Freethought & Rationalism Archive

sakrilege · 01-25-2003, 08:41 AM

When did sleep start in evolution? What species don't sleep? Am I asking the questions correctly? Does anybody really know what time it is?

philechat · 01-25-2003, 05:13 PM

I only know that most fish species have some form of sleep. Silkworms (annalids) alternate between regular periods and "sleep" period each about a week. After each "sleep" silkworms shed their skins and enter a new phrase of growth.

Dreams, i.e. REM sleep seem to appear in primitive forms among the reptiles. Some birds and most mammals have definite REM periods at night. The precise contents of mammalian dreams, however, is difficult to observe.

lpetrich · 01-26-2003, 12:40 AM

Silkworms are really the caterpillars of certain months. And that "sleeping" is a molting period.

But sleep goes far back, at least as inferred from studies of sleeping fruit flies.

lunachick · 01-26-2003, 02:34 AM

My dog definitely has doggie dreams.

sakrilege · 01-26-2003, 05:14 AM

From lpetrich's link...

Quote:

In a new study, scientists have identified two genes that regulate the balance of sleep in flies, both of which have human counterparts.

So common ancestor as opposed to convergent evolution seems to be the case. Something really basic is going on. Are there species that don't sleep or don't we know enough yet?

Quote:

Sleepy flies and sleepy humans are a lot alike. They sack out at night for about eight hours, caffeine keeps them awake, and they are hard to rouse while dozing.

Do fruit flies prefer expresso or cafe au lait? I wonder if the eight hours is significant or just coincidental. My dogs certainly sleep more than 8 hours.

lunachick, it was observing my dog having doggie dreams that inspired the post.

One of the last sane · 01-26-2003, 06:13 PM

What about sharks? I have this vague memory that someone told me they have to keep moving or they die. If they have to keep moving, do they have to swim in their sleep, or do they not sleep? Or is the whole "have to keep moving" thing a myth?

wade-w · 01-26-2003, 06:35 PM

From This site :

Quote:

Because sharks rely on ram-ventilation -- that is, their forward swimming to push oxygen-bearing water through their mouths and over their gills -- this fact begs the question: do sharks sleep at all? Dolphins are conscious breathers, actually having to think about rising to the surface, opening their blowholes, and breathing. From Russian studies carried out in the early 1970's, we know that dolphins catnap in 2 to 3-minute stretches, actually shutting down one hemisphere of their brain at a time. From experiments carried out on a small shark called the Spiny Dogfish (Squalus acanthias), we know that the 'Central Pattern Generator' that co-ordinates swimming movements in sharks is not located in the brain, but in the spinal chord. Thus, it is possible for an unconscious shark to swim.

There is even a possibility that the sharks' fore, mid-, and hind- brain shut down in sequence, resulting in the shark equivalent of sleep-walking.

In the end, I don't think anyone really knows the answer to that.

One of the last sane · 01-29-2003, 06:42 PM

Thanks, wade-w.
Sleep-swimming sharks. Interesting concept.
Another trivium to add to my collection...

Jesse · 01-29-2003, 08:15 PM

Quote:

Originally posted by One of the last sane
What about sharks? I have this vague memory that someone told me they have to keep moving or they die. If they have to keep moving, do they have to swim in their sleep, or do they not sleep? Or is the whole "have to keep moving" thing a myth?

Just did a quick google search and it's apparently a myth, although it has some basis in the fact that some (but not all) sharks need water to be moving over their gills in order the breathe. Here's someone talking about this issue:

http://www.cmnh.org/dinoarch/1996Oct/msg00192.html

Quote:

Andrew Howey says:

> I know that under normal circumstances, sharks MUST keep moving or drown.

Sorry, this is too much of a generalisation for me to let it go. Many
benthic sharks, including wobbegongs (orectolobids) and nurse sharks
(ginglystomatids), spend most of their time lying on the bottom. Many
neritic coastal forms, including lemon sharks (_Negaprion_) and reef
sharks (_Carcharinus_) will also do so regularly, and lemon sharks
have to do so for long periods of time when they are giving birth
(they are ovoviviparous).

