Curious Kids: how do fish sleep?



The Ringtail Unicornfish, which occurs in tropical marine waters of the Indo-Pacific. All fish sleep, even the weird-looking ones.
Bernard Spragg/Flickr

Culum Brown, Macquarie University


How do fish sleep? Do they keep swimming or do they sleep somewhere? – Anna, age 5, Thornleigh, NSW, Australia.



Nearly all animals sleep. Sleep is very important for refreshing the mind and body. When people sleep we close our eyes and lie motionless for a long time. We may be less aware of what is going on around us and our breathing slows down. Some people are very heavy sleepers and it takes a LOT to wake them up!

Fish don’t have eyelids — they don’t need them underwater because dust can’t get in their eyes. But fish still sleep. Some sleep during the day and only wake up at night, while others sleep at night and are awake through the day (just like you and I).

A happy puffer fish.
Flickr

How do fish know when it’s bedtime?

It’s pretty easy to tell when fish are sleeping: they lie motionless, often at the bottom or near the surface of the water. They are slow to respond to things going on around them, or may not respond at all (see some sleeping catfish here). If you watch their gills, you’ll notice they’re breathing very slowly.




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People with fish tanks at home will know that when the lights go off at night, the fish become far less active. If you turn a light on in the middle of the night you’ll see how still they are.

Like people, fish have an internal clock that tells them when to do things like sleep and eat. So even if you accidentally leave the lights on at night, the fish may settle down and go to sleep anyway.

A video showing sleeping catfish.

Some scientists have studied sleep in fish that live in caves where it is always dark. Even in some of these species there are times of low activity that look just like sleep. Of course there is no sunrise or sunset in caves so their rhythm is often different to fish that live at the surface in bright sunshine.

Some fish, like tuna and some sharks, have to swim all the time so that they can breathe. Its likely that these fish sleep with half their brain at a time, just like dolphins.

Parrot fish make a mucus cocoon around themselves at night — a gross, sticky sleeping bag which might protect them from parasites attacking them while they sleep.

Fish don’t need eyelids because dust can’t get in their eyes – but they still sleep.
Gavin Leung/Flickr

Fish may dream like people do!

One wonders if fish dream while they are sleeping. So far we don’t have the answer to that question but recent video footage of a sleeping octopus showed it changing colours, which suggests it may have been dreaming about hiding from a predator or sneaking up on its own prey (which is why octopuses change colour when they’re awake).




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Believe it or not, fish sleep is being studied to help us better understand sleep in people. Most of these studies use zebrafish and try to understand things like the effects of sleep deprivation (lack of sleep), insomnia (trouble getting to sleep) and circadian rhythm (sleep cycles).

Here is a cool video about sleep in animals, including fish.


Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au — —The Conversation

Culum Brown, Professor, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Curious Kids: where do swallows sleep?


Nests are not for sleep. They are for babies.
Flickr/Anna Hesser, CC BY-SA

Graham Fulton, The University of Queensland

Curious Kids is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.


I would like to find out something about swallows: we have noticed that they return to the same nests each year, but there must be younger birds that have no nest. Where do they sleep until they have built their new nest? – Nefeli, age 13, Corfu, Greece.


Thank you for your question, Nefeli.

It’s true that some swallows return to the same nests each year. But what do they do there?

We need to understand what nests are really for – and they are not for sleeping. They are for putting eggs into. The eggs need protection from the weather (hot and cold, wind and rain) and from other animals that would eat them. For predators, eggs taste great!

Adult swallows must build their nests away from predators and unsafe weather conditions, such as the wind, heat and cold.
merec0/flickr, CC BY-NC

Eventually the eggs hatch, then a blind and featherless baby swallow emerges. The babies are called nestlings or sometimes chicks. So nests are not for sleeping, they are for raising a family.

The babies that hatch from the swallow’s eggs are called nestlings or chicks.
Rafael V/flickr, CC BY-NC

It is true that when an adult is sitting on eggs and nestlings, it may sleep, especially at night.

But the young swallows who don’t have a nest to return to must build their own nest (to protect and feed their babies) or sleep on a tree branch, a rock ledge of a cliff face, or inside the hollow of a tree.

When swallows sleep away from the nest they sleep in places called roosts.

So remember: nests are mostly for babies; roosts are for sleep.

A swallow might sleep in a tree.
Flickr/Corine Bliek, CC BY



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Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.The Conversation

Graham Fulton, PhD student, School of Biological Sciences, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

World’s largest wind farm study finds sleep disturbances aren’t related to turbine noise


Simon Chapman, University of Sydney

During the Abbott government, the often recalcitrant Senate cross bench was thrown a big, juicy bone plainly intended to sweeten their disposition toward government bills which needed their support to pass. The anti- wind farm Senators were outraged with the National Health and Medical Research Council’s (NHMRC) 2015 report on wind farms which found no strong evidence of health effects from turbine exposure. There have been 25 reviews with similar findings published since 2003. The government may have promised these Senators the gift of the office of the National Wind Farm Commissioner which by February 2015 had received just 42 complaints about 12 wind farms, seven of which have not even been built.

In August 2015, the Senate Select Committee on Wind Turbines published its report. The Committee was chaired by Senator John Madigan, an open opponent of wind farms, and consisted of eight members. Six of these had form in savagely criticising wind farms. The content of their final report was therefore utterly predictable, with Labor’s Senator Anne Urquhart’s minority dissenting report shining like a beacon of respect for evidence.

There was no greater display of the naked demonising agenda of the Madigan-aligned group’s anti wind farm show trial than the total absence in their report of any mention of the world’s largest and most important study of the question of whether living near wind farms was harmful to health.

