La daphnia o pulga de agua, es un crustáceo del tamaño de un grano de arroz y nació de un huevo de 700 años recuperado del fondo de un lago enMinnesota, EE.UU.

 Los científicos recolectaron varios huevosque habían dormido durante años, pero al descubrir que esta diminuta dafnia, se sorprendieron con su edad.

Su organismo ha permitido a los investigadores mostrar cómo ha impactado en la evolución de estos animalesla presencia humana en los alrededores del lago South Centre Lake, en Lindstrom.
Las dafnias producen unos huevos durmientes con una capa extra que los cubre, llamada efipio, cuya función es protegerlos y asegurar su supervivencia en condiciones adversas.
“El efipio es como una vaina, si imaginas como abrir una vaina de arvejas, y tienes una pequeña pieza dentro, es algo así”, explica a BBC Mundo Dagmar Frisch, investigadora de laUniversidad de la Estación Biológica de Oklahoma.
Uno de sus pioneros, Nelson Hairston, de la Universidad de Cornell en el estado de Nueva York, logró revivir un copépodo, otra especie de crustáceo, de 300 años, según apunta Frisch.
Frisch y sus colegas recogieron muestras de los sedimentos del lago de Lindstrom y las dataron con el método radiométrico por plomo-210. Así pudieron saber que el núcleo de sedimentos tenía 1.600 años, y que la edad de su dafnia era de 700 años, según informó la BBC.
Analizando los sedimentos, los científicos pudieron ver cómo aumentó la concentración de fósforo con la aparición de una población estable dedicada a la agricultura, provocada por el uso de fertilizantes que llegan hasta el lago.

BBC

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