobfish look like unhappy internal organs. Here's a brief refresher for the unintitiated:

Blob sculpin (Psychrolutes phrictus) at the surface. Image: NOAA Fisheries

That ghoulish appearance has landed the deep-sea inhabitants (genus Psychrolutes) on many an "ugliest animals" list, but a video from the research vessel EV Nautilus shows that it's not always fair to judge a fish out of water. 

On a dive off the coast of northern California, the team encountered a blob sculpin (Psychrolutes phrictus) and watched on as the fish guarded a brood of tiny, pink eggs. The trio above are the same species as this living specimen, but as you can see, the animals look a bit different at depth! In fact, they're actually kind of cute.

Blobfishes occupy a habitat some 2,800 metres (9,200 ft) beneath the waves – a zone that's exposed to incredible pressures. Because they're such deep divers, these animals have a number of physical adaptations for dealing with the harsh conditions. For starters, blobfish bones are extremely soft, and therefore less prone to cracking. That evolutionary workaround is a great way to stay alive when your home is constantly trying to crush you, but get stuck in a trawl net and things start to go awry.

Many fish use an air-filled swim bladder for buoyancy, but that's a dangerous piece of kit for a deep-sea fish, as changes in pressure could expand the swim bladder, forcing the other internal organs out of the mouth. Instead, blob sculpin rely on their gelatinous flesh – which is slightly less dense than seawater – to stay afloat. This means they don't have to worry about "vomiting" up their own stomachs (yes, it really happens), but that blobby frame carries problems of its own. The fish have very little built-in structural support, so it's all that deep-sea pressure that actually holds everything together. When hauled to the surface, however, blobfish encounter a rapid pressure drop, and the anatomy that works so well at great depths suddenly turns on them, expanding and falling into a gooey mess.

Most of what we've learned about these fish comes from dead specimens, so encountering one alive in its natural habitat is always a treat – even for the seasoned crew of the Nautilus. "I've always wanted to see one!" one of the scientists can be heard saying in the clip. "They just look so sad!"

The research team notes that the larger of the pair could be the brooding female, but because there is still a lot we don't know about blob sculpin biology, it's tough to say with certainty. You'll also notice an octopus in the background, likely lurking for a chance at those tiny protein-packed eggs. 

Because their eggs are an ideal snack for passing fish and cephalopods, sculpin lay them in vast numbers. It's estimated that a single nest can contain 100,000 eggs, but just one percent of those would-be blobs will make it to adulthood. Nest-guarding is thought to be a rarity in the ocean's black depths, and in fact, the behaviour had never been observed in a deep-sea species until a blob sculpin was seen standing guard at a nest site in 2003. These fish are ambush hunters, so staying put serves a double purpose here: guard the next generation, and wait for tasty invertebrates to pass by for the taking. 



Top header image: NOAA EV Nautilus/Screengrab from YouTube