Tag Archives: venomous animals

Friday Fellow: Greater Blue-Ringed Octopus

by Piter Kehoma Boll

Tropical waters are always thriving with diversity, therefore it is hard to keep away from them. Today’s Friday Fellow is one more creature from the tropical oceanic waters, more precisely from the Indo-Pacific waters. Being found from Sri Lanka to the Phillipines, Japan and Australia, our fellow is called Hapalochlaena lunulata and popularly known as the greater blue-ringed octopus.

This adorable octopus is very small, measuring only about 10 cm, arms included. It is, however, easy to caught attention because its whitish to dark-yellow body is covered by about 60 rings that show a beautiful electric-blue color with a black outline. As with most octopuses, the color may change according to the animal’s needs in order to make him more or less visible.

A specimen of the greater blue-ringed octopus in Indonesia. Photo by Jens Petersen.*

This adorable color pattern, which may look attractive to us, humans, is nevertheless a warning sign. The grater blue-ringed octopus is a venomous creature and may even kill a human being if threatened. As other octopuses, it is a predator and feeds mainly on crustaceans and bivalves and immobilizes them with a toxin before consumption. This is a mild toxin, though. The real danger is on its defensive behavior.

When threatened, the greater blue-ringed octopus usually begins a warning display by flashing its rings in strong colors. If this is not enough to make the threatening creature retreat, it will atack and bite its harasser. The bite is usually painless but deadly. The venom injected is nothing more nothing less than the infamous tetrodoxin, the same thing that makes a pufferfish a dangerous meal. As you may know, tetrodoxin is a potent neurotoxin that kills within a few minutes to a few hours by blocking the action potential in cells, leading to paralysis and death by asphyxia. In the greater blue-ringed octopus, tetrodotoxin is produced by bacteria that live inside their salivary glands.

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A greater blue-ringed octopus swimming. Photo by Elias Levy.**

A study analyzing the sexual behavior of the greater blue-ringed octopus showed that mating occurs during encounters of both male-female and male-male pairs. The mating ritual of octopuses consists of the male introducing the hectocotylus, a modified arm specialized in delivering sperm, into the female mantle. In male-male pairings, one of the males always put its hectocotylus into the other male’s mantle and there was no attempt from the receptive male to avoid the act. The only difference between males mating with females or with other males was that they only delivered sperm to females and never to males. What can we conclude? Have octopuses found an efficient way to be bisexual creatures by having fun with other males while still able to keep their sperm to give it to females?

The diversity of life always fascinates us!

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References:

Cheng, M. W.; Caldwell, R. L. (2000) Sex identification and mating in the blue-ringed octopus, Hapalochlaena lunulataAnimal Behavior 60: 27-33. DOI: 10.1006/anbe.2000.1447

Mäthger, L. M.; Bell, G. R. R.; Kuzirian, A. M.; Allen, J. J.; Hanlon, R. T. (2012) How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings? Journal of Experimental Biology 215: 3752-3757. DOI: 10.1242/jeb.076869

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Friday Fellow: Deathstalker

by Piter Kehoma Boll

The name of today’s fellow may sound intimidating, and it is for a good reason. Scientifically known as Leiurus quinquestriatus, the deathstalker, which is also known as the Omdurman scorpion, Naqab desert scorpion, Palestine scorpion or Israeli scorpion, is considered one of the most venomous scorpions in the world.

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A deathstalker in Israel. Photo by Wikimedia user מינוזיג.*

The deathstalker is found in arid regions of North Africa and the Middle East. There are two subspecies, L. quinquestriatus quinquestriatus found in Africa from Algeria and Niger to Somalia and Sudan, and L. q. hebraeus found from Turkey to Iran and Yemen. They are relatively large, measuring up to 11 cm in length.

The venom of the deathstalker has been shown to contain a variety of different neurotoxins, including several inhibitors of potassium and chloride channels, which affect the transmission of nervous impulses through the nervous system. Although very painful, the sting of a single scorpion would hardly kill a healthy adult human, but immediate medical treatment with antivenom is always required to avoid any unpleastant consequences. Children, elderly people, or adult people with heart problems or allergies, however, can easily be killed.

One of the toxins, chlorotoxins, which affects chloride channels, has shown potential to be used in the treatment of brain tumors.

Despite its danger, the deathstalker is often raised as a pet. Why? Because humans…

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References:

Castle, N. A.; Strong, P. N. (1986) Identification of two toxins from scorpion (Leiurus quinquestriatus) venom which block distinct classes of calcium-activated potassium channel. FEBS Letters 209(1): 117–121. DOI: 10.1016/0014-5793(86)81095-X

EOL – Encyclopedia of Life. Leiurus quinquestriatus. Available at < http://eol.org/pages/10208954/overview >. Access on January 7, 2018.

