You light up my life, Vargula.

You light up my life, Vargula

You probably won't see connect-the-dotspictures in sex manuals, but the dot-direct approach seems to work for a tiny crustacean that cruises Caribbean reefs in search of females. Male members of the genus Vargula leave behind spots of blue luminescent chemicals as they swim in patterns through the water, hoping to attract a female. But the flashy display isn't just for show. Although the animals can swim 60 body lengths a second, speed isn't enough in this water sport--at least 100 males have to share a single female, according to biologist James G. Morin, who has spent seven years observing the Vargulasingles scene.

"Males squirt light out and leave behind a trail like askywriter,' says Morin, a professor at the University of California at Los Angeles. "[The female] lines up the dots and swims up to the male.' Morin named the species capable of this light display "firefleas' because of their similarity to fireflies: "Both use their lights for sex, but in the fireflies, the females light up for the same reason.' Firefleas secrete the light-generating chemicals from glands on their upper lips (above cleft on right side of photo). Morin told SCIENCE NEWS he suspects that other chemical substances also may be involved in the sexual attraction between firefleas, one of the few types of marine animals that copulate.

Not to be outshone, female firefleas also release the distinctivelight, but apparently do so for an entirely different reason that comes under the "burglar alarm hypothesis,' according to Morin. When attacked by small predators, both sexes can release softball-sized clouds of light, which attract even larger predators to gobble up the smaller fish. Fish, therefore, are a little leery of approaching firefleas. Morin has observed some species that use this protective device but do not use the light to attract mates.

Visible through at least 30 feet of water, dots of light emittedby most types of male firefleas last for 10 to 15 seconds during a nightly hour-long exhibition that starts after sunset. Each of the 39 light-emitting species (Morin has found 35 of those) has its own characteristic pattern of lights, says Morin, who studies both wild and captive firefleas.