Id please, three legged starfish

[rwreef]

I found several of these on my rocks. I noticed them once I saw white spots on my rocks where coraline algea had been eaten. I am sure there are more and wondering if they are friend or foe. Any help is appreciated.

 

[bradreef]

Asterina star. Pest but not to bad

 

[rwreef]

Asterina star. Pest but not to bad

I have noticed some of my zoanthids receding, I bet it's these little dudes! Grr thanks!!

 

[Jekyl]

I have noticed some of my zoanthids receding, I bet it's these little dudes! Grr thanks!!

It's not. Had hundreds in my tank and they never contributed to a coral issue. I think it's a myth.

 

[ISpeakForTheSeas]

I have noticed some of my zoanthids receding, I bet it's these little dudes! Grr thanks!!

It's not. Had hundreds in my tank and they never contributed to a coral issue. I think it's a myth.

In this specific case, it might be, as Aquilonastra stars with that dark of a body color are pretty uncommon:

I've heard some species eat corals and others don't - I've seen convincing evidence for one species (a very darkly colored one - hence why I say they might be an issue in this specific instance), and one piece of somewhat convincing evidence for one different species, but the vast majority of these guys seem to be at least mostly safe.

With regards to whether or not the average "Asterina" (technically Aquilonastra - Asterina is a separate genus within the Asterinidae family) eat corals, it might be a species specific thing, it might be a you have way too many starfish so they're out of other food options thing, it might be they're eating the slime coat/mucus on the coral rather than the coral itself (see below), or they might just opportunistically eat unhealthy corals. Based on how starfish eat, it seems plausible to me that it may also be coincidental (i.e. the star goes to eat something off the coral and the coral just happens to be one that is able to be negatively effected by the star's everted stomach). Regardless, Zoas are just about the only coral I've heard about regular "Asterina" stars potentially going after with any sort of frequency.

A quote I like to refer to for this:

Timfish said:
It's an Aquilonastra spp. starfish and is a great scavenger. I see them with anywhere from 4 to 12 legs. The whole discusion around them seems to me excellent examples of misidentification, mistaken behaviour and assumed causality based just on heresay without looking at the research. Asterina spp starfish are preditary but only reproduce sexually and are shortlived so while it's possible some might get into a tank even if it did happen it's not going to be around long. Aquilonastra are one of the uncommon species that reproduce fissiparous or by splitting so are easy to identify by the different sized legs regrown after splitting. They perform an important function not only feeding off algae films but also feeding off microbial films including those on corals (at least ones that don't sting). FYI the mucus coating on corals ages and corals have to periodicely shed it to renew it and maintian healthy microbial processes (Ref 1, Ref 2). If Aquilonastra are feeding on zoas or softies I'll argue they are either benign or even beneficial as they may be reducing the unhealthy older mucus which can be full of unhealthy microbes which the animal is trying to get rid of and are far more likely to be the actual problem.

Here's an example, this Toadstool is doing one of it's periodic sheddings. The Aquilonastra have been in this system for years but only climb onto the Toadstool when it's shedding. In the first picture you can see the old mucus film, Aquilonastra starfish and areas they have cleaned off. The second picture shows the Toadstool a week later.

 

[vetteguy53081]

These breed like mice, will get into your intakes and plumbing and simply break a leg why it looks like three legs and reproduce into another eventually over-populating the tank and often eat zoa coral. Remove while you can by hand or net off of glass

 

[I never finish anythi]

These breed like mice, will get into your intakes and plumbing and simply break a leg why it looks like three legs and reproduce into another eventually over-populating the tank and often eat zoa coral. Remove while you can by hand or net off of glass

Does anything eat them ?

 

[ISpeakForTheSeas]

Does anything eat them ?

Harlequin shrimp do, bumblebee shrimp might, and larger stars (such as Linckias) do too. Harlequins are the most effective.

 

[vetteguy53081]

Does anything eat them ?

Harlequin but very slowly and Bumble bees are hit and miss (may or may not)

 

[rwreef]

Absolutely eating a healthy zoa colony. I will look into getting a shrimp. However I have a blue headed fairy wrasse that may like a shrimp for. Snack.

 

[Tired]

Harlequin shrimp will starve when you run out of starfish. Manual removal is probably a better option.