Through Unique Eyes, Box Jellyfish Look out to the World Above the Water

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Box jellyfish may seem like rather simple creatures, but in fact their visual system is anything but. They've got no fewer than 24 eyes of four different kinds. Now, researchers reporting online on April 28 in Current Biology, a Cell Press publication, have evidence revealing that four of those eyes always peer up out of the water, regardless of the way the rest of the animal is oriented. What's more, it appears that those eyes allow the jellies to navigate their way around the mangrove swamps in which they live.

It is a surprise that a jellyfish -- an animal normally considered to be lacking both brain and advanced behavior -- is able to perform visually guided navigation, which is not a trivial behavioral task," said Anders Garm of the University of Copenhagen. "This shows that the behavioral abilities of simple animals, like jellyfish, may be underestimated."

In fact, scientists have known for more than a century that box jellyfish had a unique array of eyes. It was known that they could rely on vision to respond to light, avoid obstacles, and control their rate of swimming. But box jellyfish generally live in shallow waters with plenty of obstacles. The species Garm's team studied, Tripedalia cystophora, lives between the prop roots in Caribbean mangrove swamps, where they stay close to the surface to catch and eat copepods that gather in high densities in light shafts formed by openings in the mangrove canopy. They are never found out in the open, where they might risk starvation. That means they must stay within a rather restricted area, less than two meters wide. And it now appears that they have eyes that help them do this.

The researchers examined the function of one of two types of "upper lens eyes," already known to form images, to work out just what those eyes can see and how well. It turns out that those four eyes cover precisely the visual field needed to see through the water's surface up into the world above. The researchers calculated that the jellies should be able to detect the mangrove canopy from a distance of at least eight meters. Behavioral experiments of the jellies in the field supported those conclusions, revealing that the jellyfish can use those eyes to navigate based on their view of the canopy alone. When the canopy was obscured from view, they could no longer get around.

"We have shown that the box jellyfish can use vision to navigate in their habitat, and we now want to understand how their simple nervous system supports such advanced behaviors," Garm said. They also want to know if other box jellyfish species do the same thing in the places where they live.

Overall, this new understanding of the upper lens eyes points to a more general strategy for managing complex sensory tasks without a big brain. "Instead of having a single pair of general-purpose eyes like most other animals, box jellyfish have several different types of eyes used for special purposes," Garm said. "This means that each individual eye type is dedicated to support only a limited number of behaviors. The eyes can then be built to collect precisely the information needed, minimizing the need for further processing in a big brain. The automatic orientation of the upper lens eyes to constantly look through the water surface is a clear example of this."

Thanks to Science Daily

Kathy Dowsett

www.kirkscubagear.com

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How to avoid dying from deadly Jellyfish

For the previous post, we talked about certain kinds of non-lethal jellyfish. As for this post, we’ll be identifying the kinds of deadly Jellyfish that you don’t want to meet when you’re down under the sea and what to do if ever you get stung.

The Box Jelly – It’s also known as the Sea Wasp or Chironex Fleckeri. It’s found off the shores of Northern Australia, Papua New Guinea, Malaysia, Indonesia, Philippines, Thailand and Vietnam. This marine animal has a boxy bell head the size of a basket ball, 4 parallel brains [one on each corner], 24 eyes and 60 arseholes.

There are 5,000 deadly stinging cells on each of its 10- 60, two meter long tentacles. They are usually a problem from October to May. They are the most toxic creatures on Earth. These are the symptoms of an attack of the Box Jelly:

- Severe pain

- Headache, nausea, vomiting, diarrhea

- Skin swelling/wounds/redness

- Difficulty breathing, swallowing and speech

- Shivering, sweating

- Irregular pulse/heart failure

Irukandji jellyfish – Irukandji jellyfish are very small, with a bell about one centimeter wide and four tentacles, which range in length from just a few centimeters to up to 35 cm in length. The stingers (nematocysts) are in clumps, appearing as rings of small red dots around the bell and along the tentacles. They are found in Australia.

