Parasites mimicking host prey Aggressive mimicry

just predators such angler fish have structure lures prey, parasites mimic host s natural prey, roles reversed; parasite gets eaten host. deception provides parasite easy entry host, can feed upon, allowing them continue life cycle. researchers may able predict host of such parasites based on appearance , behavior.

one such case genus of shellfish, lampsilis, feeds on gills of fish in larval stage of development. once mature, leave fish adult mollusc. gaining entry host not easy task though, despite fact several hundred thousand larvae released @ once. case in flowing water bodies such streams, cannot lie on substrate , wait taken in course of foraging. female lampsilis have evolved special technique delivering offspring suitable host, however. structures on edge of mantle able capture interest of fish. resemble small fish themselves, eye spots, tail , horizontal stripes, , may move in similar fashion, if facing current (rheotaxis). when overshadowed fish, larvae forcefully expelled, becoming ectoparasites on unsuspecting host.

cercaria mirabilis, trematode, has large larval stage (known cercarium) looks small crustacean or mosquito larva. mimics locomotory behavior of such animals, allowing eaten predaceous fish.

another parasitic trematode example seen in terrestrial setting. leucochloridium genus of flatworm (phylum platyhelminthes) matures in intestine of songbirds. eggs pass out of bird in feces , taken in succinea, terrestrial snail lives in moist environments. eggs develop larvae inside intermediate host, , must find way digestive system of suitable bird. problem here these birds not eat snails, sporocyst must find way of manipulating future host eating it. unlike related species, these parasites brightly colored , able move in pulsating manner. sporocyst sac forces way snail s eye stalks, , pulsates @ high speed, enlarging tentacle in process. affects host s behavior: snail moves towards light, avoids. these combined factors make sporocysts highly conspicuous, such eaten hungry songbird. snail regenerates tentacles, , leucochloridium carries on life cycle.