Can spiders swim?

Waubra Preschool students, Victoria, Australia

What a great question!

Most spiders don’t swim by choice. But they sure can survive in water when they need to. From floating like a boat, to paddling like a rower, to carrying their own scuba bubbles, spiders have developed brilliant ways to deal with water.

Let’s dive into the science in some more detail, and look at how spiders handle getting their paws wet, with examples from our local bush.

Spiders can run across water

Water has surface tension – this acts like a kind of invisible skin that can hold up small, light objects.

Many spiders are tiny and have water-repellent hairs on their legs, so they can stand or run on water without sinking.

For example, fishing spiders wait at the water’s edge and scuttle across the surface to grab insects, tadpoles or even small fish.

If prey escapes underwater, this spider can even hide beneath the water’s surface briefly, then come back up.

Spiders can hold their breath underwater for days

Spiders don’t have gills, so they can’t get oxygen from water like fish do. But they have evolved clever strategies for staying alive if they stay in the water for a long time.

For example, the Australian Sydney funnel-web spider often falls into backyard swimming pools. People might see one and think it drowned, but it can actually survive underwater for hours by holding its breath much longer than a human could.

That’s because it breathes much more slowly than we do. Like many spiders, it has both tracheae (tiny air tubes) and book lungs (they look like a book with many pages) for breathing. Some spiders can close these and become watertight, to hold their breath for a long time.

Some trapdoor spiders have been recorded only taking a breath every six minutes.

Do not burst their bubble

Some spiders take the air with them like a scuba diver.

On the Great Barrier Reef coast, a little intertidal spider called Desis bobmarleyi actually lives part of its life under seawater. At high tide, it hides in a silk-lined air pocket in coral or shells. It uses the long hairs on its legs and body to trap a bubble around itself so it can breathe underwater between the tides. When the tide goes out, this spider comes out to hunt on the wet reef.

And in other parts of the world, there’s the famous diving bell spider, the only spider that spends its whole life entirely underwater.

It weaves an underwater silk web that it fills with air – like an underwater house. This spider can stay underwater for more than a day at a time by letting its air-bubble vessel actively pull oxygen from the water.

Flood proofing, trapdoor spider style

Some spiders sit tight and make their homes flood-proof. Remember those trapdoor spiders we mentioned? Trapdoor spiders live snug in burrows underground with a silken lid on top (like a little trapdoor).

In areas that get sudden heavy rains, a trapdoor spider might build its burrow with a raised entrance – a bit like a chimney – so water flows around or over it rather than straight in.

Some Australian trapdoor spiders in the outback clay pans have been found to build thick muddy silk doors that fit perfectly like a bath plug into the surrounding soil. The water just goes straight over the top.

Even if water does get in, some trapdoor spiders can seal their bodies and essentially hold their breath. They don’t swim in their flooded burrows, but they can wait out a flood without drowning.

What to do with a soggy spider

If you ever find a spider struggling in water – say in a swimming pool or even in a bucket – you can help as long as you’re careful.

First, always ask an adult before trying to assist a spider. Nobody has died in Australia in 60 years from spider venom. But some (such as the Sydney funnel-web) can still be fatal, so you must be sure not to touch or provoke it.

A good way to save a spider in a pool is to use a net or a scoop with a long handle. Gently lift the spider out and put it on the ground away from the water. The spider might look dead at first, but don’t be surprised if it “comes back to life” as it dries out – just like trapdoor spiders do.

And remember: never poke a spider with your bare hands, even if it seems lifeless. Spiders such as funnel-webs can still bite underwater or right after being rescued, and they will defend themselves if they feel threatened. So, play it safe and use tools or ask an adult or a spider expert to help.

If anyone is bitten, get an adult to seek medical attention immediately.

Next time you’re exploring nature (or even looking into the toilet), keep an eye out for our eight-legged friends and how they interact with water. You might spot a little spider boat captain or an air-bubble diver right in your backyard.

Leanda Denise Mason, Vice Chancellor Research Fellow in Conservation Ecology, Edith Cowan University

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

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome: find out how to enter at the bottom. You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.

My question is I am wondering why dogs get ‘snow nose’ in winter, and is it something to do with blood circulation? - Maddy, 11, Melbourne.

That is a very clever answer, Maddy! But the truth is, we don’t know why some dark brown, black or tan dogs’ noses fade during the winter months.

The dark colour in the nose (or any skin on the body) is called melanin. The more melanin you have, the darker your skin. If it happens to collect in patches, we call those freckles.

Melanin protects your skin from ultraviolet light by absorbing radiation. When you spend more time in the sun, the body makes more melanin.

During winter, or if you don’t spend much time in the sun, that pigment fades.

The cells that make that melanin are called melanocytes. If your body doesn’t make melanocytes, or if those melanocytes don’t make any pigment, then you have albinism.

Because these melanocytes are so involved in absorbing radiation from the sun, they are a bit prone to damage. If they get too damaged, they might become cancer.

Tumours of melanocytes are called melanoma, which is a big problem in Australia and why you must always wear a hat, sunnies and sunblock!

Dog skin is exactly the same and yours and mine. Hair colour and skin colour is the result of how much melanin is in the hair or skin. Most all the different colour variations you see are really just a result of how much melanin is in the skin and hair.

In some dogs (particularly breeds like the husky and some retrievers) their noses will lose some pigment in the winter. Occasionally this is permanent, but usually it fades in winter and gets darker in summer.

It is the melanin coming and going, just like a tan.

