In Defense of Larvae

Larva. To a lot of people, the word signifies something half-formed, ugly, and likely to devour food stores, winter clothing, or green leaves. As a rule, we glorify the butterfly and dismiss the caterpillar. Exceptions may be made for tadpoles, which at least, like us, are vertebrates. Perhaps humans are inclined to this form of prejudice because we are direct developers, going from babyhood to reproductive maturity without changing much more than our bodily proportions. Yes, as embryos we have gills, and along the way to adulthood we pick up a few secondary sex characteristics, but we do not truly metamorphose. And when fictional humans undergo transformations in books and films, it's almost always bad news (think Gregor Samsa in Kafka's "Metamorphosis" or Vincent Price in The Fly).

Fortunately for Natural History's readers, some people appreciate metamorphosis and have made the study of larvae an important part of their life's work. One is evolutionary biologist Gregory A. Wray, who in this issue's special section, "A World Apart", provides a corrective to direct-developers' chauvinism by pointing out that the larval lifestyle is the most common developmental pathway in the animal kingdom. Sea stars, nudibranchs, sea lilies, corals, clams, and barnacles are among the multitude of marine invertebrate organisms that spend days or months in larval form, swimming or drifting near the surface of the world's oceans. For Wray and the other seven scientists who write about larvae this month, these intermediate forms offer beauty, mystery, and a wealth of insight into developmental biology.

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