Bioluminescence is used by living things to hunt prey. Anglerfish, like this female, use the long, illuminated filament on their head to lure prey. Smaller fish only see the giant jaws lurking behind the bright bobble too late.

Photogrpah by Darlyne A. Murawski, National Geographic

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  • Ah, the female anglerfish. Majestic. Regal. Vaguely terrifying. 
    Behold the fleshy blob sticking out from her nose. It actually lights up, beckoning gullible guppies close to the enormous, toothy maw hidden in the murky darkness.
    But wait! It’s not just guppies! The female anglerfish is an equal-opportunity predator. She can consume prey twice her size. How? By doubling the size of her entire jaw and stomach, of course.
    Stuck Together
    Female anglerfish also have a strange relationship with their male partners. You see one of them in this photo. That’s him, right below her tail. 
    That little male anglerfish spends his whole life sniffing out a female anglerfish. Really—he has outstanding olfactory cells and won’t stop swimming until he finds the source of those enticing pheromones wafting through the water. Once he does, he grabs hold of her and won’t let go.
    (It’s actually a fantastic adaptation. The benthic environment where a lot of these anglerfish live is a dark and lonely place. The odds of running into another anglerfish-on-the-prowl are pretty low . . . once you find her, you never let her go.)
    So, he bites her. 
    Then, he dies.
    Sort of.
    When the male anglerfish bites the female, he releases an enzyme that dissolves the tissue around his mouth and her skin, fusing them together, right down to their blood vessels. The male atrophies. This means he basically dissolves—first he loses his eyes, then his internal organs—until he’s just a sac of tissue and reproductive organs hanging off the female’s belly. A female can have as many as six atrophied males attached to her body.
    At this point the anglerfish is basically a hermaphrodite, able to fertilize its own eggs whenever it feels like it. 
    Instructional Ideas
    Have students read through the short, whimsical text on the anglerfish above (available in the “Student” version of this media spotlight) either individually or as a class.
    • Have students express the ideas of the text (the predatory and mating habits of the anglerfish) in their own words. Re-write the text, draw a diagram or series of illustrative/cartoon panels, create an animated video, etc.
      • (California Reading Standards for Literacy in Science and Technical Subjects 6–12, standard 2: Determine the central ideas or conclusions of a text; provide an accurate summary of the text distinct from prior knowledge or opinions.)
    • Familiarize students with the concept of anthropomorphism. Explain that anthropomorphism is the practice of attributing human characteristics to anything that is not a human being—plants, forces of nature, or, in this case, fish. Explain that anthropomorphism is not based on “reasoned judgment.” 
      • Have students identify words that may anthropomorphize the physical or behavioral characteristics of the anglerfish. Review how this language is suggestive or leading.
      • Discuss how students would present the same information using less anthropomorphic language. 
      • (California Reading Standards for Literacy in Science and Technical Subjects 6–12, standard 8: Distinguish among facts, reasoned judgment based on research findings, and speculation in a text.)
    • Although some female anglerfish can grow up to a meter (3 feet) in length, this one is only about 8 centimeters (3 inches). The male is less than a centimeter (about a quarter inch) in length.
    • Some male anglerfish have a stunted or incomplete digestive system. They have to find and attach themselves to females or die of starvation.
    • Like most fish, female anglerfish lay hundreds of (unfertilized) eggs at a time. One species of anglerfish (the monkfish) ejects a slimy sheet of material that holds the eggs. The sheet can be about a meter (3 feet) wide and 10 meters (33 feet) long. (Most fish have to rely on a passing male fish to fertilize the waterborne eggs. The female anglerfish, of course, can do it herself with the male organs attached to her body.)
    • The esca—the fleshy filament protruding from the female anglerfish’s head—is actually part of her spine.
    • There are more than 200 species of anglerfish. 
  • Term Part of Speech Definition Encyclopedic Entry
    adaptation Noun

    a modification of an organism or its parts that makes it more fit for existence. An adaptation is passed from generation to generation.

    Encyclopedic Entry: adaptation
    atrophy Verb

    to waste away or degenerate.

    beckon Verb

    to lure or entice.

    benthic Adjective

    having to do with the bottom of a deep body of water.

    bioluminescence Noun

    light emitted by living things through chemical reactions in their bodies.

    Encyclopedic Entry: bioluminescence
    blood vessel Noun

    tubes through which blood circulates.

    consume Verb

    to use up.

    entice Verb

    to lure, or lead on with hope and desire.

    environment Noun

    conditions that surround and influence an organism or community.

    enzyme Noun

    proteins produced in living cells that act as catalysts to accelerate the vital processes of an organism.

    esca Noun

    long, thin, fleshy growth from the head of an anglerfish.

    fantastic Adjective

    excellent or very good.

    fertilize Verb

    to make productive or fertile.

    gullible Adjective

    easily fooled.

    hermaphrodite Noun

    organism with both male and female reproductive organs.

    majestic Adjective

    very impressive and formal.

    maw Noun

    mouth and throat of an animal, usually a carnivore.

    murky Adjective

    dark and unclear.

    olfactory cell Noun

    tiny structure that allows animals to smell.

    organ Noun

    group of tissues that perform a specialized task.

    pheromone Noun

    substance released by an animal that influences the behavior of other animals of the same species.

    predator Noun

    animal that hunts other animals for food.

    prey Noun

    animal that is hunted and eaten by other animals.

    prowl Verb

    to slink about in search of prey.

    regal Adjective

    resembling or having to do with royalty.

    reproductive organ Noun

    collection of tissues (organ) that works to reproduce a species.

    tissue Noun

    cells that form a specific function in a living organism.

    waft Verb

    to carry or convey lightly and smoothly, usually through air.