Dr. Alaa Eldin Eissa, D.V.M, Ph.D. Associate Professor Department of Fish Diseases and Management Faculty of Veterinary Medicine , Cairo University Giza, 11221 Egypt aeissa2005@gmail.com https://www.researchgate.net/profile/Alaa_Eissa2
AN OVERVIEW ON THE TOP 10 MOST DANGEROUS FISHES IN THE WORLD
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AN OVERVIEW ON THE TOP 10 MOST DANGEROUS FISHES IN THE WORLD A POISONOUS VERSUS VENOMOUS FISH ? •
Poisonous and venomous are terms often used interchangeably whereas a venomous fish has a means of inoculating their venom into another creature, but a poisonous fish can only infuse their toxin in a more passive mode through touch or ingestion.
1. SILVER CHEEKED TOADFISH (Lagocephalus scleratus) •
Ecology: o It is a common species in the Indian and Pacific oceans. o Silver cheeked Puffer fish has recently migrated from Suez Canal to the eastern Mediterranean Sea through what is called “Lessepsian migration pattern” . It has been recently caught off the shores of Egypt, Libya, Tunisia, Israel, the south of Turkey , Lampedusa , Rhodes and Malta (Eissa et al. 2011). o Most recently Eissa et al. (2012) have detected the H5N1 Influenza virus in the kidney tissues of Silver cheeked toadfish (Lagocephalus scleratus) collected offshore of Abou Qir district at Alexandria , Egypt.
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Toxin and its dangerous effects: o Similar to other puffer fishes, the silver-cheeked puffer fish (silver cheeked toadfish) is extremely poisonous if ingested because it contains “tetrodotoxin” in its ovaries , liver and to a lesser extent in its skin / muscles, which protects it from voracious predators. It becomes poisonous as it ingests bacteria that contain the toxin. o Tetrodotoxin is neurotoxic and inhibits neural transmission leading to weakness, paralysis even death at relatively low concentrations (~2mg). o This lethal substance causes voluntary muscles paralysis (diaphragmatic muscles), which may cause its victims to stop breathing or induce heart failure. Fatal poisoning of several families at coastal
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areas in Egypt (Alexandria, Marsa Matrouh, Suez) and Israel ( Java, Haifa) have been reported .
Figure 1. Anatomy of Silver cheeked toadfish (Lagocephalus scleratus). Pictures are courtesy of Dr. Alaa Eldin Eissa ( Faculty of Veterinary Medicine, Cairo University).
2. STONEFISH (Synanceia verrucosa ) •
Ecology: o Stonefish have gained the title of ‘Most Venomous Fish’ in the recent few years. They nearly looks like encrusted stones, Intermingling into their natural habitat with ease. o They inhabit the Indo Pacific region and northern Australia.
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Venom and its dangerous effects: o Stonefish inoculate their venom through a row of spines on their dorsal region that can be erected when feels danger or incidentally stepped on. Venom is swiftly released when the fish get pressed and the amount of the venom is directly proportional to the degree of pressure . o Stonefish stings can occur on the beach, not just in the water, with stonefish being able to stay out of the water for up to 24 hours. A sting from this fish can cause severe pain, rapid edema, necrosis, muscle weakness, temporary paralysis, and in very rare cases death. o After stonefish venom injection, the amount of anti-venom given depends on the number of puncture wounds from the stonefish spines. o Stonefish antivenom is the second-most administered in Australia. 3
Figure 2. Stonefish (Synanceia verrucosa). The picture is a courtesy of SeanMack
3. LIONFISH ( Pterois volitans) •
Ecology: o The lionfish is a predator native to the Indo-Pacific. It aggressively preys on small fish and invertebrates. o They can be found around the seaward edge of reefs and coral, in lagoons, and on rocky surfaces to 50 m deep. o Many universities in the Indo-Pacific have documented reports of Lionfish aggression towards divers and researchers.
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Venom and its dangerous effects: o Lionfish are known for their venomous fin rays, an uncommon feature among marine fish in the East Coast coral reefs. Lionfish venom produced negative inotropic and chronotropic effects due to nitric oxide release. In humans, Lionfish venom can cause systemic effects such as extreme pain, nausea, vomiting, fever, breathing difficulties, convulsions, dizziness, redness on the affected area, headache, numbness, paresthesia (pins and needles),heartburn, diarrhea, and sweating. o Rarely, such stings can cause temporary paralysis of the limbs, heart failure, and even death. Fatalities are common in very young children, 4
the elderly, those with a weak immune system, or those who are allergic to their venom. Their venom is rarely fatal to healthy adults, but some species have enough venom to produce extreme discomfort for a period of several days. o There is a possibility for a human to be stung without any venom being injected. If venom is injected, the sting will hurt more than just briefly.
