The Secret Life of Lobsters (5 page)

A
t the age of twenty-five Jelle Atema had left the Netherlands on a plane bound for America. He had athletic good looks and a promising international career, and was a gifted flute player—a student of the French master Jean-Pierre Rampal. In high school Jelle's goal had been to sculpt himself into a Renaissance man. If he had known that in the United States his obsession would become the sex life of the American lobster, would he ever have left Europe?

Four years later it was best, Jelle supposed, not to dwell on such questions. He chuckled, dropped a chunk of fish into each lobster's tank, and surveyed his charges—half of them male and the other half female. Within moments the lobsters flicked their antennae at the scent of prey and began waving their feeding mandibles. In a few seconds his lobsters were gnawing on their food. It was astonishing to Jelle how fast the American lobster worked.

Each lobster lived in a thirty-gallon Plexiglas tank with flowing seawater. Jelle had spent the past several days setting up cameras and lights next to the tanks and fine-tuning his behavioral coding system for male-female interaction. All that remained was for one of the females to get undressed.

The basic reproductive cycle of the American lobster begins when the female sheds her old shell. This arrangement gives the female time between molts to mate, lay her eggs, and carry the eggs until they hatch before she sheds her shell again—a schedule made necessary by the fact that the eggs
are attached to the shell and would be lost during a shed. Jelle had heard reports of American lobsters copulating even when the female's shell was hard, but most female lobsters seemed to mate when their bodies were soft, immediately after molting. Jelle's first female to get lucky would be the one that molted first. It was June and they were all on the verge of shedding.

As a graduate student in the Netherlands Jelle had studied how a species of small shark detected vibrations and electric fields in the water. While finishing his Ph.D. in 1966 Jelle had been invited to join a group of scientists at the University of Michigan who were studying how fish sensed chemicals. In Ann Arbor Jelle became entranced with the catfish, and how it used smell and taste. Underwater, smell and taste are, in a sense, simply two aspects of the same thing—the detection of molecules in water. The difference has to do with the organs employed and the purposes to which detection is put. Jelle's catfish used their sense of smell to socialize and select mates, identifying one another as individuals by means of unique odor signatures. They used taste to search for food, licking the water, as it were, to find dead flesh.

Jelle's research on the subject was getting under way when the prestigious Woods Hole Oceanographic Institution in Massachusetts offered to build him a seawater laboratory on Cape Cod. It was an offer he couldn't refuse, especially when Jelle learned that the institution wanted him to head up an ambitious new program: the study of chemical communication in the sea. There was growing concern over the possible effects of oil pollution on marine populations. It was thought that molecules from petroleum products could interfere with both smell and taste, upsetting the ability of organisms to feed, socialize, and reproduce.

Jelle moved to Cape Cod in February of 1970. The first question was what organism to study. He needed a creature that was easy to acquire, handle, and manipulate and that had accessible organs of smell and taste. An animal to which elec
tronic devices could be attached would be useful. And Jelle himself had a discriminating sense of taste. A high level of postexperimental edibility would be a bonus.

Jelle knew nothing about lobsters, but a bit of lore he'd picked up intrigued him. Old-time fishermen claimed that a brick soaked in kerosene would attract lobsters to a trap. What better way to begin a study on the effects of petroleum products on undersea organisms than to test this theory? Hoping that his investment would pay off, Jelle purchased a supply of lobsters from the local fishermen's wharf.

Soon Jelle had confirmed that lobsters were attracted to the hydrocarbons in petroleum products such as kerosene. But that discovery would tell him little without an understanding of how odors and tastes governed the behavior of lobsters. Searching for food, socializing, and selecting mates were obvious aspects of lobster life that might rely on water-borne chemicals. Mate selection in particular, Jelle thought, could be revealing.

Smell is an important part of sex for any animal that releases pheromones, including humans. But little was known about how sex pheromones worked in creatures such as insects or crustaceans. All Jelle had to go on was a German study of silkworm moths. The female moth sits in a tree and emits her scent. The male moths catch the scent and fly upwind in a race to reach her. Jelle guessed that lobster mate selection might work similarly. The female lobster would find a place to perch and emit her scent, and the males would sniff her out and come running. The first one to reach her would win.

