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How would the disappearance of anglerfish affect our environment? – Bella, age 6, Sydney.
As I am sure you know, anglerfish live deep in the ocean. The females have an enlarged fin overhanging their eyes and their mouth that acts as a lure – much like bait on a fishing line – and this explains their name. (“Angling” is a method of fishing.)
The fact is we understand very little about the deep sea and how its inhabitants, including anglerfish, will respond to change. In fact, more people have walked on the Moon than have been to the bottom of the ocean.
But I will do my best to answer your question.
The food web
Close your eyes and imagine a spider’s web. All parts of it are connected, and if a bug gets tangled in one part, it can cause a completely different part of the web to wobble or break.
It helps to remember that all species are interconnected via something called the “food web”. The food web is not a real web like a spider’s web. It’s just a way of thinking about how species are connected to each other. Basically, the food web tells us who eats whom.
If you make a change to one part of the food web, that can have an ripple effect that can cause changes on another part of the web.
Less of one animal can mean more of another
Anglerfish usually eat small fish, as well as relatives of shrimp.
It is likely that if all the anglerfish in the ocean disappeared, their prey would explode in number and another predator would then “step in” to replace them.
And any species that likes to eat the anglerfish would have to start eating another species instead – or risk dying out.
At the height of the whaling industry, about 100 years ago, whales nearly disappeared. That meant that the number of krill (the tiny animals that whales eat) exploded, providing a feast for other animals that also eat krill – such as seals. That is how a food web works.
Weird and wonderful
There are around 200 different types of anglerfish. Although one giant species grows to over a metre, most anglerfish are tiny – less than 10cm long.
Only female anglerfish have lures. These lures often glow in the dark, thanks to the bio-luminescent bacteria inside them, which presents a tempting (but fake) meal to their unsuspecting prey.
Anglerfish don’t form large schools like many other fish and this represents a problem for them – they need to find a mate. The tiny males have found a solution: if they do happen to find a female, they grasp onto her with their mouths and never let go.
These males tap into the females’ blood stream and never have to eat again. Scientists call this behaviour parasitic. Sometimes more than one male can be attached to a single female. Imagine someone’s father being 100 times smaller than their mother and being permanently attached to her.
Nature is truly weird and wonderful.
Among the biggest problems for a lot of fish species are disease and overfishing by humans. But it’s highly unlikely that these threats could wipe out anglerfish.
Anglerfish are found between 300 and several thousand metres of water. At this depth, it is constantly dark and the water is cold.
As they live in such deep water and do not form schools, they are not targeted by fishermen, a common threat for many shallow water fish.
And anglerfish are so widely spread across the world’s oceans that any disease is highly unlikely to spread among them.
There is one threat that might affect angler fish – the threat of global warming. Temperatures in the deep ocean are very stable, they simply don’t change much.
Anglerfish live their entire lives at depth with near constant temperatures; hence even small shifts in temperature may affect them. It remains unclear whether increasing temperatures really will threaten angler fish – only time will tell.
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What would the world be like without frogs? Earth is in its sixth mass extinction event and amphibians are among the hardest hit.
But in the island of New Guinea, home to 6% of the world’s frog species, there’s a rare opportunity to save them from the potential conservation disaster of a chytrid fungus outbreak.
The amphibian chytrid fungus is a microscopic, aquatic fungus that infects a protein in frog skin. It interferes with the balance of electrolytes and, in turn, effectively gives frogs a heart attack.
If the amphibian chytrid fungus invades New Guinea, we estimate 100 species of frogs could decline or become extinct. This disease, which emerged in the 1980s, has already wiped out 90 species of frogs around the world.
Collaborating with 30 international scientists, we developed a way to save New Guinea’s frog species from a mass extinction, one that’s predictable and preventable. We need urgent, unified, international action to prepare for the arrival of the deadly fungus, to slow its spread after it arrives and to limit its impact on the island.
It’s rare we can identify a conservation disaster before it occurs, but a long history of amphibian declines in Australia and South America has equipped us with the knowledge to protect areas where the amphibian chytrid fungus is yet to reach.
Why we should care about frogs
Like Australian frogs, New Guinea frogs may be particularly vulnerable to the chytrid fungus. These frogs share a close genetic relationship suggesting that, if exposed, New Guinea frogs may respond similarly to Australian ones, where around 16% of frog species are affected.
Losing so many species can have many terrible impacts. Tadpoles and frogs are important because they help recycle nutrients and break down leaf litter. They are also prey for larger mammals and reptiles, and predators of insects, invertebrates and small vertebrates. They help keep insect plagues, such as those from flies and mosquitoes, in check.
Frogs are also an important source of human medical advancements – they were even used for a human pregnancy test until the 1950s.
A call to action to protect frogs
Frogs are one of the most threatened groups of species in the world – around 40% are threatened with extinction.
And species conservation is more expensive once the species are threatened. They can be more costly to collect and more precious to maintain, with a greater need for wider input from recovery groups to achieve rapid results.
In our study, we highlight the increased costs and requirements for establishing captive breeding for two species of closely related barred frog, one common and one threatened. We determined that waiting until a species is threatened dramatically increases the costs and effort required to establish a successful breeding program. The risks of it failing also increase.
Our research draws on lessons learned from other emerging diseases and approaches taken in other countries. By addressing the criteria of preparedness, prevention, detection, response and recovery, we detail a call for action to protect the frogs of New Guinea. It will require dedicated funding, a contingency plan for the likely, eventual arrival of the disease and a task force to oversee it.
This task force would oversee active monitoring for disease and prepare an action plan to implement on the disease’s arrival. We have already begun to establish facilities that can handle captive breeding and gene banking for frogs in collaboration with PNG counterparts.
The need for amphibian conservation in New Guinea also presents an opportunity for investment and training of local scientists. More species unknown to science will be described and the secret habits of these unique frogs will be discovered before they are potentially lost.
Conservation in New Guinea is complicated
The island of New Guinea is governed by Papua New Guinea on the eastern side and Indonesia on the western side. So it will take a coordinated approach to reduce risks in both countries for successful biosecurity.
Historically, New Guinea has had little import or tourism. But as the country develops, it becomes more at risk of emerging diseases through increased trade and and entry of tourists from chytrid-infected regions, especially with little biosecurity at entry ports.
What’s more, many species there are unknown to science and few ecological studies have documented their habitat requirements. Unlike Australia, many of New Guinea’s frogs have adapted for life in the wet rainforest.
Rather than developing into tadpoles that live in water, more than 200 frog species in New Guinea hatch from their eggs as fully formed baby frogs. It’s difficult for us to predict how the amphibian chytrid fungus will affect these frogs because Australia has only a handful of these types of species.
We don’t know how to remove the amphibian chytrid fungus from large areas once it has invaded, so strict biosecurity and conservation contingency planning is needed to protect New Guinea’s frogs.
For example, all incoming goods into New Guinea should be inspected for possible hitchhiker frogs that could carry chytrid. Camping or hiking equipment carried by tourists should also be closely inspected for attached mud, which could harbour the pathogen, as is the case in Australia.
International researchers have experience in emerging amphibian diseases. Papua New Guineans and Indonesians have traditional and ecological expertise. Together we have the opportunity to avert another mass decline of frogs. Without taking action, we could lose a hundred more species from the world and take another step towards mass extinction.