Calling all citizen scientists: hunt for shark egg cases launches in Australia
March 20, 2023: CSIRO, Australia’s national science agency, is calling on citizen scientists to find and record egg cases washing up on Australian coasts, so researchers can better-understand oviparous chondrichthyans: egg-laying sharks, skates and chimaeras.
The Great Eggcase Hunt, an initiative of United Kingdom-based charity The Shark Trust, has launched in Australia in partnership with CSIRO to help provide new data for scientists studying the taxonomy and distribution of oviparous chondrichthyans.
Helen O’Neill, CSIRO Australian National Fish Collection biologist, said recording sightings of egg cases on beaches and coastlines would help scientists discover what the egg cases of different chondrichthyans look like, with some species still unknown.
“Egg cases are important for understanding the basic biology of oviparous chondrichthyans, as well as revealing valuable information such as where different species live and where their nurseries are located,” Ms O’Neill said.
Cat Gordon, Senior Conservation Officer at The Shark Trust, said the Great Eggcase Hunt began in the United Kingdom 20 years ago and has since recorded more than 380,000 individual egg cases from around the world.
“We’re really excited to be partnering with CSIRO to officially launch this citizen science project in Australia and to be able to expand the Shark Trust’s eggcase identification resources," Ms Gordon said.
"There’s such a diversity of species to be found around the Australian coastline, and with a tailored identification guide created for each state, they really showcase the different catsharks, skate, horn sharks, carpetsharks and chimaera eggcases that can be found washed ashore or seen while diving,” she said.
Also known as mermaids’ purses, egg cases come in many different shapes and colours, ranging from cream and butterscotch to deep amber and black. They range in size from approximately 4 to 25 centimetres.
Some egg cases have a smooth and simple appearance, while others have ridges, keels or curling tendrils that anchor them to kelp or coral. Port Jackson sharks have corkscrew-shaped egg cases that they wedge into rocks.
Each different species' egg case has a unique morphology that is helpful in taxonomy, the science of describing and naming species.
“At the Australian National Fish Collection, we are matching egg cases to the species that laid them,” Ms O’Neill said.
“We borrow egg cases from other collections, museums and aquariums around the world and use our own specimens collected from fish markets and surveys at sea or extracted from the ovaries of preserved specimens in our collection,” she said.
Chondrichthyans have the most diverse reproduction strategies found among vertebrates, encompassing parthenogenesis (no father), multiple paternity (more than one father of the litter), adelphophagy (baby sharks predating each other in the womb) and various modes of egg laying.
Egg cases found on beaches rarely contain live embryos, whose incubation times range from a few months up to three years, depending on the species.
“Egg cases found washed up on beaches have likely already hatched, died prematurely due to being washed ashore or been predated on by creatures like sea snails, who bore a hole in the egg case and suck out the contents,” Ms O’Neill said.
The Shark Trust is a United-Kingdom-based charity dedicated to safeguarding the future of sharks, skates, rays, and chimaera through positive change. The Trust achieves this through science, education, influence and action.
To get involved in the Great Eggcase Hunt, you can record sightings via the Shark Trust citizen science mobile phone app or through the project website: www.sharktrust.org/greateggcasehunt
Photo: Port Jackson shark egg on Station Beach at Pittwater. Image PON/AJG
The Port Jackson shark (Heterodontus portusjacksoni) is a nocturnal, oviparous (egg laying) type of bullhead shark of the family Heterodontidae, found in the coastal region of southern Australia, including the waters off Port Jackson. It has a large, blunt head with prominent forehead ridges and dark brown harness-like markings on a lighter grey-brown body, and can grow up to 1.65 metres (5.5 ft) long. They are the largest in the genus Heterodontus.
The Port Jackson shark is a migratory species, traveling south in the summer and returning north to breed in the winter. It feeds on hard-shelled mollusks, crustaceans, sea urchins, and fish. Identification of this species is very easy due to the pattern of harness-like markings that cross the eyes, run along the back to the first dorsal fin, then cross the side of the body, in addition to the spine in front of both dorsal fins.
These sharks are are oviparous, meaning that they lay eggs rather than give live birth to their young. The species has an annual breeding cycle which begins in late August and continues until the middle of November. During this time, the female lays pairs of eggs every 8-17 days. As many as eight pairs can be laid during this period. The eggs mature for 10–11 months before the hatchlings, known as neonates, can break out of the egg capsule.
