Review: September 2009

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So bizarre is the seahorse, its disembodied head, neck, and tail decorated with extravagant filigree, that someone who had never seen a living specimen might dismiss it as fantasy—no more real than a mermaid or a unicorn. Not so. Marine biologist Helen Scales reassures us that seahorses not only exist, but are found in almost every marine environment around the globe. For all their apparent weirdness, they sport the standard anatomy of a fish: gills, internal air bladder, and spine. Straighten out their curlicue tails, which the fish use to grip vegetation, and they resemble their cousins, the long and slender pipefish.
 
Don’t expect to spot seahorses at your local beach, however. Even Scales, who has spent a lot of time exploring under the waves, had to do quite a bit of hunting before she saw her first live seahorse. Timid and solitary creatures, seahorses cling to sea grass strands, mangrove roots, or knobs of coral, waiting to snatch small shrimp as they swim by. Because they can’t swim far or fast themselves, seahorses evade predators—and curious ichthyologists—by changing the color of their skin to match their background, a disappearing act that is ideally suited to what Scales calls “life in the slow lane.”

So what else is special about seahorses? For one thing, they can literally make their bodies talk, emitting sharp chirps and snaps by rubbing together two protuberances on their heads. For another, their males get pregnant. When two seahorses make love, it’s the female who deposits eggs through a slender tube into a pouch on the belly of the male. From then on, dad’s in charge, gestating the fertilized eggs for three weeks until the little sea colts are ready to emerge. Males even go through labor, which can last as long as three days. No sooner is his ordeal over, and the diminutive herd dispersed, than mom returns to possibly impregnate him again. Seahorses are monogamous, staying together for at least one breeding season, and often for a lifetime, up to ten years.

Unfortunately for seahorses, their fantastic appearance has given rise to a rich tradition of myths about their magical powers, in particular their ability to work wonder cures. The Greek physician Dioscorides, writing in the Roman Empire of the first century A.D., recommended a mixture of charred seahorse and goose fat as a remedy for baldness. Traditional Chinese medicine, which still flourishes today, incorporates seahorse in tablets to control cholesterol, increase virility, and treat a host of ailments from ulcers to bone fractures. As a result, there’s a lively trade in seahorses, which, despite their elusiveness, are regularly caught as byproducts of commercial trawling.

And so the delicate seahorse is in trouble. Six of the thirty-seven known seahorse species are listed as “vulnerable” by the World Conservation Union, largely, Scales believes, as a result of the medicinal trade. Regulation of commercial fishing may help some. So may the promotion of alternatives to seahorse among practitioners of Chinese medicine: those in the know agree that English walnut seed and possibly human placenta have similar benefits. Equally important, though, is a book like this, elegant and engaging, that informs us about the marvels of these little creatures and exhorts us to help the seahorse keep on hanging on.