Microphallus occurs as genus of parasitic trematodes (flukes) in the family Microphallidae. A Greek title means "tiny penis".

It is parasitical in the kind of molluscs, crustaceans, birds, and mammals, some coinage getting complex life oscillations involving additional than of these carrier. E.g., M. piriformes parasitizes a rough periwinkle (Littorina saxatilis); when which are actually eaten by herring gulls it infects a bird & lays its eggs in the bird's ordure to swarm in newly periwinkles.

Many metal money come notable for even manipulating or influencing their hosts. M. piriformes is a causal agent of its hikers, the rough out periwinkle, to move upwards, making it supplementary vulnerable to predation by herring gulls. M. pseudopygmaeus chemically castrates its host, a snail Onoba aculeus, & induces it to develop big than convention (these are non clear whenever this gigantism advantages the unsuspecting hosts or even even organisms or in case these are a non-dysfunctional side-outcome). M. papillorobustus drives its carrier, a 'lagune sand shrimp' (Gammarus insensibilis) to swim upwards, making it more vulnerable to predation. A bit of metal money of this genus "hitch-hike" on the manipulations of more metal money; for instance, M. hoffmanni parasitizes a equivalent sand shrimps when M. papillorobustus however doesn't manipulate a shrimps itself, instead benefiting from either a latter's manipulation of the unsuspecting hosts.