 |
Welcome
|
What's New! Ask a Marine Scientist: answers to Cnidaria questions! Index To Questions JELLYFISH CORALS
ANEMONES
HYDROZOANS
JELLYFISH
A. Those are really good questions! DIVISION
OF LABOUR REPRODUCTION After
fertilization and initial growth, a larval form called a "planula" develops.
This planula larva is small, and is covered with cilia. After
a free living stage in the plankton, this planula larva settles
onto a firm surface, and changes into a scyphistoma. The scyphistoma
resembles BODY
FORM
Q: I need pictures and any information available on the mushroom jellyfish (Rhopilema verrilli). A: The mushroom cap jellyfish (Rhopilema verrilli) has a deep swimming bell without tentacles on it's margin. It is a creamy while colour with darker markings on the sturdy central tentacle structures. It grows up to 20" in diameter and although it has long finger-like appendages hanging from its feeding apparatus, it is not hazardous to people. There's not much in the way of specific photos of this animal on the web, but a good jellyfish info page is the Sea Science Jellyfish page.
Answered by Dr. Andy Spencer
A: This is an interesting question, because your observations are correct - jellyfish do not have what we normally think of as a stomach or intestines! Jellyfish are in a group of animals (or a phylum) called Cnidaria. The Cnidarians (which include anemones and coral as well as jellyfish) have structures that are fairly simple. One thing that is common among all cnidarians is the fact that they have a digestive system with only one opening. A jellyfish captures small animals with its tentacles, which have many stinging cells all over them. Another characteristic of this group is the presence of these stinging cells, call nematocysts or cnidae. The animals that are captured by the jellyfish are usually zooplankton, which consists of animals that cannot swim against a current. Larger jellyfish may sometimes be lucky enough to capture a fish. The captured animal is usually paralysed by the nematocysts, and is drawn into the single opening (the mouth). The food then enters the stomach or gastrovascular cavity, where it is digested. Anything that cannot be digested is expelled through the mouth.
A: A
Portugese man-of war is definitely something that you don't want
to run into while snorkelling. It is in the phylum Cnidaria,
and has stinging cells which are characteristic of this group
of animals. Within this phylum, we can be more specific, and
put the Portuguese man-of-war into the order Siphonophora. (see
the OceanLink answers page for more information about this group).
Q:
I am doing a project for school about the tropics and the Portugese
Man-O-War. A: The Portuguese Man-Of-War is found from Florida to Texas and Mexico, in the Bahamas and West Indies. Occasionally they are carried northward and near shore by storms. Australians call them Blue-Bottle because of the blue float on the top of the water used as a sail. The tentacles contain one of the most potent toxins in the marine environment, and a sting from this animal can inflict severe burns, blisters and swelling, even after the animal is dead and is lying on the beach. The stinging tentacles catch any fish or plankton that may be passing by. The captured animal is usually paralyzed by the nematocysts (stinging cells in the tentacles), and is drawn into the mouth. The food enters the gastrovascular cavity (stomach), where it is digested. These Physalia physalis (scientific name for Portuguese Man-Of-War) are predators, because they catch all their own food, instead of scavenging from others. They are in fact a colonial hydroid, consisting of a large colony of smaller marine organisms. Each have its own duty, such as reproduction, feeding, and defence. Hopefully this information will help you with your project. Sorry I couldn't tell you more. Answered by Julie Vandenbor
Q:
Could you please let me know what Family the Portuguese man-of-war
belongs to? A: Yes, the information the classification of the Portuguese man-of-war is correct, but you have one spelling mistake, Phylum Cnidaria and remember when you present the genus and species name that they are either in italics or underlined (Physalia physalia). The family of the Portuguese man-of-war is Physallidae.
A: Our
resident Australian expert tells us that this was an easy question!
The Portugese man-of-war (Physalia physalis) is commonly
known as a "blue bottle" down under. He also says that
they are not too well liked this time of year, especially by
surfers.
Q: There is a rumour that two people got stung (in separate incidents) by a Portugese Man-of-War off the coast of Southern New Jersey. Is it possible that a Portugese Man-of-War would be present off the coast of southern New Jersey? A. The Portugese man-of-war, Physalia physalis, is normally found from Florida to Texas and Mexico; in the Bahamas and West Indies. However, the animal is occasionally carried northward and near shore by storms. This species has been found from the Gulf Stream as far north as Cape Cod. With the relatively warm weather that the eastern coast of North America has received this summer, I would think that it is certainly possible to find this species as far north as New Jersey. The tentacles of this siphonophore (closely related to jellyfish) contain one of the most potent toxins in the marine environment. Stings from the tentacles of these animals can inflict severe burns, blisters and swelling, even when the animal is found dead on the beach.