But Jelle also guessed that some sort of special sex pheromone, and not just any female scent, might be required to induce lobsters to mate. Most of the time, male and female lobsters couldn't stand each other. Prior to the molting season Jelle had paired a male and female lobster in a tank. Immediately the animals had grown agitated and flicked their small antennae rapidly. The small antennae, called antennules to differentiate them from the large antennae,
serve as an underwater nose; flicking them is the lobster's way of sniffing.

Detecting each other's scents, the male and female both opened their claws wide and raised them overhead, then whipped the water with their large antennae in a tactile search for the offending odor. The belligerent shoving and snapping of claws that followed made Jelle glad he wasn't in the tank along with his subjects.

Before attempting to mate any of his lobsters outright, Jelle devised a preliminary test. Since females usually mated immediately after molting, perhaps they released a special sex pheromone when they shed their shells. When Jelle's first female molted, he bailed some of the water from her tank into a tank occupied by a male. From the presence of the water alone the male grew agitated, but in a manner quite distinct from what Jelle had observed in his earlier experiment. This time the male sniffed with his antennules, but instead of opening his claws and raising them overhead he closed and lowered them. Instead of adopting an aggressive stance he stood delicately on tiptoes. Instead of hunting cautiously he probed the tank with abandon.

Sadly, he would never find the female that had aroused his libido. Her scent lingered maddeningly in his tank, but by then Jelle had lifted her tender, defenseless body into the tank of another male.

 

Observers of the natural world as far back as Aristotle have wondered how lobster sex works. In the fourteenth century the Italian philosopher and physician Simone Porzio wrote that the lobster's “organs of sex and reproduction are constructed in such a way that I cannot discover any obvious way in which the seed of the male could be ejaculated, poured, or otherwise introduced into the body of the female.” The problem was that the male lobster appeared not to have a penis.

Later investigators thought they had discovered the secret
of this vexing omission in the male lobster's swimmerets. Male and female lobsters both possess these little fins, arranged in five pairs along the underside of the tail. But the male's first pair, located at the midriff, are quite unlike those of the female. Instead of the flexible, flattened flippers that adorn the rest of his tail, the male's first pair are hard and pointy. Perhaps it wasn't that the male lobster was missing a penis, but that he had two.

In the 1830s the French naturalist Henri Milne-Edwards, who gave the American lobster its scientific name of
Homarus americanus,
put an end to this speculation. The male lobster's two members, Milne-Edwards wrote, couldn't possibly penetrate the female, on account of their small size. At best, Milne-Edwards thought, the first pair of swimmerets might be “exciting organs”—tools of foreplay.

But leaving female lobsters frustrated wouldn't do, so Milne-Edwards hypothesized the existence of a huge penis that the male kept hidden away except during intercourse. Similar to a collapsible telescope, this membranous appendage would emerge on demand, formed by an erection of the walls of the seminal tube inside the male's abdomen. But the collapsible penis turned out to be a fantasy. By the 1890s the world's first great lobster scientist had set things straight.

Francis Herrick, a graduate student in the zoology department at Johns Hopkins University, was studying snapping shrimp when he chanced upon the lobster for comparison. Snapping shrimp are essentially miniature lobsters. The snap in their name originates from their claws—they stun their prey with the sound of an air bubble popping between their snapping pincers, which clap together so quickly that they emit a flash of light. The American lobster is slower on the draw and can't dazzle anyone with fireworks, but Herrick would come to believe that it did have two penises after all.

The question that most intrigued Herrick about the lobster's sex life was whether the female fertilized her eggs internally or externally. In 1850 a French naturalist named G. L.
Duvernoy had speculated that lobsters never copulated; instead, the male simply fertilized the eggs externally when the female extruded them from her body onto her tail. Herrick didn't believe Duvernoy's hypothesis was correct, but he felt the Frenchman was onto something. Where previous scientists had noted the absence of a lobster penis, Herrick had noted something else—the female lobster's lack of a vagina.

