The Strait of Messina is a little strand of Mediterranean Sea which lies sandwiched in between Calabria (the toe of Italy) and Sicily. It is typically known for beautiful sandy beaches, crystal clear blue water and hot Italian sun. Despite its calm appearance, this narrow strait can be more than 2000m deep and of a very turbulent nature. Peculiar water movements can cause rather common stranding events of deep water creatures, which made the Strait of Messina was the home birth of deep-sea fish research in the Mediterranean.

Strait of Messina seen from Mount Dinnamare (author: Edd48)
Strait of Messina seen from Mount Dinnamare (author: Edd48)

It is considered the “Belly button” of the Mediterranean Sea as it connects the Tyrrhenian Sea to the north with the Ionian Sea to the south. The tides of the two meeting seas alternate every six hours: when it is high tide in the Thyrrenian Sea, it is low tide in the Ionian Sea, and vice versa. This creates a strong water instability that gives rise to vigorous currents, frequent whirlpools and upwelling phenomenons (upward movements of seawater).

Illustration of Scylla and Charybdis (author: Vivò)

Ancient greeks living in these waters 2500 years ago, could not find an explanation for the strong and turbulent nature of the Strait, instead they created the myth of the marine monsters Scylla and Charybdis. Scylla (‘she who rends’) was described by Homer in the Odyssey as a terrifying creature with six dog’s heads who hunted sailors. The marine monster Charybdis (‘she who draws in’) was believed to suck in huge amounts of water to then violently spit it out, creating strong whirlpools and destroying the nearest ships.

Since the 19th century, scientific interest in Mediterranean deep-sea fish has been stimulated by fishermen’s tales describing monstrous and luminescent fish caught onto their nets, often called in the vernacular ‘devil fish’. Even if Scylla and Charybdis live only in our fantasy and popular stories, other incredible creatures live deep under the blue of the Strait of Messina.

Deep sea creatures

The strong and frequent upwelling phenomenons caused by the alternating tides, bring to the water surface -and sometimes even ashore– unexpected creatures coming from deeper zones of the Strait. These animals are called ‘bathypelagic’, because they are from the bathyal zone (also called midnight zone because of the absence of light), which extends from a depth of 1000m down to 4000m. The study of these organisms was made possible by the presence of stranded individuals (both already dead or still alive) on the shores of the Strait. The knowledge gained from the examination of the stranded specimens contributed to the creation of the first book of Mediterranean deep-sea fauna.

These ‘monstrous’ fish usually exhibit big eyes, sharp teeth and particular bioluminescent organs called photophores, which can emit light through the reaction of two enzymes: luciferin and luciferase. Bioluminescence is used by these organisms to achieve three main goals in the darkness: find food, avoid being eaten and find a mate.

A specimen of half-naked hatchetfish found stranded on the shores of the Strait of Messina (author: Sergio De Matteo)

The half-naked hatchetfish (Argyropelecus hemigymnus) is one of the most common bathypelagic fish found stranded on the shores of the Strait. It is only 4-6cm long, but it is found at depths between 460 and 1082 m. The body is bright silver in color with dusky coloration at night and its sides are covered in a multitude of downward directed bioluminescent photophores. These are used to escape from predators using ‘counter-illumination‘. The photophores match the light intensity with the light penetrating from the water above, so the fish does not appear darker from the top and cannot be seen by predators.

 

Stranded specimen of Sloane’s viperfish. Top picture: the fish ingested a prey almost as bit as itself  (author: Sergio De Matteo)

Another very common bathypelagic fish found in the surface waters or on the shores of the Strait of Messina is the Sloane’s viperfish (Chauliodus sloani). Despite its terrifying alien look, this viperfish only grows up to 3cm long. In the Strait it can be found at a depth range of 473-1192m, but it has been observed to move to shallower regions to hunt at night. It hunts in the darkness luring the prey with a specialised elongated dorsal fin with a bioluminescent ‘bait’ attached at the end of it. Unlike other species of bathypelagic fish, this creature can unlock its lower jaw to form an angle of up to 180º. This skill is used to ingest prey that are bigger than its stomach, a very useful ability when living in an environment like the deep sea, where food is very scarce.

 

Blunt-nose six gills shark showing the six gills and green-blue eyes. In southern Italy it is also referred as the “green-eyed shark” (author: Andy Murch from elasmodiver.com and www.arkive.org)

Among all the animals living deep in the blue of the Strait of Messina, the one which inspired the most the creation of the myths of marine monsters is most likely to have been the Blunt-nose six gills shark (Hexanchus griseus). Often referred as “Cow shark” (“vaccarella” in Italian), it is the largest hexanchoid shark, growing up to 7.9m in length. As its name anticipates, it has a large and blunt snout, small fluorescent blue-green eyes and it is one of the only three shark species to have six gill slits (other sharks have five). It is usually found around 180-1100m deep, but in the Strait of Messina it has been observed to move at night in waters as shallow as 12m deep to feed. Because of its feeding habits in surface waters, it is not uncommon to spot a six gills shark in the Strait. As a consequence, this giant is very vulnerable to fishing exploitation and by-catch, and it is listed as near threatened in the IUCN Red List.

Many other creatures of the deep sea are found stranded on the shores of the Strait of Messina. Among them we have: the bent-tooth lightfish Cyclotone braueri, the brittelmouth fish Gonostoma denudatum and the saber-tooth fish Evermannella balbo. These stranding events are still very common and they are extremely important for the scientific community to increase our understanding on Mediterranean deep-sea fauna, especially during periods where deep-sea research funding is limited.

The mythological monsters Scylla and Charybdis may not exist, but these and many other incredible creatures still inhabit the waters of the Strait of Messina, hiding beneath its turquoise surface.

 

References:

Baguet F (1995) Bioluminescence of deep-sea fishes in the Straits of Messina. In: The Straits of Messina Ecosystem (Guglielmo L, Manganaro A, De Domenico E, eds.). pp: 203-212

Bannerman P, Russell B, Nunoo F and Poss S (2015) Evermannella balbo. The IUCN Red List of Threatened Species 2015 (Downloaded on 25 October 2017).

Bignami F and Salusti (1990) Tidal currents and transient phenomena in the Strait of Messina: a review. The physical Oceanography of Sea Straits 95-124

Cook SF and Compagno L JV (2005) Hexanchus griseus. The IUCN Red List of Threatened Species 2005 (Downloaded on 25 October 2017).

Defant A (1940) Scilla e Cariddi e le correnti di marea nello Stretto di Messina. Geofisica Pura Applicata 2: 93-112.

Gibbs RH (1984) Chauliodontidae. p. 336-337. In PJP Whitehead, ML Bauchot, JC Hureau, J Nielsen and E Tortonese (eds.) Fishes of the north-eastern Atlantic and the Mediterranean. UNESCO, Paris. Vol. 1.

Haddock SHD, Moline MA and Case JF (2010) Bioluminescence in the sea. Annual Review of Marine Science 2:443-493

Harold A (2015) Cyclothone braueri. The IUCN Red List of Threatened Species 2015 (Downloaded on 25 October 2017).

Kobyliansky S, Herrera J and de Sola L (2015) Gonostoma denudatum. The IUCN Red List of Threatened Species 2015 (Downloaded on 25 October 2017).

Mytilineou C, Politou CY, Papaconstantinou C, Kavadas S, D’Onghia G and Sion L (2005) Deep-water fish fauna in the Eastern Ionian Sea. Belgium Journal of Zoology, 135(2):229-233.

Widder EA (2010) Bioluminescence in the Ocean: Origins of Biological, Chemical, and Ecological Diversity. Science Magazine 328:704-708

 

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