The ecological impact of the entry of marine Invasive Alien Species (IAS) is increasingly being well documented. However, the public health hazard of the introduction of some of these aliens is probably less well-known. In fact, while the threat posed by stinging, venomous IAS, most notably lionfish species and jellyfish such as the nomadic one, is increasingly coming to the fore, the corresponding threat posed by toxic IAS, which unleash their wrath upon being consumed, is more elusive to many.

Take the Tetraodontidae fish family, which includes different species of pufferfish, triggerfish, porcupinefish as well as the ocean sunfish which holds an unenviable reputation of being the repository of one of the most potent toxins in the sea. Tetrodoxin (TTX) is a neurotoxin which is reputed to be several times more potent that the feared cyanide, with the lethal TTX dose for mice being equivalent to just eight micrograms per kilogram. TTX blocks sodium ion channels in neurons, thus shutting down the nervous system by thwarting communication between neurons. In large doses, this is lethal, since it results in the paralysis of the diaphragm and thus to respiratory failure, leading to death by asphyxiation.

The most intriguing aspect about TTX is that it is generated by bacteria found within the water column and within marine sediments belonging to genera such as the Pseudomonas and Vibrio ones, with pufferfish simply accumulating the toxin with age within different organs, most notably ovaries, the liver, intestines and skin.

The occurrence of TTX is a primary line of defense for the pufferfish (which leads to them being spitted out by potential predators), which compensates for their slow movements, besides the ability to inflate and bristle up their miniature spines by ingesting large quantities of water within their highly elastic stomachs.

At least four alien members of this family (Lagocephalus sceleratus, L. suezensis, L. guentheri and Torquigener flavimaculosus) has been recorded  from the Mediterranean to date,most of which are of tropical (Indo-Pacific) origin, while L. lagocephalus (minfaħ in Maltese) is native to the Mediterranean while Sphoeroides pachygaster (blunthead puffer) has a circumglobal distribution. The level of toxicity of different pufferfish species differs, with some of them (for example L. sceleratus – the silver-cheeked toadfish) being so toxic that they are not even included within the list of fish used for fugu preparation purposes in Japan.

Fugu is considered a delicacy in Japanese culinary tradition, although a highly trained cook needs to be entrusted with its preparation.

The silver-cheeked toadfish was first recorded from Maltese waters by the Spot the Alien Fish ( in August 2014, with the same species being recorded at least a handful of times from the same waters since then. Most of these individuals have been promptly removed from circulation by members of this citizen science campaign, so as to avoid local fatalities.

Submission of information relating to the sightings of marine alien species is welcomed by the Spot the Jellyfish, Spot the Alien Fish and the Spot the Alien citizen science campaigns, through the ad hoc websites, social media pages or by e-mail (, with all three campaigns being managed by the Department of Geosciences at the University of Malta and being financially supported by the International Ocean Institute (IOI).

Sound bites

• The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Chemistry 2020 to Emmanuelle Charpentier, Max Planck Unit for the Science of Pathogens, Berlin, Germany, and Jennifer A. Doudna, University of California, Berkeley, USA “for the development of a method for genome editing”.  These scientists have discovered one of gene technology’s sharpest tools: the CRISPR/Cas9 genetic scissors. Using these, researchers can change the DNA of animals, plants and microorganisms with extremely high precision. This technology has had a revolutionary impact on the life sciences, is contributing to new cancer therapies and may make the dream of curing inherited diseases come true.

• Being previously infected with a coronaviruses that cause the ‘common cold’ may decrease the severity of severe acute respiratory syndrome coronavirus (SARS-CoV-2) infections, according to results of a new study. Led by researchers at Boston Medical Center and Boston University School of Medicine, the study also demonstrates that the immunity built up from previous non-SARS-CoV-2 coronavirus infections does not prevent individuals from getting COVID-19. Published in the Journal of Clinical Investigation, the findings provide important insight into the immune response against SARS-CoV-2, which could have significant implications on COVID-19 vaccine development.

For more soundbites, listen to Radio Mocha every Saturday at 7.30pm on Radju Malta and the following Monday at 9pm on Radju Malta 2

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