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Portuguese Man O'War

Posted: Wednesday 13th September 2017 by The Isles of Scilly Wildlife Trust

Portuguese Man O' War in Scilly October 2016 ~ Image BarFoot PhotographerPortuguese Man O' War in Scilly October 2016 ~ Image BarFoot Photographer

You've probably seen the sensationalist headlines? "Deadly Portuguese Man o’ War invasion" and "terrifying Portuguese Man O'War wash up en masse" are jumping out at me as I write this but I want to calm things down a bit and shed some light on these beautiful creatures of the currently not so deep...

It would seem that these fascinating creatures are causing no end of drama across the South-West, according to the national press, and yes they are unusual but not uncommon for our part of the world at this time of year.

Most years Scilly ends up with a handful of these beasties washing ashore, or being seen at sea; last year was a particularly "good" year whereby they washed up in their 10's if not 100's on St Mary's Southern coastline (as I've previously said I counted 50 or more at Porth Hellick during one morning walk to work in October 2016).  

This year large numbers (but not as many as last year, yet) are washing up up on the more Westerly facing beaches (the popular beaches) and as a result are being seen by more residents and visitors, but we are not being invaded and there really is no need to panic.

Yes, they can be dangerous and their stings can be fatal but the more you know about them the safer you will be (and they really are awesome creatures!)

What is the Portuguese Man O'War (PMO'W)?

At the Trust we've been using the hashtag #NotAJellyFish on Social Media when sharing pictures of PMO'W for one very simple reason; they are not Jellyfish.  

It's important that people are aware of this for a number of reasons which I'll get on to in a bit.  Not only are they not a Jellyfish, a "single" PMO'W is not even an "it," but a "they"!

The PMO'W is a siphonophore, an animal made up of a colony of organisms working together.  The PMO'W comprises of four seperate polyps.

 

  • Polyp One:  The Float ~ This is the most visible and recognisable part of the PMO'W.  It is a beautiful purple, blue or pink (or any combination of these) gas filled float, looking very much like a balloon.  The gas that it is filled with is Argon (Number 18 on the atomic table) and it can be deflated to escape surface predators or inflated to aid with "sailing".  The float acts as an umbrella for the other polyps that are bunched beneath it and provides the PMO'W with it's main source of propulsion by acting as a sail.  The float may project either to the left or to the right; the left-handed forms sail to the right of the wind and vice versa. Thus, if the sailing angle of one form leads to its stranding on the shore, the others sailing to the opposite side of the wind may escape.
  • Polyp Two:  The Dactylozoids or Tentacles ~ This is the most feared part of the PMO'W.  Tentacles can reach up to 165 feet in length but an average of about 30 feet is more common.  They are covered in venom-filled nematocysts used to paralyse and kill fish and other small creatures.  For us, a PMO'W sting is incredibly painful, but rarely deadly and the treatment for stings is different to that of Jellyfish; hence remembering #NotAJellyFish.  PMO'W can still sting you when they are washed ashore or dead, and have been known to do so weeks after coming ashore, so it is best not to touch them; if you rub tentacles that are already on you or treat with the wrong method you can cause further triggering of nematocysts or sting cells.
  • Polyp Three:  The Gastrozooids or digestive organisms ~ This is situated under the float and muscles in the tentacles draw prey upwards.  The digestive polyps are the 'stomachs' of the colony and respond quickly to the presence of food, wriggling and twisting until they fasten their flexible mouths to it. Once attached they become all mouth, spreading out over the surface of the trapped prey. The resting polyp measures only 1-2 mm in diameter but the mouth may expand to more than 20 mm. PMO'W digest food by secreting a full range of enzymes that variously break down proteins, carbohydrates and fats. 
  • Polyp Four:  The Gonozoids or Reproductive Organs ~ PMO'W are asexual (neither male nor female) and the fourth polyp is responsible for creating baby PMO'W and continuing the dynasty.  A single PMO'W produces both sperm and eggs, which are released into the ocean. The sperm will fertilise eggs in the water column to produce a planktonic larval form; asexual division of those cells then produces the different polyps/types of animal which then live in this one colony becoming the PMO'W as we know it.

Pretty cool eh?

If you want to see some amazing picture of these stunning creature head on over to the National Geographic feature containing images from photographer Aaron Ansarov!

So, why are they in Scilly?

Velella Velella (By-The-Wind-Sailors) stranded on ScillyFound mostly in tropical and subtropical seas, PMO'W are propelled by winds and ocean currents alone, and sometimes float in legions of 1,000 or more!  At certain times of the year when wind and tidal conditions are just right we end up with a number in our area; blown off course and a long way from their home.  

The numbers washing ashore would suggest that whole flotillas or legions have been blown off course and met their doom in colder seas further north than they would ordinarily be; the same thing happened in October last year in much larger numbers than we are currently seeing.

Similarly, at certain times of the year we also get influxes of Velella Velella (By-The-Wind-Sailors) stranded on our beaches; they too are reliant on wind and tide to move around but do not have the same kind of reputation as the PMO'W, given that they are practically harmless.   

Treating a Sting 

Last year information was published both on Radio Scilly and This is Scilly regarding what to do if you get stung, with advice given by Dr Garman around treatment.  These are summed up below:

  1. Remaining tentacles should be lifted (NOT rubbed) off with a towel or stick. Do NOT rub with sand.
  2. Rinse the wound with saline NOT fresh water.
  3. Apply an ice-pack. This is an effective topical analgesic.
  4. The use of topical treatments to inactivate un-fired stinging cells (including alcohol, meat tenderisers and baking soda) is controversial, but unlikely to be of benefit. The application of vinegar is no longer recommended as this may initiate nematocyst firing.
  5. Seek medical attention.

Ultimately, these creatures of the deep have ended up in a place they shouldn't be and are sadly either going to die or are already dead.  

They are nothing to be afraid of, but should definitely be respected.  So if you are curious and want to see one, by all means go and take a look, they are truly remarkable in every aspect.  You will currently find them in most areas where the wind is blowing on shore, amongst the weed and other marine debris that's adorning our coastline.  

If you find any in your travels you can report them to the Marine Conservation Society who are including PMO'W in their Jellyfish Survey and let us know, either via Twitter, Facebook or Instagram so that we can keep our followers up-to-date with where they are so they can either be seen or avoided.  Remember by all means take photos but please do not touch.

If you're just not a curious bod and want to keep yourself and your four legged friend well away then I would suggest sticking to the coastal paths and beaches where the wind is currently blowing offshore.

Read The Isles of Scilly Wildlife Trust's latest blog entries.

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