You think your life is a struggle? Be grateful that you're not this beetle.
But that's not even the half of it.
Arthropods are invertebrates with a crisp crunchy outer shell, and jointed legs. The phylum Arthropoda is arguably the most successful animal phylum on Earth, boasting more species than any other. It includes beetles, cockroaches, wasps, crabs, spiders, centipedes, and anything else that is crunchy and leggy.
They sneer at death. Some are capable of surviving over 100 times as much radiation exposure as humans. Cockroaches, while not particularly resistant to radiation (despite popular opinion), can survive being stamped on, flushed down the toilet, or sprayed with insecticide. Sea spiders can regenerate segments of their abdomens.
But how do arthropods get their incredible resilience?
Arthropods are made of segments. Some segments are able to be closed off from the others, as sections of a building can be closed off using fire doors.
When an arthropod faces a situation where limb loss is necessary (for example, if caught by a predator or stung in the leg by a wasp), it can choose to cast off the limb by severing along an autotomy plane. Essentially, the airlock is shut before the cargo is jettisoned. The autotomy plane ensures all the necessary fluids are contained in the insect, and don't flood out of the wound; infection is also kept out.
So, losing a limb is nothing more than a bad day for most arthropods. However, when other arthropods start eating you from the inside out - that's just rude. Parasitoid wasp larvae develop inside caterpillars, spiders, cockroaches, or other arthropods. As the larva matures, it feeds on various parts of its host, such as the fat or the haemolymph (blood). All this time, the host is alive. The wasp larvae can grow to take up a lot of room inside the host, but the host still lives. Most of the time, the host stays - ahem - "fresh" until the wasp emerges from its doomed shell, but sometimes the host may survive the process of being parasitised and become a surprisingly healthy adult, despite the deep trauma it endured as a larva.
Back to our beetle.
The entire contents of the abdomen have been scraped out, probably by a parasitoid, but possibly by a predator or some other means. However, the beetle just keeps on keepin' on. It will die, of course. But for now, the part of its nervous system which controls movement remains unhindered by the catastrophic injury it has endured.
Insect nervous systems consist of a large brain (in the head) and a string of ganglia, like Rosary beads, running from the brain to the final segment. The ganglia act as little brains, control functions such as movement or feeding that would, in mammals, be solely the domain of the brain. This is known as a decentralised nervous system: instead of all the functions being controlled in one place, they are spread out a little, although the bulk of sensory and organ activity is controlled and monitored by the brain. This is why, if you remove a cockroach's head, it will probably keep walking around for some time afterwards - though it has no idea of where it's going.
So the little beetle carries on, its movement controlled by its ganglia, while it slowly dries up and starves to death.
Sure, we have to pay rent and taxes. We have to work with annoying people. We have to put up with soggy chips, greasy pizza, and stale bread.
But at least we're not walking around as dried-up husks, missing vast sections of our abdomens.
*Or non-accidentally, if you're a cruel person.
— ZanBizar (@ZanBizar) June 17, 2020If you've ever accidentally* pulled a leg off a spider, or partially squished a wasp, you'll have experienced first-hand how resilient some invertebrates are to maiming. If a human's leg is pulled off, they will probably die without hospitalisation, but the same injury to a beetle barely interrupts its stride.
But that's not even the half of it.
Arthropods are invertebrates with a crisp crunchy outer shell, and jointed legs. The phylum Arthropoda is arguably the most successful animal phylum on Earth, boasting more species than any other. It includes beetles, cockroaches, wasps, crabs, spiders, centipedes, and anything else that is crunchy and leggy.
They sneer at death. Some are capable of surviving over 100 times as much radiation exposure as humans. Cockroaches, while not particularly resistant to radiation (despite popular opinion), can survive being stamped on, flushed down the toilet, or sprayed with insecticide. Sea spiders can regenerate segments of their abdomens.
 |
| Have you lost everything below your belly button? Not a problem, says the sea spider. Just keep swimming. You'll grow a new one. [photo source] |
But how do arthropods get their incredible resilience?
Arthropods are made of segments. Some segments are able to be closed off from the others, as sections of a building can be closed off using fire doors.
When an arthropod faces a situation where limb loss is necessary (for example, if caught by a predator or stung in the leg by a wasp), it can choose to cast off the limb by severing along an autotomy plane. Essentially, the airlock is shut before the cargo is jettisoned. The autotomy plane ensures all the necessary fluids are contained in the insect, and don't flood out of the wound; infection is also kept out.
 |
| The leg of a praying mantis, showing the position of the plane of autotomy. [image adapted by this source from original] |
Back to our beetle.
The entire contents of the abdomen have been scraped out, probably by a parasitoid, but possibly by a predator or some other means. However, the beetle just keeps on keepin' on. It will die, of course. But for now, the part of its nervous system which controls movement remains unhindered by the catastrophic injury it has endured.
Insect nervous systems consist of a large brain (in the head) and a string of ganglia, like Rosary beads, running from the brain to the final segment. The ganglia act as little brains, control functions such as movement or feeding that would, in mammals, be solely the domain of the brain. This is known as a decentralised nervous system: instead of all the functions being controlled in one place, they are spread out a little, although the bulk of sensory and organ activity is controlled and monitored by the brain. This is why, if you remove a cockroach's head, it will probably keep walking around for some time afterwards - though it has no idea of where it's going.
So the little beetle carries on, its movement controlled by its ganglia, while it slowly dries up and starves to death.
Sure, we have to pay rent and taxes. We have to work with annoying people. We have to put up with soggy chips, greasy pizza, and stale bread.
But at least we're not walking around as dried-up husks, missing vast sections of our abdomens.
*Or non-accidentally, if you're a cruel person.
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