Q: I read a mystery novel set on the Washington State coast. The author describes a "jellyfish" called the "blue medussa". It supposedly sails and is washed up on shore. When dried it is eaten, by humans (Asians?). Would you know what she is referring to? A: The jellyfish you are referring to is called Velella velella or the "by-the-wind-sailor". This is an open ocean colonial jellyfish species that is often washed onto beaches in late spring and early summer. The float of this animal is flattened, chambered, chitinous, clear, 4 to 6 cm in length, and acts like a sail on the surface of the water. Underneath the float is a central feeding polyp surrounded by a fringe of tentacles whose body tissue is blue in colour. It is found on the Pacific Northwest coast. I am not familiar with people eating this jellyfish, but it is definitely possible. Check out this site for a picture of Velella velella:
Q: My name is Magnus. I´m a student in an english speaking class in Gothenburg, Sweden. I´m doing a project about Cnidaria and I am wondering how these animals breath and eat. Please can you reply? Yours sincerely, Magnus A: The phylum Cnidaria includes many different types of animals including hydras, jellyfish, sea anemones and corals. Cnidarians have a circle of tentacles that surround the mouth which help to catch and eat food. The feeding methods used by cnidarians varies between the different types. All cnidarians have stinging cells called nematocysts that surround the mouth and shoot out from capsules and are attached to strings. Nematocysts capture prey by entangling them and may inject a toxin that paralizes the prey. Almost all cnidarians are carnivores, and feed mainly on small crustaceans (shrimps, amphipods, etc.). Once the prey is entangled in the discharged nematocysts it is moved into the mouth and digested in its gastrovascular cavity (sort of like our stomach). Cnidarians do not have lungs like humans or gills like fish and other invertebrates. Gas exchange (breathing), in cnidarians, occurs across the general body surface.
Q: Looking for information on medusa of gonionemus (tiny cnidarian) approx. size 20mm. They seemed to have invaded our lake. Are they hot weather induced? what info do you have. Thank you A. Members of the Gonionemus genus are hydrozoan jellyfish in the Suborder Limnomedusae, Family Olindidae. These jellyfish are freshwater species possessing small solitary polyps and free medusae. The medusae typically crawl about the bottom, attaching to vegetation with their tentacles. Near the end of the tentacles, there are pads that are used for adhesion to the substrate. These animals feed on almost anything organic that they can find suspended in the water column or on the bottom. The jellyfish catch food particles with their tentacles and then bring the food items to the mouth, which is located inside the bell. I am not sure if the hot weather would help the reproductive success of these organisms. Good Luck!
Q: I want to know why there are so many jellyfish on the outer banks this year. Sometimes there are hardly any. A. There are many possible explanations for your observations of an increase in jellyfish numbers on the VA coast. This year may have been a good year for jellyfish, with favourable conditions resulting in a high reproductive success rate. Populations of cnidarians are known to fluctuate significantly in accordance with a variety of environmental parameters. Food abundance, ambient water temperature, and fluid dynamic regimes are just a few of the variables that could be operating to produce an unusual abundance of jellyfish in your area. If they are offshore species that are not normally seen along the coast, it may be that currents are bringing the animals in towards the banks. I understand that the weather on the East coast has been rather warm this summer, which may also be an important factor. The warming of surface waters and high light intensities in the Atlantic may have produced phytoplankton blooms and subsequent high levels of production in other trophic levels. You may want to contact the Marine Biological Laboratory in Woods Hole, MA to see if they have observed similar patterns a little further north. There may even be someone there that is studying the phenomenon!
Q: How do jelly fish sting? What on the jelly fish stings you? A. Jellyfish are cnidarians, all of which have stinging cells called cnidocytes. On the tentacles of most jellyfish there are high densities of these stinging cells. The jellyfish will trail their tentacles through the water to collect their food, which often consists of plankton, fish and other forms of marine life. When the tentacles are stimulated by the proper tactile and chemical stimuli, tiny needle-like organelles, called nematocysts, are discharged from the cnidocytes. The nematocysts often contain toxins which act as a sedative on the captured prey. Sometimes people get stung by jellyfish upon contact with their tentacles. Species that can be dangerous to humans are the lionsmane jellyfish, the sea wasp and the Portugese man-of-war.
Q: My 65 year old mother was visiting Japan and was wading in the Sea of Japan and got stung by a jelly fish (we think). The tentacle was wrapped around her leg in a spiral from knee to ankle and she required 2 days stay in a hospital. We believe she had an allergic reaction and I do not yet have details of what treatment was given. Her blood pressure was hard to control. Do you know what types of stinging jelly fish or other creature would cause this injury? Are there likely to be any long term effects?
