The Medusa touch

A large swarm of tiny, transparent jellyfish-like creatures, which turned out not to be jellyfish, caused something of a panic amongst bathers at Ghajn Tuffieha.

The scientific name is ‘Velella velella’, popularly known as By-the-Wind Sailor, Purple Sailor or Admiral’s Hat. Despite a passing resemblance to a colourless ‘baby’ jellyfish, they turn out to be completely harmless to humans.

“Although these creatures superficially look like jellyfish, they are not jellyfish but are more closely related to the Hydra,” Prof. Patrick J. Schembri, of the University of Malta’s biology department, said. “Velella is a floating colonial hydroid composed of a number of individuals (called polyps) whose bodies are actually confluent with each other. The polyps are suspended, causing the whole colony to float at the water’s surface.”

Schembri points out that while unusual, these sightings are by no means unique. “This is not a new record in Maltese waters. Velella is an offshore species, but occasionally wind and currents aggregate large numbers in inshore waters.”

Floating peril
The same cannot be said for this summer’s unwelcome visitor, Physalia physalia, commonly known as the Portuguese Man-Of-War.

“The Portuguese Man-of-War is not a jellyfish but another type of floating colonial hydroid, which looks like a transparent bluish blown-up plastic bag floating on the water,” Schembri says, warning that the Portuguese Man-of-War is considered dangerous “since its toxins are more potent than those of the common Purple Stinger (Pelagia noctiluca)” – the jellyfish that is frequently seen on our shores.

Their appearance in the central Mediterranean is still rare as the Portuguese Man-Of-War is really a species native to the tropical and sub-tropical Atlantic. Nonetheless, Schembri acknowledges that some individual specimens have been found near the coast and even beached on local shores. “My first record of this species from local waters was from 2001 and I have additional records from 2008, 2009 and now this year.”

This creature is quite visible floating on the water, albeit with very long tentacles and so far there have been no reports of the creature occurring in swarms.

“There are many theories as to the sudden appearance of Portuguese Man-of-War in the central Mediterranean,” Schembri adds. “These animals cannot swim against the current and go only where the wind or current takes them. Their sudden appearance may be due to a change in the surface currents and changes in temperature; the past few decades have witnesses a general warming trend in Mediterranean surface waters.”

Fishy tales
Other ‘new’ species have been witnessed in Maltese waters in recent years, including fish. In September 2009, MaltaToday reported a sighting of the ‘African Hind’, or Blue Spotted Sea Bass (Cephalopholis taenops) – a species related to the Grouper, normally found in tropical waters.

Alex Buttigieg, a marine conservationist, told this newspaper that the phenomenon was probably related to climate change.

“Over the past five to six years we have noticed a number of new species, many of which would have come from the Red Sea,” he said. “Rising sea temperatures have a lot to do with the fact that this fish was found in Maltese waters. The Mediterranean is getting warmer, and as a result the African grouper may have spread its migratory range to include the Mediterranean.”

“What is not known is if this trend will last for a few decades, or whether it is much more long term.”

Current fishing methods are believed to contribute directly to the depletion of the oceans’ top marine predators, including sharks, tuna, swordfish, grouper and others – including turtles and dolphins, often ‘accidentally’ caught in fishing nets, which in turn may directly result in an explosion in jellyfish. This may happen for two reasons above others: Firstly, some of the overfished predators that naturally target jellyfish have dropped in numbers, boosting jellyfish populations.

Secondly, a drop in numbers of predatory species that target smaller fish such as sardines and mackerel, would also open up new niches for other predators which share the same prey – most species of jellyfish and polyp.

This article appears in today's edition of MaltaToday Midweek