Garcia, M. L.; Garcia-Calvo, M.; Hidalgo, P.; Lee, A.; McKinnon, R. (1994) Purification and Characterization of Three Inhibitors of Voltage-Dependent K+ Channels from Leiurus quinquestriatus var. hebraeus Venom. Biochemistry 33(22): 6834–6839. DOI: 10.1021/bi00188a012

Gueron, M.; Ilia, R.; Shahak, E.; Sofer, S. (1992) Renin and aldosterone levels and hypertension following envenomation in humans by the yellow scorpion Leiurus quinquestriatusToxicon 30(7): 765–767. DOI: 10.1016/0041-0101(92)90010-3

Lyons, S. A.; O’Neal, J.; Sontheimer, H. (2002) Chlorotoxin, a scorpion-derived peptide, specifically binds to gliomas and tumors of neuroectodermal origin. GLIA 39(2): 162–173. DOI: 10.1002/glia.10083

Sofer, S.; Gueron, M. (1988) Respiratory failure in children following envenomation by the scorpion Leiurus quinquestriatus: Hemodynamic and neurological aspects. Toxicon 26(10): 931–939. DOI: 10.1016/0041-0101(88)90258-9

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Friday Fellow: Tulip Cone

by Piter Kehoma Boll

The year has almost ended, but if you would touch today’s Friday Fellow, it would end for you right now, and without a new year coming.

Living along the coasts of the Indian Ocean, including East Africa, Madagascar,  India, West Australia and several archipelagos such as Mascarene Islands and the Philippines, our fellow, Conus tulipa, is popularly known as tulip cone. Despite its beautiful name, however, it is not a nice species to have nearby.

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A live Conus tulipa in La Réunion, Mascarene Islands. Photo by Philippe Bourjon.*

The tulip cone is a species of the genus Conus, predatory sea snails that feed on a variety of animals, such as fish, worms and other mollusks. They capture prey by stinging them with a venomous harpoon that is made of a modified tooth of their radula (tongue). The harpoons are stored in a sack and shot on a nearby prey. Because many species feed on fast moving prey, such as fish, they have a very powerful venom able to kill the target in a few seconds. In some species, including the tulip cone, this powerful venom is strong enough to kill an adult human being.

As with all other venomous species, though, not everything is bad. Several different toxins and other components have been recently isolated from the venom of the tulip cone, many of which may eventually be used to develop new medicines.

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References:

Alonso, D.; Khalil, Z.; Satkunanthan, N.; Livett, B. G. (2003) Drugs From the Sea: Conotoxins as Drug Leads for Neuropathic Pain and Other Neurological Conditions. Mini Reviews in Medicinal Chemistry3: 785–787.

Dutertre, S.; Croker, D.; Daly, N. L., Anderson, Å,.; Muttenhaler, M.; Lumsden, N. G.; Craik, D. J.; Alewood, P. F.; Guillon, G.; Lewis, R. J. (2008) Conopressin-T from Conus tulipa reveals an anatagonist switch in vasopressin-like peptides. Journal of Biological Chemistry283, 7100–7108.

Hill, J. M.; Alewood, P. F.; Craik, D. J. (2000) Conotoxin TVIIA, a novel peptide from the venom of Conus tulipa. The FEBS Journal, 267 (15): 4649–4657.

Wikipedia. Conus tulipa. Available at < https://en.wikipedia.org/wiki/Conus_tulipa >. Access on December 28, 2017.

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Friday Fellow: Portuguese Man o’ War

by Piter Kehoma Boll

And so we finally reached the 100th Friday Fellow! In order to commemorate, we will have two Friday Fellows today, just as we had during the 50th one. And to start I chose a cnidarian that always caught me attention.

Living in the Atlantic Ocean and known popularly as Portuguese man o’ war, its binomial name is Physalia physalis, both words derived from the Greek word for bubble, physalis. And the Portuguese man o’ war is, in fact, like a floating bubble with some stuff attached, or at least it looks like that.

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A Portuguese man o’ war lying on the beach. Photo by Anna Hesser.*

Most people may think that the Portuguese man o’ war is a jellyfish due to its looks, but it is actually part of another group of cnidarians, the siphonophores. Their body is not a single individual, but rather a colony of several smaller animals, called zooids, which are speciallized to have different functions within the colony and cannot live separately. They are all derived from the same embryo, thus being clones from each other.

The upper portion of the Portuguese man o’ war has a gas-filled sack, which is called the pneumatophore and is the original organism derived directly from the embryo. Below the pneumatophore there are several different kinds of organisms, such as nectophores for swimming, dactylozooids for defense and capture of prey, gonozooid for reproduction and gastrozooids for feeding. The long tentacles, which reach more than 10 m in length, are composed by dactylozooids and fish for prey throughout the water.

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Floating on the sea. Photo by Regine Stiller.*

As other cnidarians, the Portuguese man o’ war has nettle-like cells which sting and inject venom. In humans, the venom usually cause pain and let whip-like marks on the skin where the tentacles touched. Sometimes more severe complications will results and in rare cases it may result in death.

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References:

Stein, M. R.; Marraccini, J. V.; Rothschild, N. E.; Burnett, J. W. (1989) Fatal portuguese man-o’-war (Physalia physalis) envenomation. Annals of Emergency Medicine 18(3): 312–315.

Wikipedia. Portuguese man o’ war. Available at <https://en.wikipedia.org/wiki/Portuguese_man_o%27_war&gt;. Access on June 16, 2017.

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