baby star fish?!?!?!
- Thread starter brazilian
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:yay:
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Asterina starfish. Some species will kill zoas so I would opt on the side of caution and remove it. Most however are beneficial so you could roll the dice and most likely you'd be just fine.
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Personally, I think this is a whole "chicken or the egg" type of deal. I personally dont think asterinas are harmful at all ( as I feel about bristleworms). yet, there is always a claim that someone watched it eating a coral. Was the coral dying so the star ate the dying tissue, or was the tissue dead because the start ate it? Personally, I beleive the former, but it is just my opinion.
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I've seen the asterina starfish kill zoas in my own tank. I had been having an issue with some zoas dieing. Sometimes they would end up inverting themselves... and sometimes they would just close up never to open again. I couldn't locate any of the usual zoa bugs so I was watching the tank late at night for whatever had been harming them. I watched in fascination as an asterina cruised over 3 polyps of bambams and paused on each one for a few minutes. I then removed it from the tank and kept it in a cup.
Those 3 polyps shriveled up and died over the next few daysand never opened up again. The rest of the colony was fine. All the polyps the day before were open as well. Could it have been that those 3 polyps were going to die anyways? That could be but I don't think so. So, I continued to watch my zoa colonies carefully and saw the same thing happen on two other separate occasions. Darren also reported seeing the same thing with some zoas in his tank and took the drastic step of removing the stars entirely which solved his zoa die-off.
So, I went postal and started removing the stars from the tank. I found that there were actually 3 different species of asterina in my tank. They look similar but they are different. Only one of those species harms zoas and it may not even do it intentionally. The perpetrator clearly can be found grazing on bare rock and on the glass. It is however most commonly found on the rocks. I don't know exactly what it eats, I imagine it eats film algaes and may simply be killing zoas to create more grazing room? I dunno, but I don't think it directly derives nutrients from the zoas.
What I do know is that after removing this particular species I stopped having zoa die off. I left the other two species in tact as asterina are general very benefitial to the tank. In my opinion this particular species was the cause... and unfairly gives the whole genus a bad rap. That is of course my opinion from personal observation. I wouldn't have suspected them at all though if others like Darren hadn't shared their findings.
Those 3 polyps shriveled up and died over the next few daysand never opened up again. The rest of the colony was fine. All the polyps the day before were open as well. Could it have been that those 3 polyps were going to die anyways? That could be but I don't think so. So, I continued to watch my zoa colonies carefully and saw the same thing happen on two other separate occasions. Darren also reported seeing the same thing with some zoas in his tank and took the drastic step of removing the stars entirely which solved his zoa die-off.
So, I went postal and started removing the stars from the tank. I found that there were actually 3 different species of asterina in my tank. They look similar but they are different. Only one of those species harms zoas and it may not even do it intentionally. The perpetrator clearly can be found grazing on bare rock and on the glass. It is however most commonly found on the rocks. I don't know exactly what it eats, I imagine it eats film algaes and may simply be killing zoas to create more grazing room? I dunno, but I don't think it directly derives nutrients from the zoas.
What I do know is that after removing this particular species I stopped having zoa die off. I left the other two species in tact as asterina are general very benefitial to the tank. In my opinion this particular species was the cause... and unfairly gives the whole genus a bad rap. That is of course my opinion from personal observation. I wouldn't have suspected them at all though if others like Darren hadn't shared their findings.
I would remove it. It is not worth taking the chance. I second what Jin said. I had them in my old tank and lost a lot of zoos. Ever since I moved the zoos to my new tank I haven't lost any. I often saw these astrina stars wrapped around different zoos in my tank. I used to have to pick them off.
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Interesting account. I find it extraordinarily unlikely that this animal (without a brain), is clearing land for culture of a food source. As a mobile invertebrate, if it is killing them, it is likely eating them too 9or a product of them - ie- slime, feces, etc). From an evolutuionary biology standpoint, it is very difficult to believe that these species of starsthat appears so similar in size, shape, etc., can have such dramatically different functional biologies. One as a herbivore, and another grossly similar, near identical one, as a invert predator.
Nonetheless, if it makes you uncomfortable, remove them. Their benefit, if any existed, is likely marginal or negligent.
Jin, what made the "zoa killer" species look different from the "harmless' ones?
I have some asterinas that like to live on the acrylic of my 6 gallon where I was losing zoas, but I didn't suspect the asterinas b/c they were living off a film on the acrylic and not crawling over the zoas (that i could see, but i wasn't looking that hard)
I have some asterinas that like to live on the acrylic of my 6 gallon where I was losing zoas, but I didn't suspect the asterinas b/c they were living off a film on the acrylic and not crawling over the zoas (that i could see, but i wasn't looking that hard)
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Jeremy - Clearing space is just a theory I threw out there on a whim 
. I really can't say exactly why or even how they have a detrimental effect on zoas. All I can really do is try to draw reasonable conclusions from my observations. I do believe though that they are primarily film algae eaters like every other asterina and for some reason happen to kill zoas when they cross paths. Whether they kill due to predation or incidental to their regular biological functions is beyond me. I think its more of the latter than the former. There's so much we don't know... its frustrating.
Soarin - I'll try and dig up some pics for you. I didn't really document any of this myself but I'll look for representative pics online.
. I really can't say exactly why or even how they have a detrimental effect on zoas. All I can really do is try to draw reasonable conclusions from my observations. I do believe though that they are primarily film algae eaters like every other asterina and for some reason happen to kill zoas when they cross paths. Whether they kill due to predation or incidental to their regular biological functions is beyond me. I think its more of the latter than the former. There's so much we don't know... its frustrating. Soarin - I'll try and dig up some pics for you. I didn't really document any of this myself but I'll look for representative pics online.
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