By Cole Quinton
Grab your mask and snorkel and start regulating those oxygen tanks as we dive into the open ocean and explore the world of the Glaucus atlanticus where we meet the little beauty that is the world’s only underwater dragon. If you are in the middle of the Atlantic, Pacific or Indian ocean and are in calm waters, then you may be lucky enough to spot a Blue Dragon. It will be floating along the surface with the help of the air bubble it has stored in its stomach, or if you are a beach goer then you may be unlucky enough to run into a “blue fleet” (a group of Blue Dragons which were taken ashore). How do you know what a Blue Dragon looks like? It has a silvery grey colour on its dorsal side which is facing the waters below because it floats upside down. This is a form of counter-shading allowing it to blend in with the light at the sea surface when viewed from below, concealing it from predators (Loggerhead sea turtles being the only known marine predator). The Blue Dragon is dark and pale blue on its ventral side with blue stripes on its hea – this darker blue colouring allows them to camouflage into their surroundings when viewed from above. It has a flat, tapering body and 6 appendages that branch out into rayed, finger like cerata, and is only a miniscule 3 cm in length.
Though the Blue Dragon lacks in stature it is not something to take lightly – they take on fearsome beasts of the sea, like the mighty Portuguese Man-of-war (Physalia physalis) – a strange creature that looks like a single jellyfish but is actually made up of a colony of specialized polyps and belongs to the order Siphonophorae. Somee Blue Dragons have even been documented to be cannibalistic, but only when faced with an injured or recently deceased fellow Blue Dragon. To appreciate the Blue Dragon’s defence we need to first understand the defence of the creatures that it feeds on. The Portuguese Man-of-war, one of the oceans creatures with one of the most painful and deadly stings, uses cnidocytes that are cells that shoot off threadlike nematocysts that enter their prey and inject a venom. When the Blue Dragon eats its venomous prey they don’t completely digest them, they keep the stinging cells cnidocytes (with their unfired nematocysts) and store them in the tips of their cerata to use as a defence tool. If you’ve heard of the power of the sting that the Man-of-War posses, this could be enough to send shivers down your spine every time you hear their name. Unwary people who pick up a Blue Dragon may recieve a very painful and potentially dangerous sting.
You must be wondering how more of these bad boys get made. Well they are hermaphroditic, and they cannot fertilize their own eggs so there is no time to be antisocial because they must find a mate to reproduce with. Our small blue friends produce eggs in long, spiral shaped egg strings that float freely in the water or stick to surfaces, but typically they lay their eggs in their prey’s dead carcasses. So, would you like to go swimming with these beautiful blue devils?
References:
Heimbuch, J. (February 16, 2017). 3 fascinating facts about the blue dragons of the sea. Mother Nature Network. Retrieved November 27th, 2019 from https://www.mnn.com/earth-matters/animals/blogs/3-fascinating-facts-about-blue-dragons-sea
Hines, N. (June 19, 2018). Meet the blue dragon, the world’s most beautiful – and deadly – slug. Allthatsinteresting. Retrieved November 27th, 2019 from https://allthatsinteresting.com/glaucus-atlanticus
Kelly,A. & Olson,E. (August 7, 2014). Featured creature: Blue Dragon. PBS Nature. Retrieved January 10th, 2020 from https://www.pbs.org/wnet/nature/blog/inside-nature-featured-creature-blue-dragon/
Photo at top taken by : Sylke Rohrlach, March 3, 2013, at Bronte Beach, Sydney, NSW , https://commons.wikimedia.org/wiki/File:Blue_dragon-glaucus_atlanticus_(8599051974).jpg
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Photo at bottom by : Biusch, taken at Tayrona national park, Colombia https://commons.wikimedia.org/wiki/File:Physalia_physalis,_Tayrona_national_park,_Colombia.jpg
