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FAQs about Sea Star Behavior

Related Articles: Sea Stars, Brittle StarsAsterina Stars, An Introduction to the Echinoderms:  The Sea Stars, Sea Urchins, Sea Cucumbers and More... By James W. Fatherree, M.Sc.

Related FAQs: CC Star Behavior, Linckia Behavior, Sandsifting Star Behavior, & Sea Stars 1, Sea Stars 2, Sea Stars 3, Sea Stars 4, Brittle StarsSeastar ID 1, Seastar Selection, Seastar Compatibility, Seastar Systems, Seastar Feeding, Seastar Reproduction, Seastar Disease, Asterina Stars, Chocolate Chip Stars, Crown of Thorns Stars, Fromia Stars, Linckia Stars, Linckia Stars 2, Sand-Sifting Stars,

Starfish; beh.       3/23/15
I asked my zoology
<Ahh; my undergraduate degree... in a school (SDSU) that no longer has such organismal specialties>
teacher a question she didn't know the answer too so she suggested I look online. I couldn't find an answer but I found y'alls email. Starfish extrude their stomach when eating. Could a clam close its shell while the starfish is feeding and cut the stomach off?
<Mmm; good question; in that I don't know either. Have never observed such; nor seen reference>
If it did would the starfish repair its stomach like it does with its legs or would it starve?
<My guess is that it can, does regenerate; else am sure we'd see a bunch of pinched-off stomach Seastar corpses about>
Thank you for any answer you can give!
<Welcome. Bob Fenner>

Seastar Regeneration       11/29/12
Hi, I recently joined a science research course and I am studying the regeneration of Seastars. I was wondering if you knew if there was a certain
age or life cycle stage that is the best time for Seastars to regenerate.
<I do not; but would not be at all surprised that there is such real scientific research that has been done re. I encourage you to read this short piece on scientific literature searches:
and seek out the assistance of a reference librarian at a college w/ a life science dept., or just on-line!>
Also I was wondering if over a 6 week period if you cut a piece of a leg off the Seastar would there be visual results of regeneration by the end of 6 weeks?
<I suspect so; yes. Bob Fenner>
Thanks so much!

star fish memory     10/5/12
A number of years back I was commercial fishing (I think, at the time, pound fishing) on the Chesapeake Bay. Took a common star home and set up a marine aquarium. It thrived - we fed it every few days with pieces of fresh oyster.
We'd tap at one corner of the aquarium (the same corner each time) and it would skittle over, come to the surface, flop over two of its legs, expose its mouth, and we'd put the oyster bits in. He'd remember this process between feeding times. I had read that stars have a short term memory but have seen little research on how this is possible. Any ideas? Thanks.
<I think Seastars and Ophiuroids (Brittlestars) are largely overly discounted in terms of "intelligence"... their phylum, the Echinodermata, are ranked/placed just before ours (the chordates)... and Brittlestars are determinate organisms in MANY marine habitats, largely determining what other livestock can/does live on tropical to coldwater, shallow to abyssal reefs. They're smarter than most people appreciate. Bob Fenner>
Howard Fisher

Starfish beh., & More re: starfish 12/04/08  12/5/08 Why do they settle at the top of the tank along the edge of the waterline? <Likely because there's a lot of algae and other "bio-gunk" (bacterial slime, etc.) that sometimes accumulate at the water line which they like to munch on...> Marcy Lynch Internship Coordinator Finger Lakes Workforce Investment Board, Inc. <Best, Sara Digital Imaging Sales Associate Best Buy, Inc.> <<Mmm, not always, or predominantly the "reason" in my experience. Generally there is "something" missing in the environment and they're really trying to "get to a better place"... Often pollution, a lack of food or oxygen... A very good idea (particularly in a commercial setting, with several to many specimens at risk), is to move the animals to another system who show this behavior. Bob Fenner>