Port Jackson shark adults are often seen resting in caves in groups, and prefer to associate with specific sharks based on sex and size. Juvenile Port Jackson sharks, on the other hand, do not appear to be social. A captive study showed that these juveniles did not prefer to spend time next to other sharks, even when they were familiar with each other (i.e. tank mates). Juvenile Port Jackson sharks have unique personality traits, just like humans. Some were bolder than others when exploring a novel environment and they also reacted differently to a stressful situation (in choosing a freeze or flight response).
Juvenile Port Jackson sharks are also capable of learning to associate bubbles, LED lights, or sounds with receiving a food reward, can distinguish different quantities (i.e. count), and can learn by watching what other sharks are doing.
At least in some of these lab experiments males are shyer than females and boldness increases with consecutive trials of the same experiment. In experiments with different music genres, none of the sharks tested learned to discriminate between a jazz and a classical music stimulus.
Port Jackson Sharks are considered harmless to humans, although the teeth, whilst not large or sharp, can give a painful bite.
Heterodontus portusjacksoni. Photo: Mark Norman, Museums Victoria
Scouts are out & About
Over the past few months, all age groups in Scouting across Sydney North Region have been doing everything from canoe trips, hikes, and abseiling, to craft and community cleanups.
There's no better time to get into Scouting, with sections for ages 5-25, plus lots of satisfying leadership opportunities for adults.
Young people can have a four-week trial period, and Active Kids vouchers can be used towards membership fees.
Scouts are everywhere! Connect with your local Scout Group via sydneynorthscouts.com
school holidays activities: Art workshops + Sailing
Narrabeen Lakes Sailing Club
Common Crow Butterfly Euploea core
You may be seeing a few of these butterflies around our area at the moment, the Common Crow Butterfly Euploea core.
It belongs to the crows and tigers subfamily Danainae (tribe Danaini). E. core is a glossy-black, medium-sized 85–95 mm (3.3–3.7 in) butterfly with rows of white spots on the margins of its wings. E. core is a slow, steady flier. Due to its unpalatability it is usually observed gliding through the air with a minimum of effort. As caterpillars, this species sequesters toxins from its food plant which are passed on from larva to pupa to the adult. While feeding, it is a very bold butterfly, taking a long time at each bunch of flowers. It can also be found mud-puddling with others of its species and often in mixed groups. The males of this species visit plants like Crotalaria and Heliotropium to replenish pheromone stocks which are used to attract a female during courtship.
It is found in southern Pakistan, Sri Lanka, India, Bangladesh, Myanmar, Russia, and Australia. In its range E. core is found at all elevations, right from sea level up into the mountains to 2,400 metres (8,000 ft). It can be observed in all layers of vegetation and in all types of regions from arid land to forested areas. It can as commonly be seen gliding over the treetops as flitting about a foot off the ground searching for nectar flowers. In thick forests it is often seen moving along open tracks or following the course of a river.
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Photo taken in Careel Bay, March 2023. Pic; AJG
The butterfly, being protected by its inedibility, has a leisurely flight. It is often seen flying about shrubs and bushes in search of its host plants. It visits a large variety of flowering plant species. When gliding E. core holds its wings at an angle just greater than the horizontal plane, maintaining its flight with a few measured wingbeats.
E. core is a nectar lover and visits flowers unhurriedly. It seems to prefer bunches to individual flowers. When feeding the butterfly is unhurried and is not easily disturbed. It can be approached closely at this time. On hot days large numbers of these butterflies can be seen mud-puddling on wet sand. E. core is an avid mud-puddler often congregating in huge swarms along with other Euploea species as well as other danaids.
Eggs are laid on the underside of young leaves of the host plants. The egg is shiny white, tall and pointed, with ribbed sides. Just before hatching the eggs turn greyish with a black top. Throughout its life the caterpillar stays on the underside of the leaves. The caterpillar is uniformly cylindrical, vividly coloured and smooth. It has alternate white and dark brown or black transverse bands. Just above the legs and prolegs, along the entire body is a wide orangish-red band interspersed with black spiracles.
The adult butterfly has a life span of 11 - 13 weeks. The adults feed upon nectar from various flowering plants, including eucalypts.
Curious Kids: what happens when fruit gets ripe?
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.
What happens when fruit gets ripe? - Rachel, age 3, Melbourne.
Hi Rachel. You have asked a very interesting question.
Fruit ripening is all about plants getting animals to eat the seeds that are inside their fruits.
When the animals have finished eating, they move around and drop the seeds in a different place when they do a poo. This helps the plants get their seeds to somewhere new where they can grow into a new plant.