We know that’s not the whole story, because it’s not the entire nose that loses pigment, it’s down the middle and along the top. But it’s the best idea we have!

Maybe it also has to do with temperature, and that will be influenced on blood flow, just like you suggested! Your answer might be “right on the nose” after all.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:

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Aaron Herndon, Senior Lecturer – Small Animal Internal Medicine, The University of Queensland

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

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

Why is air colder the higher up you go? Shouldn’t it be hotter as you’re getting closer to the Sun? – Flynn, age 6, Sydney.

Thank you Flynn, that’s a great question. A lot of people have probably wondered this.

As you may know, hot air rises. So why is it so cold at the top of a mountain?

Well, it helps if you imagine the ground here on Earth as a big heater. It keeps us warm, and if you move away from the heater you feel cold.

So what “heats up” the heater? The light and warmth from the Sun. Scientists call this light and warmth “radiation”.

Light and warmth travel from the Sun

The light and warmth from the Sun travel through space towards Earth, and pass through our atmosphere. (The “atmosphere” is what we call the swirling air that surrounds our planet.)

But the atmosphere isn’t very good at holding onto the warmth from the Sun. The heat just slips straight through it. (For the adults reading: that’s because air at higher altitudes thins out as the gas particles expand and lose energy.)

Eventually, the heat from the Sun hits the ground and the ground soaks it up. This especially happens in forests and oceans, which are very good at absorbing heat. Other places, like snow fields, are more likely to reflect the radiation – meaning it bounces back toward the Sun instead of being soaked up by the ground.

Up, up, up

The higher up you go, the further you are away from the “heater” that is keeping us all warm – the ground that has absorbed the warmth from the Sun. At the top of mountains it can get so cold people could die within minutes without special protection. That’s because the air up there is just really bad at “holding onto” the radiation coming from the Sun, and the warmth passes straight through it on its journey toward the ground.

And all the way up in space, there is a lot more radiation from the Sun, and astronauts wear special suits to protect themselves from it. But there’s also no air in space, which means there’s really nothing much at all to “hold onto” the warmth of the Sun and make the temperature around you feel warm.

So if you were unlucky enough to be caught in space without a suit, you would freeze to death before the Sun’s radiation would get you.

Zoran Ristovski, Professor, Queensland University of Technology and Branka Miljevic, Senior Lecturer, Queensland University of Technology

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

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

How is snow made? – Tenley, age 7, Rockford, Michigan

The thought of snow can conjure up images of powdery slopes, days out of school or hours of shoveling. For millions of people, it’s an inevitable part of life – but you may rarely stop to think about what made the snow.

As a professor of atmospheric and planetary sciences, I’ve studied how ice crystals floating in the sky become the snow that coats the ground.

It all starts in the clouds.

Clouds form when air near the Earth’s surface rises. This happens when sunlight warms the ground and the air closest to it, just like the Sun can warm your face on a cold winter day.

As the slightly warmer air rises, it cools – and the water vapor in that rising air condenses to form liquid water or water ice. From that, a cloud is born.

Endless pathways

When temperatures are well below freezing on the ground, the clouds are primarily made of water in the form of ice. Under 32 degrees Fahrenheit – that’s zero degrees Celsius – the frozen water molecules arrange themselves into a hexagonal, or six-sided, crystalline shape. As ice crystals grow and clump together, they become too heavy to stay aloft. With the help of gravity, they begin to fall back down through and eventually out of the cloud.

What these ice crystals look like once they reach land depends on the temperature and humidity of the atmosphere. As the humidity – or the amount of water vapor in the cloud – increases, some of the ice crystals will grow intricate arms at their six corners. That branching process creates what we think of as the characteristic shapes of snowflakes.

No two ice crystals take the same path through a cloud. Instead, every ice crystal experiences different temperatures and humidities as it travels through the cloud, whether going up or down. The ever-changing conditions, combined with the infinite number of paths the crystals could take, result in a unique growth history and crystalline shape for each and every snowflake. This is why you’ve likely heard the saying, “No two snowflakes are exactly alike.”

Many times, these differences are visible to the naked eye; sometimes a microscope is required to tell them apart. Either way, scientists who study clouds and snow can examine a snowflake and ultimately understand the path it took through the cloud to land on your hand.

Liquid water as glue

When snow falls from the sky, you don’t usually see individual ice crystals, but rather clumps of crystals stuck together. One way ice crystals aggregate is through what’s called mechanical interlocking. When ice crystals bump into each other, crystals with intricate branches and arms intertwine and stick to others.

This mechanism is the main sticking process in cooler, drier conditions – what people call a “dry snow.” The result is a snow perfect for skiing, and easily picked up by the wind, but that won’t hold together when formed into a snowball.

The second way to stick ice crystals together is to warm them up a bit. When ice crystals fall through a region of cloud or atmosphere where the temperature is slightly above freezing, the edges of the crystals start to melt. Just a tiny bit of liquid water allows ice crystals that bump into each other to stick together very efficiently, almost like glue.

The result? Large clumps of ice crystals falling from the sky, what we call a “wet snow” – less than ideal for hitting the slopes but perfect for building a snowman.

Snow formed in clouds typically reaches the ground only in winter. But almost all clouds, no matter the time of year or location, contain some ice. This is true even for clouds in warm tropical regions, because the atmosphere above us is much colder and can reach temperatures below freezing even on the warmest of days. In fact, scientists who study weather discovered that clouds containing ice produce more rain than those that don’t contain any ice at all.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Alexandria Johnson, Professor of Atmospheric and Planetary Sciences, Purdue University

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