I wasn't exactly sure about the long term effects so I did a little bit of research, and this is what I came up with. I found a discussion group about venoms and toxins, and this is what they said about these two species: Chrysaora - Chrysaora quinquecirrha (Sea nettle) is another dangerous species capable of causing death. Effects include extreme edema with systemic effects characterised by renal damage, with the possibility of renal necrosis, and cerbral ischemia (Muhvich, Sengottuvelu et al. ; Hach,Mebs et al. 1987). A single lethal protein has been isolated but the mechanism is not entirely clear (Long and Burnett 1994). Cyanea - While not being lethal Cyanea capillata (Lions mane jellyfish), produces an extremely painful sting that can be dangerous and potentially life-threatening due to its shock inducing properties with Cyanea lamarcki (Violet Jellyfish) having similar effects (Exton, Fenner et al.1989).
A: Jellyfish are in the class Scyphozoa, which is contained within the phylum Cnidaria. Other animals in the phylum Cnidaria include corals, anemones and hydroids. With few exceptions, adult jellyfish, or scyphozoans are dioecious, which means that each animal is either male or female. The gonads may number four or eight, and are usually located in the gastrodermis (tissue near the stomach or gastrovascular cavity). A group of animals releases sperm or eggs, which may mix in the water column and become fertilized, or, in the case of the moon jelly (Aurelia) the eggs become lodged in pits on the oral arms, which form a temporary brood chamber where fertilization takes place. After fertilization and initial growth, a larval form called a "planula" develops. This planula larva is small, and is covered with cilia. You could think of it as looking like a tiny hairy football. After a free living stage in the plankton, this planula larva settles onto a firm surface, and changes into a scyphistoma. The scyphistoma resembles a tiny hydra - cup shaped with tentacles surrounding the a single opening. This scyphistoma reproduces asexually (no mixing of genetic material) by budding. New scyphistomae may be produced, or new jellyfish (medusae) may be formed. These young jellyfish swim off, and grow up into adults.
Q: Can you give me the weight of a jellyfish? It can be of any kind of jellyfish. A: The bodies (the bell) of jellyfish is made of a material called mesoglea. Mesoglea is a jelly-like material that is elastic because of there are fibers that connect together in the mesoglea. The other main body part a jellyfish is the gut and it contains mostly water and digestive juices. Since most of the material of a jellyfish is the exact density of water. If you weigh water about the same size as the jellyfish you want to know the weight for, you will get weight of the jellyfish. I suggest you weigh some water at home or school that is about the same size as a jellyfish that interests you and you will get an approximate weight of a jellyfish.
We're not sure how you got the idea that the box jellyfish was a newly discovered animal - they have been well known for many years. We also hope that you're able to find this answer, as you neglected to leave us your e-mail address!!!
Q: I need to know what a Lion's Mane is, what it looks like, and how it is dangerous to scuba divers. A: I believe the animal you're referring to is the Lion's Mane Jellyfish (Cyanea capillata). This organism can reach more than 2 m in bell diameter, although the majority are not larger than 0.8 m in diameter. The organisms found in the local waters off British Columbia are approximately 50 cm in bell diameter and 2 m in tentacle length. They are usually reddish-brown or white in colouration, and their trailing tentacles and frilly oral lobes are loaded with stinging capsules called nematocysts. C. capillata appears to be the only local species of jellyfish dangerous to humans. Scuba divers often encounter these organisms in fairly shallow water (less than 60 ft) and may mistakenly swim into their long, trailing tentacles which may be difficult to see. Generally the diver is protected by their wetsuit or drysuit, however their face is exposed and may get stung. In addition, scuba divers must be careful when removing their gear, because broken tentacles can stick to suits and gear and still give a nasty sting since the nematocysts remain active even though the tentacles are no longer attached to the jellyfish. And I must tell you from personal experience, the sting from a Lion's Mane Jellyfish is very unpleasant and can persist for hours.
