Does snails & fish run on bio-logical clocks!

[Mazain]

Does snails & fish run on bio-logical clocks? I was suprised to find that leaving the aquarium lights on at night, all the burrowing snails were out and the fish were at their usuall place resting as if the aquarium lights were switched off.

 

[Rusty_Shackleford30 146]

Fish definitely adhere to a circadian rhythm. They need a regular, consistent, day/night cycle.

 

[Mazain]

Fish definitely adhere to a circadian rhythm. They need a regular, consistent, day/night cycle.

Guess snails & fish are stronger than mamals. External factors do not affect their circadian rhythm.

 

[Rusty_Shackleford30 146]

Guess snails & fish are stronger than mamals. External factors do not affect their circadian rhythm.

That's incorrect. External factors DO effect a fishes circadian rhythm, chief among them is light as fish have no external eye lids and can't "close their eyes"

Circadian Clocks in Fish—What Have We Learned so far? - PMC https://share.google/9CoGzHV8VIcSEJ5RK

 

[Mazain]

That's incorrect. External factors DO effect a fishes circadian rhythm, chief among them is light as fish have no external eye lids and can't "close their eyes"

Then why did they sleep when the lights are on. And the borrowing snails wake up.

 

[Rusty_Shackleford30 146]

Then why did they sleep when the lights are on. And the borrowing snails wake up.

I was suprised to find that leaving the aquarium lights on at night, all the burrowing snails were out and the fish were at their usuall place resting as if the aquarium lights were switched off

You answered your own question.
The fishes circadian rhythm told them it was time to sleep as the usual pattern at that time had the lights off and the fish sleeping. Then one day you left the lights on all night and the fish followed their circadian rhythm amd slept at their normal time. This proves that the fish follow a cycle.
You can perform this experiment on yourself. Go to bed every night at 10pm for a month. Then one day try to stay up till midnight. I bet at 10pm you will start yawning and have a hard time keeping your eyes open. Your body is used to going to bed at 10pm so it's trying to tell you it's time to rest.

Now was it truly a normal, totally dark sleep. Probably not. Because of the light I bet the fish were more active than they would usually be in a normal dark period.

 

[Fishmanic31 147]

I myself, when I haven't slept well the night before, can be in my recliner watching TV with the lights on and if I am very tired, will fall asleep and sleep for an hour or two. Maybe fish get tired too and eventually fall into sleep if the lights have been left in the on state for an overly extended period.

 

[Mazain]

Maybe fish get tired too and eventually fall into sleep if the lights have been left in the on state for an overly extended period.

Research shows worlwide that fish is the 3rd popular house pet after cats and dogs.