Can Bald Fish Get Lice?

As kids, many of us had the incredibly embarrassing experience of acquiring head lice. You tried on a friend's silly hat at school and a few days later your head won't stop itching. You tell an adult, and she says, "Oh no, you have lice!" You have to go to the store to buy a special fine-tooth comb, and a stinky, unpleasant shampoo. While the shampoo kills the adult lice, the eggs are protected inside their shells. The eggs are stuck to the strands of your hair, and it's necessary to spend hours painstakingly removing them with the fine-toothed comb, or even painstakingly searching your scalp and picking the nits off your hair with fingernails. If all that is just too much work, you might even have your head shaved. This is quicker, but can lead to awkward conversations at school.

Lice are found in the fur and feathers of almost every species of mammal and bird. In humans, they live in hair or in clothes. But what about animals without fur or feathers? Can naked, bald fish get lice?

The answer is both yes and no. Yes, fish do get lice, but they are very different from the lice you might have had in grade four. Your lice were insects, but the lice found in the ocean are not. Like crabs and lobster, oceanic lice are crustaceans. Crustaceans and insects are actually both a part of the same phylum (arthropoda), and may even be directly related. But because fish lice don't have lots of fur to hang onto, they have to be creative, attaching to their host using suckers and their antennae.

While suctioned onto or grabbing the fish with their antennae, lice feed off the mucus, skin, and muscle, often causing bleeding and infection. For a large, healthy fish, a few lice are unpleasant but seldom fatal. However, too many lice can kill a fish, especially a small one.

Since fish rarely share (or wear) silly hats, how do their lice pass between one fish and another? Unlike the lice found on humans, young (juvenile) fish lice can swim. Female salmon lice release their eggs into the water, where they float until the young lice hatch. Juvenile salmon lice hang out in areas where they can sense a boundary between fresh and salt water, like the mouths of rivers. Since salmon are born in rivers, swim out to the sea, and then return to rivers to lay eggs, this is the most likely place to run into a salmon. The salmon may even see a louse and swim toward what it thinks is dinner, only to find itself with an unwanted hitchhiker. Fish farms make it easier for the lice to find a host, because many fish are crowded into the same place. Not only are the fish in the farm affected, but also wild fish that swim by the farm. Precise timing of anti-parasite medicine can help keep the lice from infesting the farm, but the ecological effects of dumping parasite-killing chemicals into ocean are unknown.

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Whale lice are very different from salmon lice, in that they live on the whale for their entire lives and can only move to another whale when the whales touch each other. Right whale calves get whale lice from their mothers. Whale lice hang on by poking the whale's skin with sharp, hook-like legs. Jessie Huggins, a biologist who responds to stranded whales in Washington State, has experienced whale lice first-hand. While working with whales on or near the beach, she says, "Live lice would jump ship and grab onto the people around the whale." Jessie explains that the lice "will latch on with their pointy little feet. It doesn't hurt, but it does make it harder to brush them off, kind of like ticks." Although she says they don't bother her as much as spiders, the sensation of whale lice crawling on her arms does give her the "heebie-jeebies."

There are about 35 species of whale lice, most of which specialize on a specific species of whale. Some species of whale are especially lousy; right whales have three species, all of which prefer a specific region of whale (Cyamus ovalis sets up house on the raised calluses on the head, C. gracilis likes the spaces between these calluses and C. erraticus prefers to colonize wounds and genital/mammary slits). Some right whales have as many as 7500 whale lice. Just thinking about it is enough to make anyone feel itchy. The whales generally do not appear to be bothered by this many lice, although lice populations can explode on sick or injured whales. When the whale's immune system is not healthy, it loses the ability to heal, and lice can spread over its entire body.

Humans actually can have quite a large impact on whale immune systems. The whale in the photo above had a fishing net entangled in its mouth, making it difficult for it to eat, swim and stay healthy. Pollution from farms and cities also flows into the ocean, where the chemicals can weaken whale's immune systems. Whales and fish in the ocean swim immersed in the pesticides, fire retardants, and plasticizers that humans use in their everyday life. If you want to do something to keep whales and fish healthy and lice-free, think hard about how the items you use in your everyday life might impact the ocean. Even items like your couch (which contains fire retardant chemicals) and your dinner (which may have been caught in an unsustainable fishery) can be important.

But hey, lice aren't all bad. Research on the evolution of human lice has even been able to estimate when people first started wearing clothing (about 170,000 years ago)! Similar research has used whale lice to learn about the evolution of right whale populations. With data from whale lice DNA, they have estimated that north Atlantic, south Atlantic, and Pacific right whales have been genetically isolated from each other for several million years. Even though lice under the sea are very different than lice on land, they are both exceptionally useful for learning about the evolution of the animals they live on. And also incredibly, awesomely, gross!

Alexis Rudd is on twitter as @SoundingTheSea

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References

Gerrodette, T., & Rojas‐Bracho, L. (2011). Estimating the success of protected areas for the vaquita, Phocoena sinus. Marine Mammal Science, 27(2), E101-E125.

Godard-Codding, C. A., Clark, R., Fossi, M. C., Marsili, L., Maltese, S., West, A. G., ... & Stegeman, J. J. (2011). Pacific Ocean-Wide profile of CYP1A1 expression, stable Carbon and Nitrogen Isotope Ratios, and Organic Contaminant Burden in sperm whale skin biopsies. Environmental health perspectives, 119(3), 337.

Johnson, S. C., Treasurer, J. W., Bravo, S., Nagasawa, K., & Kabata, Z. (2004). A review of the impact of parasitic copepods on marine aquaculture. Zool Stud, 43(2), 229-243. (Open Access)

Kaliszewska, Z. A., Seger, J., Rowntree, V. J., Barco, S. G., Benegas, R., Best, P. B., ... & Yamada, T. K. (2005). Population histories of right whales (Cetacea: Eubalaena) inferred from mitochondrial sequence diversities and divergences of their whale lice (Amphipoda: Cyamus). Molecular Ecology, 14(11), 3439-3456.

Krkošek, M., Lewis, M. A., Morton, A., Frazer, L. N., & Volpe, J. P. (2006). Epizootics of wild fish induced by farm fish. Proceedings of the National Academy of Sciences, 103(42), 15506-15510.

Peacock, S. J., Krkosek, M., Proboszcz, S., Orr, C., & Lewis, M. A. (2012). Cessation of a salmon decline with control of parasites. Ecological Applications. (Open access).

Regier, J. C., Shultz, J. W., Zwick, A., Hussey, A., Ball, B., Wetzer, R., ... & Cunningham, C. W. (2010). Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences. Nature, 463(7284), 1079-1083.

Ross, P. S., Ellis, G. M., Ikonomou, M. G., Barrett-Lennard, L. G., & Addison, R. F. (2000). High PCB Concentrations in Free-Ranging Pacific Killer Whales, Orcinus orca: Effects of Age, Sex and Dietary Preference. Marine Pollution Bulletin, 40(6), 504-515.

Ross, P. S. (2006). Fireproof killer whales (Orcinus orca): flame-retardant chemicals and the conservation imperative in the charismatic icon of British Columbia, Canada. Canadian Journal of Fisheries and Aquatic Sciences, 63(1), 224-234.

Toups, M. A., Kitchen, A., Light, J. E., & Reed, D. L. (2011). Origin of clothing lice indicates early clothing use by anatomically modern humans in Africa. Molecular biology and evolution, 28(1), 29-32.