They are known as Irukandji jellyfish because they cause symptoms known as Irukandji syndrome (a condition that is induced by venomization that is seldom fatal, but if immediate medical action is not taken, within only 20 minutes the victim could go into cardiac arrest and die). They are usually a trouble from November to May, though recently they have been recorded present in all months except July and August. The most common known jellyfish of this type are Carukia barnesi and Malo kingi. Symptoms of an attack:

- Lower back pain, intense headache.

- Muscle cramps and shooting pains, nausea, vomiting.

- Catastrophically high blood pressure.

- Restlessness and feeling of impending doom.

- Death from heart failure or fluid on the lungs.

Of course we won’t leave you with just these symptoms of death and doom. So here’s what you should do when you get stung by one of these deadly Jellies:

- Rinse the area with sea water. Do not scrub or wash with fresh water which will aggravate the stinging cells. Do not pour sun lotion or spirit-based liquid on the area.

- Deactivate remaining cells with a vinegar rinse before removing them; otherwise inactive nematocysts may be triggered. If no vinegar is available use urine – but NOT for Box jelly and Irukandji stings. Ask a mate for a golden shower! Really! Preferably male urine as it’s considered to be more sterile

- Lift off any remaining tentacles with a stick or something similar.

- If cells still linger, dust with flour and carefully scrape off with a blunt knife.

- After all tentacle sections have gone, pain can be treated with a cold pack and/or a local anesthetic such as a sunburn lotion or insect bite treatment that lists ‘ocaine’ as an ingredient.

- If there is continued swelling, or itchiness, apply a light steroid cream e.g. Hydrocortisone eczema cream.

- If muscle spasms persist see a doctor.

Some additional treatment for the Box Jelly.

- Use pressure-immobilization on limbs if possible. e.g. quickly wrap a light bandage above and below the sting (if you can’t get two fingers under the bandage, it’s too tight).

- Immobilize/splint the stung area and keep it at heart level [gravity-neutral] if possible. Too high causes venom to travel to the heart, too low causes more swelling.

- Do not drink alcohol, or take any medicine or food.

Now that you’ve read all these information, I believe it’s still best to remind ourselves of these basic yet very helpful guidelines.

- Take extreme precautions if you have an existing heart condition as Jellyfish deaths are normally attributed to cardiac arrest [or pulmonary congestion]. You are in great danger from the Toxic Boxes’ venomous sting unless treated immediately as the pain is so excruciating that you may go into shock and drown before reaching the shore. So swim with a partner if possible.

- Avoid swimming in the October-May high-jelly season.

- Wetsuits or Lycra ’stinger suits’ offer good protection especially the sophisticated models with hands, neck and head coverage. Feet may be covered by fins or swimming shoes.

- Take notice of warnings! Bathing areas prone to toxic jellies may have safety signs.

Keep your eyes peeled when swimming in areas where the more dangerous variety live (though Irukandji jellyfish are very small and barely visible to see, so accomplish first steps first before relying on this one).

With these in mind and heart I believe you will be able to achieve a more wonderful and wary diving experience. Make sure that you have a healthy heart, because that is the organ that is directly affected by Jellyfish venom. Cardiac arrest is mostly the cause of death by jellyfish. That’s why Will Smith died in the movie 7 Pounds, not because he was electrocuted by some jellyfish (whoops, spoiler alert… haha).

Jellyfish are wonderful creatures, and they will treat you wonderfully too if you treat them and their habitat in the same manner.

Thanks to Sean from Expedition Fleet Liveboards

Kathy Dowsett

www.kirkscubagear.com

Related articles

• Jellyfish stings - All Information (umm.edu)
• Why don't jellyfish sting each other? (boingboing.net)
• S.F.: Thousands of dead jellyfish on Ocean Beach (sfgate.com)