Figure 3. A Lionfish, Pterois volitans, along Roach Wall, the Admiralty Group, Lord Howe Island. Source: Dianne J. Bray.
4. STINGRAYS •
Ecology: o Stingrays are a group of rays, which are cartilaginous fish related to sharks. o Stingrays are common in coastal tropical and subtropical marine waters throughout the world. o Some species, such as Dasyatis thetidis, are found in warmer temperate oceans, and others, such as Plesiobatis daviesi, are found in the deep ocean. o The river stingrays, and a number of whiptail stingrays (such as the Niger stingray and Nile stingrays), are restricted to fresh water. o Most stingrays are demersal (inhabiting the next-to-lowest zone in the water column); but some, such as the pelagic stingray and the eagle rays, are pelagic.
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Stingers: 5
o Most stingrays have one or more barbed stingers (modified from dermal denticles) on the tail, which are used exclusively in selfdefense. o The stinger may reach a length of approximately 35 cm (14 in), and its underside has two grooves with venom glands. o The stinger is covered with a thin layer of skin, the integumentary sheath, in which the venom is concentrated. •
Dangerous effects : o Stingrays do not aggressively attack humans, though stings do normally occur if a ray is accidentally stepped on. o Contact with the stinger causes local trauma (from the cut itself), pain, swelling, muscle cramps from the venom, and later may result in infection from bacteria or fungus. o The injury is very painful, but seldom life-threatening unless the stinger pierces a vital area. o The barb usually breaks off in the wound, and surgery may be required to remove the fragments. o Fatal stings are very rare, but can happen, most famously in the death of Steve Irwin in 2006, in which the stinger penetrated the thoracic wall.
Figure 4. A Stingrays ,a stinger piercing a human leg and a dramatically injured / sutured human foot. The Pictures are adopted from Wikimedia commons.
5. BOXFISH •
Ecology: o Boxfish are generally a very pretty, colorful family of fish belonging to the family, Ostraciidae. These include cofferfishes, cowfishes and trunkfishes. o Boxfish are small fish (between about 5 and 18 inches long, but most are at the low end of that range) that frequent the shallow areas of the warmer parts of the world’s oceans, like coral reefs and seagrass beds. 6
o They spend their lives passively pruning algae and small invertebrates like crustaceans, worms, and sponges off rocks and coral with their tiny, delicate mouths. •
Poison and poisonous effects : o Boxfish are closely related to pufferfish. While these fish are not nearly as poisonous as puffers, they do have an impressive way of defending themselves with poison. o Their bodies are encased with armor plating, excellent for deterring would-be predators, but this is where it gets interesting, they also have a chemical defense system. This consists of a potent toxin, known as “ostracitoxin”, which they exude in their slime when they are threatened , frightened or pressed and as for their bright colors, this is a very typical warning sign to would be predators across the animal kingdom. o What makes boxfish toxicity different from other fishes toxicities is the chemical unlikeness to any other known fish toxins, and their usage in an entirely different way, they don't sting or need to be touched or eaten to be toxic. o Ostracitoxin possesses hemolytic effect on human blood.
Figure 5. A yellow boxfish . The picture is a courtesy of Animalia Life.
6. ELECTRIC EEL
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Ecology: o Electric eels are one of more than 500 fish species that are capable of producing electricity. o They live in shallow, muddy areas of Amazon and Orinoco rivers in South America. o Electric eels tend to live in muddy beds in calm water, eating fish and small mammals. o Electric eels can grow up to 2.5 meters and only need to surface for air every 10 minutes due to the eels complex circulatory system. Despite the name electric eel, the electric eel is actually related most closely to a catfish and not the common eel fish . o Many electric eel adults tend to be smaller than their eelfish relatives. o The electric eel is also known for its unusual breeding behavior. In the dry season, a male electric eel makes a nest from his saliva into which the female electric eel lays her eggs. As many as 17,000 young electric eels will hatch from the eggs in one nest. These young electric eels feed mainly on invertebrates found on the river bed, however, first-born baby electric eels have been known to bolt up the eggs from sets of other electric eels that were laid only a short time after themselves. o Electricity production and its dangerous electric effects: o Electric eel has around 6000 cells (electrocytes) that produce electricity. They can generate a power of 600 volts, which is 5 time stronger than the electricity generated in the standard US wall socket. o Electric eel can produce electric shock strong enough to knock down a horse or a rhinoceros . o Man can die if an eel hits him with several electric shocks. o 20 foot long eel can produce enough electricity to light 12 light bulbs. o Since eels have poor eyesight, they generate low-level electric charge (up to 10 volts) that helps them see their surrounding and locate a prey.
