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After the Jellyfish Dilemma, What Other Dangerous Species Are Invading the Mediterranean?

10 July, 2017
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Throughout the early summer, thousands of jellyfish have flooded the Mediterranean coast, raising the question of how imbalanced the ecosystem has become. Yet, the Rhopilema nomadica jellyfish species are not the only invaders we should be worried about.

Invasive alien species (IAS) are considered one of the major threats to global marine ecosystems for impacting their structure, function and services, the Steinhardt Museum of Natural History and Tel Aviv University’s Bella Galil stated.

“A small number of marine IAS engenders human health impacts,” explained Galil. Human health hazards of IAS are expected to worsen, benefitting from climate change and the enlarged Suez Canal—the main pathway of IAS introduction into the Mediterranean Sea, Galil explained. “In conjunction, these will enable the spread of thermophilic alien species to yet uncolonized regions, and admit entrance to additional species from the Indian Ocean and the Red Sea.”

Excluding the R. nomadica, below is a list of known species invading the Mediterranean: 


Photo credit: Yaron Halevy

The striped eel catfish Plotosus lineatus is considered one of the most dangerous venomous fishes known, causing fatal envenomations. Venom glands are associated with the serrate spines on the dorsal and pectoral fins and its skin secretions contain protinaceous toxins. Injury causes immediate throbbing pain, followed by cyanosis, numbness and swelling.

During a survey of injuries from marine organisms conducted among Israeli professional fishermen in 2003-2004, 10% of fish-related injuries in Israel were caused by P. lineatus.


Photo credit: Oren Klein

The lionfish Pterois miles has recently been recorded in Lebanon, Turkey, Cyprus, Greece and as far west as Tunisia and Sicily, Italy, following a major enlargement of the Suez Canal in 2010.

The venom apparatus consists of grooved spines and their venomous glands. Envenomation, or process by which venom is injected into an animal, produces intense pain and swelling, which may continue for several hours, depending upon the amount of venom released.

No lionfish injuries have been reported as of yet in the Mediterranean Sea. However, their presence along coastlines popular with tourists is a marine health hazard.


Photo credit: Zvika Fayer

The two species of rabbitfish (Siganus) have been found as far west as France and Tunisia. The venom apparatus consists of grooved spines and their venomous glands, which rupture and release their contents upon penetration. Their venom is not life-threatening to adult humans, but causes severe pain and swelling that can last for several hours.


Photo credit: Wikipedia

The reef stonefish Synanceia verrucosa was first recorded in the Mediterranean Sea in 2010 off the coast of Israel and shortly thereafter was found in the Gulf of Iskenderun, Turkey and Tyr, Lebanon.

It is considered to be one of the most dangerous venomous marine fish, and its stings are potentially fatal. Venom is released from paired venomous glands placed in lateral grooves at the base of each spine. Envenomation results in excruciating pain to the point of losing consciousness and gross oedema. No stonefish injuries have been reported in the Mediterranean Sea, but if their population were to flourish, their presence along coastlines popular with tourists presents a marine health hazard.


Photo credit: Oren Klein

The silverstripe blaasop, Lagocephalus sceleratus, was found in 2003 along the southwestern coast of Turkey. Soon after, its Levantine populations greatly increased and spread clear across the Mediterranean Sea to Spain and also crossed into the Black Sea.

Tetradotoxin (TTX) is one of the most potent, nonprotein poisons known. Symptoms include perioral paraesthesia (numbness or tingling of the lips, tongue, around the mouth), nausea, vomiting, dizziness, headache, abdominal pain and progressive muscular paralysis, eventually causing death due to respiratory paralysis. Comas have been reported in severe cases of TTX poisoning and in the final stages before death.

Following the establishment of L. sceleratus in the Mediterranean Sea, evidence of severe TTX poisoning was noted. Between 2005 and 2008, 13 victims of TTX poisoning, aged 26–70 years, have been hospitalized in Israel. Similar cases were reported from Lebanon and Cyprus. Despite official prohibitions, the species is being sought by recreational fishers and occasionally commercially marketed. Both naïve local and tourist consumers are at serious risk given the high level of toxicity of L. sceleratus.


Photo credit: Wikipedia

The long-spined urchin Diadema setosum was found in waters near Lebanon, Turkey and Greece. Its brittle spines may inflict deep penetrating wounds and break off easily to become embedded in the tissue. Their venom is mild, but may cause inflammation, swelling and acute pain, which gradually declines after a few hours. No long-spined sea urchin injuries have been reported in the Mediterranean Sea. Were their numbers to increase, their presence along coastlines popular with tourists would certainly become a health concern.


Photo credit: Wikipedia

The feathery stinging hydroid Macrorhynchia philippina has existed in the southeastern Mediterranean Sea since the 1990s, and has since expanded northwards to the Turkish coast.

A brush with its feathery nematocyst-laden branches may cause a mild stinging sensation, but a more extensive contact results in a burning sensation. Victims generally develop pinpoint lesions, a blotchy red rash, blisters and raised itchy weals, which may last for up to ten days before fading away.

An increase in the abundance of M. philippina along the Levantine coastline may cause damage to recreational activities, such as swimming and snorkling.

Tags Mediterranean Sea invasive species marine life jellyfish ecosystem Environment