Nothing in Life is More Important than Sex

Animal Attraction in San Francisco

By Laurie McAndish King

“Nothing in life is more important than sex.” So says Steinhart Aquarium Director Bart Shepherd, and I’m inclined to agree. Shepherd recently announced the opening of a new exhibit at the California Academy of Sciences about sex, mating, and evolution.

Exhibit entry — Photo by JM Shubin

This first new gallery since the new Steinhart Aquarium opened in 2008 is also the first public aquarium to use iPads as exhibit labels, allowing visitors to flip through gorgeous images, watch videos of reproductive behaviors in action, and guide their own digital explorations using interactive touch screens throughout the exhibit.

 The family-friendly exhibit manages to present hermaphroditism, sexual cannibalism, multi-organism mating chains, cloning, cradle-snatching, and other seemingly unusual sexual behaviors as just what they are: highly evolved natural behaviors that serve Mother Nature’s purposes quite well.

Gimme Shelter

Photo: Cal Academy

Consider the coconut octopus (Amphioctopus marginatus), which can use a coconut shell as a personal—or should we say octopoidal?—shelter. This creature carries its den around with it, and is, Shepherd says proudly, the only invertebrate known to use a tool. (Bart collected this specimen on an expedition to the Philippines, and it’s one of his personal favorites.)

Steinhart is the only public aquarium to display this species, which is solitary except when mating—perhaps because of the female’s aggressive tendencies. Male octopuses use one of their eight arms (usually the third right arm) to pass sperm over to a female, often keeping the rest of their bodies as far away as possible during the transfer in order to avoid being bitten. After laying eggs, the female tends them by squirting jets of water over the eggs to protect them from bacterial infections. When they hatch—mission accomplished!—she dies.


Photo: Cal Academy

Terrestrial Biologist Eric Hupperts turned me on to the reproductive eccentricities of the banana slug (Ariolimax californicus), that emblematic denizen of the redwood forest. The banana slug is a simultaneous hermaphrodite, which means each individual is both a male and a female at the same time—and has the parts to prove it. In fact, its male sex organ is huge, and can become nearly as large as the slug itself during reproduction.

Slugs do require a partner to mate, and because the genital opening is near the slug’s head, reproduction occurs in a yin-and-yang-like circle. As one might imagine (if one were to imagine the sex life of a slug), the creatures often have difficulty disengaging after the act. So, when necessary, they perform apophallation: one gnaws off the other’s stubborn organ. No, it does not grow back.

 But do You Love Me?

Living as it does in the darkest depths of the sea, it can be tough for a male anglerfish to find a mate—so once he locates a female, he uses his razor-sharp teeth to latch onto her belly, and he never lets go. The dwarf male (he is much smaller than the female) becomes fused to the female at the blood vessel level and eventually begins to atrophy, first losing his digestive organs, then his brain, heart, and eyes. Eventually, “he” is nothing more than a pair of parasitic gonads drawing nutrition from his female host, and serving only as a source of sperm. Yes, multiple males can be incorporated into a single female anglerfish.

Like a Fish needs a Bicycle?

Sharks are violent animals, and their mating “dance” often leaves the female scarred. But there may be other options; sharks may also be parthenogenic, with virgin females laying viable egg cases on their own. Steinhart Aquarium Senior Biologist Nancy Levine is about to find out. Levine has been tending egg cases from the Aquarium’s three resident brown-banded bamboo sharks, which are all females and have had no contact with males for six years. Levine found a viable egg, which hatched to become what appears to be a healthy baby shark and is now about four inches long. Genetic testing and evaluation will determine whether this individual is indeed the offspring of only one parent.

Photo: Cal Academy

Talk about Teamwork

At the climax of their courtship, male and female splashing tetras (small silver fish native to the Amazon) lock together and leap out of the water to lay and fertilize clutches of eggs on the undersides of overhanging leaves, away from the reach of predators. At that point, Mom’s job is done, but Dad hangs around for another three or four days, using his tail to splash water on each egg cluster at one-minute intervals, until the eggs hatch and fall into the water, at which point parental care ceases.

iPad labeling — Photo by JM Shubin

Fairy basslets (Pseudanthias species) all begin life as females, but they can turn into males if the situation requires. Biologists Matt Wandell and Richard Ross explained that typically these magenta, pink, yellow, and orange beauties live in schools—nearly all female—ruled by one dominant male, notable for his brighter colors, larger fins, and more prominent … nose. Staking out his territory, the flamboyant male rules over his harem, producing enough sperm for all the females and thus conserving energy for the group.

If the male dies, the largest female undergoes a sex change, and can within a week become the new ruling male. Sometimes several females change, fighting each other for the new position, but in the end only one becomes dominant, driving her—or rather his —rivals away. And once a “she” fairy basslet has turned into a “he,” there’s no going back.

Photo by JM Shubin

The coral banded shrimp (Stenopus species) is notable for its antisocial sexual behavior. Males kill all other males in their territory, and females kill other females, resulting in a monogamous-yet-sociopathic couple who set up housekeeping in a coral reef. There they establish a grooming station—a sort of underwater spa—where they pick parasites and loose scales off the client fish who swim in for a few minutes of healthful rejuvenation. Because they don’t venture far from their station, coral banded shrimp take their reproductive cues from the water temperature and moonlight, sending their gametes out in a synchronized spawn.

Photo by JM Shubin

These are just a few of the exhibit’s 22 examples of weird, wild, and wonderful strategies for reproduction. Viewing the creatures up close, talking with docents, and playing with the iPhone interpretive stations makes for a delightful afternoon of sex education. It also makes me glad to be a human!

The California Academy of Sciences is home to Steinhart Aquarium, Morrison Planetarium, Kimball Natural History Museum, and world-class research and education programs—all under one living roof. Admission to the Academy is: $29.95 for adults; $24.95 for youth ages 12 to 17, Seniors ages 65+ and students with valid ID; $19.95 for children ages 4 to 11; and free for children ages 3 and younger. Admission fees include all exhibits and shows. Hours are 9:30 a.m. – 5:00 pm Monday – Saturday, and 11:00 a.m. – 5:00 p.m. on Sunday. During peak periods, including some holiday weekends, an admission surcharge and extended hours may apply. Visit or call (415) 379-8000 for more information.

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