Spiders need appreciation: Portia & Darwini

in #science7 years ago (edited)

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Now you may be aware that I find ants to be some of the most incredible organisms the Earth has to offer. They've dominated the globe, they adapt to all environments and they are a symbol of what human society could one day become.

But they're not the only animals that have claim to the throne. In fact, many creatures outnumber ants. In total, insects alone outnumber humans 200 million to one. With their fast breeding and constant necessity to adapt, we've ended up with thousands of crazy looking creatures being discovered every year.

Insects are cool and all, but so are spiders (yes, spiders are not insects). In fact, spiders arguably have just as much claim to the entire world as ants do, leaving almost no habitat on earth without them thriving:

Today I want to show my appreciation for two of the more incredible, scary and downright bizarre of the 35,000 species of spider (currently known).

Portia

A lovely, easy name to start off. Portia is a genus with 17 species within, spreading around much of South East Asia and parts of Southern Africa.

Though its name sounds kind of effeminate and cute, as does its appearance in my opinion, it actually lives a rather brutal hunting lifestyle with astonishing intelligence the likes of which are unseen in any creature of such size - no larger than 10mm across.

Intelligence

This intelligence allows the portia to actually solve problems and work its way around obstacles and difficulties that other spiders would be hopeless to achieve. This has indeed been observes and can be classified as intelligence; a portia will try out different tactics to approach a prey, and through trial and error discover and then remember the technique for use at a later date.

They have also been observed taking detours that take them out of sight of their prey in order to get to a better position. This is incredible behaviour for a creature with a brain containing barely 600,000 neurons. If the brain was put on the tip of your finger, you'd barely see it, if at all.

Portia are spider-eating spiders, so they have to have some degree of intelligence to figure out how to get to a spider in the middle of a sticky web. This can involve a large detour to find an overhand where it can dangle down and leap on the unsuspecting spider from behind, or even plucking on the strings of the web to mimic a struggling insect, luring the stupid spider to its doom. These techniques are successful on prey even when they're 2-3 times its own size.

Vision

But having brain power is not the only thing that makes this genus impressive.

They also have excellent vision, which seems obvious when you look at their pretty, googly eyes. This is in stark contrast to much of their prey, which are often blind. They have 8 complex eyes that together allow a high level of spatial acuity, with a full 360° field of vision.

To put their vision into perspective, their two main eyes have a field of vision 6 times greater than even the most wide-eyed insect species and can even see more clearly than house cats.

It makes sense to have these eyes for the portia, since it depends 100% on them for hunting. Smell, sight and hearing are not active in hunting, only the sensing of movement , appearance and distance.

Extra super cool features

There are even more surprises in the portia genus! As stated, they are jumping spiders - impressive ones - able jump over 50 times their own body length across trees, away from or toward other creatures at strikingly fast speeds.

They're also adapters, happy to hunt the traditional way, on foot, scavenge for corpses and even subsist off nectar. When the time calls for it, they are even social, with some species like portia africana sharing prey.

And to put a cherry on top, the portia has powerful regenerative abilities, able to regrow an entire leg within a week of moulting.

Darwin's bark spider

The second spider is equally amazing as Portia, but for an entirely different reason. This spider, scientifically known as Caerostris darwini, has an astounding ability to make cobwebs.

Cool right?

Ok maybe not, but when you hear that this orb weaver spider reaches barely 18mm in size, it comes as a surprise to hear that it can create a web 4,300 square inches in size, hanging on a support line Twenty-five metres in length.

This is not something they work on over a period of days. The Darwin spider sits on a riverbank, braces itself, and launches a full 25 metres from its abdomen, until the far end sticks on to something stable. Then it walks out to the middle, hanging over the middle of a river or stream and immediately begins on the world's largest orb web, much to the confusion of scientists who still haven't an answer for how it's physically possible. To make things even more astounding, the silk from C. darwini is the toughest biological material ever discovered, far more than other spider silk.

In numbers, the silk's strength comes in at 520 MJ/m3. To compare, that's more than twice as strong as any other spider silk, and about 1000% tougher than Kevlar if they were to be laid out equally in size. This makes sense when you have to dangle dragonflies off a 25 metre wide trap in the middle of a river.

If the line breaks or fails, the spider will simply reel it back in, eat it, and it can be recycled for later on.

Bigger is better?

Not always, but in the case of this orb weaver, it is strategic brilliance. Deep in the rainforests of Madagascar, the rivers that break up the trees act as a free-flying corridor for thousands of dragonflies, mayflies and other flying insects. By maximizing the spread across their migrating path, one web can get sufficient nourishment (one observed with 32 mayflies at a given time) to make up for all that web. Of course, the other benefit is that it's a biological niche; no other spider can work in these particular conditions.

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Most of you hate spiders, I know. I get it. We tend to hate weird, unfamiliar shapes and things with too many (or not enough) legs. But just by looking at these two wonders, I hope you can at least find some appreciation for the arachnids that, let's be real, keep themselves to themselves and rid us of pests as a free service.

If you're still not convinced, stick around for part 2!

Sources:

Logo spider
Spider distribution map
Googly spider eyes
Portia field of view
Darwin's Bark Spider
Darwin's Bark Spider, web making
Giant Bark Spider web - A screenshot from BBC's The Hunt
Most information from here and the direct links within

Previously:

Convergence
Stupid Design
Weird Evolution
The Axolotl
Mutual Symbiosis
Parasitic Symbiosis Part 1
Parasitic Symbiosis Part 2
Weird Sex Part 1
Weird Sex Part 2
Humanity in Nature
Amazing Ants Part 1
Amazing Ants Part 2

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Awesome article! My Wife hates spiders but I'm all for them. Especially these:

This is the bird eating Goliath! Let me know if you ever come across one of these!

Never 'come across' one, but they're very notorious! Love it =D

I had one...so safe to say...i like spiders. :)

That's so cool. My sister had a snake... it escaped and became wild in the streets of England lol. Saw it months later all feral

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These small creatures are full of amazes..loved it...

I had never realised spiders could be so intelligent, being able to remember specific methods that worked when hunting down prey or talking detours to avoid them. I cannot believe that the Portia spiders have a full 360 degree field of vision, or that they have so many eyes pointing in different directions.

Very interesting stuff, I knew barely any of these facts!

Such is the wonder of nature. We can't know everything... too much awesome!

Interesting :)

I also dig spiders.

wow mobbs! I didn't know you like spiders. We have 4 tarantulas in my house. It's going to be scary if they escape. You were right, they are smart. One spidey was able to escape last time. Good thing my sister found it right away! It was in the sofa. Damn!

Haha wow, I can't imagine anybody I know having them as pets... Everyone would die from fear lol...

But me, I love all life, not just the fluffy cute ones... I'm a naturalist =D

I will write an article about those 4 tarantulas this week. =)

Since you mentioned fluffy, I adopted a kitten earlier. =)

I'm also naturalist. I enjoy being with nature. Like Tarzan and Jane. =)

I respect 'most' life - can't say I love it all and spiders are just one of those I can deal with from a safe distance only. Dangling above my head as I settle to sleep, or running over my hand as I pick up a loaf of bread freaks me out. Running around in the garden or dangling off tree branches - I'm ok with that. Just not on my turf... That said, they are, like most insects (I know, they're not insects), very fascinating.