Lamprey

Image: NOAA

Pray, little lamb! Pray for your tiny soul!

They call it the uncanny valley - that uneasy realm where a robot looks so much like a real human, but not quite like a real human, that it's incredibly creepy and unsettling. Maybe not as creepy and unsettling as the guys who get married to their robot, by their robot or to some other not-really-a-person, but it's all very strange nonetheless.

Do I hear the *whir* pitter *whir* patter of tiny feet?

Lampreys occupy a whole other uncanny valley. They look a lot like a fairly normal fish. A long, thin, slimy fish that doesn't have any scales, but we usually just call such things "eel" and move on. However, Lampreys aren't eels and when you see their mouth...

Image: USFWS - Pacific Region

It's not so much odd-looking as nightmarish.

The thing about Lampreys is they're jawless. They have NO JAWS! No mandibles!

They can't chomp, champ or chew

Neither nip, nibble or gnaw

They don't masticate or ruminate

For the Lamprey has no jaw

Image: Mr. Theklan

What they have instead is a sucker, a kind of funnel affair, like a sink plunger with an array of teeth embedded within. At the centre of the funnel is something like a tongue... also covered in teeth.

Image: USFWS - Pacific Region
The artistic parasite

Many Lampreys are famous for the nasty way they use their toothy sucker-mouth to clamp onto hapless fish, then bore into their flesh with the toothy tongue so they can drink the flowing blood. It's what Dracula would do if he wasn't a count, and didn't bother with etiquette and polite society. I bet the Lamprey doesn't even know his desert spoon from his soup spoon.

But most Lampreys don't actually do any of this. Many feed on small invertebrates instead and some don't eat at all once they reach adulthood. In fact, "Lamprey" comes from the Latin for "stone-licker". I guess people saw Lampreys using their suction to rest on stones and didn't see much of the vampirism. People are usually keen to point out blood-suckers after all. Stone-sitters, not so much.

Image: NOAA

There are almost 50 species of Lamprey ranging between 10 and 100 cm (4 and 40 in) long and found in the cooler parts of the world both north and south of the tropics. Some spend their entire life in rivers or landlocked lakes, while others enter the open ocean as adults and return to freshwater when it's time to breed. It's a less appreciated version of those salmon that do the same.

Video: NatGeoWild

Lampreys are extremely ancient, being largely unchanged for some 360 million years. Jaws were a fairly new innovation for fish back then and fearsome predators like Dunkleosteus was showing those jawless suckers how useful a good set of gnashers could be. It must have been clear that jawless fish were on the way out, but I doubt even old Dunklechops could predict that one day a whole movie franchise would one day be dedicated to the terrible power of JAWS.

And yet through it all, the stone-lickers survived. As you might imagine, a lack of jaws is not the only peculiar feature retained by these old survivors.

Image: Helen Simonsson
Skeleton with the huge branchial basket

Check out their skeleton for a start! As in sharks, it's made of cartilage rather than bone. Like Sturgeons, they retain their notochord for life and never replace it with a proper backbone. The skeleton they're left with is dominated by the branchial basket, which is a structure that supports the gills.

Image: USFWS - Pacific Region

Lampreys have seven gills on either side of their head and they look like a row of little holes behind the large eyes. On top of the head is one hole which acts as a nostril and also a patch of translucent skin which covers the pineal organ.

Image: USFWS - Pacific Region
Lampreys lack paired fins, like the pelvic and pectorals

The pineal gland is very important since it releases hormones to regulate sleep and seasonal functions. Almost all vertebrates have one somewhere in their brain; it tells hares to go mad in March, Arctic foxes to turn white in September and Scandinavians to get depressed in winter. But the Lamprey is odd in that instead of being buried deep in the brain, their pineal gland is on top of the head so that light can shine right onto it.

Video: Discovery Networks
Sea Lampreys (Petromyzon marinus) have become invasive in the Great Lakes between the United states and Canada.
But not to worry, for they can both smell and PANIC!

Changes of the season are very important for Lampreys since they all need to get frisky, travel upstream and turn that thing into a giant, Lamprey singles bar. Some of the marine Lampreys can travel for hundreds of miles during the two years they spend out at sea, in part by hanging onto larger, swifter fish. Others may have only just reached adulthood and have nothing else to do but breed. Either way, they must swim upstream at least a little.

Image: USFWS - Pacific Region
Shifting rocks to make way for a nest

Now they can start building a nest near to suitably-sized gravel. Large rocks are moved aside to make a shallow depression in the riverbed. Whether the male or female is tasked with the job is dependant on species.

Video: hvilesteddk
Lampreys mate repeatedly, laying a few eggs each time

Lampreys mate by getting together and releasing eggs and sperm into the water. Sometimes a pair will do it in the nest, other species get into groups of several dozen. I hope they enjoy themselves either way, because they all die soon after mating.

Image: Carol
If Lampreys looked after their young like birds do, it'd probably look like this!

The eggs are sticky and soon fall into the gravel and sand and covered in even more gravel and sand, hopefully protecting them from predators.

And what do you think hatches from the eggs?

Image: Biopix: N Sloth
Larval Lamprey or ammocoete

Baby Lampreys, of course! But baby Lampreys aren't simply small Lampreys. They look quite different and have a completely different lifestyle from their parents.

Image: Biopix: N Sloth
Buried in the sand

Larval Lampreys are known as ammocoetes. They don't have eyes, they don't have teeth and they can't do the sucker thing. Instead, they bury themselves tail-first in the sand with their little heads poking out.

Image: Biopix: N Sloth
Oral hood

Over their mouth is an oral hood, which is kind of like a huge upper lip. Its inner surface is covered in tiny hairs called cilia and lots and lots of mucus. The ammocoete uses its gills to draw water toward its upper lip, tiny, plankton food gets stuck onto the mucus and then the cilia work to bring it into the mouth.

Interestingly enough, the looks and life of a larval Lamprey is reminiscent of the Lancelet, or Amphioxus. These are the small, brainless, boneless, invertebrate chordates that look like something between a fish and a fish fillet.

Lancelets stay that way for the whole of their lives, but ammocoetes have places to go and things to suck. The big, ocean-faring Lampreys may remain at the larval stage for as many as 7 years before their 2 year, blood sucking sabbatical in the open seas. Other Lampreys spend only 3 years neck deep in the mud. Eventually though, all Lampreys hope to go through several months of drastic metamorphosis and claim the glorious eyeballs and sucker of their forebears for themselves.

Image: NWCouncil

And maybe go use them in the most despicable way they can think of.