Figure 6. Electric eel topography and electric eel attacking crocodile. The Pictures are adopted from Wikimedia commons.
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7. GOLIATH TIGERFISH (Hydrocynus goliath) •
Ecology: o Goliath tigerfish definitely lives up to its name. A native of the Congo River basin, the Lualaba River, Lake Upemba and Lake Tanganyika in Africa, it's the largest member of the tigerfish family, a genus of fierce predators with protruding, bladelike teeth. o The biggest one on record was nearly 5 feet long and weighed 154 pounds. Locals say it's the only fish that doesn't fear the crocodile and o This reputation, combined with its strength, has earned it an almost mythical status among anglers, and it has been called the "greatest freshwater gamefish in the world. that it actually eats smaller ones.
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Dangerous Effects: o The Goliath tigerfish has an olive-colored back and a silvery underbelly. If you see one, what you'll remember is its mouthful of 32 jagged, razorlike teeth. Each tooth can be up to one inch long. The Goliath's teeth are set at the edge of the jaw , the monster has barely any lips. when those teeth slam down on prey, it's a clean, almost surgical cut. Those attributes, combined with its muscular physique, make the Goliath a state-of-the-art mayhem machine. o It likes turbulent waters, where fish who are less powerful swimmers struggle against the current, rendering them vulnerable to attack. It has excellent eyesight and the ability to sense low-frequency vibrations emitted by prey. It generally circles the unlucky fish before striking with the brutality of a piranha. o The Goliath has been known to pounce on a 60-pound catfish and literally slice it in half. The Goliath's lifespan in the wild is uncertain, but they've lasted 10 to 15 years in captivity. o A number of incidents have been reported in The Congo of this fish attacking humans. o According to locals living near the river, the evil spirit "mbenga" would enter the fish and make it attack people.
Figure 7. Goliath Tigerfish (Hydrocynus goliath) exhibiting their razor like blades tooth. The Picture is a courtesy of Wikimedia commons. 9
8. GOONCH CATFISH (Bagarius yarelli) •
Ecology: o Bagarius yarrelli, it’s also known as the giant devil catfish or goonch o It is a very large species of catfish in the genus Bagarius found in rivers at South and Southeast Asia. o It is found in large rivers, including rivers with fast current, but never in small streams. o This fish might reach up to 2 m (6.6 ft) in length, and weighs over 200 pounds. o It may be largest species in the genus.
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Dangerous attacks: o The Kali River goonch attacks were a series of fatal attacks on humans believed to be perpetrated by maneating Goonch catfish in three villages on the banks of the Kali River in India and Nepal, between 1998 and 2007. The first attack occurred in April 1998, when at 13:00, 17-year-old Dil Bahadur, while swimming in the river, was dragged underwater in front of his girlfriend and several eyewitnesses. No remains were found, even after a threeday search spanning 5 kilometers. Three months later, at Dharma Ghat, a young boy was pulled underwater in front of his father, who watched helplessly. No corpse was ever found. The final attack occurred in 2007 when an 18-year-old Nepalese man disappeared in the river, dragged down by something described as like an 'elongated pig'.
Figure 8. Scary mouth and tooth of Goonch catfish (Bagarius yarelli). The Pictures are adopted from Wikimedia commons.
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9. PIRANHA •
Ecology: o Piranha, also called caribe or piraya is a common name for any of more than 60 species of razor-toothed carnivorous predator fish at South American rivers including Amazon. o Most species, however, are scavengers or feed on plant material. Most species of piranha never grow larger than 60 cm (2 feet) long. o Colors vary from silvery with orange undersides to almost completely black. o These Piranhas have deep bodies, saw-edged bellies, and large, generally blunt heads with strong jaws bearing sharp, triangular teeth that meet in a scissorlike bite. o Piranhas are widely spread through a wide range of rivers at the regions range from northern Argentina to Colombia, but they are most diverse in the Amazon. o This species, which can grow up to 50 cm (about 20 inches) in length, hunts in groups that can number more than 100. Several groups can converge in a feeding frenzy if a large animal is attacked, although this is rare.
