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Lanman's Acropora-Eating Flatworm (AEFW) Thread


lanman

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In early September, 2009, I discovered that I had AEFW on some corals in my 240-gallon display tank. For several reasons (among them the fact that a photographer was coming in a couple of weeks to take pictures for my October WAMAS TOTM selection), I did not immediately take drastic action to try and get rid of them. Once I got used to the idea that I had an infestation, I decided to take the opportunity to study them, and gather more information. Information about Acropora Eating Flatworms, other than how to kill them, is not as available as I had expected it to be. In fact, very little was known about their life cycle, and we're not even sure what family of polyclads they belong to.

 

I am not a biologist, just an interested hobbyist. But during the course of my infestation I did learn to preserve specimens in alcohol and formalin for DNA and histology studies. I gave these specimens to a biologist (Eric Borneman), and hopefully he and a researcher interested in flatworms (Kate) will add to the available information.

 

Most of the information I will be posting in this thread was previously posted in a thread in the 'members only' section of the WAMAS forums. Knowing the limits of my abilities, I didn't want to post incorrect information in public. This way, I can skip such errors as identifying a flatworm as 'juvenile AEFW', only to find out later that they were an unrelated acoel flatworm.

 

bob

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Identifying the problem.

These are Acropora-eating flatworms. They are quite good at camouflaging themselves. But it does not appear that they can 'change color' to match their background. AEFW appear to slowly 'take on' the color of the coral that they are eating. When they are not eating well, they become white. AEFW reach a maximum size of about 3/8" (1cm) when stretched out a bit, with 1/4" being common.
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Ventral view:
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The damage done to corals by AEFW shows up as small round 'bite marks'. The more AEFW there are on a branch of coral, and the longer they have been there, the more noticeable the damage. If you have corals that show 'lighter areas', look more closely. The bite marks are very distinctive.
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Eggs:

Each AEFW egg contains multiple larva. They lay a LOT of eggs when they reach maturity. Each flatworm has both male and female reproductive organs. This is a picture of a gravid AEFW - the eggs can be seen in the ovaries:
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The eggs are layed on dead coral tissue, rock, and frag plugs - never on live tissue. Look on the bottom of your frag plugs. The eggs are tiny - about 1mm in diameter, but are usually in 'clusters', which makes them easy to spot under a magnifying glass.
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Note the white, crystalline substance the eggs are laying on and in. This is secreted by polyclad flatworms, and seems to act as a glue. It is very hard.

bob

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(edited)

So what can you do about AEFW?

 

I tested killing AEFW with Potassium Permanganate, Revive, Flatworm eXit, and crushed garlic tablets (garlic dip!). All except eXit killed AEFW. I only tried eXit up to 3 times the recommended dosage - because I figured for a full-tank treatment with any dilution stronger than that there would be a rather large investment if trying to treat a 240-gallon tank. Others have claimed that eXit at stronger concentrations killed AEFW - but 3x the recommended dose didn't even seem to slow them down. My notes will be posted below, but most people are just going to want a summary.

 

Potassium Permanganate in the concentrations I tried certainly killed flatworms. But it seemed to be quite harsh on the corals as well. This bears further experimentation.

 

The garlic dip is excellent - but I was hoping for a 'whole tank' treatment with this, and it would have taken about 500 crushed tablets - and leaves a white 'precipitate' behind. The nicest thing about the garlic is that it doesn't seem to cause any stress to the corals at all. Corals survived even after an hour in it. If I had a good light over the dipping tub, some corals would extend their polyps while bathing in it. It also doesn't kill 'pods' or hermits. I forgot to test it on snails. The recipe will be posted separately.

 

Revive seems to be the best choice, among the treatments that I tried. 15 minutes in Revive at the recommended dosage, followed by some good agitation of the water will knock all of the flatworms off. They die within an hour if you leave them in the Revive solution. I do not recommend dipping corals in Revive for over 15-20 minutes. While I didn't document it well, it seemed that corals dipped for 30 minutes would start to STN from the bottom up within a few days after their return to the isolation tank.

