Assassin Snails ... All you need to know and more
I started this over on the Arizona Inverts Forum but the mods annoyed me enough I thought I would post it here. (okay they asked really nicely so I gave in)The Assassin Snail[You must be registered and logged in to see this image.]
Your friendly neighborhood Assassin Snail
I became interested in this little snail when I began to be overrun with MTS. I was looking for a new and non toxic way to remove the excess snails from my tanks, little did I know it would lead to an obsession with inverts. So off into the happy world of the internet I went only to end up more confused and lost than when I started. The person who says ignorance is bliss got it so right. Now in no way is this to be a definitive article but more or less a place to gather all of the info I can find and put it into a format that may help someone else interested in these neat little snails.
So here is what I have found:
* Kingdom Animalia: Metoza
* Phyllum: Mollusca
* Class: Gastropoda Orthogastropoda Caenogastropoda Cox, 1959
* Order: Sorbeoconcha Hypsogastropoda Muricoidea da Costa, 1776
* Family: Buccinidae Rafinesque, 1815
* Senus: Anentome Cossmann, 1901
* Species: Anentome Helena/Clea Helena*
* Common Name: Assassin Snail/Killer Snail
* Diet: Carnivorous/Scavenager
* Temp: 74-82
* PH: 6.2-8.2
* Size: 1"
*Now from what I have been able to deduce there are 11 very similar snails spread all over Asia with the closest relative in Thailand. The Thailand Snail from what I have been able to deduce is actually Clea Helena where the Clea Anentome Helena is the Indonesia species we call the Assassin Snail. So I wonder if the Clea has the same habits why we have not seen it in the trade before, although I will admit the markings on the Anentome are a lot more defined and colorful. Basically all 11 are freshwater Whelks snails and feed off of mainly meaty remains or as in the case of our sweet little snail, will hunt down other live snails. From what I have been able to gather all 11 will hunt down other snails but that has not been confirmed.
Our Assassin Sails as we know them were first described in 1847 but did not appear in the hobby until around 2007 due to a whole lot of different reasons. Found in the Sulawesi region of Indonesia they are present in ponds, rivers, streams, and lakes throughout the region so they are a hardy little snail. I keep mine in a 15 gallon tank with loads of MTS, PS, Ramshorn, and Cherry Shrimp. The 5 adults I originally received dove in after a couple of days and started hunting down MTS like there was no tomorrow.[You must be registered and logged in to see this image.]
Assassin taking down an MTS half it size bigger
Assassins they will eat on average 1 snail a day, half to half again their size. They do have a preference for snails like the Ramshorn where the body is easier to get to and there is no door for the victim to pull back and hide behind. I have seen them track like a cruise missile all the way across the tank to get a Ramshorn and passed up the slower MTS to chase down the Ramshorn and devour it. I put 3 PS in my tank to start a colony for the baby Assassins and all but 1 was gone in less than 24 hours. The last PS's days are numbered I'm sure. Right now the PS hangs at the top of a Val where the Assassin's can't get to it. I was lucky in the fact that they did lay 3 egg batches before being devoured. Assassins as far as I know will not attack their own kind nor eat their own kind if they die. They will eat other snails that are dead, this was confirmed when an assassin took down a larger MTS and couldn't finish the meal about 4 hours later another Assassin came across the remains and finished it off. Also Assassins will gang feed on a snail larger than themselves. I saw 2 of my babies’ gang up on a larger MTS and then feed side by side until the snail was gone. They have also been known to gang up on larger snails like the Apple/Mystery snails to take them down.
Assassins feed by first grasping the prey and then inserting a feeding tube into the snails shell and basically liquefying the snail and sucking out the remains. They will also actively hunt, but also lay in ambush of another snail. I moved a few of my babies over to a tank with sand in it and they proceeded to bury themselves to a point where all that stuck out of the sand was there little trunk appendage. They would then wait until a snail of suitable size was close then motor out of the sand and grab the snail. This type of behavior has led me to 2 conclusions the first being that the trunk is used for smelling and hunting down prey, and the second is that they do come from both rocky and muddy/sandy substrate areas.
