Category Archives: mollusks

Friday Fellow: Strawberry Top Snail

by Piter Kehoma Boll

Look at this thing:

It is so beautifully red like a strawberry that I feel my mouth salivating and an urge to bite it. But instead of a juicy sweet fruit like a strawberry, this is a hard salty seashell belonging to the species Clanculus puniceus that has the appropriate common name of strawberry top shell.

This species is found in the Indian Ocean along the eastern coast of Africa, from the Red Sea to Cape Agulhas, including nearby islands such as Madagascar and the Mascarenes. It belongs to the family Trochidae, commonly known as top shells or top snails because their shell resembles a spinning top.

Strawberry top shell in South Africa. Photo by iNaturalist user jaheymans.*

The shell of the strawberry top snail measures, in the adult, at least 15 mm in diameter, reaching up to 23 mm, and has a beautiful red color, caused by uroporphyrins, that can vary from orange-red to crimson. The spiral of the shell, when seen from above, has a line formed by black dots, caused by melanin, intercalated by two or three white dots. When seen from below, there are two additional lines with this pattern that run side by side near the shell opening.

The shell seen from several angles. Photo by H. Zell.**

As usual among top snails, the strawberry top snail lives in intertidal and subtidal zones and feeds on algae that it scrapes from rocks using its toothed tongue (the radula). They are dioecious, i.e., there are male and female individuals, as in most sea snails, but there is no sexual dimorphism.

Due to its beauty, the shell of the strawberry top snail is highly desired by shell collectors. However, little is known about the natural history of this particular species. I wasn’t even able to find a photograph in which the snail itself is visible.

This was the only photograph I found in which the soft part of the body of a snail in the genus Clanculus is visible. The species, from Taiwan, was not identified. Photograph by Cheng Te Hsu.***

If you work with this species or at least has a photograph of a living specimen showing the snail inside the shell, please share it! We need more available information on the wonderful creatures that share this planet with us.

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More marine snails:

Friday Fellow: Ornate Limpet (on 3 May 2019)

Friday Fellow: Tulip Cone (on 29 December 2017)

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References:

Herbert DG (1993) Revision of the Trochinae, tribe Trochini (Gastropoda: Trochidae) of southern Africa. Annals of the Natal Museum 34(2): 239–308.

Wikipedia. Trochidae. Available at < https://en.wikipedia.org/wiki/Trochidae >. Access on 29 July 2019.

Williams ST, Ito S, Wakamatsu K, Goral T, Edwards NP, Wogelius RA, Henkel T, Oliveira LFC, Maia LF, Strekopytov S, Jeffries T, Speiser DI, Marsden JT (2016) Identification of Shell Colour Pigments in Marine Snails Clanculus pharaonius and Cmargaritarius (Trochoidea; Gastropoda). PLoS ONE 11(7): e0156664. doi: 10.1371/journal.pone.0156664

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Friday Fellow: Ornate Limpet

by Piter Kehoma Boll

Gastropods are the most species-rich class of animals on Earth after insects but it’s been a long time since I presented one here. So, today I’m bringing you one from the coasts of New Zealand, the ornate limpet Cellana ornata.

Two ornate limpets on the coast of Northland, New Zealand. Photo by iNaturalist user pedromalpha.*

Its cone-shaped shell, like in most limpets, has a characteristic pattern that can be used to recognize it. There is a series of elevated ridges running from the dark center toward the margins of the shell. They are usually eleven in number and have an orange tinge, sometimes very strong, almost red or brown, and sometimes very weak, almost white. The region between the ridges is darker, usually black, and has a row of white nodes running parallel to the ridges, sometimes with an additional row of smaller nodes on each side. The pattern may be obscured by other organisms growing on the shell, especially algae and barnacles.

An ornate limpet covered by barnacles. Photo by iNaturalist user pedromalpha.*

As common among limpets, the ornate limpet lives in the intertidal zone on the surface of rocks. It feeds on algae growing on the substrate, scraping them from the rock using their radula, the toothed tongue of gastropods. When the waves are striking the rock or the rock is exposed to the sun and drying, the ornate limpet lowers its shell against the substrate and remains firmly attached using its powerful foot. Only when the conditions are ideal, i.e., when the rock is wet and without strong waves, does the ornate limpet move around.

A beautiful specimen of the ornate limpet in Stewart Island. Photo by iNaturalist user naturewatchwidow.**

The ornate limpet lives about two years and its reproduction happens during summer, around February, which means that each individual reproduces a maximum of two times before dying. Environmental conditions probably affect longevity, because specimens living in less exposed rocks have a higher metabolism than those inhabiting a substrate that is constantly subject to desiccation and that forces them to remain inactive for long periods.

Compared to other closely related species, the ornate limpet has a short life and few reproductive events. Nevertheless, it is still a common species around New Zealand, having developed an increased fecundity that allows it to flourish.

