Like actors in a scene from a bawdy farce, many squid don't know whom to woo when the lights go down. Deep in California's Monterey Bay, small squid belonging to the species Octopoteuthis deletron suffer from frequent cases of mistaken identity, a new study suggests. Males commonly try to mate with males as well as females, hinting that in the dark, these invertebrates may settle for whatever squid passes by. But their indiscriminate attention might improve the odds that they are occasionally successful.
For years, biologists have had few opportunities to explore the lives of deep-sea squid and their octopus relatives, save by dragging them up in nets or harvesting them from the bellies of dead whales. Today, crewless submarines plumb the depths of a handful of marine habitats, including Monterey Bay. Often, the images these vehicles send back to the surface paint a very different picture of the deep from early land-based assumptions, says Michael Vecchione, a zoologist at the National Marine Fisheries Service's National Systematics Laboratory in Washington, D.C.
He points to certain squid that store ammonia in their tentacles, perhaps for buoyancy. Because ammonia floats, many researchers figured the eight-limbed critters swam with their tentacles over their heads like cactuses. "But then we got to go down," he says. "It was the other way around: They keep undulating their fins to maintain the arms-down position."
Off the California coast, underwater cameras sometimes catch another surprising sight: squid with what appears to be sea acne. Since 1992, submarine surveys conducted by the Monterey Bay Aquarium Research Institute in Moss Landing have spotted as many as 108 O. deletron squid at play. These often-reddish animals—most about as big as a human hand—troll about 400 to 800 meters below the sea surface. In a recent survey, study co-author Hendrik Hoving, a marine biologist at the institute, and colleagues discovered that many seemed to be dotted from head to tentacles with tiny "white bulbs." Those bulbs, it turns out, weren't blemishes but empty pouches that once contained squid sperm.
In the deep sea, scientists suspect that squid courtship involves little romance and lots of pirate warfare. When males spot a passing female, they smear them with sperm-laden globs called spermatophores, using obscenely long organs. Once plopped down, the spermatophores likely burst open, releasing clingy sperm pouches that then glom onto the female's torso and tentacles. Hoving's team spotted these telltale signs of attempted liaisons on O. deletron females and males in seemingly equal numbers, the group reports online today in Biology Letters.
In the dark, males and females may all look alike to a wandering squid, Hoving suggests. Alternatively, because the largely solitary males can breed for a short window of time only once in their lives, they may drop their spermatophores onto every squid they encounter rather than risk missing an opportunity to breed. Quick copulation is a potentially safer mating strategy, too, he adds. Many squid species are known cannibals, so it benefits males to "quickly deposit their spermatophores and go away."
The team's findings are certainly strange, says Vecchione, who was not involved in this study. Because scientists know so little about the bizarre creatures that prowl the deep sea, this strategy may be more common than many think, he says. "It's the biggest living space on Earth," Vecchione says. But "it's the most poorly studied part."
Correction: A previous version of this article referred to octopuses that store ammonia in their tentacles for buoyancy. The animals in question are squid.