Nature’s Oddities Part 1: The Lamprey

I am opening a new series on odd creatures. Today we will begin with my favorite oddball creature, the lamprey.

Lampreys have an eel-like appearance (but they are not eels!) and a cartilaginous skeleton (like sharks and rays). They have a single olfactory nostril, which is possibly the most sensitive “nose” of all animals. They have strangely shaped circular gills, usually 5 or 7 of them on each side. The most primitive vertebrate, the hagfish (covered tomorrow), does not have a true spine and only very primitive “vertebra”—the bones protecting the spinal nerve. The lamprey is a bit more developed, but still quite unlike all other vertebrates which have fully developed spinal columns, vertebra, and jaws. So in the entire subphyla vertebrata two very primitive groups exist (“jawless” hagfish and lampreys) and many other advanced groups exist (“jawed” mammals, birds, reptiles, and ray-finned fish [the dominant group]).



Here is nice picture of the business end of the lamprey--it’s jawless rasp-like sucker mouth. I am glad I am not a trout!



As you can guess, lampreys are parasitic in their adult life stage. They cling on to a fish and suck their blood, usually killing their host and moving on to a few more before settling down and making babies. I have heard that a single lamprey (which weights only a few ounces) can kill 25 lbs of fish, which makes them quite destructive to fish populations. Interestingly, some fish have a reflexive jerk when you poke them on their lower flanking quarters (the area lampreys usually attack). This is of course to avoid getting stuck by a lamprey. The reflex uses the same type neuronal pathway that humans use when doctors bump our knees. I suggest trying it yourself next time you catch a fish.



Lampreys (and hagfish, probably) have a primordial immune system rather unlike our own. Humans (and almost all other vertebrates) have immune systems that operate using anti-bodies, small molecules secreted by B-lymphocytes that attach to pathogens and other foreign substances in the body. The antibodies cause the pathogens to clump together and flag them for destruction by cytotoxic T cells and phagocytic (cell-eating) cells, like macrophages. Some antibodies damage the pathogens themselves. This is all part of what is known as the “adaptive immune response” since it is an adaptive process. Antibodies are tailored to the pathogen at hand. This is different from the activity of natural killer T cells, which attack any cell without characteristic features (such as MHC receptors) of the organism’s own cells. Natural killer cells do not need antibodies to be raised in order to attack. Lampreys are different in that they have an adaptive immune response with no antibodies.

Antibodies are the hingepin of the entire immune response. This is due to their “hyper variable” region. Antibodies’ hyper variable regions can be adapted to almost any pathogens’ unique surface receptor proteins (called antigens). There are millions of different pathogens that are constantly adapting to avoid selection by antibodies, consequently, antibodies are constantly adapting as well. What allows for the enormous flexibility of the antibody is the many ways genes can recombine to produce different immunologlobin domains (areas of activity) in the hyper variable regions of he antibody. It was long thought that nature had a very limited capacity of arranging these genes in order to achieve this variable nature. The mechanism used was though to be the only one. This was found to be incorrect when the lamprey’s immune system was examined.

Lampreys use an entirely different molecule called a VLR (variable lymphocyte receptor) to do the work of anti-bodies. And this VLR is produced in a completely different way genetically. Where all jawed vertebrates have their antibody genes regulate by the RAG genes from two different sources to generate diversity, lampreys have a very simple “cassette” of VLR genes that are clipped at different regions to produce variability. This may not seem like it is that different. But it is. Let me make an analogy. To make a cake, one baker takes some cake mix and some milk and eggs and combines them in variable amounts to produce different tasting cakes. Another baker chooses to take the cake mix with all the ingredients already combined and remove the unwanted ingredients to make different tasting cakes. It is clear now that the person who combines different ingredients has greater ability to alter the contents of the cake, since he chooses what ingredients to add. This is why the antibody method has been dominant in the world, though the simpler Lamprey system is quiet effective. It is also important to note that there is no clear way for the jawed system to develop from the jawless system. They are completely different mechanisms, but with similar functions. Sort of like the old Macs and PCs before they started doing commercials together.

Lampreys are also an exotic species to the Great Lakes. When the St. Lawrence Seaway was opened, lampreys began to swim down it from the Atlantic (like many primitive fish, lampreys can live in salt and fresh water). They started to spawn (and a single female can produce 10,000-20,000 eggs every year) and were very successful, greatly reducing the fish yields. Since then, war has raged against the Lamprey.



