There's a shrimp all up in my Crocea

[Echidna09]

So I'm staring at my tank because it's my day off and I have nothing to do and as I look at my Crocea I see a clear with black spots little shrimp that will not for the life of him go away. He goes inside the clam where the clam intakes water (sorry I don't know the name for it). The clam is fully extended and looks beautiful but doesn't close up when I cover the light above him like he used to. Only time he closes is if I touch him. Is the shrimp bothering him? If so I should be able to get him out of there he just sits on the clam I even picked the clam up to get a better look at the shrimp and he still just stayed right where he was.

Thanks

[E-A-G-L-E-S]

There are small shrimp that take home in clams. Don't know the name though. Do you see any stress issues with the clam? If not then you are lucky to have one.

Maybe mbbuna will chime in.

[Echidna09]

So far I haven't seen anything but I just noticed the shrimp. I haven't gotten a lot of time to look at my tank lately because I've been working so much and only can really watch it after work and there's only about an hour that the lights are on when I get home. In that hour I have to scrub algae and feed, do a water change (20% daily is working to get my dKH down. It's already almost in acceptable levels), and make sure nothing is sick. The clam always looks nice so I don't get a lot of time to look at him.

I'll try to get a picture but I don't know if I will be able to I can barely see him when I just look at the clam. He's mega cool I hope he's good.

[E-A-G-L-E-S]

If he closes up then it's bad, but I'm guessing he is some kind of commensal(sp?) shrimp.
Look that up and see if it goes with what you have seen.

[Echidna09]

Sorry, disregard the comment in my 1st post that he doesn't close when I put my hand in the way of his light. I just tested it again (couldn't find shrimp, must be in the clam right now), and he closed up.

[Echidna09]

The clam spit the shrimp out tonight. This time I got pictures (You're excited I can tell). He's easily spotted in every shot once you know what to look for. Again he's clear with black spots all over and white eyes. Posted them this way so I could get the images full size.


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http://www.jeffsreallycoolwebsite.co...081007_025.jpg

[mbbuna]

its a commensal shrimp, wont hurt the clam at all. there are a few different species of them.

heres a good photo of them.

[E-A-G-L-E-S]

I got one right, woohoo

[scubajsm]

I've had one in my Squamosa for over a year, mine had bright purple/b;ue spots. Do you know the name of the shrimp you posted about?

[mbbuna]

here are some of the species known to live in clams

Anchistus murigera, Anchistus miersi, Parachistus biunguiculatus, Conchodytes tridacnae and the crab Xanthasia murigera

[scubajsm]

Thanks, I've been looking for over 6 months and haven't been able to identify my little friend.

[SitBackAndWatch]

i have looked at the photos about 5 times a piece.... i dont know if im blind or retarded..... where exactly is the shrimp in picture number 1-5

[mbbuna]

in #1 its directly to the right of the excurrent syphon and #5 it below and to the right of the excurrent syphon( look for the 2 white dots=eyes)

[jfatherree]

It's Anchistus miersi

not harmful

[mbbuna]

Originally posted by jfatherree
It's Anchistus miersi

not harmful

hey J, how are you IDing the shrimp? are you doing it buy the species of clam its in or can you tell them apart? they all look the same to me

[jfatherree]

I just realized that I ID'd the shrimps in the pic you posted - not necessarily the ones from Echidna's crocea. Moving a little too fast for myself... The pic frokm Clams Direct is definitely miersi - I used the same pic (or a very similar one) in my book, and had Daniel Knop look at it. I've got some papers that have some descriptions/pics too. Echidnas looks to be the same thing, though (to me anyway).

BTW - there is no report of commensal shrimps living in croceas in the scientific literature. Barry told me he's seen a few, though. So, Echidna is very lucky to have them!

[jfatherree]

Free article on the topic! I wrote this for Calfo's C Journal a while back. I own the rights though, so I can post it here too...


Commensal Shrimps of the Giant Clams
James W. Fatherree

A symbiotic relationship is one in which two different types of organisms live in a close association with one another, and many such relationships exist in nature. I’m sure the best known amongst reef aquarium hobbyists in the relationship between single-celled algae and reef-building corals and with the giant clams. In this case, both the algae (better known as zooxanthellae) and the animal host benefit from their relationship, and this type of symbiosis is called mutualism.

