There are some nasty creatures that live in our world — and by nasty I mean animals whose way of life is just creepy, or cruel. Such is the case with today’s animal, a very unpleasant parasite. I guess most parasites would be considered ‘nasty’ by nature, but the sea lamprey definitely is one of the meaner creatures out there.

Sea lampreys live in the Atlantic Ocean, tending to stay near the coasts. They can be found along the coast from Massachusetts to Florida and from Norway to the Mediterranean. They have also been introduced to the Great Lakes, where they are considered an invasive species. The species is anadromous, meaning they return to fresh water to breed, but spend their adult lives in the ocean.

A fish with a pair of sea lampreys attached. Image by Sweeting, Roger Photographer, UK, CC BY-SA 3.0, via Wikimedia Commons

Despite looking a lot like eels, lampreys aren’t that closely related to them. They belong to a group of fish called Agnathans, which do not have jaws. Lampreys are fairly primitive fish: their entire skeleton is composed of cartilage, not bone, and they lack a swim bladder or lateral line system. They are the largest specie of lamprey, measuring up to 100 cm as adults. They are generally dark green or grey as juveniles and lighten with age.

One of the most terrifying parts of a sea lamprey is its mouth. It is oval shaped, with rows upon rows of teeth. When you look at a lamprey mouth that is fully extended, it really is reminiscent of a sand worm from Dune or the sarlacc from Star Wars. The lampreys use this horrifying mouth to attach themselves to fish. Once attached, the lamprey secretes an anticoagulant that keeps juicy blood flowing right into the lamprey’s mouth. When it’s had its fill, the lamprey detaches, leaving a gaping wound that takes a long time to heal. Often victims of lamprey attacks die from blood loss or infection. As I said, lampreys are nasty.

In order to spawn, lampreys must return to fresh water. Once a male has found a suitable nesting site, he clears away debris to make a nice comfy depression in the ground. He then releases some pheromones into the water to let nearby females know he is ready to mate. She lays her eggs in the nest (30,000 to 100,000 of them), and then he fertilizes them. After spawning, the parents die and let their kids grow up all alone.

After a few weeks, the eggs hatch and the larvae burrow into the sand. They filter feed, eating algae and other floating food that drifts along in the water. This phase of development can last a long time, sometimes over three years. When they feel ready, the larvae metamorphosize into adults, and start to feed, though they remain in fresh water for another year. When they finally move out to sea, the lampreys develop sexual organs and reach maturity.

I’ve never been a big fan of parasitic creatures — there’s just something icky about them. But still, discrimination is wrong, so I guess sea lampreys are alright. I just wouldn’t ever want to meet one.

Cover image by Drow_male, CC BY-SA 4.0, via Wikimedia Commons