A fruit wants to be eaten but only when the time is right
But plants need to make sure that their fruits are only eaten when their seeds are ready to be spread around.
So before the seeds are ready, the plants make sure that the fruit are not easy to see and are horrible to eat. This means the fruits may stay green and may stay hidden among the leaves, so it’s harder to pick them. They are also very hard and bitter to taste, so animals (including humans) don’t like eating them.
When the seeds are ready, the fruit become ripe and good-looking, making animals keen to eat them.
When the fruit are ripe they become brightly coloured. Apples, strawberries and peaches become red, bananas become yellow and, of course, oranges become orange.
Next time you go the supermarket, look at the beautiful colours of the fruit in there and see how many different colours you can find.
Softer, sweeter and nicer to smell
At the same time as fruit change colour, they also become soft. This is because fruit are made from many tiny things called cells.
In plants, each cell has a wall. There is stuff in the cells’ walls that changes to make the fruit soft, and it is this softening that makes them juicy.
I bet the thing you most like about fruit is that they are sweet and yummy to eat. When the fruits ripen, the plant cleverly removes all of the bad-tasting stuff from the fruit and replaces them with sugars. That, of course, makes the fruit sweet and nice to eat.
The last thing that changes when fruit ripen is that they make stuff that helps them smell really nice, which makes animals and people want to eat them.
Different fruits have different stuff in them that makes them smell the way they do. That is why we can tell a pear from a strawberry, just by smell alone.
A tricky gas called ethylene
These changes that happen when fruit ripen (the change in colour, smell, sweetness and softness) all happen at the same time.
To make this happen, many fruit use another special thing called ethylene. This ethylene is helpful.
The bananas you eat come from farms in Queensland. They are picked when they are green and a bit hard. They are picked before they are ripe so they don’t get damaged while they are being taken to shops near your house in Melbourne.
When they arrive in Melbourne, the people in charge of those green bananas will put some ethylene gas near them to ripen them up. Then they are put in shops so we can buy them when they are yellow and ripe to eat.
The most important thing about all fruits is that they are very good for us.
The sugars inside them are a great way to get energy that helps us work and play all day.
They are also full of vitamins that help us become big and strong. So it’s important that we eat lots of fruit. But don’t forget your veggies, as they are also very good for us!
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.
Paul Holford, Professor of Agricultural Biotechnology, Western Sydney University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Curious Kids: what makes an echo?
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.
What makes an echo? - Minnie, age 4.
That’s a tricky question. The simplest way to answer is to say that an echo is a sound that later comes back to where it came from.
Before we get into what makes an echo, we need to have a think about sound.
What is a sound?
What we call “sound” is really just the air in our ears moving back and forth.
The air can move fast or slow. We can hear air moving back and forth between 20 and 20,000 times per second. That’s really, really fast! (For the grownups reading right now, human hearing is from about 20 - 20,000 Hertz, which means repetitions per second).
But did you know that there are faster and slower air movements that can be heard by other animals, but not people?
Where does sound come from?
If we hear the air moving in our ears, where did that moving air come from?
A sound can come from anything that vibrates or moves back and forth.
It could start with the moving string of a guitar or the vocal folds in your voice box that move when you speak or sing.
Once the air starts to move, it travels in all directions until it finds something to stop it.
Bounce back!
When sound travelling in air (we call this a sound wave) hits a hard flat surface, like a tiled bathroom wall, most of it bounces back. Maybe this is why people like to sing in the shower.
But to get a really good echo, that sounds the same as the original sound, we need a very big bathroom, or another very big, hard-walled place – like a valley or a canyon!
Here’s a video of a man playing trumpet in a canyon. The vibration of his lips makes the sound, which bounces back from the hard wall of rock on the other side of the valley:
For a sound to bounce back and make an echo, there has to be a lot of space between the sound source and the thing (wall or mountain) that it hits and bounces back.
Why? Because it takes time for the sound to come back as an echo. If there’s no big space, it won’t sound like an echo because the sound that comes back will get mixed up with the original sound.
Noticing changes in the sound can still be useful. Some animals like bats and dolphins, and even some children, can use this to tell where they are. This is called “echolocation”.
So if you don’t have a very large bathroom, you may want to try a bushwalk in a valley, or perhaps an underground carpark to find your echos.
If you know of any good echo spots, leave a comment below. I can start you off by telling you that there is a place called Echo Point at Katoomba in NSW.
Did you know?