Q: what is sea wasp? Where can i found information? A: Here's something I found on the net on MidLink Magazine : The sea wasp, or the box jellyfish ( Latin name Chironex fleckeri Southcott) is one of the most deadly stinging animals in the sea. The sea wasp has a large transparent body shaped like a box or a bell, that can be as large as a bucket, and can weigh as much as 2 kilograms. A cluster of 16 long (up to 3 meters in length) semi-transparent, extendible tentacles stream out from under the bell of the box jellyfish. Millions of stinging capsules cover each of the 16 long tentacles. The stinging capsules discharge lethal poison through a penetrating thread into the skin of any creature that touches them. The sea wasp is found in coastal waters, creeks, and rivers in Australia north from about 22-degrees south latitude. The box jellyfish ranges from the Queensland coast on the eastern coast of Australia into the Northern Territory, and around the northern coast of Western Australia. The sea wasp is most prevalent during the Australia summer months from November to mid- March. The sea wasp uses its deadly venom to catch prey, which usually consists of prawns. However, when the box jellyfish moves into the coastal areas, rivers, and creeks, particularly during the wet Australia summer season, the sea wasp becomes a deadly menace to swimmers and fishermen in the area. On clear, calm days, the semi-transparent sea wasps can usually be seen and avoided. However, during the wet season, the coastal waterways are often flooded, muddy, and turbid, and the sea wasps are difficult to see until it is too late. The sea wasp is the cause of numerous deaths to swimmers and bathers along the north Queensland coast of Australia, and because of the potent poison injected by the sea wasp, most children who have been stung by the sea wasp have died within minutes of being stung. The sting of the box jellyfish causes an excruciating pain that increases quickly. Where the tentacles have contacted the skin, large brown or purple lines and welts appear quickly, causing the victim to appear as if he/she has been whipped. The poison injected by the sea wasp causes death by shock to the heart, complete circulatory failure, and respiratory paralysis. If the severe symptoms are not treated quickly, death can occur in minutes, even to an adult. The venom also attacks the victim's red blood cells and severely damages the skin where the poisonous capsules have penetrated the skin. An anti-venom for the sting of the sea wasp has been developed, but it must be administered relatively quickly. Because the venom from the sea wasp seriously affects the victim's breathing, it may be necessary to perform continuous CPR to keep a victim alive until professional medical assistance can be obtained. There are two other cousins to the deadly sea wasp or box jellyfish that are sometimes mistaken for the sea wasp. These are the Carybdea alata Reynaud and the Chiropsalmus quadrigatus Haeckel. Both of these marine animals are also know as sea wasps, but they are not as poisonous or as deadly as the box jellyfish or Sea Wasp (Chironex fleckeri Southcott). As you have learned from this description, we would just as soon not see any sea wasps or box jellyfish in the wild near Darwin. I'm perfectly satisfied seeing these types of marine animals swimming in an aquarium, behind a protective glass barrier.
Q: What is the most dangerous kind of jellyfish and where can it be found? What should you do if it stings you? A:
The most dangerous jellyfish is probably the Box Jellyfish
or Sea Wasp (Latin name Chironex fleckeri Southcott)
that is common to shores of Australia and south-eastern Asia.
Their bodies (or bell) are box-shaped, and can be as big
as a basketball. It's tentacles are numerous (up to 60 on
one jelly) and very long (up to 15 feet!).
In Australia, there are "stinger resistant enclosures" which are areas of the shore that are closed off from stinging jellyfish. People outside the enclosures are encouraged to wear lycra suits or pantyhose on their bodies, which prevent the microscopic nematocysts from reaching their skin. The stinging jellyfish season in Australia is from October to May. There's a lot of confusion about what to put on a jellyfish sting, because the nature of the venom is not entirely understood. The most important thing to do is to call an ambulance right away. Hospitals have access to antivenoms and will probably know best how to prevent the internal effects of the sting. As far as quick action, I've heard that in Australia they dowse the sting with vinegar. According the Vancouver Aquarium Aquafacts pages, you should rinse the area with seawater and remove any tentacles, but avoid using freshwater, rubbing alcohol or urine, as these tend to trigger the nematocysts. Again, the less fuss and the more ambulance calling, the better. You
can find out more about the box-jelly and other jellies in
our answer file under "Sea Wasp" and in OceanLink's Cnidarian page. I found most of this
information in an article about Box Jellyfish in the
August 1994 issue of National Geographic.
A: That's a good question, considering that jellyfish don't have eyes! They "see" in a very basic way. They get by with a nerve net, which consists of parts able to detect light, odor, chemicals and other stimuli. They have nerves in their tentacles that tell them when they are touching something, and then stinging cells (nematocysts) that paralyze their prey. If it's something that they can eat, then they sting it with their tentacles, and eat it. It would be something like you going to your fridge with your eyes closed, opening the door, and feeling around until you felt something that you thought would be good to eat.
Q: How did the Portuguese Man-of-War get its name? A:
Man-of-war is another name for warship, and I believe (although
I couldn't find it written) that the animal was so named because
it resembled Portuguese warships that a) were common at the time
or b) were known to be particularly vicious..