 

I was unable to determine if any of the above solutions killed the eggs. I set up a separate 'flatworm system' to try and figure this out, but despite regular water changes, all of the corals in the system lost tissue and died, and the system became a real mess before I could determine if the eggs were still viable. Now that I have refined my procedures considerably, I will try to make this determination if I encounter any more AEFW and eggs on any of my frags.

 

AEFW life cycle:

I allowed a frag plug with a lot of AEFW eggs on it to hatch and grow. It appears that AEFW have a very long incubation period - 3-4 weeks. It takes another 2 weeks for the AEFW to reach a size where they start munching on corals (about 1/8"), and about another week until they are mature enough to start laying eggs. By 4-5 weeks, the AEFW is reaching old age, and it appears that the adults all die before their eggs hatch.

 

So what does all this mean as far as 'curing' your AEFW problem?

 

The simplest (quickest) solution is to remove only healthy coral from your colonies or frag plugs, dip them once with agitation for 15 minutes in Revive, mount them on new, uninfested rock or frag plugs, and quarantine the original, possibly egg-carrying rock and frag plugs for a few months before inspecting and re-using. For your nicely encrusted frags and colonies, this is somewhat like 'starting over'. But the alternative is weekly dips of the entire colony and the rock attached to it in Revive for 5 weeks, and no cross-contamination from other corals that might have egg-laying adults (which could crawl over and deposit a few eggs on your treated corals/rocks). For new corals that you purchase or receive in trade - follow the same procedure of removing the coral from the rock or frag plug, ensuring that there is no 'dead' coral skeleton, dipping, rinsing and re-mounting.

 

I will follow this with posts of my testing procedures, dilutions, etc.

 

bob

Edited by lanman
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Experiment #1 - Revive! (Sep 22, 2009)

Mixed one quart of Revive according to directions on the label - 4 capfuls per gallon.

Put a frag of acropora nana with a flatworm and some eggs in a cup.
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00:00 - Added Revive

00:15 - Flatworm writhing in obvious distress - let go of coral at all but one attachment point.

00:30 - Flatworm falls to the bottom of the cup. AND - so did one that I hadn't seen. Copepods are writhing on the bottom of the cup, as well.
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03:00 - Flatworms still moving in distress.

15:00 - Coral rinsed and returned to saltwater. No signs of distress - no sliming, etc. Eggs still there, but who knows if they are actually viable at this point:
gallery_2631296_1352_23071.jpg

15:00 - Flatworms still moving - returned to salt water. Copepods still moving, but almost dead.

30:00 - Flatworms still moving.

45:00 - All movement has ceased. They're dead, Jim!

Conclusion - Revive will kill flatworms with a 15-minute soak, even if they don't really die for another half hour or so. However, it only takes a few seconds to get them to release their hold on the coral. I think 15 minutes in Revive will be safe for almost all corals.

It would appear that repeated dips in Revive until there are no more eggs or flatworms would be a successful cure.

bob

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(edited)

Experiment #2 - 25mg per liter Potassium Permanganate

 

Used a jeweler's scale to measure out 25mg of Pot. Perm. and added it to a liter of water. VERY purple!!

 

Selected a frag of Davelin's xmas tree acro with a really big flatworm on it, and a lot of eggs.

 

Put the piece of coral in an 8 oz cup, and added enough solution to cover it.

 

00:00 - Can't see the darned flatworm because the purple is so dark!

 

00:30 - Shook the coral a bit in the solution - and the big flatworm, and one small one fell off to the bottom of the cup.

 

01:00 - No sign of movement from the flatworms. They never moved again.

 

15:00 - Removed coral and flatworm corpses to clean saltwater, and rinsed.

- Coral shows no obvious signs of stress, but will have to wait until tomorrow and see if it has polyps.

- Flatworm corpses were basically disintegrating.

- Eggs did NOT dissolve - but they are dark brown in color, and may no longer be viable.

 

Based on the rapidity with which the flatworms died - I am going to try again tomorrow with a solution of 10mg/liter.

