My oddballs - Terrestrial nemerteans and flatworms

Umbra

Arachnopeon
Joined
Dec 1, 2013
Messages
48
In light of the fantastic slug and leech threads, I figured I'd dedicate a post to some of my slimy, spineless wonders, the nemerteans (ribbon worms) and flatworms. I feel these are even more obscure in the pet trade than the others - the only flatworms most people know of are the species that are seen in science labs/freshwater shrimp aquariums. Ribbon worms most people have probably never seen outside of a few viral videos featuring marine species. I'd bet out of those who are familiar with them the majority aren't aware of the terrestrial species.

I'll start with my freshwater ribbon worm, Prostoma cf. canadiensis. These were collected in a local river through the use of a bottom sampling dredge. They are pretty neat little predators of other worms, insect larvae and small crustaceans. The max size seems to be around 35mm. Their distribution is sporadic at best, being very common in some stretches and absent in others. Clear runs with mixture of cobble and sand sediment with an abundance of rooted plants seem to produce the best. They have been breeding for me on and off and seem to have a decently long lifespan.



Next up is my terrestrial nemertean, Geonemertes pelaensis. These guys are much larger than the aforementioned species, with some of my specimens passing the 120mm mark. They are voracious predators of arthropods - mine have been eating primarily crickets although they'll take whatever else I'll throw in there for variety. The white isopods I put in there as clean up crew look to have been eaten as well. They are exceedingly shy and light sensitive, and only come out and forage in the dimmest of light or pitch blackness. As a result of this behavior I've only ever seen prey capture once.
G. pelaensis are cyclic hermaphrodites, transitioning back and forth between male and female and some literature suggests that they may be capable of self fertilization during some points of their transitions. I've found a few egg sacs but I haven't seen any produce viable young yet. I keep a constant supply of springtails going in there just in case.




I also have some unidescribed Caenoplana sp. These are not nemerteans but are terrestrial planarians. They appear to be generalist predators but seem to have a strong penchant for spiders in particular. This species reproduces by fragmentation - I've never seen them breed, never seen an egg case but I've seen them multiply by splitting. This has been confirmed by a professor in Australia who is an authority on terrestrial planaria. They don't appear to be as arboreal as G. pelaensis nor are they anywhere near as active even after lights out - they are more than content to simply sit in the same spot for days on end until it's time to feed. The largest one I have is about 85-90mm fully extended.


I also have a small species of terrestrial planarian, Rhynchodemus sylvaticus. These are tiny, maybe 30mm max but are efficient predators nonetheless. Mine have taken down prey as large as yellow sac spiders and small Trochosa sp. wolf spiders but I feed them primarily on Drosophila and springtails. They reproduce quite quickly and can populate a small vivarium very quickly. Most notable of this genus are the pair of conspicuous eyes on the head, they are IMO one of the neatest looking little worms. I don't have any good photos right now but I will try and get some good ones in the upcoming days. For now here is a photo of the vivarium I'm keeping them in!


I have a few more species that I will post about at a later date - if anyone has any experience keeping any ribbon worms/flatworms I'd love to hear about your experiences!
 

Umbra

Arachnopeon
Joined
Dec 1, 2013
Messages
48
Here is a short video showing the movement and feeding of Prostoma canadiensis. You can even see the proboscis firing and injecting its cocktail of toxins!

 

LawnShrimp

Arachnoangel
Joined
Dec 9, 2016
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907
I've always wondered how to keep terrestrial planarians! When I was in Florida last week, I observed two species: Bipalium kewense and dark brown one with clear eyes. I collected a few of them, but they disintegrated in their container, which was kept cool, humid, and with an earthworm to prey on. I found several more, but decided they were better off where they were. I'd love to try again with flatworms, though.
 

MTA

Arachnosquire
Joined
Aug 1, 2016
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Those are really cool, I have a Bipalium kewense but I haven't found anything it will eat.
 

Umbra

Arachnopeon
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Dec 1, 2013
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Bipalium kewense is a more or less obligate predator of earthworms - related species may be slug or snail specialists so you could give those a try as well.

As for the dark brown with eyes, 2 species found in Florida immediately spring to mind - Dolichoplana striata and Platydemus manokwari. The former is long and thin, the latter short and thick and bears a yellow dorsal line running down the length of the animal. D. striata is another predator of earthworms while P. manokwari is a generalist with a preference for gastropods.
 

Umbra

Arachnopeon
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Dec 1, 2013
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48
So it turns out I spoke too soon about G. pelaensis not giving me viable egg sacs...


 

Hisserdude

Arachnoking
Active Member
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Apr 18, 2015
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2,274
Very neat little critters, I love terrestrial planarians, and the ribbon worms look cool too! :D

I've kept a couple Bipalium kewense before, (or at least a similar species), actually caught them here in Idaho, really surprised me to see them here, used to see them in FL all the time. Fed them earthworms, which they loved, got a couple large eggs from mine, they never hatched though.

Would really like to keep some again one day, I like the planarian species with the "hammerhead" look the most. :)

Anyway, great thread, keep us posted on these unique little beasts!
 

klawfran3

Arachnobaron
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Feb 6, 2013
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560
I've kept a land planarian or two in the past, I never got them to feed. I heard they like earthworms?
 

plantecarnivore

Arachnosquire
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Mar 4, 2013
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79
They are nice! I didn't know planarians were kept in terrarium!
I guess they are fast? Harmless to humans?
 