Q: Two questions to answer please. 1. How do jellyfish breathe? 2. How can whale hunting cause heatstroke in whales? A:
Jellyfish are from the Pylum Cnidaria and like most Cnidarians
breathe through gas exchange over their entire body surface.
They do not have lungs or gills like most other marine species
do. It would certainly be interesting if us humans could breath
through our skin! To answer your second question when whales
are being hunted they tend to swim harder than they would otherwise.
This creates excess heat buildup in their bodies. Whales cannot
get ride of excess heat easily except through their fins and
flippers because of their layers of insulating blubber. So if
whales overheat during the whaling process they can die from
overheating.
Q: I was attacked by a jellyfish about ten years ago and the tendrils went from my foot to my upper thigh. Recently I have been experiencing pain in the area where the jellyfish attacked me. Could I still be suffering the effects of the sting? A: I don't know enough about jellyfish stingers to really say whether it would be related to the venom. But it might be possible that the jellyfish attack damaged some of your nerves in your leg when it attacked. If this happens you could get some pain and tingling in your leg (sort of like pins and needles I would think or maybe even worse) I would go to see a doctor about it and tell him your symptoms and about the jellyfish attack.
CORALS
Q: Where can I get information about coral reefs and the conservation of them? Here are some sites that you might find useful: 2) International Coral Reef Initiative
Q: I know that coral reefs exist in warm and shallow waters, like in the Caribbean Sea and the Indian Ocean. I live in southern California. Where would be the nearest coral reef? And in terms of the ocean floor, since coral reefs exist in shallow waters, I assume that would be the continental shelf. Am I correct in this assertion? Also, what is the sort of wave activity in coral reefs? I'm thinking that the motion of the ocean in these parts are mild, with not much crashing and breaking of waves... And last but not least, thanks in advance for your input! A. Coral reef formation is initiated with the attachment of free-swimming coral larvae to the submerged edges of islands or continents. As the coral grows and expands, a fringing reef is formed as a band along the coast or around an island. This type of reef is predominant in the West Indies. It is also the first stage in the process of forming atolls. If the fringing reef is attached to the edges of a volcanic island or other land mass that is slowly sinking, while the coral continues to grow upward, a barrier reef will eventually form. Barrier reefs are separated from the land mass by a lagoon of deep open water. The Great Barrier Reef in Australia is the best known of this type. Atolls are the last stage in the geological process. When a volcanic island subsides below sea level, the coral reef is left as a ring around a central lagoon. Continued coral growth maintains the circular reef, but calm conditions and increased sedimentation in the lagoon prevent reef development in this area. Hundreds of atolls can be found in the South Pacific, all of them located far from land but attached to underwater seamounts. Reefs are located exclusively in waters bounded by 20 degree Celsius isotherms, and so are virtually confined to the tropics. Reef building corals cannot tolerate temperatures below 18 degrees, and optimal growth usually occurs between 23 and 29 degrees Celsius. Also, corals (which are animals in the Phylum Cnidaria, which means they are closely related to jellyfish and anemones)require high salinity waters (32-42 ppt), high light levels and relatively calm waters. High turbidity waters tend to carry suspended sediment which can smother the corals and clog their feeding mechanisms. Corals are generally absent from the waters along the west coast of the Americas between 30 degrees south and 30 degrees north. These areas experience upwelling, where cold, nutrient rich seawater rises along the coast. In these nutrient rich waters, phytoplankton grow in great abundance, reducing light levels and preventing the establishment of corals in these regions. I would guess that the closest coral reefs are near Hawaii and other islands in the Pacific.
Q: How are coral reefs made or developed? A: Coral reefs are composed mainly of calcium carbonate, which is produced by corals (phylum Cnidaria, class Anthozoa, order Madreporaria = Scleratinia) with small additions from calcareous algae and other calcium carbonate secreting organisms. Coral is found throughout the world, but reef forming coral (hermatypic coral) are found only in tropical waters. Hermatypic coral grow by continually secreting calcium carbonate to its skeleton. It is the continual deposition of calcium carbonate that builds a coral reef. Corals are living animals that feed by using tentacles containing stinging cells (nematocysts) that catch planktonic prey. Hermatypic coral have algal symbionts that live within their tissues called zooanthellae. Zooanthellae is extremely important in the deposition of calcium carbonate. The organic compounds produced by the zooanthellae are used as food for the coral. Without sunlight, the zooanthellae cannot photosynthesize and the coral does not grow. If lack of light persists the coral will die, demonstrating that hermatypic corals cannot live without their algal symbiont.
