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Being a parent requires a lot of time and energy, but some animals are extremely devoted to caring for their young, and these five might not be the ones you would expect.

Hosted by: Hank Green

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Sources:
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Images:
https://commons.wikimedia.org/wiki/File:FMIB_43537_Metopaulias_depressus.jpeg
https://commons.wikimedia.org/wiki/File:Aechmea_paniculigera.jpg
https://commons.wikimedia.org/wiki/File:Nicrophorus_vespilloides5.jpg
https://en.wikipedia.org/wiki/File:N._orbicollis_habitus_together.jpg
https://fishesofaustralia.net.au/home/species/1487
https://en.wikipedia.org/wiki/File:Tsetse-BKF-3.jpg
https://en.wikipedia.org/wiki/File:Tsetse-BKF-2.jpg
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Go to Brilliant.org/SciShow to learn how you can take your STEM skills to the next level! [♪ INTRO]. Let’s face it.

Parenting, whether it’s one baby or one hundred, is not for the weak. It requires a lot of time and energy to keep babies safe and healthy. Of course, some species take the hands-off approach, letting nature take its course with the next generation.

At the other end of the spectrum there are parents so devoted that their offspring want for nothing. Humans, for example, can be a great example of that. But there are other animals that are really invested in caring for their young, and these five might not be the ones you would expect.

The tiny bromeliad crab is found in Jamaica, living in bromeliad plants. The plants have hollow cavities that collect and store rainwater, creating tiny ecosystems where these crabs live. They spend their entire lives there, even raising their babies in the rainwater.

Bromeliad crabs are the only crab species known to actively feed and care for their young and they do it during the eight weeks the babies spend in their rainwater nursery. Most crustaceans only invest a small amount of care in their offspring. Usually that takes the form of attaching their eggs to their bodies to keep them safe from hungry predators.

However, researchers have found that crustaceans who live in freshwater or on land become more protective and provide more care for their offspring than their marine cousins. These environments are a lot more stressful than marine environments, which means a bit more parental care ensures offspring are more likely to survive to adulthood. Bromeliad crabs take their job as a doting parent very seriously.

The mother crab is constantly making adjustments to the nursery, removing debris, keeping the water moving, and even adding empty snail shells. Scientists realized this behavior helps maintain the water quality of the pool. Circulating the water adds oxygen to it, and the snail shells buffer the acidity and add calcium.

The mother also keeps her young safe from predators, since crabs are not the only occupants of bromeliad pools. It’s the preferred breeding site for damselflies, whose nymphs are a common predator of crab larvae. Thanks to the mother crab diligently removing damselfly nymphs, though, her young are 60% less likely to be eaten.

Burying beetles are members of the carrion beetle family, a type of beetle that makes its living, just degrading vertebrate carcasses. Most carrion beetles will find a carcass, stop for a snack, lay their eggs, and then skedaddle on outta there, leaving their offspring alone to hatch and hopefully live long enough to get their snack on. The burying beetle, however, buries dead animals in order to care for their young inside the carcass.

Like a lovely little corpse nursery. These little beetles make short work of getting a carcass underground. A pair of beetles can get an entire rabbit underground in just a few hours.

Once the body is buried, both parents work to remove the fur or feathers and then coat the skin with antibacterial secretions, which slows down decomposition and keeps their young safe from disease. But they don’t stop there. Not only do they provide their babies with a safe, disease-free corpse house, they also are extremely attentive when it comes to feeding their young.

In fact, in this respect, they behave more like birds than beetles. Once hatched, the beetle larvae beg for food, and the parents respond by regurgitating food into the babies’ mouths. Not only is it dead animal, it’s dead animal puke!

The larvae are actually perfectly capable of feeding themselves; from the carcass that makes up their nursery. But research has shown that babies grow faster if their parents feed them; and both parents are happy to oblige. The males and females both take on a share of their parental duties, such as feeding the babies and keeping the carcass clean.

That’s pretty unusual behavior for any animal species, other than human. It’s even weirder in an invertebrate, so researchers are still trying to work out not only why these beetles are such great parents, but also why both Mom and Dad are so on board. Fish are not exactly well known for their parenting skills.

Many of them are not able to recognize their own babies and mistake them for prey, gobbling them up as soon as they see them. Enter the discus, a tropical freshwater fish in the cichlid family, a fish that could win awards for the amount of time and energy they invest in their young. After their babies hatch, both parents tend to them diligently, keeping the fry, or young, very close to their bodies.

The parents alternate who’s on duty, transferring all the fry at once with a well-timed flick of their bodies in order to give each other breaks when one parent needs to go off in search of food. And this is because for the first three or four weeks of life, the fry’s primary food source is the mucus on their parents' bodies. And before you go “Ew, yuck, mucus,” remember that we mammals are in the business of secreting a nutritious fluid for our young, too.

