Science Explains Why Your Lab Is Always Hungry

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iStock

Dogs love food. Some love it more than others, and some of those are Labrador retrievers—the bottomless pits of the canine world. Scientists announced today that they’ve found a gene variant in labs that may explain that constant state of "Please Feed Me." The findings were published last year in the journal Cell Metabolism.

Dog obesity isn't something we talk about a lot, but there sure is a lot of it. In the U.S. and other wealthy countries, between 34 and 59 percent of dogs are overweight. And yes, fat dogs are cute, but they’re also in danger of some serious health problems. Canine obesity can cause heart disease, strain on a dog’s joints, diabetes, and can even shorten a dog’s lifespan.

Some breeds, like black labs, chocolate labs, and golden retrievers, are more obesity-prone than others. This is likely because, like many of us, they are highly motivated by food. Labs’ human companions learn quickly that a treat is the trick to getting their dog to behave. But those treats add up.

The domesticated dog, Canis familiaris, is a single species with a lot of variations. Great Danes and Chihuahuas are both dogs, but their bloodlines, and therefore their genes, are dramatically different. And all those differences within a single species make dog breeds a great resource for scientists studying genetics.

Researchers recruited nearly 400 adult Labrador participants. Of those dogs, 310 were pets recruited through an email invitation from the UK Kennel Club, and 80 were part of an assistance-dog breeding colony. Some of the dogs were fat, while others were not, but all of them were healthy, with no pre-existing conditions.

First, the dogs were weighed. Then the scientists collected drool samples from 33 of the dogs and sequenced the DNA within. The dogs’ owners then completed a survey about their labs’ eating habits.

As relatives, of course, the labs had a great deal of genetic material in common with each other and with other dog breeds. But they also had one gene variant that stood out: the deletion of 14 base pairs from a gene called pro-opiomelanocortin, or POMC. Previous studies of this POMC variant have shown a relationship with appetite and a feeling of fullness.

Each dog could have one copy of the POMC variant, two copies, or none. The more copies a dog had, the fatter and more food-motivated it was. And about 23 percent of labs are carrying at least one copy of the variant.

"People who live with Labradors often say they are obsessed by food, and that would fit with what we know about this genetic change," Cambridge University metabolism expert and lead author Eleanor Raffan said in a press statement.

Her co-author, Stephen O’Rahilly of the Wellcome Trust-Medical Research Council Institute of Science, says these findings have implications beyond kibble. "Common genetic variants affecting the POMC gene are associated with human body weight and there are even some rare obese people who lack a very similar part of the POMC gene to the one that is missing in the dogs. So further research in these obese Labradors may not only help the well-being of companion animals but also have important lessons for human health."

The Weird, Disturbing World of Snail Sex

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iStock

Romance is rare in the animal kingdom. Instead of wooing their partners before copulating, male ducks force themselves onto females, depositing genetic material with spiky, corkscrew penises. Then, there's tardigrade sex, which is less violent but not exactly heartwarming. Females lay eggs into a husk of dead skin. The male then ejaculates onto the eggs while stroking the female, and the whole process can take up to an hour.

But you can't talk about disturbing mating rituals in nature without mentioning snails. If you're unfamiliar with snail sexuality, you may assume that snail sex falls on the vanilla side: The mollusks, after all, are famous for being slow-moving and they don't even have limbs. But if you have the patience to watch a pair of snails going at it, you'll notice that things get interesting.

The first factor that complicates snail sex is their genitalia. Snails are hermaphrodites, meaning individuals have both a male set and female set of parts, and any two snails can reproduce with each other regardless of sex. But in order for a couple of snails to make little snail babies, one of them needs to take on the role of the female. That's where the love dart comes in.

The love dart, technically called a gypsobelum, isn't exactly the Cupid's arrow the name suggests. It's a nail-clipping-sized spike that snails jab into their partners about 30 minutes before the actual sex act takes place. The sliver is packed with hormones that prepare the receiving snail's body for sperm. Depending on the species, only one snail might release the dart, or they both might in an attempt to avoid becoming the female of the pair. You can watch the action in the video below.

