Photo: Raja Sambasivan/CC BY-NC 2.0

UPDATE: We've narrowed down the entries to these three. Which do you think is funniest?

Every week we post a funny animal photo that’s begging for a caption. Join in the fun! You’ve got til 11:59 pm (Eastern time) on Sunday to enter your suggestion (click “Read more” below). On Monday we’ll choose our three favorite captions and list them under the image.

A hermit crab in an eelgrass bed in the Salt Creek Recreation Area, Washington. Photo by: Luke McGuff/ CC BY-ND 2.0

Tiny crustaceans have a big impact on marine ecosystem health, new research shows. 

The shrimp-like herbivores, called mesograzers, are smaller than a thumbtack, but gobble up substantial amounts of algae. Keeping the plants in check makes for clearer waters, which gives seagrass beds access to light and oxygen, researchers report in Ecology. The wee arthropods, in turn, serve as a meal for small fish, which are eaten by larger fish and birds, and on up the food chain.

  A Keystone XL Pipeline pumping station in rural Nebraska

  (Photo by shannonpatrick17 / CC BY 2.0)

President Obama is due to make a decision on the Keystone XL pipeline later this year, but in the meantime, some members of Congress have decided to take matters into their own hands. As the deadline for the Keystone XL pipeline decision inches closer, the predictable political battles are being fought. 

A Mariana Fruit-dove, extinct on Guam, but alive in the San Diego Zoo

(Photo by Dick Daniels, carolinabirds.org via Wikimedia Commons)

The Mariana Fruit-dove—a vibrant creature decorated with what looks like multicolored puffs of spray paint across it chest and crest—is just one bird of many on the forested island of Guam that will never again be spied through a birder’s lens. The pigeon disappeared famously along with many other native birds in the wake of an invasion by brown tree snakes after World War II. Only now are scientists starting to piece together the effects—among them a thinning forest canopy increasingly riddled with holes, like Swiss cheese, the researchers say.

A Chinese fishing vessel is escorted into an Australian harbor. Photo by Mateus/ CC BY-NC-SA 2.0

China has the world’s largest human population, coming in at 1.2 billion, and boasts some of the globe’s most progressive technologies and industries. It’s no surprise then that the country created one of the grandest fisheries fleets at the turn of the 21st century, one that included specialized bottom trawlers, squid jiggers, and mother ships that delivered catches to advanced ports.

For decades I’ve traveled to southeast Florida with my family. But it wasn’t until a trip two years ago that we discovered Wakodahatchee Wetlands thanks to a friend. Now, every time I’m there, I drag whomever I’m with to the manmade marsh.

This time, it was my mom.

Belugas are born gray and turn white as they mature. Photo: myprins/CC BY-ND 2.0

UPDATE: We've selected the finalists, now it's up to you to choose the winner!

Every week we post a funny animal photo that’s begging for a caption, like this shot of a young beluga and a gull. Join in the fun! You’ve got til 11:59 pm (Eastern time) on Sunday to enter your suggestion (click “Read more” below). On Monday we’ll choose our three favorite captions and list them under the image.

A European Green Crab looking particularly crusty (Photo by dreed41 / CC BY-NC-SA 2.0)

The European green crab’s demeanor has made it a long-despised and feared invasive. Originally carried from Europe’s northern coastline across the pond by ballast water, this cranky crustacean has aggressive tactics that destroy the species it hunts and drive away native competitors. But now researchers reveal in a study that this aggression is serving a positive purpose, as it helps to heal the cordgrass stretches of Cape Cod, New England.

A female Gunnison sage-grouse. Photo by Shell Game/ CC BY-NC-ND 2.0

Like most North American birds, the Gunnison sage-grouse is gearing up for breeding and nesting season. These birds, though, kick things off with a bit more zest than many other species, with a courtship display that is elaborate, unique, and extravagant. The males attract females by calling and strutting around while flapping their wings. But what they’re best known for is inflating two yellow air sacs on their white breasts and making a popping sound. It is one of the bird world’s great spectacles   a true sight to be seen   but it may not exist for long.

Panama City edges into the bay (Photo by thinkpanama / CC BY-NC 2.0)

The Bay of Panama—made up of a rich patchwork of wetlands, mud flats, and mangrove forests—is vital habitat not only for two million migrating birds like western sandpipers and whimbrels, but for turtles, monkeys, and jaguars. On top of that it is a key source of the nation’s seafood industry.