In order to research goo repellers I must capture a gooy Pandoran, so I capture a Goo Acheron, but the research did not open.
If I recall correctly, the same applies to goo spitting Scyllas. Only goo Chiron will unlock research.
I don’t know if it is intended, but it was mentioned and devs did not say a word about it.
I think Scylla with Spitter-head is a valid Pandoran for the research, IIRC