Global Warming's Fish-Gender Effect

A small increase in water temperature among sensitive fish like the South American pejerrey can result in a population that is 98% male
Cousseau, B. and Perrotta, R.G. / Fishbase.org

(See original article at www.time.com)

Once scientists began studying the impact of global warming on everything from tourism to asthma, it was only a matter of time before they got around to sex. Now two biologists at Spain's Higher Council for Scientific Research (CSIC) have done just that, at least when it comes to fish.

You may have missed it in biology class, but in some finned species, like the Atlantic silverside — as well as in many reptiles — sex is determined not by genetics but by temperature: the undifferentiated embryo develops testes or ovaries on the basis of whichever option conveys evolutionary advantages for that particular environment. Now, in a study published in the July 30 edition of the scientific journal Public Library of Science, Natalia Ospina-Alvarez and Francesc Piferrer have gone a little further in explaining how that mechanism works. In laboratory tests, they have demonstrated that higher water temperatures result in more male fish.

"We found that in fish that do have temperature-dependent sex determination [TSD], a rise in water temperature of just 1.5 degrees Celsius can change the male-to-female ratio from 1:1 to 3:1," says Piferrer, the study's co-author. In especially sensitive fish, a greater increase can throw the balance even more out of whack. Ospina-Alvarez and Piferrer have found that in the South American pejerrey, for example, an increase of 4 degrees Celsius can result in a population that is 98% male.

What makes these findings especially troubling, of course, is that the International Panel on Climate Change (IPCC) predicts that ocean-water temperatures are likely to rise by 1.5 degrees over the course of this century — and they may even go up a few degrees more. "If climate change really does result in a rise of 4 degrees, which is the maximum the IPCC predicts, and if species can't adapt in time or migrate, then in the most sensitive cases of TSD, we're looking at extinction," says Piferrer.

Most research into fish sex determination has been done in the lab (for obvious reasons), but the pejerrey is one of the few species that scientists have been able to study in the field. And those studies have revealed that already, its proportion of males to females is skewed. "It could be because of chemical pollution or it could be because of climate change. We don't know," cautions Piferrer. "But the field data matches our predictions."

At this stage, it is hard to tell what these results bode for already declining fish populations around the world. Of the estimated 33,000 piscatorial species, only 5,000 have had their sex-determination mechanism affirmed. But the study by the two CSIC scientists also suggests that the percentage of TSD fish is lower than previously believed. In tests of 59 species believed to be reproductively sensitive to temperature, only 40 proved to be true TSDs.

That would be good news in this grim era of climate change if it weren't for one factor: even genotypic sex determination can be affected by anomalous conditions, including anomalous temperature. "Basically, if you freeze it or cook it enough," says Piferrer, "you can get whatever sex you want."

Fish pedicures: Carp rid human feet of scaly skin

See the AP story here.

By MATTHEW BARAKAT Associated Press Writer

ALEXANDRIA, Va. (AP) -- Ready for the latest in spa pampering? Prepare to dunk your tootsies in a tank of water and let tiny carp nibble away.
Fish pedicures are creating something of a splash in the D.C. area, where a northern Virginia spa has been offering them for the past four months. John Ho, who runs the Yvonne Hair and Nails salon with his wife, Yvonne Le, said 5,000 people have taken the plunge so far.

"This is a good treatment for everyone who likes to have nice feet," Ho said.

He said he wanted to come up with something unique while finding a replacement for pedicures that use razors to scrape off dead skin. The razors have fallen out of favor with state regulators because of concerns about whether they're sanitary.

Ho was skeptical at first about the fish, which are called garra rufa but typically known as doctor fish. They were first used in Turkey and have become popular in some Asian countries.
But Ho doubted they would thrive in the warm water needed for a comfortable footbath. And he didn't know if customers would like the idea.

"I know people were a little intimidated at first," Ho said. "But I just said, 'Let's give it a shot.' "
Customers were quickly hooked.

Tracy Roberts, 33, of Rockville, Md., heard about it on a local radio show. She said it was "the best pedicure I ever had" and has spread the word to friends and co-workers.
"I'd been an athlete all my life, so I've always had calluses on my feet. This was the first time somebody got rid of my calluses completely," she said.

First time customer KaNin Reese, 32, of Washington, described the tingling sensation created by the toothless fish: "It kind of feels like your foot's asleep," she said.

The fish don't do the job alone. After 15 to 30 minutes in the tank, customers get a standard pedicure, made easier by the soft skin the doctor fish leave behind.

Ho believes his is the only salon in the country to offer the treatment, which costs $35 for 15 minutes and $50 for 30 minutes. The spa has more than 1,000 fish, with about 100 in each individual pedicure tank at any given time.

Dennis Arnold, a podiatrist who four years ago established the International Pedicure Association, said he had never heard of the treatment and doubts it will become widespread.
"I think most people would be afraid of it," he said.

Customer Patsy Fisher, 42, of Crofton, Md., admitted she was nervous as she prepared for her first fish pedicure. But her apprehension dissolved into laughter after she put her feet in the tank and the fish swarmed to her toes.

"It's a little ticklish, actually," she said.

Ho said the hot water in which the fish thrive doesn't support much plant or aquatic life, so they learned to feed on whatever food sources were available - including dead, flaking skin. They leave live skin alone because, without teeth, they can't bite it off.

In addition to offering pedicures, Ho hopes to establish a network of Doctor Fish Massage franchises and is evaluating a full-body fish treatment that, among other things, could treat psoriasis and other skin ailments.

Ho spent a year and about $40,000 getting the pedicures up and running, with a few hiccups along the way.

State regulations make no provision for regulating fish pedicures. But the county health department - which does regulate pools - required the salon to switch from a shallow, tiled communal pool that served as many as eight people to individual tanks in which the water is changed for each customer.

The communal pool also presented its own problem: At times the fish would flock to the feet of an individual with a surplus of dead skin, leaving others with a dearth of fish.

"It would sometimes be embarrassing for them but it was also really hilarious," Ho said.

[ed. - Ewww.....]