Gastropod first intermediate hosts for two species of Monorchiidae Odhner, 1911 (Trematoda): I can’t believe it’s not bivalves!

•Sporocysts and cercariae corresponding morphologically to those of monorchiids are reported from vermetid gastropods.•These are the first monorchiid intramolluscan stages from gastropods and represent a striking intermediate host shift.•All other known monorchiid life cycles use a bivalve first intermediate host.•The infections are genetically matched to two species of Hurleytrematoides, H. loi and H. morandi.•The exceptional feeding biology of vermetids might be key in their adoption of some trematode groups.