Without a vagina, internal fertilization was impossible. Herrick turned his attention to another part of the female's anatomy. At the base of the female's tail, near the same place that the male lobster had his two hardened appendages, she had a tiny pouch. Herrick realized it was a seminal receptacle, where the female could store a male lobster's sperm until she was ready to extrude her eggs. This gave the female lobster the advantages of both internal and external fertilization. Instead of having to entice a desirable male at the exact moment she extruded her eggs, as Duvernoy had proposed, she could adopt a more opportunistic approach to copulation, mating whenever a desirable male was available. But she also avoided the burdens of pregnancy. She simply kept the sperm on hand in a kind of fanny pack. When she was ready to squirt the eggs out onto the underside of her tail, she unzipped the pouch and performed the external fertilization herself.

Given the position of the pouch, it seemed obvious to Herrick that the male's pair of hardened swimmerets were involved in the transfer of sperm. The appendages didn't need to be long for deep penetration, because the female's receptacle was on the outside of her body. But the skeptics had been correct to point out that the swimmerets weren't exactly penises. They didn't contain hollow tubes necessary for delivering sperm.

But a groove did run along the inside edge of each swimmeret, and their pointed tips matched the size of the hole in the female's receptacle. By dissecting lobster testes, Herrick discovered that the male lobster wrapped his sperm up into gelati
nous, tubular capsules called spermatophores. He noted that the duct delivering sperm from the testes opened exactly at the base of the hardened swimmerets—“as if,” he wrote, “they served for conducting the spermatophores through the elastic, slit-like orifice of the seminal receptacle.”

In essence Herrick had gotten it right. Later researchers confirmed that the male brings his hardened swimmerets together to form rails like a train track, the pointy tips propping open the female's receptacle. Sperm packets are ejaculated through the seminal duct and guided down the rails into the pouch. The trailing edge of the final spermatophore hardens to form a plug that blocks the opening in the seminal receptacle, preventing another male's sperm packets from entering. It isn't exactly a penis-and-vagina situation, but it's pretty close.

Herrick spent five years writing a 250-page treatise titled
The American Lobster: Its Habits and Development
. Published in 1895, it was the first in-depth study of the species. In the text he seems to lament the fact that the lobster misses out on the pleasures of internal copulation. For comparison Herrick describes the mating of crabs, where the male crab runs to the female, embraces her, pulls her to his belly, and ceremoniously penetrates her with his penis.

Herrick needn't have worried. He did his best work on lobsters at a seaside laboratory in the little town of Woods Hole, Massachusetts. Many decades later, working in the same location, Jelle Atema discovered that the American lobster could be a most tender lover, penis or no.

 

When Jelle's freshly molted female flopped into the new tank, she was so soft she couldn't stand. She didn't need to, however, because the male came to her.

Jelle was worried. This female was his first defenseless subject; having just shed her shell, she was without protection. Jelle hoped the male wasn't simply going to brutalize her, as he might have normally. Jelle was betting that a special sex
pheromone, the presence of which he'd still only hypothesized, would do the trick.

Again, the male responded immediately to the soft female's scent. Sniffing with his antennules, he closed and lowered his claws, stood on tiptoe, approached the female, and circled her. As he circled he began to stroke the female's soft body with gentle sweeps of his large antennae.

Not only was the male not going to brutalize her, he evidently had an enormous reserve of patience, for his circling and stroking continued for another quarter of an hour. Finally the female raised herself to a standing position. This indicated, Jelle guessed, that her shell had hardened just enough for the male to handle her safely, and sure enough, the male now mounted the female from behind. Pressing his tail flippers and claws to the floor of the tank for support, he grasped her body underneath his with his walking legs and rotated her onto her back. The two lobsters lay face-to-face, as it were, with the male on top. Both lobsters fanned their soft swimmerets against each other in a flurry of excited stroking. Jelle caught a glimpse of the male's hardened swimmerets pressed against the female's abdomen and saw him thrust several times. Apparently, lobster sex occurred in the missionary position—but with double the male genitalia.