Litonotus cygnus

[janvangastel]

I am pretty sure this is Litonotus cygnus.

[Bruce Taylor]

Yes! Extensile "neck" with toxicysts all along the ventral side, single contractile vacuole in the posterior (the similar-looking Amphileptus procerus has a large number of smaller CVs).

Nice video!

[janvangastel]

Thanks again Bruce. Are toxicysts really toxic? If yes, what then is their function? Are they used when hunting?

[Bruce Taylor]

Yes, they're toxic, and used to immobilize prey. They're an ancestral character of the class Litostomatea (though parasitic & endosymbiontic members of the group have lost them).