Also I just told you about corpse-puking beetles. Now mammals may have mastered this technique, but it’s not unique to us. After all, an easy-to-find food source that comes straight from the parent is a great way to aid your offspring’s survival.

Researchers took a close look at this mucus and found that its composition changed over time, in tune with the fry’s needs. We see similar changes take place in mammalian milk. For example, around the time of birth, it’s packed full of things like antibodies, growth factors, proteins, and hormones that give babies a passive form of immunity until their own immune system kicks in.

The fish’s mucus is also set up to pass along immunity to their offspring. At the same time the parents lay their eggs, the antibody and protein composition of their mucus bulks up. Other cichlid fish have also adopted the strategy of giving their young delicious mucus to eat.

However, discus are the only fish we know of where the parent’s mucus is required for their fry to survive. Multiple attempts have been made to raise orphaned discus fry in captivity, but they can’t eat live food, so they don’t survive long. Discus fish must be some super patient parents, putting up with that constant nibbling 24/7!

Sounds awful! Now when you consider all the places you might put your babies in order to keep them safe and sound, your mouth might seem like the, like the worst option. But in fact, about two percent of fish species have evolved this peculiar trait of keeping their young, or at least their eggs, safe and sound inside their mouths.

Mouthbrooding is an extremely costly investment in their young, because as you can imagine, it's very difficult to eat when your mouth is full of babies. In the deep sea, where food resources are extremely scarce, scientists assumed that all fish species would therefore take the hands-off approach, releasing their eggs and sperm into the water and letting them meet up and develop on their own. That is, until researchers happened to discover that a deep sea fish, the parazen, is most likely a mouthbrooder.

Little is known about this deep sea fish. To start, scientists don’t even know if there is more than one species. That’s what they were trying to figure out when they discovered eggs inside the mouth of a female specimen.

For a fish like the parazen to have evolved this strategy is a bit of a head scratcher, due to where it lives and how it eats. Parazens are what’s known as winnowers: to eat, they scoop up big mouthfuls of sand and sift through it to find their food. If your mouth is full of eggs, this means that you don't eat for the entire incubation period, or the eggs are somehow so securely attached that eating doesn’t knock ‘em loose.

The latter is probably the case for these fish, as these eggs were found clumped together near the parazen’s gills and attached by a membrane. This finding helps to fill in some of what we don’t know about these fish, like the fact that researchers have never found a parazen larva. A mouthbrooding strategy may help to explain why.

Scientists hypothesize that the parazen may be investing more energy in their young than other deep sea fish because of where they live: open, sandy areas that have very few spots to hide from predators. They might be resorting to mouthbrooding to ensure more of their young survive than if they were left on their own to be spotted and gobbled up. Many invertebrates, especially insects, have parenting strategies that allow them to produce a lot of offspring over the course of their short lives.

However, this is not the case for the tsetse fly; a large biting fly native to Africa that’s known for transmitting a deadly sleeping sickness. Tsetse flies are larviparous, which means they don’t lay eggs. Instead, the larva hatches from an egg inside the female fly.

Tsetse flies only produce one baby at a time, and only a handful over the course of their lives, which is typically just a few short months. A single larva develops inside the female’s uterus, and while it’s in there, it gets fed by milk glands that make a nutrient-dense liquid. Once again we’re making comparisons to mammalian milk, and with good reason.

Tsetse fly milk transfers a lot of good stuff to the larval fly, like beneficial bacteria, without which females are unable to reproduce as adults. Once the larva is developed enough, after about nine days, the female tsetse fly gives birth. The newly born larva immediately burrows into the soil and becomes a pupa. 30 days later, it crawls back out of the dirt as a full grown adult.

This unusual reproductive strategy sets the tsetse fly apart from other insects, but it ensures that their babies have a very strong chance of surviving to adulthood. In this case, they’re investing a lot of effort into a single larva at a time, rather than making lots and leaving them on their own. However, this also means that their populations are slower to recover from control efforts, unlike mosquitoes or other insects who produce a lot of offspring.

This may help public health officials get a handle on their populations and control the spread of sleeping sickness, which is especially life-threatening to rural populations. Going the extra mile looks very different from species to species. Even so, all five of these creatures are lining up for parent of the year awards.

Maybe some of you parents out there, or future parents, can aspire to the attentiveness of a burying beetle! Tired of getting smarter yet? Of course you’re not.

If you want to keep going, you might enjoy a course from Brilliant. Brilliant has courses about science, engineering, computer science and math, all intended to help you hone your math and science thinking skills. Like their course Quantum Objects, which may just help you finally understand why things get so darn weird when they get small.

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