Though I haven't done my homework here, I believe that the benthic
types _can_ pump water over their gills. Those that can't, but are
still able to sit on the bottom, may utilise bottom currents. It's a
well-disproved myth that sharks must 'keep moving or drown'.

and from here:

http://www.accessexcellence.org/LC/ST/Sharks/

Quote:

QUESTION: Do all species/or some species of shark have to keep moving in order to respire or is this a myth?

ANSWER: No, all species do not have to keep moving in order to respire. In fact, more species can rest on the bottom than not. There are two methods that sharks use to extract oxygen from water. By using their pharynx as a buccal pump some species are able to pump water over their gills. Once the animal begins to move at about 1-2 body lengths per second, they simply open their mouth and do what is called "ramjet" ventillation. Some species such as the mako, great hammerhead, silky and other open ocean sharks are obligate ramjet ventillators, but as I said, many species have no problem pumping water over their gills.

Also, this page says that if they don't keep moving they'll sink, which might be fatal if the ocean floor was at a great depth:

http://www.poseidon.co.za/articles/perfectpredator.htm

Quote:

Sharks belong to the cartilage group of fish, which also includes rays and the class holocephali. Cartilage fish differ from bony fish just as the name implies, because its skeleton consists of cartilage instead of bone. Another difference between sharks and bony fish is that sharks have 5 to 7 gill openings on the side of the head. With bony fish, the gills are covered instead by special gill covers.

Most bony fish regulate their buoyancy through the air bladder. Because this does not exist in sharks, they must keep moving all of the time to avoid sinking to the bottom. Many sharks have facilitated this with the help of a large and oil-rich liver, which produces a lower density in for example bone sharks. Sharks also have large, stiff pectoral fins, which give lift in the same way as airplane wings. The asymmetrical tail fin and the form of the nose also create upward lift.

Boro Nut · 02-03-2003, 09:44 AM

Quote:

Originally posted by sakrilege
How far back does sleep go?

It goes right back to when you went to bed.

Boro Nut

01-25-2003, 08:41 AM	#1
sakrilege Veteran Member Join Date: Aug 2002 Location: Cleveland, OH, USA Folding@Home Godless Team Posts: 6,211	How far back does sleep go? When did sleep start in evolution? What species don't sleep? Am I asking the questions correctly? Does anybody really know what time it is?

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01-25-2003, 05:13 PM	#2
philechat Senior Member Join Date: Apr 2002 Location: Mind of the Other Posts: 886	I only know that most fish species have some form of sleep. Silkworms (annalids) alternate between regular periods and "sleep" period each about a week. After each "sleep" silkworms shed their skins and enter a new phrase of growth. Dreams, i.e. REM sleep seem to appear in primitive forms among the reptiles. Some birds and most mammals have definite REM periods at night. The precise contents of mammalian dreams, however, is difficult to observe.

01-26-2003, 12:40 AM	#3
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	Silkworms are really the caterpillars of certain months. And that "sleeping" is a molting period. But sleep goes far back, at least as inferred from studies of sleeping fruit flies.

01-26-2003, 02:34 AM	#4
lunachick Veteran Member Join Date: Sep 2002 Location: NZ Posts: 7,895	My dog definitely has doggie dreams.

01-26-2003, 06:13 PM	#6
One of the last sane Senior Member Join Date: Jun 2002 Location: hereabouts Posts: 734	What about sharks? I have this vague memory that someone told me they have to keep moving or they die. If they have to keep moving, do they have to swim in their sleep, or do they not sleep? Or is the whole "have to keep moving" thing a myth?

01-29-2003, 06:42 PM	#8
One of the last sane Senior Member Join Date: Jun 2002 Location: hereabouts Posts: 734	Thanks, wade-w. Sleep-swimming sharks. Interesting concept. Another trivium to add to my collection...

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