ID needed of bulletproof ?turbellarian ?trematode

[Peter Houde]

I found five of these alive in my quarantine tank AFTER two weekly treatments of praziquantel (Prazipro) at prescribed concentration (2.5 mg/l). All five are/were free living and very active on glass bottom substrate, maximum length ~8mm, round not flat in cross section, no eye spots, no antennae or other projections of head, ventrally facing small round mouth, body surface is covered with white spots and three larger pairs of white patches, one largest pair on head and two smaller pairs on body, the anterior 1/3 of the body is narrower than the posterior 2/3, no internal organs visible except the posterior 2/3 is darker beneath the white spots and turds may be visible near the anus, trident tail end. Their head pokes around a lot, mouthing the glass or very occasionally rising up just long enough to expose the mouth. They are suprisingly fast moving. What are they? Could they be harmful to fish, corals, clams, snails, macroalgae, or anything else I have in my DT? I've got a fish in the QT that I'm afraid to move to the DT until I get this figured out. Please advise if you can. Thanks in advance.

 

[Tahoe61]

Polyclad Flatworm perhaps.

Some types eat mollusks, like clams and snails. Or types eat corals like Euphyllia.

 

[ISpeakForTheSeas]

I found five of these alive in my quarantine tank AFTER two weekly treatments of praziquantel (Prazipro) at prescribed concentration (2.5 mg/l). All five are/were free living and very active on glass bottom substrate, maximum length ~8mm, round not flat in cross section, no eye spots, no antennae or other projections of head, ventrally facing small round mouth, body surface is covered with white spots and three larger pairs of white patches, one largest pair on head and two smaller pairs on body, the anterior 1/3 of the body is narrower than the posterior 2/3, no internal organs visible except the posterior 2/3 is darker beneath the white spots and turds may be visible near the anus, trident tail end. Their head pokes around a lot, mouthing the glass or very occasionally rising up just long enough to expose the mouth. They are suprisingly fast moving. What are they? Could they be harmful to fish, corals, clams, snails, macroalgae, or anything else I have in my DT? I've got a fish in the QT that I'm afraid to move to the DT until I get this figured out. Please advise if you can. Thanks in advance.

Not a flatworm that I'm familiar with - my first thought was a Runcinid headshield slug, but the tail is wrong for it unless it has been unfolded in a rather unusual way. My best guess would be some kind of Philinoidean headshield slug, but I'm honestly not sure here. If it is a headshield slug, then it's most likely herbivorous.

 

[Peter Houde]

Not a flatworm that I'm familiar with - my first thought was a Runcinid headshield slug, but the tail is wrong for it unless it has been unfolded in a rather unusual way. My best guess would be some kind of Philinoidean headshield slug, but I'm honestly not sure here. If it is a headshield slug, then it's most likely herbivorous.

The tail-end of all four I found were the same. I sure hope they aren't flatworms (by and large they weren't flat except the tail) because I put the four of them in a jar to test to see what would kill them. I asked my daughter to take care of the aquarium for the weekend while I was away. For no apparent reason she dumped the worms into the DT. I am gobsmacked. It's done.

 

[ISpeakForTheSeas]

The tail-end of all four I found were the same. I sure hope they aren't flatworms (by and large they weren't flat except the tail) because I put the four of them in a jar to test to see what would kill them. I asked my daughter to take care of the aquarium for the weekend while I was away. For no apparent reason she dumped the worms into the DT. I am gobsmacked. It's done.

The only flatworms I know offhand with tails like that are Convolutriloba species ("Red Planaria" and relatives), but this critter definitely doesn't resemble those. I'll keep digging when I have the time and see if I can't find something,

 

[Peter Houde]

OMG, the tail looks identical. You've convinced me that they are convolutids of some type. I'm screwed.

I doubt any form of Cephalaspidea because is lacks a headshield or bubble shell, lacks eyes, and lacks a broad mouth. I'm posting pics of presumed Haminoea below that I'd gotten as macroalgae hitchhikers in the past.

 

[ISpeakForTheSeas]

OMG, the tail looks identical. You've convinced me that they are convolutids of some type. I'm screwed.

I doubt any form of Cephalaspidea because is lacks a headshield or bubble shell, lacks eyes, and lacks a broad mouth. I'm posting pics of presumed Haminoea below that I'd gotten as macroalgae hitchhikers in the past.

Yeah, I know a handful of headshield slugs that don't have those characteristics, but they also don't that unique tail. So, a Convolutid flatworm of some kind may well be it; it's an oddball for sure either way.