THE OCEAN'S MENAGERIE

Accounts of oceanic invertebrates are not a genre, but this “overview of” makes a good case for it.

Of 35 animal groups, one is vertebrates, from sharks to humans. The remaining 34 have no backbones; most live in the ocean and turn out to be abundant, often grotesque, and possessed of “superpowers” useful not only in their struggle for existence but also through chemicals and structures that may improve human lives and fight disease. Fish and mammals remain in the background, but few readers will complain as marine biologist Harvell, author of Ocean Outbreak: Confronting the Rising Tide of Marine Disease, describes the creatures she loves whose complexity belies their ancient evolutionary history. Passing over billions of years of single-celled life, she begins more than 600 million years ago, when the first multicellular organism appeared, probably a sponge. A sponge has no eyes, limbs, head, or organs, and it can’t move. It’s basically a collection of cells that suck in water, extract bacteria-size food, and then expel it. Despite this simplicity, it carries on sophisticated life processes. Corals exist in symbiosis with algae, which provide them with food; together, they build the world’s largest living colonies, which may stand over 40 feet high and extend hundred of miles. Intelligent octopuses, giant clams, rapacious sea slugs, deadly jellies (they aren’t fish), and essential keystone stars (also not fish) reveal their secrets and display their superpowers, a description less hyperbolic than it appears at first. It has become traditional to conclude natural histories with bad news, and Harvell does not break the mold. Warming and acidifying oceans continue to kill coral reefs across the world. Also to blame, not surprisingly, are overfishing and pollution.

A good read about bizarre creatures.