glochidium

noun pl. -·ia-ə

1. Bot. a barbed hair or bristle, as on certain cactuses or on the spore masses of ferns
2. Zool. the parasitic larval stage of freshwater mussels (family Unionidae) which infests the gills, etc. of many fishes

Etymology: ModL < Gr glōchis, point (see gloss) + ModL -idium, dim. suffix < Gr -idion