Marine Topic Of The Week, 3/02-3/09/07

steelhealr

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We loved them since children when we would either find them on the beach or we would pull them up on our fjshing lines, but, what are these beautiful creatures and should you have them in your tank?

Classy Creatures

Sea stars belong to the Phylum Echinodermata which means 'spiny skin'. There are thousands of animals belonging to this group. There are five major classes:
  1. Asteroids
  2. Ophiuroids
  3. Crinoids
  4. Echinoids
  5. Holothuroids
echinoderms.gif


Classy Features

If you are an Echinoderm, you probably share the following features:
  • radial symmetry: their body parts are arranged about a central axis
  • 5-fold or penta-radial symmetry: their body parts are arranged in 5's or multiples of 5's
  • a water-vascular system: enables them to move, climb and pry open tough mollusks. The system consistes of tubes, channels, bladders, suckers, etc
  • regenerative powers...they can regrow lost body parts
  • a calcite skeleton covered by epidermis
starfishregenerating.jpg


The most likely creatures that we will come into contact with at our marine LFS is a sea star, Asteroidea sp.. Just a few quick notes.

Asteroidea

OK...we grew up calling them Starfish but they are not fish. They are Sea Stars. Asteroidea are probably the most common Echinoderms that you will see for sale. Asteroidea that you find will most likely:
-have five arms
-use tube feet to move around your tank while the arms stay straight
-be scavengers and move about looking for food; some can find food in your tank, even if buried, by a 'sense of smell'
-eat corals and are not 'reef-safe'
-be able to evert their stomach to eat

Photos of the Indian Sea Star Fromia indica

fromia2.jpg


fromia1.jpg


Be A Conscientious Marine Aquarist

In general, Sea Stars are scavengers/predators. Some can grow quite large. Unless you have a very large marine tank, these animals don't belong in our marine systems. As always, there are anecdotal stories of success. In the least, you should be an 'expert' to try and keep them alive and have a tank of 100 gallons or more. DO NOT try and keep them in a nano tank. There is simply NOT ENOUGH room and food diversity to keep them going and they will SLOWLY STARVE. Stars, when they die, disintegrate rapidly and will nuke your tank.

Hope this helps.

SH
 
Echinoderm trivia;

-Phylum Echinodermata is placed in the same superphylum as the phylum Chordata; thus, Starfishes are a "distant cousin" of sorts to us.
-While most people think of only Urchins as having spiny skin, there is one genus of Starfishes that beats the Urchins at their own game. This is the genus Acanthaster, and their stings are so powerful that they have but a single predator, who unfortunately has a very beautiful shell (we all know what that means). They can now multiply nearly unboundedly, and they feed entirely on corals. Destruction is left in their wake.
-Echinoderms are very successful organisms, spanning from the Cambrian period to today, and they once had many branches of descendants, that included (in theory) the genus Tribrachidium, a very mysterious organism (now extinct) that was thought to have a very high capability for intelligence, as well as three radiating vertebratal spines.
-Holothurians are capable of ejecting some of their internal organs in order to deter predators from eating them.

-Lynden
 
This is the genus Acanthaster, and their stings are so powerful that they have but a single predator, who unfortunately has a very beautiful shell (we all know what that means). They can now multiply nearly unboundedly, and they feed entirely on corals. Destruction is left in their wake.

Their introduction to foreign reef's with no known predator causes their prolific reproduction, but where they are a natural co-inhabitant, they have many predators, including Fish, Polycheates, Crustaceans etc. So, their location, and whether their environment is ready to cope with them leads to what light these creatures are portrayed in. They do munch coral, but thats a natural diet for these creatures. Their strong variability in population could be a natural variation, only their introduced populations (and heavy outbreaks in natural environments), and the "popularity" of reefs cause such negative light for this creature, which is in certain instances a natural phenomenon. :nod:

Humans are much to blame for their wide spread and extra destructive habits caused by an increase of their population. Even where they are natural, the consistent removal of fish/ crustaceans etc for the ornamental trade and shell collecting could be affecting this balance. Increased FW run-off could also be attributed to their successful reproduction.
 
Hmm, from what I've read their only predator is the Triton Trumpet, a gastropod. I would be interested to know what other predators they have, and what their natural range is? I encountered three specimens in Hawaii, and I know also that Acanthaster planci can be found in Australia... a very large distance apart. It's surprising to me that they could be introduced to other, such far away areas; they aren't Rattus after all and are not particularly resilient creatures.