Now one thing that is known is you do need a male and a female to get any eggs. At this time I do not know of any way to sex them and I don't know if there is, I have only been able to sex mine by watching them closely. Will say that my females are the largest snails in the tank and the smaller males will latch on to a female and ride around the tank for 1/2 a day or more with her. This only happens after the snails have fed. They need to be .75 of an inch to a full inch to be sexually mature.
Another rumor that has been going around is that Assassins are a live bearer that too is a myth below you will see a picture of an egg casing. It was also said that they only lay one egg every 10 days or so that is also untrue. My assassins will lay 2 to 15 eggs a day after a good feeding for a couple of days and then will stop until they feed again. I also have it from several people that they will continue to lay eggs as long as there is meaty foods like frozen blood worms present. This has been confirmed but the rate of egg production and the rate of survival of the baby assassins declines dramatically. In the absence of meaty foods it has been reported that they will survive on regular fish food. Well look at your labels folks most fish foods have a high protein count, they will survive on any high protein food if live is not around. I do know they can survive without meaty foods but egg production will decline and life span of the adults is shorter.
Now as far as hatching and growth go it seems both of these are a rather long process. With only one egg per case they will not become as invasive in your tanks as some species, but they could become the only species in a hurry. It takes 3 to 4 weeks for the eggs to hatch and that long if not longer before you will be able to readily spot the youngsters. The growth of these snails is slow compared to other 4 to 8 months to reach full size based on the amounts of food and temp of the tank. Also with needing one of each sex as soon as you can confirm the females you can remove them to another tank and that will stop any egg production, or since the eggs are so large and easy to see just remove the eggs. Here are some pictures of the snails emerging from the egg sacs.[You must be registered and logged in to see this image.]
2 baby assassins all snug in their bed[You must be registered and logged in to see this image.]
One got up and left his bed[You must be registered and logged in to see this image.]
One baby assassin off to kill a snail dead
Below you will see pictures of an assassin snail about a week old. You can already start to see the bands and where the elephant like nose is going to be. When they are first born they are hard to tell apart from MTS or PS fry without magnification. The best way to do this is watch the snail if it moves along smoothly it is either a PS or an assassin. If it moves along by pulling itself it is a MTS fry. Now to ID it from the PS fry you need to get it side on and you will see that its shell is held higher than that of a PS.[You must be registered and logged in to see this image.][You must be registered and logged in to see this image.]
__________________________________________________ ______________________________WARNING ABOUT BABY ASSASSINS
The babies apparently move to new territories in the wild kind of like baby spiders. I have seen several climb to a high point hang from some kind of string or slime trail and get caught up in the current to float around the tank for several minutes before coming to rest. This makes me think that to disperse in the wild they must do the same thing to float down stream. So using a sponge over your filter intake or a sponge filter is a must if you want your babes to survive.
A few other fun things I have Observed in no set order....
- One rumor I have heard is that when you place Assassin snails in a tank all the other snails will start to act weirdly. That could explain why every MTS in my tank is headed for the top of the tank and just keep going around and around the tank. I have seen the Assassin’s climb up latch onto a snail pull it free and free fall to the bottom to finish its meal. I can say that this is a probable thing because when I removed the adults all of the medium to larger snails migrated back to the bottom.
- When Assassins are small they go into hiding and are hard to find. When they are about the size of a grain of sand I saw them very rarely. Too find them I would take a flash light about an hour after lights out and look below the gravel line. My tank has real large gravel and they along with the baby shrimp are hiding in among it. There are about a 100 egg casing and some still to hatch and at any given time I can find no more than 15.
- After about 3 weeks they are now about the size of the plastic ball on a straight pin and you can see the stripes and their little trunk with the human eye.
- 3 weeks was when I saw my first confirmed kill by a baby so what and if they ate before that I cannot say.
- I have confirmed that the baby assassins are eating blood worms so if you are low on small snails there is a backup plan.