Traditionally we have used pesticides to reduce their numbers. Since Lampreys metamophisize (the only fish that do this!) like many insects (think of butterflies), many of the chemicals that interfere with metamorphosis work in both lampreys and insects. So we already had a well-developed arsenal against them. The problem is that when we dump pesticides into a lake (as opposed to spreading them on a field) the pesticides go where we don’t want them too, killing all sorts of aquatic insects that are crucial to the food chain. We tried to find other chemicals, called lampracides, that target the lamprey more specifically, but after billions of dollars of research between the US and Canadian investigators, we have been rather unsuccessful.

Currently we believe we are beating them by messing up their courtship process. I saw a presentation by the leading researcher in lampreys last year, and he developed a pheromone that was specific to the lamprey that would make the female lampreys try to mate in the wrong places and the wrong way. Lampreys need to line up in an “embrace” before mating in order for the sperm (which is ejected from the male’s body) can be captured by the female’s genitals instead of floating downstream. The male excretes a chemical (called a pheromone) to lead the female to the right position, since adult lampreys are nearly blind. When we mess with this pheromone, we confuse the girls and they don’t get any sperm. Good for us!



We invented “the pill” for the Lamprey. The one problem is that a few do get pregnant. Either the males have an extraordinary abundance of sperm produced or the females are quite fertile. It is also possible that they may still be able to do their dance without the pheromone. In any case, we are selecting for the lampreys that can evade this mechanism, and since they are so prolific, our mechanism will soon be overcome. The war continues.

I pointed out this fact to the professor, and he said that indeed this is a major problem. I think perhaps developing a VLR antagonist (sort of like an allergen to jawed vertebrates) could be developed to kill lampreys. After all, many allergens can be fatal. To my knowledge, nobody has tried this.

This is why I suggest peace as an alternative. Lampreys are considered a delicacy in France, but then again the French eat just about anything. They are enjoyed in England, Portugal, Korea, and Spain as well, which gives me hope that North Americans may learn to love lampreys. Their flesh is very rich and meat-like (because they suck blood) and it has perhaps the highest iron content of any food. For this reason lampreys were very popular for Catholics during fast times. It was like eating “meat” but not! Lamprey pie was a popular Lenten food in northern France. King Henry I was so fond of lampreys that he overate them and died (possibly from Iron poisoning or because they were rotten). I think we should keep our tax monies and start commercial fishing of Lampreys. The American public is so gullible! All that would be necessary would be celebrity endorsements of Lampreys during the super bowl. Suggestions of good celebrates to introduce the lamprey are welcome. I was thinking of Rachel Ray. Her indomitable perkiness may overcome people’s prejudice against the lamprey.

Here is a recipe I found on the internet:

Lamprey Stew with Garlic Mashed Potatoes

by Bob Bennett
Bennett's Bar and Grill, Duluth, MN

For Stew:

3 lamprey cleaned, peeled, and cut into 1/2-inch pieces
2 carrots, peeled and diced into medium size chunks
1 yellow onion, diced into medium chunks
2 stalks celery, diced into medium chunks
2 cups hearty red wine
2 cups fortified veal stock
1 bay leaf
2 tbsp. olive oil
salt and pepper to taste

Heat oil in a medium-size, heavy-gauge stock pot. Add lamprey and vegetables, then sear until vegetables are tender. Add the wine and reduce liquid by two-thirds. Add veal stock and bay leaf, reduce heat and simmer for 2 to 3 hours. Season with salt and pepper and serve on a bed of mashed potatoes as prepared below.

For potatoes:

2 lbs. red new potatoes
2 tbsp. butter
1 tbsp. minced garlic
3 tbsp. sour cream
salt and pepper to taste

Boil potatoes until soft, then drain. Place in a mixing bowl with the rest of the ingredients and mix with electric hand mixer until smooth. Keep warm until ready to serve.

Some resources:

http://en.wikipedia.org/wiki/Lamprey

http://www.hhmi.org/news/cooper.html

http://chemse.oxfordjournals.org/cgi/content/full/30/suppl_1/i307

Cooper, M. D. et. al. (2004) Somatic diversification of variable lymphocyte receptors in the agnathan sea lamprey Nature 430:174-180

(All pictures were taken from government websites [public domain] or from publicly released Wikipedia images)