News of the WeekEvolutionary Biology

Placentas May Nourish Complexity Studies

Science  01 Nov 2002:
Vol. 298, Issue 5595, pp. 945
DOI: 10.1126/science.298.5595.945a

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On page 1018, researchers report that placentas have evolved independently three times in closely related species of guppylike fish in the genus Poeciliopsis. Other species in the genus lack placentas, and some have partial maternal provisioning by means of tissues that might be precursors of placentas. Thus the fish present the full trajectory of steps involved in the evolution of this organ, offering a model system for studying the evolution of complex organs.