system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do ticks expand so much despite having an exoskeleton?
gpt
If you look at them way up close, using a scanning electron microscope, you can see that their exoskeleton is folded, finely corrugated, so that it can expand to what seems like a huge size. You can often see clusters or patches of bacteria on the exoskeleton, and it seems obvious that when a tick breaks open, as they sometimes do, the bacteria could easily mingle with the blood meal. That is especially bad because ticks can heal themselves when they’re torn open. When you squeeze one, trying to get it off of your skin, you can then easily inject those bacteria into your wound.