I try to encourage sponge growth in my tank because I quite like them and are also fascinated by them, however there's one particular sponge that's been giving me cause for concern recently. It hitchhiked into the tank on the shell of the large thorny oyster 9 months ago. When it first arrived it was a tiny white blob but as time has gone by it's turned grey and grown bigger. By the end of January 2022 it had completely obscured (killed?) the purple tunicate that had been growing behind it and was spreading over the thorny oyster shell as well as in front of the right side of the Frond oyster. I was beginning to wonder about the identity of this sponge, could it be the dreaded chicken liver sponge? Apparently chicken liver sponge can be invasive, growing over/killing corals and it should be removed as soon as seen. This is what the sponge looked like as of last week. I scoured my books and the internet for information on grey sponges and came across Chondrosia reniformis (aka kidney sponge). This species can be mottled brown to grey in colour *check*. Grows into smooth, irregular kidney-shaped encrustations, *also check*. What particularly caught my eye though is that colouration depends on light intensity, the brighter the illumination the darker the sponge and that is exactly what I have seen with this one. It started off white and over time has turned dark grey. I assume in the wild the sponge/Thorny oyster came from a shaded location and now in my tank is pretty much under full lighting. There is a similar species named Chondrilla nucula (chicken liver sponge, uh oh!) which is also a possibility but I'm leaning more towards the first species at this point.
I'm quite fond of bivalves as well as sponges, if things continued as they were the sponge would probably grow over the Frond oyster preventing it from feeding most likely resulting in its demise. Given the choice between the two I'd rather keep the former and loose the latter. Also if this sponge really is invasive then much more would be at stake eventually. C. reniformis is described as leathery and uses collagen fibres for support instead of calcareous spicules etc so I rather naively assumed that I could simply peel it off the shell. I tried this with a pair of tweezers but all I did was puncture the sponge in several places causing the release of some unknown grey liquid. Clearly removal was not going to be quite so simple. Also the following day I noticed that the coralline algae growing in the vicinity of the sponge was now dying off. Coincidence? I think not! Some sponges are said to be toxic to keep from being eaten so perhaps this was one of those. Also the sponge seemed not to be bothered by multiple stabbings with a pointy pair of tweezers. Plan B was to perform surgery outside of the tank in case there was a chance of any more toxins being released. I detached the spiral coral, no point in risking that too, and moved the oyster shell over to a bowl containing some tank water. I then proceeded to pick off the sponge bit by bit, when most of it was gone I scrubbed the entire area with a stiff brush. After rinsing off with some additional saltwater I plopped the shell back into the tank and crossed my fingers. A quick check with the magnifying glass did show some tiny bits of sponge still remaining on the shell, hopefully they will die off in a couple of days. The Frond oyster survived the scrubbing ordeal and was opening up again not long after being back in the tank, the Jewel Box clam however took a couple more days to feel comfortable again. It seems to be fine now thankfully. I am yet to see the feather duster reemerge, I hope I didn't squash its tube. Fingers crossed I have dealt with the sponge, either that or I've spread it around the tank. Eeek!
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It's been seven months since I introduced a pair of thorny oysters to my tank and I am sad to report that they just didn't last. The larger one died after a couple of months and the smaller one followed suit a week later. I must assume I wasn't supplying enough of the right kinds of food to sustain them or they just didn't acclimate well to my tank. It's not all doom and gloom however, some of the organisms that came attached to the outside of the larger oyster's shell are still alive. The Frond oyster, Dendostrea frons, on the top of the shell is still opening and closing, which is very cool. As is the jewel box clam (Chama sp?) at the back. This is the only photo of the clam I have taken so far, it looks the same now as it did back in July, well it's covered with a bit more coralline algae and vermatid snails now. The vermatid snails are everywhere now and they are becoming rather annoying. The other smaller bivalves have survived too along with some of sponges etc. The sponge coverage is a lot less that it was at the beginning but some bits are holding out on the more shaded areas of the shell. The grey 'blob' growing to the right of the Frond oyster has definitely grown since introduction, I assume it's a type of sponge also. Up until recently I had assumed the small tunicate originally located to the left of the grey sponge had long since perished but no, it's still hanging on in there amazingly. It looks like it's seriously getting squeezed out by the sponge though. Last but not least the small fan worm attached to the bottom of the shell is still alive and looking lovely. I think it may be Bispira brunnea however these worms generally appear in clusters (hence the common name cluster dusters). They secrete soft non-calcareous tubes but I can't tell what kind of tube this worm is living in, when the feathery head retracts you wouldn't know anything was there at all. Some of the livestock has adopted the empty oyster shell as a favoured sleeping location. The cowries like to hang out under the top shell during the day as does the Black Sea cucumber occasionally (but he's getting too big to fit into the space now). Since it was clear the oyster shell was going to be staying in my tank for the foreseeable future I decided to put it to good use. I needed a spot to fix down a new spiral coral that I picked up in October. I had tried fixing the coral to a rock in front of the yellow spiral but the two didn't appear to get along very well. The yellow one stopped extending its polyps and the flesh looked oddly puffy so I opted to pull the new spiral away as a safety precaution. This left me with a bit of a dilemma, where to place the new one. That's when I came up with the idea of making use of the oyster shell, actually there was really no where else to place the spiral to be honest. This new spiral coral is super curly and has a thicker stem than the other two I have, it is a different species being a Stichopathes sp. rather than Cirrhipathes sp. As you can see this species has polyps on one side of the stem only whereas Cirrhipathes sp. have them arranged all the way round.
