Range: Cosmopolitan Habitat: Open ocean and ocean surface Size: About 1 inch (3cm) long Diet: Blue buttons, Portuguese men-of-war, and by the wind sailors Threats: Birds and fish Life span: Unknown

Transcript:

Today on Animal Fact Files we’re talking about blue sea dragon. These animals are awesome. When asked what my favorite animal is, though unable to truly answer the question, I often ask people in return if they’ve heard of blue sea dragon. Blue sea dragons are also commonly known as blue sea slugs and sea swallows, but I’ve always thought blue sea dragon was more appropriate because of the way they look - I mean, just look at that. That looks like a dragon. Not that slugs and swallows aren’t super cool, too, of course.

The blue sea dragons get their scientific name from a shared named with a Greek God forced to dwell in the sea forever. When they were discovered, blue sea dragons were thought to be insects or fish larvae, but eventually we gained a better understanding of what they are, and now they’re classified as marine gastropods. There are currently five recognized species of blue sea dragons, but this will likely change with more research.

Blue sea dragons are found worldwide and are thus considered cosmopolitan. They are most frequently found in tropical and temperate waters and have never been recorded from polar regions. Blue sea dragons are different from many other sea slugs because they’re pelagic. Most sea slugs are benthic, which means they spend most of their time on the bottom of the water column, but blue sea slugs spend most of their lives living in the open ocean and are typically found on the ocean’s surface. Blue sea dragons float using swallowed air held in their stomachs.

There’s debate in the scientific community whether these slugs are able to move through the water of their own accord, using their hand and fingerlike projections as swimming apparatuses, or if they should be considered planktonic and really as the mercy of water and wind currents to move them around. Either way, they can still move on their own, as you can see here.

Blue sea dragons get their common name from their color. They come in a brilliant blue in order to avoid predators. We talked about countershading in our bottlenose dolphin episode, but since it’s been awhile we’ll briefly summarize here. In sea dragons, their blue blends in with the ocean water from above, and their grey blends in with the sky from below, so they’re difficult to spot! But, like upside down catfish, blue sea dragons are topsy turvy. The exposed blue of a blue sea dragon is actually coloring its stomach, meaning blue sea dragons in what most would consider a pretty relaxed posture.

Though some photoshopped pictures may suggest otherwise, blue sea dragons only reach just over an inch (3cm) in length at maximum size. They’re super tiny, but they’re able to eat large prey. Blue sea dragons are voracious predators. They eat blue buttons, Portuguese men-of-war, and by the wind sailors - all cnidarians with powerful stings, but blue sea dragons are immune to these stings. Blue sea dragons have toothlike projections in their mouths called denticles. These are used to help hold onto a prey item even in rough waters. The blue sea dragon can then eat the prey, tentacles and all! In fact, like other sea slugs we’ve discussed previously, blue sea slugs can utilize the stinging cells from their prey by incorporating the stingers into their own bodies, thus becoming stinging animals themselves!

Blue sea dragons also use their prey as cradles. Like their land-dwelling counterparts, the slugs, blue sea dragons are hermaphroditic, but need another individual to fertilize their eggs. Blue sea dragon eggs are laid in strands which may float freely through the water or may be attached to the body of a partially consumed prey item. I guess blue sea dragons really aren’t about waste. Their eggs hatch about three days later. There’s really not much information on life history of blue sea dragons and most reproduction information is from work done in labs, so there’s still more to learn!

For more facts on blue sea slugs, check out the links in the description. Thank you to shweta zarkar and Twisted Bonnie for today’s request. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files.