The name “echo” comes from a Greek legend. In that story, a kind of mountain fairy named Echo was cursed by the god Zeus’ wife Hera so that she could only repeat what was said to her.
Some people believe that when a duck quacks, it does not echo but some scientists in the UK did an experiment and said that was not true.
Many scientists like to study sounds without echoes. For this, they design special rooms called “anechoic chambers”, that stop sound from bouncing back. The Acoustics Lab at the University of New South Wales even has an anechoic pipe. It is so long that any sound that goes in doesn’t come back out.
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.
Noël Hanna, Leading Education Professional (Physics), UNSW Global, UNSW Sydney
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Why does time change when traveling close to the speed of light? A physicist explains
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 does time change when traveling close to the speed of light? – Timothy, age 11, Shoreview, Minnesota
Imagine you’re in a car driving across the country watching the landscape. A tree in the distance gets closer to your car, passes right by you, then moves off again in the distance behind you.
Of course, you know that tree isn’t actually getting up and walking toward or away from you. It’s you in the car who’s moving toward the tree. The tree is moving only in comparison, or relative, to you – that’s what we physicists call relativity. If you had a friend standing by the tree, they would see you moving toward them at the same speed that you see them moving toward you.
In his 1632 book “Dialogue Concerning the Two Chief World Systems,” the astronomer Galileo Galilei first described the principle of relativity – the idea that the universe should behave the same way at all times, even if two people experience an event differently because one is moving in respect to the other.
If you are in a car and toss a ball up in the air, the physical laws acting on it, such as the force of gravity, should be the same as the ones acting on an observer watching from the side of the road. However, while you see the ball as moving up and back down, someone on the side of the road will see it moving toward or away from them as well as up and down.
Special relativity and the speed of light
Albert Einstein much later proposed the idea of what’s now known as special relativity to explain some confusing observations that didn’t have an intuitive explanation at the time. Einstein used the work of many physicists and astronomers in the late 1800s to put together his theory in 1905, starting with two key ingredients: the principle of relativity and the strange observation that the speed of light is the same for every observer and nothing can move faster. Everyone measuring the speed of light will get the same result, no matter where they are or how fast they are moving.
Let’s say you’re in the car driving at 60 miles per hour and your friend is standing by the tree. When they throw a ball toward you at a speed of what they perceive to be 60 miles per hour, you might logically think that you would observe your friend and the tree moving toward you at 60 miles per hour and the ball moving toward you at 120 miles per hour. While that’s really close to the correct value, it’s actually slightly wrong.
This discrepancy between what you might expect by adding the two numbers and the true answer grows as one or both of you move closer to the speed of light. If you were traveling in a rocket moving at 75% of the speed of light and your friend throws the ball at the same speed, you would not see the ball moving toward you at 150% of the speed of light. This is because nothing can move faster than light – the ball would still appear to be moving toward you at less than the speed of light. While this all may seem very strange, there is lots of experimental evidence to back up these observations.
Time dilation and the twin paradox
Speed is not the only factor that changes relative to who is making the observation. Another consequence of relativity is the concept of time dilation, whereby people measure different amounts of time passing depending on how fast they move relative to one another.
Each person experiences time normally relative to themselves. But the person moving faster experiences less time passing for them than the person moving slower. It’s only when they reconnect and compare their watches that they realize that one watch says less time has passed while the other says more.
This leads to one of the strangest results of relativity – the twin paradox, which says that if one of a pair of twins makes a trip into space on a high-speed rocket, they will return to Earth to find their twin has aged faster than they have. It’s important to note that time behaves “normally” as perceived by each twin (exactly as you are experiencing time now), even if their measurements disagree.
You might be wondering: If each twin sees themselves as stationary and the other as moving toward them, wouldn’t they each measure the other as aging faster? The answer is no, because they can’t both be older relative to the other twin.
The twin on the spaceship is not only moving at a particular speed where the frame of references stay the same but also accelerating compared with the twin on Earth. Unlike speeds that are relative to the observer, accelerations are absolute. If you step on a scale, the weight you are measuring is actually your acceleration due to gravity. This measurement stays the same regardless of the speed at which the Earth is moving through the solar system, or the solar system is moving through the galaxy or the galaxy through the universe.
Neither twin experiences any strangeness with their watches as one moves closer to the speed of light – they both experience time as normally as you or I do. It’s only when they meet up and compare their observations that they will see a difference – one that is perfectly defined by the mathematics of relativity.
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.
