Secondary sex characteristics Parasitism

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parasitism has been suggested part of explanation of evolution of secondary sex characteristics in breeding male animals, such plumage of peacocks , manes of male lions. argument female hosts select males breeding based on such characteristics because act honest signals of costly handicaps. possible mechanism this, suggested ivar folstad , andrew karter, male hormone testosterone encourages growth of secondary sex characteristics such manes, @ price of reducing animal s immune defences.



the parasitic barnacle sacculina carcini (highlighted) attached crab


parasitic crustaceans such peltogaster carvatus , sacculina cause damage gonads of host crabs. in case of sacculina, testes of on 2 thirds of crab hosts had degenerated sufficiently these male crabs have gained female secondary sex characteristics such broader abdomens, smaller claws (chelae) , egg-grasping appendages. trematode zoogonus lasius causes parasitic castration of intertidal snail ilyanassa obsoleta; other trematodes directly or indirectly castrate other species of snail.








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