Re: Starfish Article  10/15/07 Hey Chris! <Hello> You are the second person today that suggested researching out starfish behavior and writing a paper on it. My old marine bio professor, whom I was hoping could shed a little light (no pun intended) on the subject, said they do have a photosensor of sorts but I should do some research on it and do some experiments. <Would be very interesting, and the literature in the hobby is quite lacking in this area.> He also told me that they excrete out their top and they have a very slow digestive system which I did not know. <Interesting creatures for sure.> Thanks again for answering all my questions, Chris...I really appreciate it. As always you guys are the best!!!! Jennifer <Welcome> <Chris>

Seastar... beh., dis., fdg.    4/20/06 First I'd like to say NOBODY has enough information on sea stars as you guys... <Okay> i just purchased a sand sifting star and a couple days later a red general... the sand sifter was very active the first day i purchased him, he would go under the sand and come out an hour later and go to the glass, it was exciting to watch him move.... i hadn't seen him what so ever for a couple days... is it possible he may have go out? <Mmm, not likely> i do have dogs, I'm sure would eat a fallen starfish... i have a top but with all the cords and tubes it's far from being inescapable... my red general hangs out on the top of the tank exposing himself to the air (purchase from the pet store today), i realize this is normal for some star fish, but is it for the general... <Not normal... something is amiss here. Likely environmental> and my final question I've heard of "target feeding" can you explain how to do this? <Placing likely palatable foodstuffs right next to the intended consumer. Bob Fenner> Nate

Short Fromia starfish behavior question... or, short question... Hi! I have a pretty Fromia (marble starfish) since a month. I think it's doing fine, but it often goes to the surface for some reason, very close to the water line. Sometimes part of a leg is out of the water. Do you know why it does this and is it a problem? Thanks! Dominique <Maybe... these stars do this... but is it always an indication of stress, trouble? A lack of oxygen, something amiss in the way of water quality? Established "reef" systems, with plenty of live rock, seem to diminish this behavior. Bob Fenner>

Lazy Fromia 7/22/05 After reading WWM and reading Bob's book, I decided against buying a Blue Linckia  starfish and getting a Red Fromia star instead. <A good choice, indeed.> Question...In my opinion, I properly acclimated him but after a day he still doesn't seem to be doing much.  He lays in the same spot of the substrate for hours and never moves at all.  But if I move him to a different location (to test and see if he's still living), his little "feet" come out, grab a hold and pull his legs down tight on the rock, substrate, etc.  I moved him again, this time close to the glass, and he reached his arm up extended the little feet out and pulled half of his body halfway up the glass with the other half still on the substrate and stopped again.  He moved rather quickly (for a starfish) to do this. And there he still sits again. motionless for hours.  He's been in the tank for about 30 hrs now. <I wouldn't lose any sleep over it. If the starfish moves when "threatened," I'd assume it was just acclimating to its new habitat. If it does not eat anything within 30 more hours, however, I'd start to think you had a problem, but I doubt it will come to that provided your tank is adequate for such a creature.> Is this normal Fromia Star behavior or should he be moving around more?   Is this a sign that he's not doing well and is going to die or is it too early to tell?   Is there anything I can do to help him? <Just wait. Listlessness is not always a problem. Best of luck, Mike G.> Thanks in advance. -Cody

Sand Sifting Star behavior 7/20/05 Hi Bob, been months since I wrote. Been nice to have a tank we can keep clean and enjoy. Sounds fishy, huh? <Watch that, this...>    After cleaning and giving the tank a water change today both starfish ran around as usual while the lights were off.  About an hour later one of my sand stars has perched itself up on it's tippy toes, well star fish style that is.  The body is straight up off the sand bed with the lower tips curled to lay on the sand floor with the very end of it's tips curled up in their usual radar style.  None of the fish seem to care.  Do you have any idea what this little guy is doing? <"Sniffing" the water so to speak most likely. Bob Fenner>   My other star is business as usual half buried in the sand. Debi Stanley-Viloria