- Okay getting bigger now I have some that are about .5 inch long so they seem to go thru a growth spurt once they actually start feeding on snails. My thoughts are at this time that they feed off detritus and other food sources until they reach a certain size and then start to feed on live snails.
- Another weird thing is that I have eggs hatching 2 months after being laid. I have not had any adults in the tank for over 2 months and I have some assassins that are hatchling size wandering around. Now I will admit it could be a slow grower or king of the tank type thing where some are bigger and some are smaller, but not this big a difference in size. Also egg casings that I thought were dead are suddenly empty. This all started after I started to seed the tank with very small snails for all the babies in the tank so it makes me wonder if hatching can be held off by lack of food somehow. *Update* I have come to the conclusion that there is 2 factors in the delayed hatching Temp and food source. When I raised the temp a little the eggs hatched quicker around 2 weeks in time. Also when i started feeding the tank small baby feeder snails the other eggs that had not hatched started to hatched. So temp and food all make a difference on the hatching rate and time.
-At 2 months most of the Assassins babes have moved up and out of the gravel and are easy to spot. I'm assuming this is because of the size of the gravel used. The ones I have in my sand bottom tanks readily bury themselves all the way up to their nose in the sand. I still have to spot a single baby in the fine graveled tank where the parents laid their first batch of eggs. I can only say at this point they may have been eaten when they were young by other tank mates. *Update* I now have confirmed babies but they did not appear until almost .25 of an inch in size in the sand tank.
-at 3 months I have also noticed that most of the snails have flipped over to a hunting life style. I'm seeing a lot of kills and even quite a few gang kills. My population of baby MTS now has to be beefed up at least once a week and that is straining my feeder tanks ability to keep up. *Update* They have completely cleaned a 29 Gallon tank of snails, except for the very small MTS. This was a tank that had close to 500+ adult MTS and probably 100+ Ramshorn snails. Now all that I have is a bunch of empty shells and hungry Assassins.
-At 2 months since eggs were first laid I have snails all the way up to the size of a pea and down to just hatchling size. These are all from the batches laid no more than a week apart so I can only assume that the hatch time is not set in stone and can vary.
-One thing that is becoming a stronger belief is that Assassins may inject a paralytic toxin into their prey. This comes from observations of some respected keepers and myself, but will take someone with a degree to confirm.
-The male from my observations tends to be the smaller one and have the thinner stripes and the female tends to be larger with bigger stripes. Now this in no way is 100% for determining which is which but is just gathered from observing my snails.
-I have started an experiment and moved some Nerites in with the Assassins in 3 of my tanks here are the stats:03.01.09
* 75 gallon 4 Nerites from a small olive in size to large zebra 8 adult Assassins lots of MTS (can't find 2 of the nerites but I can not find shells either probably up under something hiding as they are known to do)
* 15 gallon 2 large Nerites 2 smaller Assassins and 2 Adult Assassins a few feeder snails and extras added once a week or so
* 29 gallon 40+ Adult Assassins and unknown number of babes 1 large Nerite about 30 to 50 feeders added once a week but wiped out in a day or so.
This has been going on two months now and I can not report any confirmed Nerite losses yet. (05.03.09)
It has been confirmed that Assassins can and will eat dwarf shrimp. Please understand this is a very rare thing. Assassins are opportunistic feeders and it will only occur with really dumb shrimp or when the shrimp is in the wrong place at the wrong time. For a capture to occur the snail has to be in the perfect position to make a grab because most of the time the shrimp just scoot away like nothing happened. I will still stand by the statement that these snails are the best way to rid a tank of pest snails and are shrimp safe.
*Update* Sept. 28, 2011
- Assassins will survive without meat but egg production drops to almost non existent.
- Life span of the adults drops from 2 years longest I have had live to under a year without live food
So in conclusion please keep in mind as with all animals never release any into the wild I can see how these could become a real invasive species very quickly. I will also add to this as I make more observations or more confirmable facts come to light.[You must be registered and logged in to see this image.]
Betty Davis Eyes
MTS = Malaysian Tunneling/Trumpet Snail
PS = Pouch/Tadpole Snail/Bladder/True Pond type snail [i]