Dear Henk et al -

plica is a feminine noun (meaning a fold or wrinkle), and as such would
always have the same form when used as a specific name, regardless of the
gender of the genus name.
The associated adjective is plicata-plicatus-plicatum (folded; wrinkled),
which as an adjective would follow the gender ending of the genus name it
modifies.

Paul M.