Arctic Science Journeys
Radio Script


The House that Snot Built

INTRO: There lives in the ocean an organism that's close to us on the evolutionary ladder. It has a head, a heart—even a nervous system. And like we humans, this animal builds itself a house. But how it builds its house, and what it uses it for, may surprise—and even repulse—you. Doug Schneider has more, in this week's Arctic Science Journeys Radio

STORY: The ocean is filled with strange and bizarre creatures. There are deep-sea fish that dangle tiny lights that attract prey to within striking distance. There are bacteria that thrive within superheated hydrothermal vents. And there are a whole host of animals with bizarre sexual abilities I'm not allowed to discuss on the radio. But what caught our attention is an animal that builds itself a house made of, well, there's no easy way to say this—they build houses made of snot. Dr. Russ Hopcroft is an oceanographer at the University of Alaska Fairbanks, who studies these animals, called larvaceans.

HOPCROFT: "The whole structure is very transparent. You can see right through the whole thing. The house is usually visible mainly from the material that's stuck to it, as opposed to the material itself. It's a translucent mucus material, like our body normally produces from our nose, only more organized so it has a better mechanical structure."

Larvaceans are small, only a few millimeters long. They look a lot like a tadpole, with a large head and a tail. On the head are glands that ooze the mucus used to create a cocoon-like structure around itself. The larvacean uses the mucus house as a filter to gather food.

HOPCROFT: "The animal is unique in that it secretes a filtering structure that it actually crawls inside of and then creates a feeding current to propel water through this filtration structure. And that filtration structure concentrates very small plankton into a thick soup that the animal can then literally suck up through a tube like a straw."

Eventually, these mucus filters become hopelessly clogged with food too large for them to eat. But that's not a problem. Larvaceans always seem to have another house at the ready.

HOPCROFT: "In tropical small species, the estimate is maybe 14 of these houses are produced a day, which is one every hour and a bit. It only takes about five minutes to inflate a house. The idea is that there is always one house being produced against the head or the body while the other one is operational, so that when one is cast off the other is ready to be inflated."

Untold billions of larvaceans live in the ocean, so many that they comprise roughly ten percent of the total weight of marine life. Hopcroft says they occupy an important link in the marine food chain.

HOPCROFT: "One of the things that's unique about larvaceans compared to most of the animals we usually concentrate on in marine research is that they are very, very fast growing. They grow as fast as twenty-seven times their body weight in a day. So this animal has tremendous potential in terms of channeling energy through it and making that available to higher trophic levels, to fish."

Most larvacean species live in the warmer waters of the tropics. But Hopcroft says larvaceans may play a critical role in the colder waters of the North Pacific Ocean and the Bering Sea.

HOPCROFT: "Certainly, understanding where these animals are, and where they have their hot spots of production, it would be interesting to look at then whether these are also hot spots for fish larval development, for fish nurseries."

OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider.

Thanks to the following individual for help preparing this script:

Dr. Russ Hopcroft
Institute of Marine Science
School of Fisheries and Ocean Sciences
University of Alaska Fairbanks
Fairbanks, Alaska 99775

Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.

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For more information about larvaceans, visit this web site:

Photo of larvacean: Bathocordaeus sp.