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Trematode parasitic castrator infections in the snail, Cerithidea californica. (a) Snail (shell removed) infected with the trematode, Himasthla rhigedana (photo credit: Todd Huspeni). The trematode has completely castrated the snail, replacing the snail gonadal tissue. (b) Cross section through the visceral mass of a snail infected by the trematode, Cloacitrema michiganensis.
