Xenia Parasite?

[ejls]

Dr Shimek,

Firstly apologies for bothering you like this. By my (admittedly guesstimated) logic this should still be Wednesday on your side of the pond. If not please feel free to ignore this/me :) I also apologise for giving some doubtless irrelevant information below. I just want to give as much info as possible to assist in any identification.

While looking at my tank earlier tonight I noticed some of the stalks of my white pulsing xenia were not as extended as others and the individual polyps were retracted and not moving. The remainder were looking extremely happy.

Upon closer examination I noticed areas on the contracted stalks which looked swollen and distended. The lines which run smoothly up and down the min bodies of the other stalks were blurred and not parallel and the outer "skin" looked more transparent on this patch compared to the rest.

While staring at it Iobserved some movement. It appeared to be a copepod sized creature on the stalk of the xenia itself. I discovered several others and they were only present on the stalks which were contracted.

I removed them with a pippette and pot them in a vial. I cannot get photos of them yet but my girlfriend is a doctoral student (plant biology) and she's going to try to get some hi-res photos through one of their microscopes tomorrow.

They appear to be around 1mm long and maybe half that at their widest point. Roughly elipsoidal (front to back) with the widest point of the elipse towards what I believe is the front end. In the tank it looked as though they were lifted roughly 1/2mm from the xenia on legs and may posses a pair of small antennae on the front. They are the colour of my LR, a sort of browny grey.

I am unsure whether:

a) these are the cause of the sporradic xenia contractions which has been occuring for a few days now

b) they are opportunistic feeders on the dead/dying flesh from injury/illnesses caused by some other factor

c) they are completely unrelated to the contractions and I'm merely noticing them because I'm looking for something

So far I have caught three and will endeavour to catch some more should they appear.

Which of these potential situations do you feel is most likely and could you offer any help with identification should I be able to get the hi-res photos?

Many thanks in advance for your time, next time you're over this side of the pond I'll buy you a pint!

Edward

_______________________________________

Tank stats:
5 USG total sys volume
81 Degrees F, 1.026 SG,
Ammonia, Nitrite, Phosphate all 0ppm
Nitrate 0.5ppm

No motile inhabitants save for 3 dwarf blue legs (suspect Nos 2, 3 and 4) and some bristle worms (6-8" long, red-pink, white bristles and antennae)

Other corals: Sarcophyton, Euphyllia, Montipora, Mushrooms, Blasto, Tubipora musica, Trumpet

[Travis L. Stevens]

I would check into Munnid Isopods. I had something very similar happen to me with my Kenya Tree, another soft coral. When they finally disappeared the Kenya tree was still alive and well, but it stayed contracted for several days resulting in an unhealthy but recoverable coral. That's just my thoughts, but I could be completely wrong here.

[ejls]

Thanks Travis, I'll go do some research. WHatever thy are I've decided I don't like them :(

[rshimek]

Hi,

Almost certainly they are not munnid isopods. Munnids are, amongst other things, not ellipsoidal. Without an image, I am rather dead in the water, but my guess would be some sort of copepod. There are lots of parasitic copepods found on various of the cnidaria. If these are truly ecoparasitic, they could be causing the problems.

However, there are a lot of commensal animals living on cnidarians. To these animals the cnidarians are just so much substrate, and they are not harmed by the bugs.

If you can get some good images of the animals, I might be able to steer you to some sources that could provide a reasonable answer. Your three hypotheses about them are all equally likely at this point, I think. However, my guess is that if you only have found 3 of them, they are unlikely to be the cause of the problem.

[ejls]

Thanks so much for your reply. I'm sorry not to have received an image by now but there was apparently a rather large queue for the microscopes on Friday. I'm hoping we can get some space on the SEM on Monday if you would like some REALLY hi res images.

However I think you might be right in thinking that they are not the cause. I've since found more of them (around 40 thus far) and while they do seem primarily congregated around the unhealthy xenia they are also present around the healthy stalks. I ran a further assay on 10 random locations around the tank and found them in several other places but in much lower concentrations.

Right now I'm setting up a 2USG tank with a single xenia stalk and a lump of the same LR the xenia lives on in my tank in it. I'm going to place some of the unidentified pods in a bit later and se if they tend towards either the LR or the Xenia. Furthermore, if the latter I'll see if it seems to be harmed by them.

Many thanks once again Dr Shimek and I'll keep you posted of the results.

Edward

[rshimek]

Hi Edward,

Well, more of them with the characteristics you describe might indicate that they are not causing problems, but there is still that possibility. I do suspect they may be more scavengers of damaged tissue than anything else around the Xenia, but... .

I really don't need SEM shots of them, but they would be okay, provided the fixation and drying go okay. Light microscopy would be a better first step as it would give some indications of internal anatomy as well.

[ejls]

I'll try to get Katharine to take some shots on Monday then. The SEM idea was more because I was interested to see what could be done. It'd have to have been done using the Engineering department's unit anyway which would have been interesting to explain.

"ERm... why yes this is critical research for a nature paper and is well within the remit of a plant sciences depatment PhD student... Honest"

Many thanks once again for your continued help!