Blood from the corner of her mouth puddles at the square edge of the table, glistening under sharp fluorescent lights. Her skin is thick, but soft and peppered along her left side and back with scars from boat propellers. A trickle of white liquid drips from the crook of her left flipper. Not long before she died, she was nursing a calf.

She has been dead for 15 hours. Alex Costidis, a marine biologist, looks down at her through tired eyes. This was one he thought he could save.

Five other biologists and a veterinarian bustle about the lab. One takes a slice of her tail to conduct a genetics test. Another removes the eyes to send to a researcher. Still another cuts tissue samples from the lower back to test for the toxin that indicates Red Tide.

When a manatee dies in Florida, it comes to a lab in St. Petersburg. Here, at the Marine Mammal Pathobiology Lab, the animal is dissected, its parts examined closely. Much of what we now know about the anatomy of marine mammals was discovered at this lab. It was here that scientists discovered that Red Tide, one of the most pervasive killers of marine mammals, is transmitted through the digestive system, not the respiratory, as was originally assumed.

The primary purpose of the lab, though, is to determine cause of death, a task accomplished by conducting a necropsy, an autopsy for non-human animals. In a certain capacity, the lab is a morgue. The data collected here is used to inform state officials of how the animals are dying.

Two weeks ago the Florida Fish and Wildlife Commission, which funds the pathobiology lab, down-listed the manatee from endangered to threatened. Statistics indicate that the population of the popular sea mammal has stabilized over the past several years. Scientists estimate that at least 3,000 manatees live in the waters off the Florida coast. The number may be significantly higher, but since the animals migrate frequently, making a precise count is nearly impossible.

What scientists do know is that 396 manatees died last year. Many were shocked by cold water and Red Tide. Roughly a quarter of those were killed by boats.

The manatee that Costidis cuts into now is marked by deep slashes across her upper back, a tell-tale sign of propeller blades.

Sentiel Rommel, the scientist who runs the lab, examines the wounds with Costidis. Soon, the two biologists will publish a paper in the Journal of Marine Mammal Science explaining how, simply by measuring propeller wounds, scientists can determine the size of the boat that hit a manatee. That information will tell state officials what kind of boats hit manatees most often, allowing them to make informed decisions about where to put manatee-safe slow-speed boating zones.

Costidis blinks his eyes, hard. He barely slept last night.

At 6:30 p.m. the day before, the manatee was alive and Costidis was chest deep in a dirty dead-end canal in Port Charlotte. The canal had been hit hard by Hurricane Charlie, and Costidis stepped carefully, having already found a hunk of roof and a rusty rabbit cage submerged near his feet. He had spent two hours chasing the injured manatee, attempting, with little success, to guide her toward a heavy net hanging off the back of a rescue boat.

Costidis, 28, is thin and wiry, fit from a lifetime of free diving. Growing up in Greece, he dove nearly every day, once diving 24 times in six days. He came to St. Petersburg after high school and enrolled in the marine biology program at Eckerd College. During his sophomore year, he volunteered at the pathobiology lab, which sits on the edge of campus. Not long after he earned his degree he was hired full-time.

The biologists who staff the lab often double as rescuers. If an injured animal is found along Florida's west coast north of St. Petersburg, the call comes straight to the pathobiology lab. Since this manatee was found in Port Charlotte, the call first went to a small field station there. Within a half-hour, Costidis and another biologist from the pathobiology lab were in a truck, boat in tow.

The rescue crew found the manatee wedged against the sea wall, floating off-balance, her right side bobbing on the surface. Manatees have two separate lung cavities, each with its own independent diaphragm. When a manatee tips, it means a lung cavity is filling up with one of two things -- air or blood. In order for that to happen, it has to have a hole in it.

This one had several, punched through its back by a boat. But despite the severity of her injury, the manatee showed remarkable strength. As soon as Costidis approached her she snapped her tail and took off across the canal.

Two hours later, she was back against the sea wall, and Costidis was exhausted. He pushed and prodded, but the 9-foot-long animal weighed nearly 900 pounds, and she didn't budge. In a last ditch effort, he gripped the base of her paddle-shaped tail, planning to tug her away from the wall and out into the canal.

It worked - sort of. In one violent motion, she bucked, toe to tail, tearing herself from Costidis' grip and tossing him back several feet. He surfaced and swam after her.

The rescue crew had laid a net across the canal, and, she swam right into it. In minutes the crew was pulling her headfirst onto the boat, bringing a wave of canal water onboard with her. The rescue boat, an open transom mullet skiff, is old and waterlogged. It floats precariously low in the water, even without a manatee on board. With five crew members restraining the massive animal and canal water rushing in the stern, Costidis ran to the helm and gunned the engine.