I believe one theory for their extreme multiplication is runoff of debris and pollution; which is highly plausible since in this case it is the filter-feeders such as sponges that are given a boost. Acanthaster planci's larvae are planktonic filter-feeders.

Certainly these starfish are natural animals, and they do not deserve to be portrayed in such a negative light. However, if man truly is the reason they have become so abundant in many areas, then it is probably our responsibility to fix our mistakes. Saying that they should be allowed to proliferate madly in their non-native areas is like saying that cats and rabbits should be allowed to do the same on Australia (not to say that that was necessarily your message). I don't think that we should let this phenomenon, natural or not, upheave the most vibrant environments on Earth.

-Lynden
 
Lynden, Harlequin(sp?) shrimp will eat Crown of thorns.So will Cheilinus undulatus the humphead wrasse which feed on larvae or small adults.


They say that Crown of thorns numbers may be because off agricultural runoff.
 
Excellent way to expand the topic. I hope we can always do this. SH
 
Excellent way to expand the topic. I hope we can always do this. SH

Be glad to. :)

I would imagine that Manta Rays and other filter feeders would also consume the larvae... but I find it hard to believe that a couple of 2'' shrimp could possibly cart off a multi-pound, 15'' plus in diameter fully adult Acanthaster. The small specimens, sure... but the large adults I could not imagine the shrimp killing.

I thought about Wrasses or Triggers eating a full-sized specimen, but even then... the spines may prove to be too dangerous for even those fish. I know I certainly wouldn't be poking one of those monstrosities.

-Lynden
 
Excellent way to expand the topic. I hope we can always do this. SH

but I find it hard to believe that a couple of 2'' shrimp could possibly cart off a multi-pound, 15'' plus in diameter fully adult Acanthaster. The small specimens, sure... but the large adults I could not imagine the shrimp killing.


-Lynden


More than a "couple of 2'' shrimp" they hunt in groups. I am not saying that they can take down a lot of them but they do eat crown of thorns. Also have you ever seen Harlequin(sp?) take down a star fish? They rip them to bits and store most of the star for later.
 
More than a "couple of 2'' shrimp" they hunt in groups. I am not saying that they can take down a lot of them but they do eat crown of thorns. Also have you ever seen Harlequin(sp?) take down a star fish? They rip them to bits and store most of the star for later.

I have seen them attack a Starfish; they in fact eat the tube feet so it is in the shrimp's best interest to keep them alive. They usually work from the tip of an arm right to the central disc, all the while making sure the hapless echinoderm does not escape or die.

However never have I read or seen them attacking in groups (only pairs or by themselves) or ripping an animal to bits; could you verify these claims? One of us has been misinformed.

-Lynden
 
More than a "couple of 2'' shrimp" they hunt in groups. I am not saying that they can take down a lot of them but they do eat crown of thorns. Also have you ever seen Harlequin(sp?) take down a star fish? They rip them to bits and store most of the star for later.

I have seen them attack a Starfish; they in fact eat the tube feet so it is in the shrimp's best interest to keep them alive. They usually work from the tip of an arm right to the central disc, all the while making sure the hapless echinoderm does not escape or die.

However never have I read or seen them attacking in groups (only pairs or by themselves) or ripping an animal to bits; could you verify these claims? One of us has been misinformed.

-Lynden


The BBC had a program on TV about Crown of thorns, Showed about 4 Shrimp rip all of the arms of a crown of thorns and stow them for later .Thats what it said they do store them for food.

And a star fish with no legs can not have that good odds to live, even if they can grow them back.


"One of us has been misinformed" that would be me i guess :blush: it may be just an old Program I saw.
 
The BBC had a program on TV about Crown of thorns, Showed about 4 Shrimp rip all of the arms of a crown of thorns and stow them for later .Thats what it said they do store them for food.

And a star fish with no legs can not have that good odds to live, even if they can grow them back.


"One of us has been misinformed" that would be me i guess :blush: it may be just an old Program I saw.
No, actually, it may have been me. :blush: I consider BBC documentaries to be highly reputable. Sounds interesting (if not diabolical on the shrimp's part :hyper: ). I should try to watch it sometime.
 
Hmm, from what I've read their only predator is the Triton Trumpet, a gastropod. I would be interested to know what other predators they have, and what their natural range is?

Dont know their natural range, but I have found there are more predators than just a gastropod. :D See below. Search WWM and the net. Even Google Scholar.

