Creature Feature: The Blue Dragon (Glaucus atlanticus)

The first time I saw a picture of this little guy I thought it had to be a photoshop thing; some little creature made up by some talented artist. It made me want to delve deeper, and you know what I found - It really does exist!

Believe it or not, this little sea slug or nudibranch, is pelagic (lives in the open water). It is often found floating upside down on the surface of the ocean in temperate and tropical waters in such regions as the east and south coasts of South Africa, Mozambique, European waters, the east coast of Australia, and the islands of Hawaii. They also have been spotted in the waters of Bermuda. Its average size when fully grown is a whopping 3-4cm. The blue dragon's floating abilities are due to a gas-filled sac located in its stomach. Because of its location, this sac causes the slug to float upside down exposing its blue-white foot to the surface of the water, leaving the silver-gray dorsal surface facing downward into the water. This is an example of counter shading, where the coloration helps to protect the organism from it predators both below and above. These slugs spend most of their lives drifting along, directed by currents and winds. They are generally not observed by humans except on those occasions when strong onshore winds bring masses of them (often called the "blue fleet") to beaches, causing much pain for swimmers and beach-goers.

Common names for this beautiful slug are blue dragon, blue glaucus, blue sea slug, blue ocean slug, and sea swallow. G. atlanticus is carnivorous and preys on other, larger pelagic organisms such as the venomous Portuguese Man o' War, the by-the-wind sailor, the blue button, and the violet snail. They have also been know to become cannibalistic.

The blue dragon is immune to the venomous nematocysts of the Portuguese Man o' War, and when consuming this animal, appears to select and store the most venomous nematocysts in specialized sacs called cnidosacs on the tip of its feather-like fingers. Because it is able to store up this venom for future use, ironically it can produce a more powerful and deadly sting than the man 'o war upon which it feeds.

Blue dragons are hermaphrodites (have both male and female reproductive organs). After mating, both animals produce 4-6 egg strings within an hour that float freely in the water or are placed on the remains of prey. These busy little slugs can produce from 3300-8900 eggs per day.

References:

1. Glaucus atlanticus Forster, 1777. World Register of Marine Species, accessed 3 April 2010.
2. "Marine Species Identification Portal : Glaucus atlanticus". Species-identification.org. http://species-identification.org/species.php?species_group=pelagic_molluscs&id=189. Retrieved 2011-11-21. 
3. Rudman, W. B. (6 November 1998). "Glaucus atlanticus Forster, 1777". Sea Slug Forum. http://www.seaslugforum.net/factsheet.cfm?base=glauatla. Retrieved 26 February 2011. 
4. Debelius, H.; Kuiter, R. H. (2007). Nudibranchs of the world. IKAN-Unterwasserarchiv. ISBN 978-3-939767-06-0. 
5. http://seaslugsofhawaii.com/species/Glaucus-atlanticus-a.html
6. http://www.thecephalopodpage.org/marineinvertebratezoology/glaucusatlanticus.html

Chris’ Dive Experiences: Unlock A Passion For Sharks And Shark Diving

 If you hang around anybody that was diving in the 70’s to early 80’s in Southern California chances are you’ve heard the stories of how healthy our ocean was back then. From just snorkeling in a few feet of water off La Jolla and pulling up trophy sized abalone with little time and effort, to sitting at the face of an overhang underwater and trying to decide how many trophy sized California Spiny Lobster you were going to take, to being on a local SoCal dive boat and getting bored at seeing more blue sharks on the way to your dive site off Catalina Island because it basically always happened. 

Unfortunately, gone are days of any of the above experiences happening without a lot of time, money, and effort. But if you are willing to spend a couple hundred bucks and a full day on a small boat you just may unlock something you didn’t even realize was buried deep inside you, a passion for sharks and shark diving.

Our day started before the sun rose, meeting with the group and loading up our gear on the boat before it was backed into the water in Mission Bay. Once outside of the Mission Bay channel the Captain hammered the throttle and we arrived off Torrey Pines to start chumming in no time flat. As we sat and waited stories were shared of past diving trips and future plans of travel and diving. The hours passed and we all wondered if we were going to get skunked and not see any sharks. 

As the clock neared 1:30pm the single word that everyone was waiting to hear was screamed, “SHARK”! Some of us started scrambling into gear while others got up to get their first view of a pelagic shark outside of an aquarium. As the young Blue Shark circled the chum bucket behind the boat we started to gently slide into the water, one by one, in our snorkel gear. The first time a Blue shark approaches you to see what you are, you are instantly in awe of its huge inquisitive eyes, sleek powerful body, and last but not least, the eye popping iridescence of its skin as the sun rays dance upon it.

Close encounters continued throughout the afternoon, with the Blues swimming to and from the chum bucket and weaving in and out of the snorkelers, gently checking each of them out. Blues tend to investigate by bumping, and as they would swim by to check snorkelers out, these sharks would usually turn in toward the snorkeler. If you ever find yourself in this situation, just keep your cool and remember all that is needed is a little redirection with your hand to steer them away from you. This kind of shark diving provides a truly intimate experience between you and the shark, leaving you with a lasting impression of the beauty, power, and elegance of diving with Blue Sharks.

As the remaining hours of sunlight burned off, we enjoyed the experience of 3 different Blue Sharks coming to check the chum and the snorkelers out, giving each snorkeler ample time to shoot pictures and video of the sharks. Each and every person had a cheek to cheek smile when describing their encounter with the Blue sharks on this day.  As we pulled back into the Mission Bay Channel, the sun disappeared below the horizon ending a very special, intimate day diving with the majestic Blue Sharks of San Diego.

What do you think? Do you have a passion for sharks? Do you have a hidden passion for shark diving waiting to be found? Will you join the ranks of the few that chase sharks around the world seeking out special, sometimes mere seconds worth, of an encounter that will always remain in the shark divers memory? Maybe, maybe not. Let me know if you would like to experience this for yourself.