 

 

Update on experiment #2 - Pot. Perm. at 25g/Liter. (24 Sep 2009)

 

Coral frag looks VERY beat up today - a lot of missing tissue. I don't recommend this for killing AEFW on Acropora. Montipora's must be hardier. Will try 10g/liter, and maybe a shorter dip, if the FW's die as quickly as they did in 25g/liter.

 

bob

Edited by lanman
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Hey Guys, let's leave this thread alone while Bob finishes his updates on it. I have raised the question of where the best place to put this thread is with board administrators so give us a chance to figure it out and then we'll put it where it belongs (and keep it available to everyone including bulletin board members).

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More information on Potassium Permanganate experiments:

This is what Potassium Permanganate looks like at 25mg/liter:
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Flatworm on Davelin's xmas tree acro. I am including a lot of these so people will be able to recognize them.
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Eggs before treatment with Pot. Perm. at 25mg/liter:
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Eggs after treatment at 25mg/liter. Note how brown they are:
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Today's treatments were Pot. Perm at 10mg/liter, and 5mg/liter.

At 10mg/liter:
00:00 Added Potassium Permanganate at 10mg/liter.
00:30 Flatworms released from coral immediately, but were still moving on the bottom of the cup for a while.
06:00 Removed coral from treatment and rinsed in saltwater. Put the frag in the isolation system. Will wait and see how it looks tomorrow.

At 5mg/liter:
Cut off a small frag with 1 AEFW on it:
gallery_2631296_1352_8179.jpg
00:00 Added Pot. Perm at 5mg/liter.
00:30 Flatworm released one end from coral (similar to Revive):
gallery_2631296_1352_20637.jpg
01:00 Flatworm released from coral and dropped to the bottom of the bucket. Still moving, but obviously dying.
03:00 Removed coral from treatment and rinsed in saltwater. Put the frag in the isolation system. Will wait and see how it looks tomorrow.

Hoping that one of these dilutions will actually leave the coral healthy. Potassium Permanganate is much less expensive than Revive - especially at 5mg/liter. A lifetime's supply is about $20.

Update: Because the temporary system I put these corals into did so poorly, I can't be sure if the deaths of the corals was due to the Pot. Permanganate, or the water quality. This part needs to be repeated with healthy corals and a healthy coral system to determine what the effect of Pot. Permanganate on corals really is.

bob

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RESULTS OF TRIALS TO KILL ACROPORA-EATING FLATWORMS WITH GARLIC TABLETS Oct 11, 2009

 

1 Tablet/cup of water.

One crushed tablet of Allicin 6000 (Vitamin Shoppe store brand) was dissolved into a cup of tank water. Allicin is the active ingredient in garlic, and the tablets claim to have 6000mcg of Allicin Yield per tablet. Tablets also contain Thiosulfinates and Sulphur. $13.99/100 caplets.

A small frag of acropora nana with one Acropora-eating flatworm (AEFW) was placed into the solution.

00:30 - AEFW stressed, writhing on coral.

01:00 - AEFW hanging by one end from coral - not moving.

02:00 - Dislodged AEFW from coral with gentle agitation

05:00 - AEFW obviously dead already. Coral rinsed and returned to tank. Coral looks fine.

45:00 - Coral looks healthy and polyps are extended.

============================================================

1 Tablet/liter of water.

One crushed tablet of Allicin 6000 was dissolved into a liter of tank water.

A small frag of acropora nana with one Acropora-eating flatworm (AEFW) was placed into the solution.

01:00 - AEFW falls off of coral - writhing in obvious distress.

05:00 - AEFW is on the bottom of the cup, still writhing in distress.

10:00 - AEFW is writhing very slowly on the bottom.

15:00 - AEFW shows very occasional movement. A small copepod that was on the frag is swimming happily about, and seems to be eating the precipitate. This copepod survived the treatment unscathed.

30:00 - AEFW appears dead - not moving, even in response to stimulus.

60:00 - Coral frag appears to be healthy, and polyps are extended.

===========================================================

1/2 Tablet/liter of water.

One crushed tablet of Allicin 6000 was dissolved into 2 liters of tank water.

A small frag of acropora nana with one Acropora-eating flatworm (AEFW) was placed into the solution.

