Tag Archives: gastropods

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.

800px-conus_tulipa

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: Sea Swallow

by Piter Kehoma Boll

As the second species of today, I’m bringing a terrible but beautiful predator of the Portuguese man o’ war, the sea swallow Glaucus atlanticus, which is, in my opinion, one of the most beautiful sea creatures.

Glaucus_atlanticus

Isn’t it a magnificent creature? Photo by Sylke Rohrlach.*

Also known as blue dragon, blue glaucus and many other names, the sea swallow is a small sea slug that measures up to 3 cm in length as an adult. This species is pelagic, meaning that it lives in the open ocean, neither close to the bottom nor close to the shore.  Although it is found in all three oceans, genetic evidences indicate that the populations from the Atlantic, the Pacific and the Indian oceans have diverged more than 1 million years ago.

The sea swallow has a gas-filled sac in the stomach that makes it float upside down in the water, meaning that its ventral side is directed upward. The wide blue-bordered band running along the body, as seen in the picture above, is the slug’s foot. It’s dorsal side, which is directed downward, is completely white or light gray.

Being a carnivorous species, the sea swallows feeds on several cnidarian species, especially the Portuguese man o’ war. It usually collects the cnidocytes (the sting cells) of its prey and put them on its own body, so that it becomes as stingy as or even stingier than its prey. If you find one lying on the beach, be careful.

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References:

Churchull, C. K. C.; Valdés, Á.; Foighil, D. Ó (2014) Afro-Eurasia and the Americas present barriers to gene flow for the cosmopolitan neustonic nudibranch Glaucus atlanticus. Marine Biology, 161(4): 899-910.

Wikipedia. Glaucus atlanticus. Available at < https://en.wikipedia.org/wiki/Glaucus_atlanticus >. Access on June 18, 2017.

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Land snails on islands: fascinating diversity, worrying vulnerability

by Piter Kehoma Boll

The class Gastropoda, which includes snails and slugs, is only beaten by the insects in number of species worldwide, having currently about 80 thousand described species. Among those, about 24 thousand live on land, where they are a very successful group, especially on oceanic islands.

The Hawaiian Islands alone, for example, have more than 750 snail species and there are more than 100 endemic species in the small island of Rapa in the South Pacific. This diversity is much higher than that in any continental place, but the reason for that is not completely understood.

Mandarina

A land snail of the genus Mandarina, endemic to the Ogasawara Islands, Japan. Photo by flickr user kmkmks (Kumiko).*

One of the most likely explanations for this huge diversity on islands is related to the lack of predators. The most common predators of snails include birds, mammals, snakes, beetles, flatworms and other snails. Most of those are not present in small and isolated islands, which allows an increase in land snail populations in such places. Without too much dangers to worry about, the community of land snails n islands can explore a greater range of niches, eventually leading to speciation.

Unfortunately, as always, the lack of danger leads to recklessness. Without predators to worry about, insular land snails tend to lay fewer eggs than their mainland relatives. If there is no danger of having most of your children eaten, why would you have that many? It is better to lay larger eggs, putting more resources on fewer babies, and so assure that they will be strong enough to fight against other snail species. Afterall, the large number of species in such a small place as an island likely leads to an increased amount of competition between species.

But why is this recklessness? Well, because you never known when a predator will arrive. And they already arrived… due to our fault.

The diversity of insular land nails was certainly affected by habitat loss promoted by humans, but also by predators that we carried with us to the islands, whether intentionally or not. These predators include rats, the predatory snail Euglandina rosea and the land flatworm Platydemus manokwari, the latter being most likely the worst of all.

800px-platydemus_manokwari

The flatworm Platydemus manokwari in the Ogasawara Islands. Photo by Shinji Sugiura.

This flatworm arrived at the Chichijima Island, part of the Ogasawara Islands in the Pacific Ocean, in the early 1990s and in about two decades it led most land snail species on the island to extinction and many more are about to face the same fate on this island and on others. Not being prepared for predators, these poor snails cannot reproduce fast enough to replace all individuals eaten by the flatworm.

We have to act quickly if we want to save those that are still left.

See also: The New Guinea flatworm visits France – a menace.

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ResearchBlogging.orgReferences and further reading:

Chiba, S., & Cowie, R. (2016). Evolution and Extinction of Land Snails on Oceanic Islands. Annual Review of Ecology, Evolution, and Systematics, 47 (1), 123-141 DOI: 10.1146/annurev-ecolsys-112414-054331

Sugiura, S., Okochi, I., & Tamada, H. (2006). High Predation Pressure by an Introduced Flatworm on Land Snails on the Oceanic Ogasawara Islands. Biotropica, 38 (5), 700-703 DOI: 10.1111/j.1744-7429.2006.00196.x

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