Michael Lam, Assistant Professor of Physics and Astronomy, Rochester Institute of Technology
This article is republished from The Conversation under a Creative Commons license. Read the original article.
book of the month march 2023: seven little australians by ethel turner
Seven Little Australians is a classic Australian children's literature novel by Ethel Turner, published in 1894. Set mainly in Sydney in the 1880s, it relates the adventures of the seven mischievous Woolcot children, their stern army father Captain Woolcot, and faithful young stepmother Esther.
Turner wrote the novel in 1893 while living at Inglewood in what was then rural Lindfield (now Woodlands, Killara, New South Wales), having moved there from the inner city suburb of Paddington in 1891. The suburban bushland surroundings quickly became important in Turner's stories. On her 21st birthday, Ethel wrote in her diary, 'Seven L. Aust. – sketched it out.' (24 January 1893) In 1994 the novel was the only book by an Australian author to have been continuously in print for 100 years. The book's original handwritten manuscript is held by the State Library of NSW.[1] The full text of the manuscript has been digitized and can be viewed on the Library's website. The original title of the novel, as written by Turner, was 'Seven Pickles'.
It has been extensively adapted for other media, including as a film, two different television mini-series, various stage plays and a stage musical.
Ethel Turner used to come to Palm Beach with her husband and children, one of whom was a founding member of Palm Beach SLSC - Adrian Curlewis. You can read more about this great book and its local connections in Ethel Turner's Seven Little Australians Added To UNESCO Memory Of The World Register - The Missing Pages Restored
PALM BEACH.
THE ROCK POOL.
God in a delicate mood parted these headlands,
Bade His unwearying waters fret Him a bay.
All the bright breakers sang at the chance to adore Him,
All the blue breakers rolled from His feet to obey.
Cream as the clouds curves the sand where the light foam races,
Green, all a-patterned with grey is the gown of the land,
The land stepping down, austere, from the hill-top places
The sky in her hair and her silver feet in the sand.
There is a pool by the cliffs that the waves wash over,
A clean-cut pool where a child may dive and play.
Low on the rocks it lies, like a sky-dropped mirror,
Never a light but it catches the live-long day.
For I have waked with the sun not over the headland,
All of the sea sun-grey, with one thrust of jade,
And in the heart of the pool, like a jewel lying,
One point of light from the cold green thrusting made.
Nearer the top of the hill, the slow sun struggles,
Primrose drifts on the sea with one purple stain,
And now in the pool's pale silver, is lying, lovely.
Violet, amethyst, amethyst, violet again.
Wild rose in the pool, white clouds and the sunset's rainbow,
A moon in the pool, a shy moon, bathing alone,
And, as I sleep, the stars sown in millions around me,
One shoots down and drowns in it like a stone.
God, in a delicate mood, parted these headlands,
God let the breakers fret Him this delicate bay,
Man made the pool, the clean-cut pool in the boulders,
God, in a delicate mood, glances its way.
ETHEL TURNER.
PALM BEACH. (1926, February 6). The Sydney Morning Herald(NSW : 1842 - 1954), p. 11. Retrieved fromhttp://nla.gov.au/nla.news-article16265379
Palm Beach: West across rock swimming pool and water to timbered ridge with scattered houses - photo by Rex Hazlewood, circa 1920-1929 Image Courtesy The Mitchell Library, State Library of NSW, No.:c046220005h
Archive of millions of Historical Children’s Books All Digitised: Free to download or Read Online
Enter the 1: Baldwin Library of Historical Children’s Literature here, where you can browse several categories, search for subjects, authors, titles, etc, see full-screen, zoomable images of book covers, download XML versions, and read all of the 2: over 6,000 books in the collection with comfortable reader views.
Find 3: more classics in the collection, 800 Free eBooks for iPad, Kindle & Other Devices.
Ingleside Riders Group Inc. (IRG) is a not for profit incorporated association and is run solely by volunteers. It was formed in 2003 and provides a facility known as “Ingleside Equestrian Park” which is approximately 9 acres of land between Wattle St and McLean St, Ingleside. 
Profile: Pittwater Baseball Club
Profile: Avalon Soccer Club
Avalon Bilgola Amateur Swimming Club ProfileWe swim at Bilgola rock pool on Saturday mornings (8:45am till 11:30am). Our season runs between October and March
Profile Bayview Yacht Racing Association (BYRA)Mona Vale Mountain Cub Scouts
Find out more about all the fun you can have at Mona Vale Mountain Cub Scouts Profile –
our Profile pages aren’t just about those who can tell you about Pittwater before you were born, they’re also about great clubs and activities that you too can get involved in!