Q:
Help! I need methodology for finding and evaluating coral reef
formations, health,etc. A. There is lots of good information on the internet relating to coastal health and monitoring coral reefs. Here is a good site with lots of reference material: Also, if you use COASTAL HEALTH in internet searches, I'm sure that you will find lots of other good info. The NOAA (United States National Oceans and Atmospheric Administration) has lots of good methodologies for that kind of thing.
The octocorallians always have eight pennate (side branching) tentacles. There are always eight complete septa, one on each side of a tentacle, and one one siphoglyph is present. The octocorallians are colonial cnidarians, and the polyps are usually small. The polyps of the colony are connected by a mass of tissue known as the enenchyme, which is mesoglea perforated by gastrodermal tubes. The amebocytes of the mesoglea secrete a calcareous material that supports the colony. The octocorallian skeleton may be composed of separate or fused calcareous spicules. The skeleton functions in support, but can also function to deter predators. The gorgonians include the whip corals, sea feathers, sea fans, and the precious red coral. Gorgonians are common reef fauna, and can be found in most tropical waters, but especially in the West Indies. Basically, the feeding mechanism of the Octocorallia is similar to other anthozoans. The polyps use their tentacles to intercept prey, which is comprised mainly of zooplankton and other small particulate matter. The tentacles often contain spirocysts or nematocysts which are used to capture and stun their prey. Gorgonia polyps are more commonly expanded during the day than at night. For identification purposes, a key to the families and genera would be a great asset. Preferably one with colour illustrations.
Q: How has the effects of humans in coral reefs, affected the growth and expansion of the reef? A: There are several human activities that have an effect on the coral reefs, and some have different affects and severity of affects. Some examples are fisheries activities, coastal construction, recreational activities (such as diving), oil pollution, and lost or abandoned gill nets. Fisheries activities has the most severe affects and the most common. In terms of what actually happens to the reefs, it has been found that there is an increase in coral bleaching and mortality as the ocean temperatures increase. As global warming heats up the oceans, corals are unable to adapt physiologically or genetically to rapid change. Human effects on growth and expansion also include changes to a limited abundance of small corals and to fewer small colonies, i.e., more individual large colonies.
Q: How does coral form? A: Coral reefs are made up of different species of animals, including: corals, coralline algae, and sponges. Most species of coral are colonial animals and their growth is aided by a symbiotic relationship with zooxanthellae (cyanobacteria). Corals and coralline algae slowly secrete calcium carbonate and sponges secrete silica. The growth of these plants and animals increases the size of the reef. The species that provide most of the structure to the reef are called "framework builders". Scerlactinia corals are the main group of coralline framework builders. Corals that grow very quickly are called "hermatypic". Growth of coral reefs is limited by temperature, salinity, light, and turbidity factors. They grow optimally in warm tropical waters with lots of light. Coral reefs are incredibly diverse environments and make up the most complex ecosystem in the marine environment! ANEMONES
Q: What is a sea anemone? Where are they usually found? Why do they exist? A: Sea anemones are in the Phylum Cnidaria, along with jellyfish and corals. Cnidarians have two body forms, one is free-swimming and is called a medusa, and the other is stationary and is called a polyp. Jellyfish have the medusoid body form, with a bell-shaped body and tentacles hanging down from the edge of the bell. A polyp such as a sea anemone is essentially a jellyfish turned on its head, with its body more tube-shaped and the tentacles directed upwards into the water column. Sea anemones are brightly coloured, soft-bodied animals which are found in both shallow and deep waters. They are quite common in the intertidal zone where they live attached to rocks or shells. Their mouth is located on top of their column-shaped body, surrounded by a ring of tentacles. Sea anemones feed on many different kinds of invertebrates, and larger species can even catch fish! Their tentacles are covered with stinging cells called nematocysts, which paralyze the prey and allow it to be carried to the mouth. Regarding your question about why sea anemones exist, I'm not sure if I have an answer for you. Anemones are just another wonderful example of the diversity of animals living in the ocean, which have all evolved to fill certain niches or habitats. For more information and a picture of a sea anemone in a tide pool, see The Mid Zone.