Giant clams aren’t always limited to a symbiotic relationship with zooxanthellae though, as they may also play host to a number of small shrimps. These are occasionally found living inside specimens of giant clams when they are collected and added to aquariums, and hobbyists are often concerned, for good reason. You’d think that finding a shrimp or two crawling around inside a clam would be a cause for alarm, but there’s actually nothing to worry about. With apparently very few exceptions, these shrimps do no harm to their hosts, and they certainly won’t kill them.

Being curious, I wanted to find out what I could about these shrimps, so I did a thorough search of the scientific and hobbyist literature, and came up with some good stuff to share with you. Holthuis (1952 & 1953) and Rosewater (1965) both include some information about which species of shrimps live with which species of giant clam, and Fankboner (1972) provides some very interesting additional information about one species in particular, too. I also talked to Barry Neigut of Clams Direct to see if he had any input, and he did.

To get started, there are four species of shrimps that live inside giant clams. Anchistus miersi, the most common of the four, has been found living in Tridacna gigas, Tridacna squamosa, and Hippopus hippopus. Anchistus mirabilis and Paranchistus biunguiculatus have also been found living in T. gigas. And, Conchodytes tridacnae has been found living in T. gigas and also in T. squamosa. While I was unable to find any such reports in the scientific literature, Barry told me that he’s found shrimps living in a few Tridacna derasa and Tridacna crocea, too, but couldn’t make a positive identification of the species. He also noted that he’s never seen any living in Tridacna maxima.

So, the obvious question is, “What are they doing in there?” To answer that, I first need to run through the basics of how giant clams work, and then we’ll get to what Fankboner reported finding after studying Anchistus miersi.

Giant clams rely on their relationship with zooxanthellae for a supply of energy and the carbon that they need. The zooxanthellae are kept in a host’s thin mantle tissue, which is exposed to sunlight when a clam opens up its shell, allowing the algae to produce energy/carbon-packed sugar via photosynthesis. They can make so much, in fact, that the zooxanthellae literally leak excess sugar into the clam’s tissues and can provide the host with more than enough to live, grow, and reproduce.

However, clams need more than just energy and carbon, as they need a long list of other nutrients, just like everything else alive. In the case of giant clams, the mantle tissue is also able to absorb nutrients directly from seawater in sufficient quantities to cover their daily needs. Thus, they really have no need to eat much, if any, sort of food as long as they get adequate lighting and dissolved nutrient levels are high enough in the surrounding waters.

To the contrary, almost all other sorts of clams must filter-feed to stay alive. Their gills serve two functions, as they also act something like mucus-covered sieves that collect food particles from the water that moves over them. The gills are covered by tiny hair-like structures called cilia, which beat rhythmically to create a flow of water that passes over them, and they’re also covered by a thin sheet of mucus. Particles are collected in the mucus, and cilia move the food across the gill surfaces into a set of grooves that run their length, which then channel the food to the mouth. Then it gets sorted and eaten.

The reason I bring all this up is that giant clams still do the same thing, too. Their digestive systems are reduced in size compared to their non-symbiotic cousins, as they can thrive without needing to feed. But, they still have all the same filter-feeding equipment that got handed down by their recent ancestors, and they do use it to some degree. It seems that giant clams will often filter-feed even when they don’t need to, and oddly enough it’s also how they get their zooxanthellae in the first place. That’s all another story though, and for a lengthy discussion of tridacnid nutrition and how they all work, you can take a look at Fatherree (2006).

Okay, back to the shrimps. While no one seems to be absolutely sure what all four species are doing, Fankboner suggested that A. miersi, again the most commonly seen species, makes a living by pilfering some of the mucus and particulate matter from the gills of its host. This wouldn’t be anything particularly unique either, as there are other sorts of crustaceans, such as the pea crabs, that steal mucus/food from other types of clams.

Fankboner also noted that there were no apparent negative side effects, as the host clams were still as healthy as could be, and that the shrimp’s impact must be negligible. Thus, these two animals are thought to be living in a commensal symbiosis, which is a symbiotic relationship between two types of organisms in which only one receives some sort of benefit from the other, without any negative effects on either. I say only one receives benefits because apparently the clam hosts don’t get anything in return, at least none that anyone has seen.