Chocolate Chip Star Problem? (6/14/05) I purchased 2 ccs fish 6/13. <Chocolate Chip Starfish per your e-mail subject line. I would not know that by the term "ccs fish."> The smaller one is all over the aquarium, but the larger one is just sitting there. His chips seem to fold up in the middle until I pick him up then everything seems to go back to normal looking. Is he just stressed out to the new aquarium or should I look for something else wrong? <Impossible to say for sure. Did you acclimate slowly over several hours, as starfish require? Starfish aren't always active, and may sit in one place for a while. Try to feed it and see what happens. Keep a close eye on it. BTW, these are voracious eaters that are not reef-safe and need to be in a fairly big tank long-term. Hope this helps, Steve Allen.>

Night Viewing Reef Creatures 5/13/05 24 Gal Nanocube (JBJ Lighting Systems) 15 Pounds of Liverock.     The Nano cube has feature installed called NiteVu LED Moonlights.  Will my Starfish (Shaggy) come out when these lights are on or do they prefer pitch black to hunt for food. Thanks for keeping my aquarium healthy, and safe. Eric Ross    <Its hard to say... various nocturnal creatures respond differently.  In this case, it likely will come out under such "moonlight." If that doesn't work, a red plastic lens over a daylight source will allow you to see many night creatures without disturbing them. For even nicer night-viewing (fluorescence) equipment, do check out www.nightsea.com best of luck, life, Anthony>

Amorous Starfish?--No Way to Know What They're "Thinking" (5/5/05) First of all: Thanks for an awesome site!  <You're welcome. It's pleasure to be a small part of it, Steve Allen.>  I've been looking through related subjects and searched the web, but still haven't been able to find the answer to this one:  I added 2 stars (4" & 3") to my 180 g tank 3 months ago. Both look to be doing really well, but the smaller is always (and I mean always) on top of the bigger one.  <Kinky>  If I remove it and place it somewhere else on the sand bed, it immediately returns.  <Obsessive>  I've heard before that this occurs in the wild when currents are too strong or during tide....another theory is that they're "affectionate" (I seriously doubt that...I mean - 3 months!).  <I could think of some humor here, but I'll pass. There's a Levitra commercial on my TV right now.>  It's no biggie, but I'm getting more and more curious as to why this happens.....oh - and how the one on top ever gets food.  TIA, Mikkel Boisen  <I honestly have no idea. Starfish have no brains, so their behaviors are strictly governed by primitive nervous systems. Maybe it has found a free ride agreeable. If it's been there for 3 months and is not wasting away, it must be eating something when you're not looking. If they both seem healthy, I chalk it up to the individual behavioral oddities of nature and leave it be.>

Starfish and Kudos - His Fate Sealed Dear Mr. Fenner; I just thought that I should drop you a line, and let you know that you and your crew do a wonderful job with your website. For me it all started when I decided that I wanted to investigate the possibility of starting a Marine aquarium. I happened across your site, and ended up spending many hours reading and researching. In the end, you sealed my fate.  About three months ago, I invested in a 20 gallon tank for a FO system. Small I know, but I only intended to keep a pair of clowns. Ah yes.... The adventure started there. After spending god knows how much time finding the optimal mix for my sea salt to water ratio, I was set. A week and a half to make sure that the tank was running nicely (specific gravity constant, temperature constant, etc.), I bought a pair of damsels to 'cycle' my tank. The initial plan was to return them to the store for credit when I was done, but I just couldn't. They're really a very nice fish, and beautifully colored. Since, I have gotten my clowns (common), and have also added an olive snail, a cleaner shrimp, and a six-legged red starfish. Today, I began the process of getting a new 35 gallon tank running to put them in. I wanted bigger, but living in an apartment, and already having a 75 gal. freshwater tank, and the existing 20 gal. Marine, I had to be sensible (for now, until I move into a house.). Anyway, I just wanted to tell you that I have greatly valued all the help you have provided through your website, and had to let you know that you've gotten another person hooked on Marine systems. I had always imagined a Marine tank being much more work, but really, it isn't too much more. I do have one question for you... Over the weekend, I woke up and found my starfish on the glass ABOVE the waterline. I put him back into the water, but it seemed as if he was dead. His legs were beginning to disintegrate, and he just lay there. I was about ready to remove him from the tank, but decided to put him upright next to the glass. Again, he went down to the bottom, and sat there, this time on his back. I was determined, so I set him down "right side up" again. I left him for about an hour, and to my surprise he was on the glass again. His legs are smaller, but he seems to be on the mend now. Hasn't fallen off the glass, and moves around regularly. Any idea as to why -or even how- he was out of the water? Also, what do you think his chances are of making a full recovery?  <Bob and the crew thank you for your kind words. As the starfish goes, it's not uncommon for them to break the waterline. Most starfish will consume bacterial slime and it's readily available on the glass/acrylic of the aquarium. My advice is to let the star roam wherever he wants.>

