By Philip Bethge
Sex in the deep sea is a difficult proposition. The problems already begin with the partner search: How do you find someone to mate with in the pitch-black depths of the ocean? And for any creature that does manage to have a rendezvous beneath the waves, failure is simply not an option.
“Seize the moment,” is how Dutch researcher Hendrik Jan Ties Hoving describes the most basic rule of undersea reproduction. “Chances are low of finding a partner a second time.”
Hoving, a biologist at the University of Groningen in the Netherlands, is in a position to know what he’s talking about, too. He recently completed his doctoral thesis on the reproduction of deep-sea squid. He studied 10 different species, from mini-squid measuring just 25 millimeters (one inch) in length to 12-meter (40-foot) giant squid. Among Hoving’s striking findings: Squid bite during sex, males drive sperm packets directly into the skin of females and brutal wrestling is part of their mating ritual.
The array of techniques is impressive, Hoving says, but also takes some getting used to. His conclusion: “Reproduction is no fun if you’re a squid.”
Most of the squid behaviors that have come to light so far are striking and bizarre. For example, researchers in California photographed one species, Gonatus onyx, caring for its brood. This squid, which measures just under half a meter (one and a half feet) long and lives in water around 2,500 meters (8,000 feet) deep, stretched its arms into a kind of web, holding a gelatinous matrix containing 2,000 to 3,000 eggs. It regularly flushed fresh water through this egg mass, presumably to aerate the embryos.
Meanwhile, American researchers Clyde Roper and Michael Vecchione caught another species, Brachioteuthis beanii, in the act off the coast of North Carolina. One squid grabbed another from behind, and the one being grabbed “bent its body and vigorously moved its arms around the head and mantle opening of the grasping squid” — one pulling the other, the second sinking toward the first. The experts’ opinion: “Probably mating.”
Now Hoving has unveiled what seems like an entire Kama Sutra of the squid world. The subjects of his study were all already dead at the time he observed them, but what the biologist found in museums, obtained from fishermen and collected from the ocean on scientific expeditions off the coast of Namibia and the Falkland Islands is nonetheless sensational:
- Using their sharp beaks or the hooks on their tentacles, males of the species Taningia danae make cuts more than five centimeters (two inches) deep into the females’ flesh. They then deposit sperm packets, called spermatophores, into the wounds.
- Females of a mini-squid species, Heteroteuthis dispar, store sperm within their bodies in a special pouch. The precious cargo can account for up to 3 percent of the squid’s total body weight.
- Some males of the species Ancistrocheirus lesueurii appear outwardly almost like females. “Possibly an adaptation for getting closer to the females,” Hoving suggests.
- For another species, Moroteuthis ingens, the males simply release their sperm packets and don’t need to do anything more. The spermatophores penetrate the female’s skin independently, using a substance that dissolves tissue.
Hoving has an explanation for this strange avoidance of bodily contact: “Mating is probably quite risky for the male,” he says. “In most species they’re smaller, and could get eaten.”
He has a similar explanation for the males’ rough behavior: “More than anything, it’s about being fast.” It seems the males are quite literally under great pressure. A few years ago, Australian biologists discovered sperm packets under the skin of a freshly caught 15-meter (50-foot) female giant squid. Covered with a “gelatinous” substance, they had presumably been “injected” by a male, the researchers reported, “under hydraulic pressure,” with a penis “up to 92 centimeters (three feet) long.”
Small wonder that things sometimes go wrong. Hoving discovered sperm packets, among other places, in the eyes of animals he studied. And one giant squid found off the coast of Norway seems to be a not atypical case: a male, it also had spermatophores under its skin. The science journal Nature offered the interpretation that the squid may have “literally shot itself in the foot.”
In the end, however, it seems fertilization does manage to take place in most cases. Squid are certainly numerous enough — according to Hoving, there are around 200 species in the deep ocean. Not even overfishing does harm to them, he says. Quite the opposite, in fact: “The squid have more to eat, since they don’t have to share their food with the fish that are caught for consumption.”
A female squid releases millions of tiny eggs into the water, but generally only once in her lifetime. When she does, the sperm stored under her skin are discharged simultaneously. The father for this legion of embryos is often the single male who got his beak or hooks on the female first.
Thus the brutal attacks by some male squid have another purpose, Hoving believes. “The females have downright negative experiences with mating, meaning that afterwards they won’t let any other male near them.”
It’s a forced fidelity for the squid, and Hoving even has a technical term ready for it: “traumatic insemination.”