Readers ask about aging perceptions, coral reefs and more

Your comments and questions on the August 3, 2019 issue of Science News

Aging mind-set

Subtle messages that can shift perceptions of aging in older people from negative to positive might lead to better health, Robin Marantz Henig reported in “Positive attitudes about aging may pay off in better health” (SN: 8/3/19, p. 22).

One study reported in the story found that older people exposed subliminally to positive age-related words performed better on memory tests compared with people exposed to negative age-related words. “I wonder if the effects were simply from negative/positive words and not necessarily age-related words. Would the results have been the same with words like ‘ugly’ or ‘smart’?” reader Jeff Haugh asked.

“It’s quite possible that people would respond negatively to subliminal exposure to words like ‘ugly,’ and positively to words like ‘smart,’ ” Henig says. In this study, the scientists went to great pains, through the use of focus groups, to be sure that the words in the experiment were specifically words that people associate with aging stereotypes, she says. But subsequent work by these scientists and others “tended to confirm that it’s the words that are both negative and age-related that do a double whammy kind of damage,” Henig says.

Coral conundrum

A coral disease discovered in Florida is spreading through the Caribbean, Cassie Martin reported in “A mysterious coral disease is ravaging Caribbean reefs” (SN: 8/3/19, p. 14). Scientists in Florida are turning to antibiotics, while researchers in the Caribbean are removing sick corals from reefs.

Readers online were concerned that the antibiotic treatment could lead to widespread drug resistance in marine ecosystems.

“We have a mixed relationship with our feeling on antibiotics,” says Karen Neely, a marine biologist at Nova Southeastern University in Fort Lauderdale, Fla. Antibiotic resistance is a concern, but the risk of not using antibiotics in this case is huge: The disease could wipe out entire coral species from Florida reefs, she says.

To lessen the chance of antibiotic resistance in the environment, Neely and others treat sick corals with a paste that releases an antibiotic directly into coral tissue instead of the surrounding water.

Mantis vision

In praying mantises, four types of nerve cells are involved in 3-D vision, Laura Sanders reported in “Tiny glasses help reveal how praying mantises can see in 3-D” (SN: 8/3/19, p. 32).

Reader David Kollas was surprised to learn that the praying mantis is the only insect known to see in 3-D. “Recently I have watched large black and white dragonflies moving quickly up and down between tightly spaced rows of young potted apple tree clones in my orchard nursery,” Kollas wrote. “When chased or chasing, they can find small openings between the trees in a row, darting to an adjacent alleyway without hesitation or collision … at full speed! I have puzzled about such confident ability. But now I am near incredulity, thinking they must do it all in what is seen as a two-dimensional world!”

Whether adult dragonflies are capable of what scientists consider to be true 3-D vision is an open question. Definitive experiments that involve studying the differences between how each eye views an object have yet to be done, says neuroscientist Ronny Rosner of Newcastle University in England.

Insect scientist Robert Olberg notes that dragonflies probably judge depth in part with a trick called motion parallax. It is the effect you get when you look out of a moving car and near objects appear to move faster than objects in the distance. “Exactly how much depth perception adult dragonflies have is still a matter of debate, but my personal opinion is that dragonflies can judge distance pretty well,” says Olberg, of Union College in Schenectady, N.Y. Dragonflies have incredibly fast visual systems, he says. That speed plus “an impressive flight control system could explain the remarkable maneuverability [Kollas] describes in his orchard nursery,” Olberg says.