Purple Linckia question Hello Bob! Great website!  I have question about a purple star I bought several days ago. <Thank you... I do hope/trust that this is actually a Tamaria stria... you can see it on WWM and elsewhere on the Net. Much hardier for aquarium use than actual Linckia species.> For the first few days, the star was very active, but today I noticed him upside down on the sand, with legs curled up so that the underside was showing. <! Very bad> I picked him up, thinking maybe he was dead, and placed him right side up on a rock.  A few minutes later his legs uncurled and lay on the rock, but only a couple of tentacles were actually extended and touching the rock I placed him on.  He started moving his legs around, but the tentacles won't extend to latch on to anything.  Also, he keeps curling his legs into weird shapes, like he's cringing.  Is he about to die? <Likely so> I also have a blue Linckia, which has been active for the past few weeks since I bought him, and he's becoming less and less active.  In fact, he's been in the same position for 2 days. is this normal? <Not atypical for them to be still for quite a while at times>   I have not target fed either star, since I read somewhere that they will find their own food.  My tank is a 29 gallon with about 50 pounds of live rock. <... oh my friend... this is MUCH TOO small a system for one of these stars> My soft corals, polyps, and fish are doing really well. Thanks in advance for any information you can give me! Vernon <Vern... do take a read through WWM... it's obvious you have not. Bob Fenner>

Sea Star biochemicals 1/4/05 Hi, I am a fifth grader and have a question that needs an answer. I hope you can help. Do sea stars have fungus grow on them and if not why? Thanks for your help. Christian <Hi, Christian. I think your good question speaks to the attributes of sea stars having biochemical abilities that reduce or kill bacteria and other pathogenic organisms. There have been studies done on this subject. Let me suggest that you some key-phrase google.com searches for "sea star, starfish, biochemical defense" in various combinations. Best of luck! Anthony

Linckia grabbin' air - 12/2/04 Hi, <Hey, man!>     We have a purple starfish, I believe Linckia. Fish store owner claims he has had great luck with them when acclimated properly (which we did). <There is a lot to acclimating these starfish.>  I read they should not be exposed to air. <Well, they should not get air bubbles trapped near their mouths> Each morning he goes close to the top of the SW tank and his rays go partially out of the water, <Normal activity> I gently moved him (without touching him with my hand) and then he went another direction. He's done this two mornings in a row. <Normal behavior>  I'm afraid I'll hurt him but also afraid the air will. <The air will not. This would be a great opportunity to feed him some small mysids or frozen krill>   We have a 125 gallon.  About 80 pounds of live rock and you've helped us before. (Thanks!) <What we do> The tank has been going for over a year.  I've searched articles but couldn't find a similar question.  Thanks. M. DeNeff <Thanks for participating. ~Paul>

Re: starfish Thanks!  He seems fine.  His behavior is the same each morning.  I will try to feed him. <Real good. Do search on the net for more info. re (key term) your "Tamaria stria". Bob Fenner>

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