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Sex, Drugs, and Sea Slime: The Oceans’ Oddest Creatures and Why They Matter

By Ellen Prager

University of Chicago Press, 200 pages, $26

How’s this for a love story? In the ocean’s vast depths, a male deep-sea anglerfish searches unflaggingly for “the one.” Upon finding her, be it based on a scent or the allure of her dark, scaleless skin, he’s committed for life, sealing the deal with an eternal kiss that would impress even Romeo: His mouth fuses with his partner’s skin. Such contact sets off a series of self-sacrifices, as most of the male’s internal organs degenerate. The female’s bloodstream becomes his sole nutritional source, and he evolves into a sperm-producing factory for the duration of her life. Oh, and she’s 10 times his size.

Such is undersea life—bizarre, gross, but also mesmerizing. Aside from inspiring wonder, however ocean communiteis—their diverse members and the way they interact—are also vital to survival on land, especially our own. Ellen Prager understands this, having served as chief scientist at Aquairus Reef Base in the Florida Keys, the world's only underwater research station. She also knows that merely preaching "save our seas" won't motivate landlubbers to protect the pygmy seahorse (pictured above) and the other organisms that lurk beneath the waves. For us to care, we on terra firma have to be wooed. In Sex, Drugs, and Sea Slime, Prager plumbs the depths for strange or marvelous organisms, first wowing us with their weirdness and then reeling us in with their worth—be it culinary, medicinal, biotechnological, or recreational. Her exuberant writing reveals a personal enthrallment with her protagonists. She's the perfect guide for an undersea exploration.

Prager’s ocean bestiary is diverse, ranging from the harmlessly tiny (think plankton) to the big and imposing (killer whales). Regardless, they’re all memorable in some way, often, as the title suggests, for their slime. Take the hagfish, for example. A primitive species resembling an eel, it releases gobs of mucous when threatened, even at the risk of self-suffocation. 

When it comes to the good stuff, however—beauty, sex, and slime—“the sea slugs have it all,” writes Prager. Of the thousands of sea slug species, most live in the tropics and can range from a few centimeters to nearly three feet. (Imagine coming across a garden slug that size.) On a basic level, these gastropods are like shell-less snails, a pair of sensory tentacles, called rhinophores, sprouting from their heads. Collectively, the species don an enviable wardrobe of outlandish costumes to rival a showgirl’s. “It is as if Mother Nature asked a children’s art class to design the sea slug and gave them instructions to use all the colors of the rainbow, to attach any sort of paper cutout for decoration, and, most especially, to use their imaginations with abandon,” writes Prager. Slugging across the seafloor with their muscular foot, sea slugs spend part of their short life (often less than a year) looking for mates. Though they’re hermaphroditic, as Prager puts it, “it still takes two to tango.” Sometimes they even get it on in groups, forming sea slug orgies of three or more.

Aside from their brilliant adornments and free love endorsements, why should we care about sea slugs? For one, they’re food for other marine organisms. But they also serve as models in biomedical research. They share some similar genes with humans, which could lead to insight on brain development. Drug compounds could also be developed by investigating the chemicals sea slugs use to defend themselves. Their relatives, the cone snails, are also proving a boon to medicine. Cone snails’ highly potent venom is a jackpot in terms of pharmacological pain research; at least seven drugs based on their toxins are in the pipeline, and one has already been approved by the Food and Drug Administration.

Prager gives sharks, other fish, and marine mammals their due as well, especially whales that distinguish themselves for certain feats. The Pacific gray whale, for instance, travels some 12,000 miles a year—one of the longest regular migrations of any air-breathing mammal on the planet. Male humpbacks, meanwhile, excel at singing, projecting “plaintive, sonorous songs that intermix deeply with high-pitched and pulsed notes.”

While Prager celebrates the ocean’s oddities, she doesn’t shy from the doom and gloom facing marine environments and their inhabitants, either. “Our insatiable and growing appetite for fish has led to the heavy exploitation of numerous species in the oceans, such as tuna, orange roughy, cod, and swordfish,” she writes, adding that up to 90 percent of large predatory fish are reportedly gone. She also highlights climate change, noting that “corals may be the poster child for the problem; worldwide they are exhibiting increased episodes of bleaching, disease, and mortality.” Considering that coral reefs cover less than one-quarter of one percent of the ocean but harbor diversity that could be comparable to anywhere else on earth, the prospect of further decline is jarring enough. Toss in the (conservative) estimate that they provide seafood and services worth more than $375 billion annually, and permitting their loss is economically ridiculous, too.

Instead of dragging us down, however, Prager again buoys our spirits with tempered hope, summarizing various efforts to revitalize the seas. For example, scientists and shipping operators are working together to prevent invasive species from appearing in nonnative waters. The two groups are targeting ballast water, developing ways to kill organisms found in it, as well as creating rules on how to lower the impact of releasing that extra agua. It’s progress, to be sure. But we’re not off the hook yet.