Well, in this case the oyster is the world. At least it is for the many epibionts associated with one of these American Thorny oysters, Spondylus americanus. Thanks to my recent success in acquiring the Spiral corals (and a Rhizotrochus!) my wish list has been looking a bit shorter recently, however it is by no means complete. Another animal that I have always wanted to keep is the Thorny oyster, I have never seen any for sale nor have I been able to source any online. I decided to ask the local shop (the one that found the spiral corals) to look for one for me. Lo and behold one week later they had some. Now I know that oysters are difficult to keep, even a small one may be a stretch too far for my mixed reef tank but I have always wanted to try. I have been able to keep the hitchhiking mussel (Septifer bilocularis?) alive for over 4 years now but it is tiny in comparison and probably also an indiscriminate filter feeder. Still I feed a lot more particulate food and phytoplankton these days so I feel I'm in a better position to give one a go (famous last words!). They had two available, one was smaller and almost certainly the better choice but the bigger one was oh so fabulous, I found it impossible to choose between the two and all form of rational thought flew right out the window. I ended up buying both of them. I have named them 'Syd' Little and 'Eddie' Large (after the British comedy double act). Eddie is covered with so much fascinating life! So far I have discovered 4 addtional bivalves, 2 hoof snails, 2 tunicates, at least 4 species of sponge and a feather worm attached to him! I'm not confident on the IDs but the bivalve on top is possibly a Frond oyster (Dendostrea frons) and the one at the back is possibly a jewel box clam, Chama sp. Of the two remaining bivalves one is an Ark clam and the other is too tiny for me to have any sort of clue what it is other than it being a bivalve. The hoof snails, Hipponix sp.?, were initially intriguing but after doing a bit of research and watching them I came to the conclusion that they were possibly bad for the oyster. I found an article online that stated Hipponix conicus eats the mucus, faeces and mantle tissue of its host plus micro algae growing on the hosts shell. I observed both of mine, on occasion, extend their feeding proboscis right inside the oyster. Perhaps they were simply feeding on mucus and faeces but eating mantle tissue absolutely cannot be tolerated. The oysters don't need that kind of extra pressure to survive, they are hard enough to keep healthy as it is. I don't like killing things but the hoof snails had to go. Apart from the two on Eddie I found another one attached to Syd. The smaller ones popped off relatively easily but the large one took a bit more effort. Each one left a black 'mark' on the oysters shell. To begin with I thought the 'marks' were actually holes in the shell. I feared that the hoof snails had bored right through the shell and by removing them had I made the oysters vulnerable to predation/infection. Fortunately closer investigation showed that the shell was still intact, the snail's foot must have ground away the outer layer of the oysters shell. It's been just over 5 weeks since Eddie and Syd were introduced and the CUC have been checking them out most thoroughly. Unsurprisingly the cowries have been eating some of the sponges, most particularly the pink one on top. I'll be sad to lose it but there's not much I can do about it other than remove the cowries and I quite like having those around too. The Ark clam that was attached bottom right has vanished so must have moved on to pastures new. Both oysters are quite reactive but Syd, the smaller one is really twitchy. He can 'see' me approaching the tank and closes up in response. I don't know if this will harm him in the long run as it must use energy to close/open up all the time, also being closed means less feeding. I will have to wait and see how they both fare. I'll sign off this post with some time-lapse fun of Eddie & friends. |
AuthorHi, my name is Lisa and I live in Derby, UK. I am a self-confessed reefaholic! Archives
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