Q: what are the problems faced by the sea anemones at the rocky shore and their corresponding adaptations ? A. There are a variety of problems that an anemone faces in the rocky intertidal habitat. The intertidal is a highly competitive area, where space is probably one of the main limiting resources. Once an anemone has found a good spot, it adheres to the substrate using the pedal disc. In wave exposed areas, the action of the waves places a lot of stress on intertidal organisms. The strong adherence of the pedal disc to the substrate allows the anemone to maintain its position. Another adaptation that anemones have is clonal (asexual) reproduction. Asexual reproduction allows an individual that has found open space to quickly reproduce and colonize the local area with genetically similar clones. To maintain space in that area, anemones have evolved special defensive tentacles called acrorhagi. These tentacles form a ring around the base of the oral tentacles, and contain stinging cells with large toxin-containing nematocysts. When another organism settles too close, the anemone can extend their acrorhagi to defend its space. The intertidal also has a relatively high rate of predation. There are several species of seastars that feed on anemones, and as a result, many species of anemones have evolved fascinating escape responses. In response to tactile stimuli, some anemones can quickly detach the pedal disc from the substrate, and then swim or use water motion to evade the predator. Anemones can also protect themselves by using spirocysts, specialized adhesive organelles, to stick bivalve shell fragments to the outside of their bodies. In this way, the soft tissues of the anemone are protected from potential predators. Desiccation is also a problem that anemones will encounter during low tides. To prevent desiccation, anemones have the ability to contract into a tight ball. This morphology reduces the amount of evaporative surface area, allowing the animal to survive to the next period of submergence. These are just a few of anemones adaptations for living in the intertidal. For more info, look for a good text on invertebrate zoology.
Q: Hi, I'm doing a research project on the intertidal zone. I need to have information regarding the special problems that anemones (specifically collared anemone, phyllactis bradleyi) have to deal with due to the harsh environment of the intertidal zone. I am especially interested in adaptations that make the anemones successful in its niche. Thanks. A: There are many different factors affecting animals living in the intertidal zone, an area alternately covered and exposed by the daily tidal movements. Some of the physical conditions that organisms living within this habitat must deal with include heat stress, desiccation (drying out), oxygen shortages, wave shock, reduced feeding opportunities and terrestrial predators. Sea anemones (Order Actiniaria) usually reside in the mid-intertidal zone, between 1.2 m (4 ft) and 0.0 (mean lower low water), and the low-intertidal zone, between 0.0 and -1.1 m (-3.5 ft). They can also be found further up on the shore in tide pools. When exposed to air, anemones contract and cover the oral disc with the upper surface of the column to retain water. The decrease in surface area due to contraction also reduces water loss. Some anemones (such as Metridium sp.) have a circular fold or collar at the junction of the oral disc and column which covers the oral surface during contraction. Anemones such as Anthopleura elegantissima congregate together, forming beds in sandy areas which retain water when the tide goes out. These anemones are known to withstand internal temperatures as high as 13 C (55 F) above the ambient air temperature, but cannot cope with serious water loss. They deal with extreme desiccation and temperature fluctuations by attaching bits of light-coloured shell and stones to themselves, which are thought to reflect light and heat.
A:
One thing that you will notice, even if you examine anemones
along the coast of Virginia, is that their colors are incredibly
diverse. Often, individual species have more than one color.
For example, one of the most common intertidal anemones on the
West Coast is Anthopleura However,
the differences in coloration of the anemone oral tentacles have
several possible explanations. Sea anemones are classified in
the group of organisms known as Cnidarians, which The "golden thread" that you saw may also be a Cnidarian. If the local people said that it is a poisonous jellyfish, then it probably is. I'm not exactly sure which species this common name refers to. It is hard to identify species based on their common names because often they vary from place to place. It may simply be the Portugese Man-of-War, or some other Siphonophoran jellyfish. There are many different species of jellyfish that can be dangerous if touched. The sea wasp, which is common to tropical waters, is a potentially lethal jellyfish that has extremely long tentacles containing a battery of toxin-filled nematocysts. Many of the larger jellyfish extend their tentacles to great lengths (30ft or more) to intercept prey items.
Q: I have a question regarding the stinging cells of Sea anemones (or any Cnidarian for that matter). Does the cell 'die' and regenerate after use, or is it reusable? A:
According to several invertebrate zoology textbooks, the cnidocyte
(stinging cell) does not regenerate a nematocyst (stinging structure)
after it has already ejected one. Instead, it is fairly quickly
replaced by a new cnidocyte which develops from a nearby interstitial
cell, or which migrates from a location on the animal where cnidocytes
are developed. What is left of the discharged cnidocyte is probably
reabsorbed by neighbouring cells.
