Accidentally breeding terrestrial planaria - or could they be nemerteans?

Every so often I've found these beautiful striped flatworms when we're in Florida, but I was never able to keep them alive for long - or so I thought.




I do remember putting one in this tank before I repurposed it for an Amblypigid, and I never saw it again until now, about a year later, when I suddenly noticed dozens in the tank!

I didn't know what they were eating until I started seeing them wrapped around crickets, as you can plainly see in the photographs.

What I'm still not sure of is whether they're only scavenging dead crickets, or actually killing them. I'd swear in some cases the crickets were moving only minutes before and weren't touched at all by Piggie.

This tank has very deep, very moist soil which I believe is part of why they're thriving. Its lid is also a solid piece of glass tightly sealed all the way around, otherwise they could very easily ooze out and escape!

I'm not sure just how big their population is, but I may set up a similar tank and transfer some, get some more populations going. They're just such an interesting, unique clean-up crew! I might consider selling some later, but I wouldn't want to run low. It took me years of trial and error to get these things to multiply, even if I only succeeded when I stopped trying.

That is awesome. They could be killing them, or more likely feeding on near dead crickets. They eat live worms, I believe.

That's what I thought, but the earthworms in the tank haven't dwindled, and instead, the isopods that once exploded in number are all totally gone!

The hammer-headed flatworms are earthworm predators, but these seem to specialize in arthropods roughly their own size whether dead, dying, or in the isopod's case, just slow and easy to corner maybe.

That is...awesome. Thanks for sharing.

Is the head shape on the flatworms like a half moon? When I lived in Hawaii, I would encounter a species with that characteristic occasionally. That species ate worms, (I saw them in the act) though it may also have fed on crickets and other insects.

Speaking of this, I actually found a pair of Bipalium sp in my front yard following a good soak. I'll edit in the pic i took of one of them..

Edit:




Would make for interesting pets. Curiously, they wanted to sit in the sunlight while the water was hitting them.

Those look similar to my Rhynchodemus sylvaticus. Probably not nemerteans - they feed using their anterior end, the flatworms crawl ontop of their prey and feed with the pharynx located somewhere closer to the middle of the body (varies depending on species). They're likely killing the crickets, mine eat sac spiders and flies that I toss into their container. I'll try and get a positive ID from an acquaintance of mine who researches terrestrial Platyhelminthes. If you ever decide to sell any I'll definitely buy them!

Could you perhaps give more details on your setup? Humidity, substrate composition, temperature?

*EDIT* They are quite formidable predators in their own right and can take down surprisingly large prey items. I'd be leery about using them as clean up crews for rare or delicate specimens. Also, they feed by employing external digestion so they actually leave a substantial about of organic waste product from their feeding.

**EDIT #2** So the ID I was given was an undescribed Caenoplana sp. Caenoplana coerulea has been recorded across the continental USA in various states and apparently this species you have found has been recorded not only in Australia (native) but also in Europe and several Caribbean islands. If it's found in the Caribbean it's likely found in Florida as well. Here's a picture with some info:



If it is indeed that species and it gets 7-10 cm, I'd keep a very close eye on them in that enclosure. There's a pic on the somethingawful forums of a Caenoplana coerulea consuming a gecko, I don't think it's far fetched for these to injure/consume other inverts if they get larger.

This is the best information I've gotten, researching terrestrial helminthes is very difficult, as if few people even care to study them.

I can't even picture how they snare something fast moving! Do they ever move quickly, or do they just sneak up on insects and quickly adhere to them?

As soon as I can get some cut glass for escape-proof lids I'll be trying to start some additional colonies.

I ought to really go out hunting for more in the wild, too.

Do you know anything about the broad, inky black species we have here? They almost look like smears of tar.

I know a professor that studies terrestrial helminthes and nemertea and I have access to a huge variety of scientific journals through my university so information isn't too hard for me to come by as long as I'm aware of what to search for. As far as I know, Caenoplana sp. leave a mucous trail like most planarians that will encumber any small creature unfortunate enough to come in contact with the trial or the planarian itself. Some species will adhere to any potential prey item on contact and others still have developed more complex means of predation. The species I have at the moment, Rhynchodemus sylvaticus, meanders along while swaying its anterior end like a finger:

[video=youtube;dUDHpWYrLq0]https://www.youtube.com/watch?v=dUDHpWYrLq0[/video]

When it comes in contact with a suitable prey item like a springtail, fruit fly, small spider, etc. it expands its cephalic hood and snares the prey item, secretes mucous to overpower its prey and then crawls on top of it to consume it. I've fed mine large yellow sac spiders I've found in my house and while I've never seen them attack and kill the spider, I always find the otherwise healthy spider dead and partially digested within a day or two. I'd assume they simply adhere to the spider, crawl on it and through a combination of mucous and digestive enzymes simply overpower it. It's quite impressive given the fact that the worms are quite small. Like R. sylvaticus, Caenoplana sp. are more adapted to predating on arthropods but at least some species will attack earthworms if the opportunity arises.

If you could get a photo of the black species I'm sure I could have it identified or at least get a better idea of what it could be. Based on the location and physical description, I would assume it would be from the subfamily Geoplaninae, possibly a Geoplana sp.

I just thought I'd drop in and mention how envious I am...I have wanted to work with terrestrial planarians for a long time but have no access to any specimens...

Carry on.
EC

If you wanna find some, try soaking your yard nice and deep during warm weather. That's how I always find mine.