01:00 - AEFW drops off of the coral, and is writhing in distress on the bottom of the cup.

05:00 - AEFW is laying flat on the bottom, occasionally moving.

10:00 - AEFW is still moving.

30:00 - AEFW is still moving. Coral removed, rinsed, and returned to tank. AEFW removed, placed on a piece of plastic, and pictures/movies taken. Returned to solution.

60:00 - AEFW moves slowly in response to stimulus.

90:00 - Still shows occasional small, jerky movements.

180:00 - Still shows occasional slow involuntary movements - but as good as dead. Coral looks to be in excellent condition, with polyp extension.

**I think this dilution is excellent for dipping corals for 30 minutes.**

======================================================

1 Tablet/gallon of water:

One crushed tablet of Allicin 6000 was dissolved into 1 gallon of tank water.

A small frag of acropora nana with two Acropora-eating flatworms (AEFW) was placed into the solution.

05:00 - AEFW's don't appear to be distressed.

20:00 - AEFW's are crawling around on the frag - much faster than usual; appear uncomfortable.

30:00 - One of the AEFW's released one end, and is in apparent distress. The other is still crawling.

40:00 - One AEFW fell off the coral with gentle agitation. The other came off - but vigorous agitation was required.

60:00 - Removed one AEFW for pictures and movies, and returned to solution. Rinsed and returned coral to tank.

100:00 - One AEFW is dead. Oddly enough, it is the one that required some effort to get it to release from the coral. One is still crawling flat on its belly - apparently not too badly hurt.

180:00 - One still obviously alive. While this dilution will loosen them up; it can't be counted on to kill them. But the coral frag looks good, even after an hour in the solution.

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RESULTS OF TRIALS TO KILL ACROPORA-EATING FLATWORMS WITH Salifert eXit. Oct 12, 2009

 

Following directions, I added one drop of Salifert's Flatworm eXit to 5 liters of tank water (direction call for 4 drops per 20 liters), and mixed well.

A small frag of acropora nana with at least three Acropora-eating flatworms (AEFW) was placed into the solution.

05:00 - AEFW are acting normal.

15:00 - AEFW are acting normal.

30:00 - AEFW are acting normal.

31:00 - Added two more drops to the 5 liters of water (triple dose), mixed, and replaced the solution in the treatment container with the triple-strength solution.

35:00 - AEFW are acting normal..

45:00 - AEFW are acting normal.

60:00 - AEFW are acting normal. Poked one, just to be sure it hadn't died in place. It responded normally to stimulus, running off across the coral.

**Conclusion - eXit doesn't harm Acropora-eating flatworms in any reasonable dosage.**

 

bob

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It looks like my infestation may be over. The last coral that I knew had AEFW in one of my frag systems has been chopped and cleaned, and the last few AEFW adults were preserved in Formalin. I'm sure as I start putting my display system back together, I will find a few more - but I know enough about them now that I should be able to keep from having any further infestations. As soon as any of them reach adult size now, I can spot the bite marks, and know a coral has them.

 

The strangest thing to happen during all of this is that my display tank never had a re-infestation. Plenty of time has passed for any eggs from the initial infestation to hatch and grow up - but the few remaining acro's in the display tank show no signs of them. No bite marks, no AEFW. I have no idea if I 'got lucky' and pulled out every coral with eggs on it, but it seems unlikely. They just didn't hatch and grow up.

 

Through all of this - I lost no corals to AEFW. I lost corals to being moved around from tank to tank, and from over-long dipping, too-harsh dips, etc. But the AEFW damage corals pretty slowly. They are pretty fragile creatures, and rarely survive more than 24 hours in a cup of water at room temperature. They have a tendency to just 'dissolve' (autolyse) when they get stressed.

 

I gave Eric Borneman preserved flatworms for DNA and histology studies, and passed on my observations to him and the researcher that plans to write a paper on them (Katharine). Hopefully within a year this will be published to add to our knowledge of these things.

 

Thanks to everyone for their support!

 

bob

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  • 4 years later...

^^LOL. I remember that tank. It was the first coast-to-coast (Calfo) overflow that I'd seen first hand. Good memories.

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