Four years ago the University of Nottingham's Dr Agnus Davison captured hearts around the world by seeking a mate for a snail named Jeremy with a left-coiled shell, a “one in a million” genetic mutation. The emotional roller coaster of the quest came to resemble a weepy movie with many a plot twist, but has also provided scientific insight into the cause of Jeremy's condition, and on similar reversed body structures in other animals, including ourselves.
Most Cornu aspersum (garden snails) have a shell that coils to the right of their body. Jeremy's coiled to the left. Snails may not bully each other for differences, but Jeremy's sexual organs were also reversed and on the opposite side of his body, impeding mating.
Davison turned matchmaker, putting out a call for left-coiling garden snails. The publicity received was so great Jeremy was dubbed a “shellebrity”, with his own Wikipedia page, but the project was not mere whimsy. Davison anticipated the genetic mutation he thought caused Jeremy's condition would appear in the offspring.
The more than 1,000 media reports of Jeremy's plight led to more than 40 lefty coiling snails being reported by citizen scientists. Famously, two of these, dubbed Lefty and Tomeau initially preferred to get it on with each other, leaving Jeremy alone again. However, shortly before Jeremy's death Tomeau laid eggs, some of them fertilized by Jeremy, and his legacy was secured.
This gave Davison the opportunity to study the children and grandchildren of left-curling parents. Snails are hermaphrodites, so have both sets of reproductive organs. Davison anticipated it would be the “mother” (that is the egg-laying snail) whose genes would determine the direction of curl, and the trait would reappear in subsequent generations.
However, in Biology Letters Davison has announced the slow slurp of tiny snail feet does not reveal the birth of a new, left curling, population. Instead, not only the children but grandchildren of Jeremy, Lefty, and Tomeau curl to the right.
“Our findings showed that it is usually a developmental accident, rather than an inherited condition, that makes a lefty garden snail,” Davison said in a statement. The cause of Jeremy's unusual form may attract less interest than the quest to find him a mate, but Davison argues it has implications for other animals. Situs inversus, where the body's organs are swapped left to right, so that the strongest part of the heart is located on the right, affects around one person in 10,000. It is usually caused by a recessive gene, encouraging biologists to anticipate this in other animals, but Jeremy challenges the assumption.
"We helped solve one of nature's puzzles, which was very satisfying,” Davison said. "We have learned that two lefties usually make a right, at least if you are a garden snail. In other snails, being a lefty is an inherited condition, but we still don't really know how they do it. If we are able to find out, then this may help us understand how the right and left side of other animal bodies are defined, including ourselves.”
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