Florida reels in annual infestation of sea lice

Coastlines along Florida and across the Gulf of Mexico are yielding infestations of sea lice, as tiny larvae slip into the swimsuits of ocean enthusiasts during their saltwater dips.

Sea lice, also known more dramatically as "sunbather's eruption" or "ocean itch," are actually the larvae of thimble jellyfish. They are tiny, roughly the size of a pepper speck: although technically visible without a microscope, the larvae are impossible to see in the water.

The thimble jelly – or Linuche – is normally found throughout the Caribbean and even into the Gulf of Mexico, Steven Haddock of the Monterey Bay Aquarium Research Institute tells The Christian Science Monitor in an email. He said their common name, "sea lice" was "an unfortunate choice" because that name has been applied more accurately to a parasitic crustacean species that affects fish. 

"I swam through large swarms of these jellies in the late 1980s," Dr. Haddock writes, "and they have been doing their thing for thousands of years."

The larvae are typically active at this time of year, says Charles Messing, a marine biologist at Nova Southeastern University in Florida, citing a study from Mexico. The jellies breed asexually from March until May, meaning their larval stage is in full swing by June. 

Swimmers cannot see, much less avoid, the jellyfish, so they can slip unnoticed through the mesh of swimsuits, Katie Landeck reported for the Panama City News Herald. When trapped, the thimble jellyfish become stressed and start to sting the swimmer.

The pain swimmers associate with a sea lice sting is temporary, and so is the movement of the jellyfish through the waters along the Florida coast. This summer, they are appearing in higher than usual numbers. Swimmers have already reported them at two of Florida's beaches, according to KTRK-TV, an ABC affiliate in Houston. 

"It depends on environmental conditions," Scott Jackson, Sea Grant extension agent for Bay County, Fla., told the Panama City News Herald. 

Many species of jellyfish swarm at irregular intervals – one year dotting the ocean surface with their brown, translucent bodies, and the next appearing to vanish entirely, Dr. Messing says. The sea lice have been around for years, but only recently have marine biologists – and swimmers – began to understand what they are and where they come from. 

Marine biologists at the University of Miami discovered the jellyfish larvae by tracing the path back to beaches where swimmers complained of stings, according to a report by the Florida Department of Health. They took water samples and discovered large numbers of cnidarian larvae – a collection of jellyfish, corals, and sea anemones, all with tiny stingers. They determined that the thimble jellyfish was the main culprit. 

If the sea lice move into a new beach, officials fly purple flags along the beach to alert swimmers to a marine life presence. Swimmers can clean out the larvae by removing their swimsuits and washing them out before showering, and rinsing the swimsuits with household vinegar or rubbing alcohol can clear out the larvae.