At the ramp, nearly 30 people had gathered to watch the rescue. They applauded when the boat arrived.

But the manatee was holding her breath - a response to fear common in marine mammals. Costidis splashed water on her eyes to snap her out of it. But she was scared. And she was seriously hurt. Seconds later, she was dead.

To see her die was sad, but, in a way, Costidis was glad bystanders were there to see it.

"It's one thing for them to know manatees get hit by boats," Costidis said. "It's another thing for them to see it, to see its pain and to see it die."

Though the condition of the manatee in Florida is better than it was 10 years ago, population growth has been modest. The species is not entirely out of danger.

"It's not that the manatee is doing great. It's still at a very high risk of extinction," says Elsa Haubold, section leader for species conservation planning at the Florida Fish and Wildlife Conservation Commission. "But it's not going to blink out tomorrow."

Back at the lab the next morning, Costidis rubs his eyes and begins the necropsy.

The carcass is fresh, but the smell of it is intense. It sticks to your hair and in your nose, for hours.

With enough force, the beef skinner knife slips through the thick flesh smoothly. The cut is shallow, made with care not to penetrate the organs inside. Costidis and his colleagues move with surgical efficiency, methodically skinning the fatty belly, each cutting with the strength of a hunter and the nervous care of a research anatomist.

The propeller wounds on the manatee's back are like a stamp, and seem to make the cause of death obvious.

But to be sure, the scientists must look inside. They work their way in carefully, saving tissue samples for university researchers and later testing. They keep their eyes open for things they've never seen before.

The abdominal cavity is peeled back to reveal a heap of organs. Each one will be removed, examined, measured and described.

They take apart the body like a jigsaw puzzle worked backwards.

Ken Arrison, one of the biologists at the lab, picks through the stomach. He describes the contents as wet, stringy, very fibrous, dark-green and light purple. Martine De Wit, the only veterinarian at the lab, enters Arrison's description into a report on a computer in the corner of the room.

Next to Ken, Jeff Curtis, a high school student at Keswick Christian School in St. Petersburg who has a summer job at the lab, slowly snips his way through the large intestine. It is 65 feet long. After that, he'll make his way through its smaller counterpart.

Curtis wears three pairs of gloves when he works on the intestines. Without them, the smell would stick to his skin for days. Arrison also doubles up on gloves. Since he started working at the lab five years ago, he hasn't eaten sushi. The work is painstaking, and gory. Once, when Rommel cut open a gassy carcass, it exploded, sending the heart flying across the room. Gas had built up inside the body as it decomposed.

But sometimes, a carcass reveals something so interesting it shocks even the most experienced marine biologist. Rommel, who has studied manatees for 20 years and is know world-wide for his work in the field of marine mammal anatomy, says he still learns something new every day.

Standing next to the body, he describes a recent discovery. Marine mammals channel their blood in very unique ways. The male manatee, in particular, regulates the temperature of its testicles, he says, by surrounding them with blood from different parts of its body. In a conversation with a biologist friend a few weeks later, the two of them discovered, haphazardly, that elephants do the very same thing. The two mammals are distant relatives.

"Even though we're finding out why it died, we're also discovering new science, and that just makes it exciting as hell," Rommel says.

Katie Brill, another biologist at the lab, prepares to cut the head in half. She will remove the ear bone to determine the exact age of the manatee. The age of many mammals can be read on their teeth, but, like sharks, manatees shed their teeth regularly, and so the ear bone must be used.

Costidis carefully slices away the diaphragm that encloses the right lung cavity. As he suspected, it is filled with air. He lifts the lung, a thin, soggy slice of flesh, and, beneath it, finds the injury.

Three ribs are snapped clean in half, their flat broken ends penetrating the thin layer of tissue that covers the inside of the lung cavity.

At the computer, De Wit types the probable cause of death: "Watercraft (propeller, chronic)."

One more killed by a boat - a number, on a list that grows each week. This is the 66th manatee to die in Southwest Florida this year.

Costidis didn't enjoy having to explain the death to a little boy who watched the attempted rescue. And he didn't enjoy loading the warm carcass into a truck and driving it back to St. Petersburg.

But he had no emotional attachment to this particular animal. His sadness was that of a scientist, and ran especially deep for this manatee because it was female, and a young mother.

Her calf, Costidis guesses, could be as old as a year. In all likelihood, another one just like it would have followed in the coming months if she had lived. Others might have followed each year after that.

The survival of the manatee population in Port Charlotte depends on reproductive females like her.

And the fate of the species may rest on the work of the scientists at this lab.