Cave­fish clocks are slow in the ab­sence of light

World of Animals - - Animal Clocks -

Be­cause the Sun rises ev­ery morn­ing, most an­i­mals ex­pe­ri­ence 24-hour days. How­ever, those that se­quester them­selves deep un­der­ground have lost touch with the so­lar cy­cle. So­ma­lian cave­fish have been in the dark for so long they no longer have eyes and have de­vel­oped a daily rhythm that lasts around 47 hours.

Two eye pro­teins mu­tated dur­ing the evo­lu­tion of this species while the eyes were be­ing phased out. These pho­tore­cep­tive opsins are re­spon­si­ble for the body clock’s con­tin­ued pres­ence even though the eye no longer ex­ists. The pro­teins have changed so much over mil­lions of years that they don’t re­spond to light any more but cause the brain to ex­pe­ri­ence a very long day in the dark.

So­ma­lian cave­fish have been in the dark for so long they no longer have eyes and have de­vel­oped a daily rhythm that lasts around 47 hours”

right The So­ma­lian cave­fish is a mem­ber of the Cyprinidae fam­ily, which also con­tains carps and true min­nows

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