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Deadly group attacks of piranhas: o Red-bellied piranhas prefer prey that is only slightly larger than themselves or smaller. Generally, a group of red-bellied piranhas spreads out to look for prey. When located, the attacking scout signals the others to share them the attacked prey. This is probably done acoustically, as piranhas have excellent hearing. Everyone in the group flashes in to take a bite and then swims away to make way for the others. o The lobetoothed piranha (P. denticulate), which is found primarily in the basin of the Orinoco River and the tributaries of the lower Amazon, and the San Francisco piranha (P. piraya), a species native to the San Francisco River in Brazil, are also dangerous to humans. o Most species of piranhas, however, never kill large animals, and piranha attacks on people are rare. Although piranhas are attracted to the smell of blood, most species scavenge more than they kill.
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Figure 9. The scary razor-toothed Piranha. Picture is a courtesy of wonderlist.com
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THE TOOTHPICK FISH - CANDIRU (Vandellia Cirrhosa) •
Ecology: o The fish is the true and exact embodiment of the notion ‘Size doesn’t matter’, the fish is about 2.5 cm long and 3.5 mm wide and is also known as ‘the toothpick fish’ or “ Candiru”. o Candiru are found exclusively in the upper Amazon River and Orinoco River basins in northern South America. o Candiru live in shallow, slow moving, acidic waterways with muddy or sandy bottoms. o These demersal fish can be found burrowed in the riverbed most of the time, only emerging to feed or mate.
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Dangerous attacks: o The fish causes relatively huge, and we really mean huge, calamity to man; Vandellia is attracted to blood and urine as it extracts its main source of food from it, which is urea. o The fish easily passes through anus, vagina or penis and starts sucking blood causing extreme pain to the victim. 12
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In many cases amputation is the only remedy to it, which is even more horrifying.
Figure 10. THE TOOTHPICK FISH (Vandellia Cirrhosa). Picture is a courtesy of National geographic .org
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REFRERENCES •
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Ahasan HA, Mamun AA, Karim SR, Bakar MA, Gazi EA, Bala CS (2004). "Paralytic complications of puffer fish (tetrodotoxin) poisoning". Singapore Medical Journal 45 (2): 73–4. Ahasan HA, Mamun AA, Karim SR, Bakar MA, Gazi EA, Bala CS (2004). "Paralytic complications of puffer fish (tetrodotoxin) poisoning". Singapore Medical Journal 45 (2): 73–4. Auerbach PS. 2007. Marine envenomations. Adapted from the 5th edition of the t extbook wilderness Medicine by Mosby-Elsevier. Barss P. 1984. Wound necrosis caused by the venom of stingrays: pathological fi ndings and surgical management. Med J Australia. 141: 854-855. Boylan DB, Scheuer PJ. 1967. Pahutoxin: a fish poison. Science. 155:5256.stingr ays. Breault, J.L. (1991). "Candiru: Amazonian parasitic catfish". Journal of Wilderness Medicine 2 (4): 304–312 Eissa, A.E. and M.M. Zaki, 2011. The impact of global climatic changes on the aquatic environment. Procedia Environ. Sci., 4: 251-259. Eissa, A.E., H.A. Hussein and M.M. Zaki, 2012. Detection of avian influenza (H5N1) in some fish and shellfish from different aquatic habitats across some Egyptian provinces. Life Sci. J., 9: 2702-2712. Fenner PJ. 1998. Dangers in the Ocean: the traveler and marine envenomation. I I.Marine Vertebrates. J Travel Med. 5:213-216. Froese, Rainer and Pauly, Daniel, eds. (2012). "Bagarius yarrelli" in FishBase. Gibson E (15 August 2009). "Puffer fish toxin blamed for deaths of two dogs". The New Zealand Herald. Retrieved 19 November 2011. Gwee MCE, Gopalakrishnakone P, Yuen R, Khoo HE, Low KSY. 1994. A review of stonefish venoms and toxins. Pharmacology and Therapeutics. 64:509-528. Lange WR (1990). "Puffer fish poisoning". American Family Physician 42 (4): 1029–33. Redmond O'Hanlon (1989) In Trouble Again: A Journey Between the Orinoco and the Amazon Penguin Books Ltd. Ricciuti, Edward R.; Bird, Jonathan (2003). Killers of the Seas: The Dangerous Creatures That Threaten Man in an Alien Environment. The Lyons Press. ISBN 978-1-58574-869-3. Spotte, Steven (2002). Candiru: Life and Legend of the Bloodsucking Catfishes. Creative Arts Book Company. Vetrano SJ, Lebowi JB, Marcus S. 2002. Lionfish envenomation. The Journal of Emergency Medicine. 23:379-382.
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