For sex to be successful, both snails must insert their penises into the other's vaginal tracts at the same time. Both snails deposit sperm, and the strength of the love dart ultimately determines whether or not that sperm fertilizes their partner's eggs.

That's assuming the snail survives the little love-stab. In human proportions, the love dart is the equivalent of a 15-inch knife. Fortunately, snails are resilient creatures, and gastropod researcher Joris Koene tells KQED he's only ever seen one snail die from the transfer.

Snails also have a way of making it up to their partners after skewering them with a hormone stick. Their sperm deposit contains a dose of fortifying nutrients, something scientists refer to as a nuptial gift. It may not equal the energy expended during sex, but its enough to give them a small post-coital boost.

14 Adorable, Vintage Photos of Rabbits

Chaloner Woods, Getty Images
Chaloner Woods, Getty Images

In honor of International Rabbit Day (held annually on the fourth Saturday of September), we've pulled photographic proof that the furry little mammals have always been appreciated by children and the adults who use a number of rabbit-related phrases and idioms more often than they probably realize.

1. DOWN THE RABBIT HOLE

Nursery school children playing with their pet rabbit Bubbles; 1939.
David Parker, Fox Photos/Hulton Archive/Getty Images

Nursery school children playing with their pet rabbit Bubbles, 1939.

2. DUST BUNNY

 A woman spinning Angora rabbit wool in her garden, 1930.
Fox Photos, Getty Images

A woman spinning Angora rabbit wool in her garden, 1930.

3. MAD AS A MARCH HARE

A young boy holds a pet rabbit, 1955.
Charles Ley, BIPs/Getty Images

A young boy holds a pet rabbit, 1955.

4. BUY THE RABBIT

A golfer makes a practice drive while his pet rabbit minds the balls; 1938.
Reg Speller, Fox Photos/Hulton Archive/Getty Images

A golfer makes a practice drive while his pet rabbit minds the balls, 1938.

5. HONEY BUNNY

School children petting rabbits; 1949.
Chaloner Woods, Getty Images

Schoolchildren petting rabbits, 1949.

6. HAREBRAINED IDEA

A woman took her Himalayan rabbit, Albrecht Durer, on a walk in Hyde Park, 1939.
Fox Photos, Getty Images

A woman took her Himalayan rabbit, Albrecht Durer, on a walk in Hyde Park, 1939.

7. CUDDLE BUNNY

A little girl petting a large rabbit, 1949.
Chaloner Woods, Getty Images

A little girl petting a large rabbit, 1949.

8. LUCKY RABBIT'S FOOT

Schoolgirls care for pet rabbits, 1932.
Fox Photos, Getty Images

Schoolgirls care for pet rabbits, 1932.

9. PULL A RABBIT OUT OF A HAT

A young magician and his rabbit, 1971.
George W. Hales, Fox Photos/Getty Images

A young magician and his rabbit, 1971.

10. SNOW BUNNY

A woman shows off her two pet angora rabbits, circa 1955.
George Pickow, Three Lions/Getty Images

A woman shows off her two pet angora rabbits, circa 1955. Angoras can be sheared to provide enough wool for two sweaters each year.

11. THE EASTER BUNNY

A little girl holds an Easter bunny on a leash, circa 1955.
George Pickow, Three Lions/Getty Images

A little girl holds an Easter bunny on a leash, circa 1955.

12. A RABBIT TRAIL

Three children hold a rabbit, 1935.
H. Allen, Topical Press Agency/Getty Images)

Three children hold a rabbit, 1935.

13. RABBIT FOOD

A boy feeds his pet rabbit a lettuce leaf, circa 1955.
George Pickow, Three Lions/Getty Images

A boy feeds his pet rabbit a lettuce leaf, circa 1955.

14. RABBITING ON

Actresses Fiona Fullerton and Clare Clifford posting some of the many letters sent to the House of Lords and parliamentary candidates to request support for World Day for Laboratory Animals which was instituted that year, 1979.
Central Press, Getty Images

Actresses Fiona Fullerton and Clare Clifford posting some of the many letters sent to the House of Lords and parliamentary candidates to request support for World Day for Laboratory Animals which was instituted that year, 1979.

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