jueves, 11 de octubre de 2007

¿Por qué los peces son de colores?

Lo mejor para un pez chico es pasar desapercibido y que no se lo coma el grande. Entonces, ¿Por qué algunos tienen colores tan llamativos? La selección natural debería favorecer aquellos cuyos tonos permiten camuflarse mejor y evitar a los depredadores. La explicación vuelve a darla la selección sexual: el riesgo vale la pena porque las hembras prefieren aparearse con los peces de colores vistosos. La interpretación evolutiva es que los coloreados, al haber sobrevivido a pesar de tenerlo más difícil, demuestran salud y buenas condiciones físicas.

De hecho los científicos han estudiado este efecto en una especie de peces cuyos individuos poseen una gran diversidad de tonalidades, y han observado que en entornos donde hay muchos depredadores, la proporción de peces de colores discretos aumenta, ya que es más práctico pasar desapercibido. En cambio, cuando la cantidad de depredadores disminuye, aumenta la proporción de peces coloreados porque tienen más éxito reproductivo.

Pero no queda aquí la cosa, los científicos también han observado un comportamiento curioso en estos peces: Durante la etapa de reproducción, y sólo cuando hay una hembra presente, los machos arriesgan su vida acercándose lo más posible a sus depredadores. El objetivo es impresionar a su posible pareja y demostrarle que se está en buena forma para escapar del ataque enemigo. Las hembras efectivamente escogen de nuevo al más valiente, en otro claro ejemplo de que en el mundo natural, reproducirse suele ser incluso más importante que sobrevivir.

Extracto del Artículo publicado originalmente enEl magazine en julio de 2005

En próxima entrega les contaré cuáles son los colores que tienen los machos en la especie humana....

28 comentarios:

Elysa dijo...

Que hermosa es la naturaleza no?!
Pero hay unas cosillas importante que aclarar:
Selección natural no es lo mismo que selección sexual. Ambas impecables teroias expuestas por Darwin luego de su largo viaje que explican los mecanismos que actúan en el maravilloso proceso de la evolución.
Pero a pesar de generar un proceso explican la evolución de rasgos diferentes: rasgos adaptativos (en el caso de la natural, por ejemplo el ojo) y rasgos no adaptativos (en el caso de la selección sexual, como por ejemplo el color de los peces)
Por otra parte existen varias hipótesis acerca de por que se da la selección sexual. Una de ellas es la de los buenos genes que muy bien expones, pero la rueda libre, el conflicto sexual, explosión sensorial etc... explican también el mecanismo y por tanto la aparición de los colores en los peces y en los hombres!!
Este tema merece una buena sentada y aprovecha luego del 23 de Oct (que presento la tesis..y estas invitadisima)que estoy fresquita con eso..
Muchos besos
E.

Carmen Mosquera dijo...

Mi querida pequeña Ely, que gustazo poder argumentar contigo, en tu comentario me parece interpretar que, finalmente, volvemos a nuestra vieja y rica discusión, pero en este caso tú me sigues en cuanto al comportamiento y claro que estaré de acuerdo contigo (como no?), en efecto, la genética NO es exclusiva de la influencia del entorno en el comportamiento...jeje mi vieja pataleta contigo!!!, verás el próximo artículo que va por esos caminos y te espero para desmenuzarlo.
Ya sabes que mi mejor energía está contigo para este final de una etapa tan importante y estoy segura que tu tesis será un éxito mas.
Te espero para "caernos a argumentos" un beso

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