Umbra

Arachnopeon
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Dec 1, 2013
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48
Land planarian diet varies from species to species, some are generalists that consume almost anything they can overpower (eg. Platydemus manokwari, Caenoplana coerulea), some are a bit more specialized and feed on arthropods/crustaceans (Rhynchodemus sp., Artioposthia japonica, Dolichoplana mertoni) and others are obligate feeders on a very specific prey item (Bipalium sp. will often only eat earthworms, slugs or snails depending on species, Arthurdendyus triangulatus feeds exclusively on earthworms). While research is always a good thing, these creatures are rather poorly studied with many undescribed species so there's a good chance that you might not be able to find any information about what a certain species eats. I'd advise searching the immediate surroundings and seeing what other creatures inhabit the area and collecting a few of each and doing feeding trials. They can go for long periods of time without feeding and can take a while to get settled into captivity. Most important is to try and keep humidity high and disturb them as little as possible - their natural microcosms tend to have little variance in temperature/humidity. I've found some species sensitive to air flow to the point that they won't feed for a good while after I open the enclosure. This is likely because air flow lowers humidity and I've noticed that many will try and retreat to a more moist and sheltered area. The best solution I've found is to have a small plug in the lid of the enclosure that you can remove and insert prey through there, thus causing minimal disturbance.

They are harmless overall as in they can't bite or physically damage you although because of the complex toxins in their mucus/their sensitivity I would advise against touching them unless necessary and obviously avoiding contact with eyes, mouth, open wounds, etc. after doing anything in the enclosure. At least one species (Platydemus manokwari) is a paratenic host for the rat lungworm so exercise caution while handling this species.
 

Umbra

Arachnopeon
Joined
Dec 1, 2013
Messages
48
This morning I was greeted by a gathering of juveniles on the piece of driftwood, plus I found another egg sac!


I'll try to get photos of the egg sac once I clear my mirrorless camera's memory card, can't maneuver my phone to get a proper shot (I've been using my phone for every photograph I've posted, I apologize for any quality issues!). I did, however, manage to get a couple shots of one of the juveniles!



And finally, an updated FTS:
 

Umbra

Arachnopeon
Joined
Dec 1, 2013
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Not a great picture but here are 2 Rhynchodemus sylvaticus consuming a yellow sac spider
 

Umbra

Arachnopeon
Joined
Dec 1, 2013
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Got a couple shots of G. pelaensis consuming crickets, I will try to get some action shots soon!


 

Ghost56

Arachnobaron
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Aug 28, 2016
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443
Amazing enclosures and pics! What camera and lens are you using?

These sound pretty difficult to keep, but definitely are fascinating.
 
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VolkswagenBug

Arachnobaron
Joined
Feb 26, 2017
Messages
486
I'm not generally a big fan of worms, but these are really cool. Eventually, I want a pet bobbit worm, strangely enough.
 

Umbra

Arachnopeon
Joined
Dec 1, 2013
Messages
48
Amazing enclosures and pics! What camera and lens are you using?

These sound pretty difficult to keep, but definitely are fascinating.
I'm using my smartphone (LG G5) and a cheap LED flashlight from Home Hardware. I also made a little macro filter out of a lens from a broken point and shoot digital camera for more magnified photos. I have a Sony NEX-5T and a macro lens but my girlfriend has been a bit slow with clearing our travel pictures and videos off the SD cards so no dice on that yet. Hopefully within a week or two I'll be able to use a proper camera!

@VolkswagenBug I have kept "bobbit" worms but not the infamous species - the actual bobbit worm (Eunice aphroditois) is nowhere to be seen in the pet trade. A variety of other eunicid worms come in with live rock and coral all the time and they vary in temperament depending on species. Some are very predaceous and will consume tankmates but they are not the well known bobbit worm that hides in the sand and has the trapdoor style jaws. These tend to bore into your live rock and come out at night, consuming anything they stumble upon.
 

VolkswagenBug

Arachnobaron
Joined
Feb 26, 2017
Messages
486
I'm using my smartphone (LG G5) and a cheap LED flashlight from Home Hardware. I also made a little macro filter out of a lens from a broken point and shoot digital camera for more magnified photos. I have a Sony NEX-5T and a macro lens but my girlfriend has been a bit slow with clearing our travel pictures and videos off the SD cards so no dice on that yet. Hopefully within a week or two I'll be able to use a proper camera!

@VolkswagenBug I have kept "bobbit" worms but not the infamous species - the actual bobbit worm (Eunice aphroditois) is nowhere to be seen in the pet trade. A variety of other eunicid worms come in with live rock and coral all the time and they vary in temperament depending on species. Some are very predaceous and will consume tankmates but they are not the well known bobbit worm that hides in the sand and has the trapdoor style jaws. These tend to bore into your live rock and come out at night, consuming anything they stumble upon.
Yeah, I've seen videos and images of hitchiking Eunice in people's aquariums, so I hope to someday buy a few specimens from people who do get them and attempt to breed them for the hobby.
 
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