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References:

Dunmore RA, Schiel DR (2000) Reproduction of the intertidal limpet Cellana ornata in southern New Zealand. New Zealand Journal of Marine and Freshwater Research 34(4): 653–660. doi: 10.1080/00288330.2000.9516966

Smith SL (1975) Physiological ecology of the limpet Cellana ornata (Dillwyn). New Zealand Journal of Marine and Freshwater Research 9(3): 395–402. doi: 10.1080/00288330.1975.9515575

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*Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 International License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Friday Fellow: Giant Clam

by Piter Kehoma Boll

One more giant is coming to our team, again from the sea, but this time from the bilvavian molluscs. Its name is Tridachna gigas, commonly known as the giant clam.

Found in shallow coral reefs of the Indian and Pacific Oceans, especially around Indonesia, the giant clam can grow up to about 1.2 m, weigh more than 200 kg and live more than 100 years, being the largest living bivalve mollusk.

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The giant clam is seen in coral reefs as a giant lump of molluscan material. Watch out, Dory! Photo by flickr user incidencematrix.*

One interesting aspect of the giant clam and its close relatives is that they live in a symbiotic association with some dinoflagellates (the so-called zoxanthellae, also found in corals), having even a special structure, the zooxanthellal tubular system, to house them. During the day, the giant clam exposes its mantle to the light in order to allow the algae to photosynthesize. Part of the nutrients produced by the algae are given to the clam. This allows the giant clam to survive in otherwise nutrient-poor environments, where its standard bivalvian feeding stile, by filtering partiles from the water, would not be enought to allow it to grow properly.

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A half-closed shell. Photo by The Central Intelligence Agency.

The giant clam is used as food in many Asian countries, especially Japan and countries from Southeast Asia and Pacific Islands. Additionally, the giant shell is considered a valuable decorative item and can be sold for large amounts of money. Due to such exploitations, the giant clam populations are starting to decline and the species is considered vulnerable by the IUCN.

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An empty shell exposed in Aquarium Finisterrae, Galicia, Spain. Photo by Wikimedia user Drow male.**

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References:

Klumpp, D. W., Bayne, B. L., & Hawkins, A. J. S. (1992). Nutrition of the giant clam Tridacna gigas (L.) I. Contribution of filter feeding and photosynthates to respiration and growth. Journal of Experimental Marine Biology and Ecology, 155(1), 105–122. doi:10.1016/0022-0981(92)90030-e

Norton, J. H., Shepherd, M. A., Long, H. M., & Fitt, W. K. (1992). The Zooxanthellal Tubular System in the Giant Clam. The Biological Bulletin, 183(3), 503–506. doi:10.2307/1542028

Wells, S. (1996). Tridacna gigas. The IUCN Red List of Threatened Species doi:10.2305/IUCN.UK.1996.RLTS.T22137A9362283.en. Access on September 1, 2018.

Wikipedia. Giant clam. Available at < https://en.wikipedia.org/wiki/Giant_clam >. Access on September 1, 2018.

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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: 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: Brown Mussel

by Piter Kehoma Boll

Until now, the mollusks featured here included a chiton, a cephalopod and two gastropods. So it is time to bring a bivalve. And what would be better than showing you a common mollusk from the South Atlantic Ocean?

Living on rocky shores around South America and Africa, our fellow is called Perna perna, or populary brown mussel. In places where it lives, it can be found in great concentrations, sometimes covering large areas of rocks. It usually measures about 90 mm in length, but some larger specimens may reach up to 120 mm. The increased surface area on the rocks they occupy attract other rock-living marine species, such as barnacles, limpets, snails and algae.

Perna_perna

Some specimens of Perna perna growing on an oyster in South Africa. Photo by Bernadette Hubbart.*

The brown mussel is a filter feeder, as most bivalves, feeding on suspended organic matter, as well as on small microrganisms, such as phytoplankton and zooplankton. As a prey, it is eaten by a variety of animals, such as sea birds, crustaceans and mollusks. Humans also consume it in both South America and Africa. Its ingestion, however, must be cautious, as it may contain toxins from dinoflagellates that it ingested, as well as heavy metals from water pollutants.

Spread through the world by humans after attaching itself on ships, the brown mussel has become invasive in other parts, especially in the Gulf of Mexico, and it continues to increase its occupied area. This can have deleterious effects both ecologically and economically, as it may displace native species and also cause damage to human equipments. It is, therefore, one more species that became a problem due to us, humans. And the damage will not be easy to be repared.

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References:

Ferreira, A. G.; Machado, A. L. S.; Zalmon, I. R. (2004) Temporal and spatial variation on heavy metal concentrations in the bivalve Perna perna (LINNAEUS, 1758) on the northern coast of Rio de Janeiro State, Brazil. Brazilian Archives of Biology and Technology 47(2): 319–327. http://dx.doi.org/10.1590/S1516-89132004000200020

Holland, B. S. (2001) Invasion without a bottleneck: microsatellite variation in natural and invasive populations of the brown mussel Perna perna (L). Marine Biotechnology 3, 407–415. https://dx.doi.org/10.1007/s1012601-0060-Z

Wikipedia. Perna perna. Available at: < https://en.wikipedia.org/wiki/Perna_perna >. Access on October 21, 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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