HYDROZOANS
Q: I am doing a report on hydrozoans and I was wondering if you could give me some information about them? A: Hydrozoans belong to the Phylum Cnidaria, along with the jellyfishes, sea anemones and corals. Hydrozoans look almost like miniature sea anemones, having a column-shaped body with a ring of tentacles surrounding the mouth. However, unlike sea anemones, hydrozoans lived in finely-branched colonies surrounded by a supportive cuticle. Most hydroid colonies are between 5 to 15 cm high, and appear as bushy or feather-like growths attached to rocks, shells, wharf pilings and floating docks. The individual hydroid polyps making up the colony are often 1 mm in length or smaller. These polyps are connected to each other via the gastrovascular cavity (almost like a continuous stomach), with the colony exhibiting polymorphism. This means that there are different kinds of polyps within the colony, each specialized for a certain function. For example, a feeding polyp is known as a gastrozooid. These gastrozooids capture and ingest food (small plankton) using their many tentacles, and share this food with the other members of the colony through the continuous gastrovascular cavity. There are also defensive polyps, called dactylozooids, which have stinging cells used to defend the colony from predators. Sometimes a colony will have reproductive polyps, called gonozooids, which produce medusoids (tiny jellyfish-like animals). However, reproduction within a colony often occurs asexually by budding off new polyps from the main stem. For some pictures and more information on hydrozoans, see the Hydrozoan page at UC Berkeley.
see also: OceanLink's Cnidaria page and Anenome page! |
There
are a variety of reproductive strategies in the phylum Cnidaria,
but most follow a basic scheme. The adult form is a medusae
(jellyfish), most of which are dioecious,
BACK
TO 
A. It
was probably a jellyfish that caused such as nasty sting. I can
think of two genera that it could possibly be, and there are
several closely related species in each of these two groups.
Both are true jellyfish, animals in the Phylum Cnidaria, Class
Scyphozoa. The Phylum Cnidaria also includes the sea anemones
and corals; all of these organisms possess stinging cells which
are called cnidocytes. One genus is Chrysoara, a yellow-brown
medusa with 24 dark brown tentacles and distinctive yellowish
manubrium (arms). The bell of this animal may reach 12" in
diameter and lengths beyond 8'. The two species C.melanaster and C.equihaarrah are
known to possess very potent stinging cells that are harmful
to humans. The other suspect genus would by Cyanea. Animals
in this genus have a flattened bell that is thick in the center
and thinner along the margin, which consists of eight lobes.
These animals have hundreds of tentacles that trail from the
margin of the bell and can reach lengths greater than 30'.
These
animals typically feed by trailing their tentacles through the
water column. There are high densities of cnidocytes (stinging
cells) on the tentacles, and when contact is made with a prey
item (i.e. fish or invertebrates) the cnidocytes are stimulated
to discharge nematocysts, tiny needle-like capsules that are
filled with venom. The venom usually consists of a mixture of
neurological toxins that act to sedate the prey, and prevents
them from escaping. When humans are stung by certain jellyfish,
inflammation and a sharp pain in the area of contact are common
symptoms. The toxins of several cnidarians have been found to
contain glycoproteins and amino acid molecules that could potentially
produce an allergic reaction in humans. Such a histamine type
response to the toxins would result in dilation and increased
permeability of the blood vessels, and a subsequent fluctuation
in blood pressure.
What makes this jellyfish
dangerous is the poisonous venom that is contained in
microscopic stingers along its tentacles. These stingers
are called nematocysts - and are released into the box-jellyfishes'
prey upon contact. All jellyfish have these stingers,
but the strength of the venom in a box-jelly discharge
is enough to kill large fish - and also enough to really
hurt - or even kill - a human that encounters it. The
jellyfish do not seem to seek out prey, they simply catch
whatever food runs into them as they swim in the water.
elegantissima.
This animal is usually green with pink oral tentacles. However,
there are some that have brown or white coloration as well. The
reason for this color variation has to do with the nature of
the photosynthetic symbionts that live within the tissues of
the anemones. Inside the cells of the green Anthopleura,
there are millions of tiny zooxanthellae (single-celled algae)
that contain green pigments. The brown Anthopleura have
brown symbiotic algal cells, and the white ones typically lack
these symbionts. The variation in colors of anemones is therefore
largely dependent on the characteristics of their algal symbionts.
includes
the jellyfish and corals. All of these organisms possess stinging
cells called cnidocytes. Cnidocytes generally function in prey
capture and defence, and vary by virtue of the type of nematocyst
or spirocyst that each contains (and there is a whole smorgasbord
of nematocyst types and functions). The nematocysts and spirocysts
are the "darts" that a cnidocyte "throws" in
response to stimuli, and may contain toxins, adhesives and other
functional molecules. Often, the different cell types of an anemone
are different colors (due to the predominant colors of the zooxanthellae,
nematocysts, or other pigments). Areas of the oral tentacles
that have high concentrations of cnidocytes are often different
colors. The contrasting bright colors usually function as a warning
sign to fend off potential predators. Also, different individual
anemones have different appearances due to genetic diversity
(i.e. think about blue,brown, or green eyes in humans).
to
the answer archive index| OceanLink Home | OceanNews | Biodiversity Students in Action | Ocean Matters | Career Info | Links |