Puffers, Trigers, some species of Polycheate, and your Harlequin Shrimp as already mentioned. They can turn the starfish upside down, and therefore remove the threat of spines, and enjoy a meal free of deadly poison. :hey: There are also a few articles referring to "fish" predators, but not being at my Uni computers, and not feeling the desire to read through papers/journals, I havnt found a species.

I believe one theory for their extreme multiplication is runoff of debris and pollution; which is highly plausible since in this case it is the filter-feeders such as sponges that are given a boost. Acanthaster planci's larvae are planktonic filter-feeders.

True, but its just a theory. Theres a few papers out, they provide interesting reads, although somewhat lengthy. Google Scholar is a great program for finding abstracts atleast (for those not on campus computers, or who dont have access to full journal articles).

Saying that they should be allowed to proliferate madly in their non-native areas is like saying that cats and rabbits should be allowed to do the same on Australia (not to say that that was necessarily your message).

I dought ANYONE would say they should be allowed to multiply in non-natural areas. BUT, they should be culled in areas where they do not exist naturally. I never said they shouldn't be killed once introduced. :nod:

I don't think that we should let this phenomenon, natural or not, up heave the most vibrant environments on Earth.

Ah, the idea rears its ugly head (not singling you out here Lynden, im referring to the entire human race). Haven't "we" learnt we cant control something natural, just because we don't like it doesn't mean its role in an ecosystem is negative or any less critical for the survival of our "most vibrant" ecosystem.
 
Ah, the idea rears its ugly head (not singling you out here Lynden, im referring to the entire human race). Haven't "we" learnt we cant control something natural, just because we don't like it doesn't mean its role in an ecosystem is negative or any less critical for the survival of our "most vibrant" ecosystem.
Since the world is basically de-naturalized already... and if the Starfish was introduced by humans to other areas... and if the Acroporids and other SPS are already facing numerous other threats (many are in theory due to humanity's presence)... then I think that my statement could be counted as an exception to the "idea". Those starfish, in their non-native areas, are an extremely destructive force (topped only by the species that put them there) that likely disturbs countless species that live near the Acroporids. If a species is contributing to loss of diversity, it's efforts should be impeded (including man's), much like the rabbits in Australia or the rats and goats on countless formerly pristine islands. How are introduced starfish any different?

Haven't "we" learnt we cant control something natural
Oh, how I would like to believe that statement. Would certainly take a load off my mind; but unfortunately all my knowledge points in the opposite direction.

Man is a truly extraordinary species (and not in a good way). We can change our ecosystems to a degree far outmatched by any other species to ever live. We are capable of causing extinctions that could likely equal or exceed that of the Permian/Triassic extinction, called "The Great Dying". We have brought lifeforms that were once abundant to their knees; we have annihilated nearly all non-domesticated land megafuana; and extremely strict laws are needed to save those remaining. We have spread to every corner of the globe, changing the ecosystems to suit our needs; we can even maintain a presence in space.

If man were to lose entirely his limited sense of conservation... ughh. It would be the end of the world as we know it. Man is the "pointy tip" at the top of the food chain, and carries the power to crush anything and everything below. Except maybe for water bears... :drool:

Our friendly (and now off-topic :blush: ) discussion shall continue... :drool:

-Lynden
 
Since the world is basically de-naturalized already... and if the Starfish was introduced by humans to other areas... and if the Acroporids and other SPS are already facing numerous other threats (many are in theory due to humanity's presence)... then I think that my statement could be counted as an exception to the "idea". Those starfish, in their non-native areas, are an extremely destructive force (topped only by the species that put them there) that likely disturbs countless species that live near the Acroporids. If a species is contributing to loss of diversity, it's efforts should be impeded (including man's), much like the rabbits in Australia or the rats and goats on countless formerly pristine islands. How are introduced starfish any different?


Oh, for sure. I meant in their natural environment they shouldn't be harmed. :good: Any measure necessary to control populations should be implemented in areas where they do not occur naturally, but where is this? What records do you have to look back too, are they accurate? Will they have scientific credibility? :hey:



Our friendly (and now off-topic :blush: ) discussion shall continue... :drool:

Any constructive addition to a conversation, including mans efforts too influence every habitat on earth is welcomed! :lol:
 
Any measure necessary to control populations should be implemented in areas where they do not occur naturally, but where is this? What records do you have to look back too, are they accurate? Will they have scientific credibility? :hey:
You know what? I don't know... :blink:

I will have to look into that. :lol:

-Lynden
 

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