Lines are 1 mm apart
OK fine. Not YOUR blood. Not even human blood (apologies to any non-humans who may be reading this). It's fish blood they want (to any fish who may be reading this: yes, YOU!).
It isn't actually a worm, though. Instead, it's just one example of the impressive, though admittedly diabolical, lengths parasitic Copepods will go to peacefully live out their dirty, little lives in or on another animal who probably deserved so much more out of life.
The "Anchor" part of the name comes from that ghastly array of antlers sprouting from its gruesome head. You won't see them, though. Not without careful use of a scalpel. They, along with that long, slim neck, are all buried deep within the flesh of some poor, suffering fish. The only thing to be seen on the outside is the bulbous back end with those strange, stringy filaments. If you try and pull it out, the antlers keep it in place so well that all you'll get is the tiny mop. The head will remain in place, cursing your name.
An yet it all starts out innocently enough. Once the eggs hatch, Anchor Worms begin life like many other crustaceans, as a minute, free-living larva known as a nauplius. They're something of a trust fund baby, though, since they don't actually need to eat anything yet.
After a couple of moults they reach the copepodid stage, same as any other Copepod. But it's now that they reveal their dark and sinister intentions. They won't go out looking for tiny food to fit their tiny mouths so that they can grow big (tiny) and strong. No. They'll be looking for their first host, the intermediate host, which is usually a fish or snail.
Now they settle in to life as a parasite, feeding on mucus and tissue of their host. Soon they moult and enter the chalimus stage, where they look much like an ordinary Copepod but with an extra little thing sticking out of their head called the frontal filament which allows them to stay attached to their host as they feed. They can now mate and with that done, the males can die at their leisure.
But the females go on. They detach from their intermediate host and go in search of their final host, usually a fish but in some species, a whale. When she discovers her final victim, she undergoes her most dramatic and despicable metamorphosis.
In her guise as the Last Abomination, her long neck allows her to delve deep into her host's flesh. Some burrow into the aorta and drink fresh blood like water from a spring. Others plunge into the liver and take other fluids. She'll use this rich diet to produce eggs, provide for the next generation and to secure a safer, more fruitful tomorrow for parasites everywhere.
I wish she wouldn't.