But, Fankboner also found that one specimen of H. hippopus, out of 18 he studied, did have some damage. Apparently, the shrimp had lacerated the gills of one host in such a way that the flow of mucus/food down the food grooves had been interrupted. He didn’t observe this happening, but noted that no other type of shrimp or crab had ever been found in H. hippopus, and that the damage looked similar to that done by the parasitic pea crabs in other types of clams. Thus, assuming that the shrimp was responsible, the symbiosis may turn parasitic, meaning only one member receives any benefit, and harms the other in the process. Still, despite the damage, the clam appeared to be healthy, anyway.

So, as I said earlier, these shrimps are nothing to worry about, as long as a specimen is getting plenty of light and there are sufficient dissolved nutrients present, which essentially nullifies a host’s need to filter-feed in the first place. I’ll keep going for a bit though, as Fankboner’s paper has some more good stuff in it, some of which may be particularly useful to hobbyists.

First, he noted that A. miersi has specialized hook-shaped tips on their walking legs, which allow them to firmly grasp the soft tissues inside the clam. This is important, as a giant clam will occasionally quickly retract its mantle and close the shell shut in a cough-like motion, which shoots water out of its body cavity in an effort to clear themselves out if there’s too much particulate matter present, or if something enters the body that irritates them. So, being able to hold on tight means the shrimp won’t be shot out into the open when a clam “coughs”, which would likely lead to them becoming a quick snack for a fishy passerby.

Fankboner also reported that the shrimp were always found in male-female pairs, and that the female was the larger of the two (Barry says he’s found only one shrimp in some clams, though). There was never more then one pair per clam, either. Infestation was variable though, as only 20% of T. gigas had shrimp inside, while 65% of H. hippopus did. This is important in as much as it shows that the clams by no means require the presence of the shrimp, and Fankboner noted that those without shrimp appeared to be just as healthy as those without. This is why the relationship seems to be of a commensal nature, rather than a mutualistic one, since the hosts don’t seem to be getting anything from the shrimp.

Additionally, after pulling out several shrimp and fiddling with them, he found that trying to mix individuals from different pairs in a bowl resulted in a fight, with the combatants pulling off each others pincers. So, you should never try to put two shrimp together in one place if they didn’t come together. And lastly, as strange as it may sound, when he tried to introduce a pair of shrimp from one host clam to another host clam of the same species, the shrimp wouldn’t cooperate. Apparently they would reject the new host specimen. Thus, it might be pointless to ever buy such shrimp separate from a clam (if the opportunity ever arose) with the hopes of taking them home and introducing them to a shrimp-less clam. I would have to guess that if given enough time in an aquarium they would eventually move into a suitable host clam, but that’s only a guess, and I don’t personally know of anyone that has tried to do so. Please let me know if you do!

And that’s about all I can come up with. The main point here is that if you ever find a small shrimp or two living inside a giant clam, there’s no need to fret. In fact, you should consider yourself lucky, as you’ve got yet another interesting little creature of the sea in your aquarium.

References:
Fankboner, P.V. 1972. On the association between the pontonid shrimp Anchistus miersi DeMan (Decapoda, Palaemonidae) and giant clams (Lamellibranchia, Tridacnidae). The Wasmann Journal of Biology 30(1):35-42.

Fatherree, J.W. 2006. Giant Clams in the Sea and the Aquarium. Liquid Medium. Tampa, FL. 227pp.

Holthuis, L.B. 1952. The Decapods of the Siboga expedition, Pt. XI. The Palaemonidae collected by the Siboga and Snellius expeditions with remarks on other species. Siboga Expedite 39:1-253.

Holthuis, L.B. 1953. Enumeration of the decapod and stomatopod Crustacea from Pacific Coral Islands. Atoll Research Bulletin 24:1-66.

Rosewater, J. 1965. The family Tridacnidae in the Indo-Pacific. Indo-Pacific Mollusca 1:347-396.

[SitBackAndWatch]

WOW... those guys are small, and nearly impossible to see. Im sure it would be easier if i could see it in person. i wishi i had a shrimp like that for my clams. that would be sick. so he was a hitch hiker? hes pretty sweet!

[Echidna09]

Thanks for the article. Good read. Is it possible (there's a lot of conflicting evidence in the article but i thought I'd ask anyway) that the shrimp came from my teardrop maxima that died? My clam doesn't seem to like the shrimp inside him for very long. The shrimp is sitting on top of the clam most of the day. Maybe this is just a characteristic of the species of shrimp or of croceas when they are found to be hosts? I know there is little data, but please help if you can.

Thanks again. If you think you can ID the species, I can try to put him in a container and take some detailed pictures of him. I would be interested to find out for sure.