Health Canada’s Wind Turbine Noise and Health study published its preliminary findings on October 30, 2014. Senator Urquhart’s minority report noted that many submissions to the inquiry recognised the great contribution of the Health Canada “Wind Turbine Noise and Health Study” to the body of knowledge on the potential impacts of wind farms on human health. But the 181-page report made no mention of the study.

The study data were collected between May and September 2013 from adults aged 18 to 79 (606 males, 632 females), randomly selected from each household. They lived between 0.25 and 11.22km from wind turbines in two Canadian provinces, Ontario and Prince Edward Island.

In March, the Health Canada study group published its full findings in a series of open-access papers in the Journal of the Acoustical Society of America, the world’s most cited acoustical research journal, and in Sleep, a leading journal in sleep research. Here is a summary of some of its chief findings.

Do wind turbines increase the prevalence of health problems and sleep disturbance?

The researchers assessed self-reported sleep quality over the past 30 days using the Pittsburgh Sleep Quality Index and a wrist monitor to record the total sleep time, and the rate of awakening bouts and how long these last, for a total of 3,772 nights.

Averaged over a year, the measured sound of the turbines reached a maximum of 46 dB(A) with an average of 35.6. Forty six decibels is around the sound of a dishwasher operating in a kitchen.

Since January 2012, I have collected and catalogued a remarkable 247 different symptoms and diseases wind farm opponents claim are caused or exacerbated by wind turbines in humans and animals.

But the Health Canada study found that:

Self-reported health effects (e.g., migraines, tinnitus, dizziness, etc.), sleep disturbance, sleep disorders, quality of life, and perceived stress were not related to wind turbine noise levels.

Both self-reported and objectively measured sleep outcomes consistently revealed no apparent pattern or statistically significant relationship to wind turbine noise levels.

But, unsurprisingly, sleep was affected by whether residents had other health conditions (including sleep disorders), their caffeine consumption, and whether they were personally annoyed by blinking lights on the wind turbines.

Sleeping problems affect around 29% of all communities, regardless of whether they are near wind farms or not.

Do wind turbines cause measurable stress?

The researchers used a recognised scale to measure self-reported stress (the perceived stress scale – PSS) as well as recording hair cortisol concentrations, resting blood pressure, and heart rate.

However, the majority (77%–89%) of the variance in the perceived stress scale (PSS) scores was unaccounted for by differences in these objective measures. And wind turbine noise exposure had no apparent influence on any of them.

Again, the study concluded that the findings did not support an association between exposure to wind turbines and elevated self-reported or objectively defined measures of stress.

Do wind turbines annoy people?

Expressions such as being “hot and bothered” are well understood. When people are annoyed by something in their life, this can lead to the onset of symptoms. Being annoyed is not health problem in itself, but chronic annoyance can have health consequences.

The Health Canada study reported:

Visual and auditory perception of wind turbines as reported by respondents increased significantly with increasing wind turbine noise levels as did high annoyance toward several wind turbine features, including the following: noise, blinking lights, shadow flicker, visual impacts, and vibrations … Beyond annoyance, results do not support an association between exposure to wind turbine noise up to 46 dBA and the evaluated health-related endpoints.

The prevalence of residents reporting that they were very or extremely annoyed by wind turbine noise increased from 2.1% to 13.7% when sound pressure levels were below 30 dB compared to when the noise was between 40–46 dB.

So in summary, those who found the turbines annoying, tended to be those who lived nearer to them.

What factors predict who gets annoyed?

Even for the most annoying features, more than 86% of residents were not very or extremely annoyed by them.

There is much variation among our families, friends working environments in the way people react to noise. A 2014 review of symptoms related to modern technology (including wind turbines) found those who were more anxious, worried, concerned, or annoyed by a source that they believed to be a health risk more commonly reported symptoms than those without such beliefs.

In this Health Canada study, while proximity to the turbines was statistically significantly associated with annoyance, the relationship was weak. It was better explained by factors such as holding negative views about the visual impact of the turbines (not liking the look of them), being able to the see aircraft warning blinking lights, the perception of vibrations when the turbines were turning and high concern about physical safety. These are all perceptual variables that bothered some but not most.

Less than 10% of the participants derived personal benefit from the turbines (such as income from hosting the turbines). Deriving personal benefit had a statistically significant, although modest relationship to not being annoyed. The authors concluded:

these findings would support initiatives that facilitate direct or indirect personal benefit among participants living within a community in close proximity to wind power projects.

This suggests that strategies such as community sharing of rental incomes, offers of free electricity or home improvement and amenity payments may reduce annoyance.

If a Labor government is elected in July, the future of the ill-conceived Office of the National Wind Farm Commissioner is likely to be vulnerable, as it may well be with the expected departure of several wind farm-obsessed cross bench senators in the double dissolution, should the Coalition be returned.

State governments are increasingly removing wind farm planning barriers and the availability now of the Health Canada health report should drive another large stake through the forces determined to slow the growth of wind energy in Australia.

The Conversation

Simon Chapman, Emeritus Professor in Public Health, University of Sydney

This article was originally published on The Conversation. Read the original article.

Sick Again


Hi all – I have been trying to keep the Blog going in recent days despite being ill again – however, as I continue to get worse it is probably wise to have a complete break for the rest of the week and get as much sleep as I can.

I have had pneumonia 3 times since November last year (twice in November and once last month) and have come down sick again. Thought I was improving over the last couple of days but have once again developed the ‘shiver me timbers (chills and fever)’ tonight. So I plan to be away from the keyboard for the rest of the week in a bid to finally get over all of this illness. I apologise for the interruption to Blog posts in the mean time.