Zoa eating “asterina” starfish experiment

[nycfreshreef]

Interesting perspective

After noticing an “asterina” starfish (I actually believe the are a different species) population starting to grow in a 1.5 year old mixed reef - I kept a close eye on my 2 colonies of illuminati zoas (as I started to see the asterinas sitting on zoas)

I was able to see 1 asterina star sitting on top of the Illuminati colony to the left that would move from polyp to polyp over the course of about 2 weeks while the Illuminati colony on the right remained completely free of asterinas

Since they are the same exact species of zoa , same size , same age , and from the same mother colony (as well as they are in the same tank conditions / par etc)

It was interesting to see what the actual effect of the asterina on the zoa was

These photos are from today (the left side Zoa has so far had a few weeks to start healing) as the asterina left once it was finished sitting on each polyp of the colony


But basically when the asterina had just finished sitting on the colony …. And moved off it , the zoas looked really bad , they had lost a lot of color (seemed to also have lost their lashes) and the stalks were shriveled up / the zoas lost a lot of size overall , all became sickly looking / etc while the exact same colony on the right (with no asterina) had no issues

So my conclusion is based on this limited comparison is , that these asterinas done eat the entire zoa , but they do some sort of damage , maybe eating parts of it which could in theory cause a colony to melt or other unforeseen issues

Last photo is the “asterina”

 

[ISpeakForTheSeas]

Yeah, they're technically Aquilonastra starfish (Asterina being another genus from the same taxonomic family), and there are 32 accepted species in the genus currently - some seem to damage zoas while others don't, but we haven't identified which are safe and which aren't yet.

So my conclusion is based on this limited comparison is , that these asterinas done eat the entire zoa , but they do some sort of damage , maybe eating parts of it which could in theory cause a colony to melt or other unforeseen issues

Them eating from just one colony of the zoas despite having two colonies of the same variety is interesting - to me, that would seem to indicate that they're either feeding on something that's only on the colony and not the other (such as specific bacteria species or biofilms), or that the other colony may be more toxic or something.

Given that they don't seem to be eating the full polyp/coral and the faded color mentioned, I'm currently inclined to think they're feeding on biofilm on the colony, and that their everted stomachs happen to be digesting/damaging parts of the zoas in the process.

Interesting stuff, and great observations!

 

[nycfreshreef]

Yeah, they're technically Aquilonastra starfish (Asterina being another genus from the same taxonomic family), and there are 32 accepted species in the genus currently - some seem to damage zoas while others don't, but we haven't identified which are safe and which aren't yet.

Them eating from just one colony of the zoas despite having two colonies of the same variety is interesting - to me, that would seem to indicate that they're either feeding on something that's only on the colony and not the other (such as specific bacteria species or biofilms), or that the other colony may be more toxic or something.

Given that they don't seem to be eating the full polyp/coral and the faded color mentioned, I'm currently inclined to think they're feeding on biofilm on the colony, and that their everted stomachs happen to be digesting/damaging parts of the zoas in the process.

Interesting stuff, and great observations!

Thank you for the taxonomy - they are a genus I am not too familiar with - but I tend to agree with you that they must be eating some sort of film or maybe mucus from the Zoa and damaging it somehow in the process - I think they may eventually make their way to the other colony if their numbers get high enough (right now they are still pretty low in numbers) only see 1 or 2 on the glass at any given time and maybe a dozen if scouring the tank looking for then at any given time

So I believe probably they would snack on the other colony as well just haven’t made their way to it yet

But another thing that is interesting to me is how the one animal managed to reach every single polyp of the colony , systematically (I was doing my best to keep track) but don’t think he missed a single polyp