The Portuguese man o’ war (Physalia physalis) is a floating siphonophore colony (not a single individual) of polyps which is found in the pleuston (upper stratum of the water column, with parts of its structure even projecting into the atmosphere above) and is equipped with a particularly potent toxin that is potentially deadly to humans. In fact, the only known mortality from a ‘jellyfish’ sting in the Mediterranean is attributed to an encounter with a Portuguese man o’ war colony that an elderly woman in Sardinia had way back in 2010. The colony has an air-filled bladder called the marissa or pneumatophore which allows it to float.
The species is commonly known as the Portuguese man-o-war by virtue of its resemblance to a 16th century vessel of Portuguese design, known as the caravel. The colonies are not native to the Mediterranean, being known from tropical and sub-tropical latitudes of the Indian, Pacific and Atlantic Oceans and being propelled into the Mediterranean through the Straits of Gibraltar by westerly winds.
The Spot the Jellyfish team, coordinated by the Department of Geosciences at the University of Malta, recently collated all sighting data it had for the species since August 2009 and teamed up with Sicilian colleagues so as to document the increasing presence of the species in the central Mediterranean.
It emerges that this venomous colony was recorded a total of 11 times within Maltese waters since 2009 (an average of one sighting per year) with the vast majority of records (nine out of 11 records) being made during the non-bathing season (January-May), although two records were made in August 2009 and June 2010. The highest number of sightings (3) of the species were made in 2010, followed by 2018 and 2019 (2 sightings each), with no sightings being made in 2013, 2015, 2016 and 2017. The vast majority of sightings were made at beaches along the north-west coastline of the Maltese islands, consistent with an Atlantic origin of the venomous colony.
Once entering the Mediterranean, it takes the same colonies at least two months to make the 2,000km-long journey to Maltese waters, feeding and growing along the way, such that the vast majority of colonies reported in Maltese waters were large, with pneumatophore diameters exceeding 15cm.
Within the Ionian Sea, there are no published records for P. physalis east of the Maltese islands, suggesting that the colonies do not make landfall once they reach this part of the basin. The treatment for the stings of such a venomous colony involves the application of hot packs and washing with seawater (never with freshwater).
The Spot the Jellyfish citizen science campaign (www.ioikids.net/jellyfish) is supported by the International Ocean Institute (IOI) and the Malta Tourism Authority (MTA) and has validated over 2,500 records of jellyfish sightings it has received from the public for Maltese waters since June 2010.
Alan Deidun, associate professor, Department of Geosciences the University of Malta.
Did you know?
• SPF stands for ‘sun protection factor’, conveying the level of protection from sunburn, that is how much of the UVB rays it blocks.
• SPF15 blocks around 93 per cent of UVB rays, SPF100 blocks 99 per cent.
• The average light-skinned person can stay in the sun for 15 minutes before they start to suffer minor sunburn.
• The SPF number is multiplied by 15 minutes to determine how long the average person can stay in the sun.
• However, reapplication of sunscreen is recommended every two hours since sweating and swimming decrease the effectiveness of sunscreen.
For more trivia see: www.um.edu.mt/think
Sound bites
• Researchers are designing a customisable smart window that is able to harness and manipulate solar power and could improve the energy efficiency of buildings. This allows people to customise the amount of sunlight in a room or minimise heating/cooling efforts. The sunlight that doesn’t pass through is captured by the solar cell in the smart window and converted into electricity.
https://www.eurekalert.org/pub_releases/2020-07/dnl-csw071420.php
• Researchers have developed a tiny plastic robot, made of responsive polymers, which moves under the influence of light and magnetism. The aim for this ‘wireless aquatic polyp’ is to be able to attract and capture contaminant particles from the surrounding liquid or pick up and transport cells for analysis in diagnostic devices.
https://www.eurekalert.org/pub_releases/2020-07/euot-war_1071420.php
For more soundbites, listen to Radio Mocha www.fb.com/RadioMochaMalta/.