Clock Ticking On Northern White Rhino
San Diego Zoo’s Research Could Help Stave Off Extinction
Monday, May 20, 2019
Credit: Courtesy of the San Diego Zoo
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San Diego Zoo researchers are caring for two pregnant southern white rhinos that are a key part in the plan to save the critically endangered northern white rhinos. The extinction clock is ticking because only two northern whites remain alive.
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San Diego Zoo researchers are caring for two pregnant southern white rhinos that are a key part in the plan to save the critically endangered northern white rhinos.
The extinction clock is ticking because only two northern whites remain alive.
“Ready?” said rhino keeper Marco Zeno as he peered through a fence. The barrier separated him from a large southern white rhino named Victoria.
The animal looked back then lifted her head. Zeno blew a whistle and offered praise.
“Nice job,” he said
Victoria is one of six southern white rhinos that made the 22-hour-trip to San Diego in 2015.
“It is pretty amazing,” Zeno said. “These animals used to be, out essentially in the wild and to come from a place where they had almost no human interaction to here and work so closely with us every day, yeah, it’s very surprising.”
Zeno cued another rhino, Helene.
“Helene, you want to show that again,” Zeno said. “ Good. Head up. You got it. Ready. Here we go. Open.”
Helene opened her mouth.
“There it is,” Zeno said.
He blew his training whistle to reinforce the behavior.
“Good girl. Oh, those are nice teeth. Very good,” Zeno said.
Showing teeth is a valuable skill, but the rhinos are here for a different reason.
Rhinos have critical mission
The San Diego Zoo’s Reproductive Physiologist Barbara Durrant wants to eventually implant northern white embryos in these six rhinos.
The first step is to impregnate each of them by artificial insemination.
“That will tell us that those females are proven females. They are capable of conceiving,” Durrant said. “They’re capable of carrying a term pregnancy and giving birth. Then we can start to use those animals after we’ve weaned their babies we’ll start to use those animals for practicing embryo transfer.”
Durrant’s team has two successes.
The first insemination happened a year ago. At that time, Durrant shared images from a live ultrasound of the 53-day-old fetus inside Victoria.
“If she’ll turn a little bit you can see her feet. Oh, now it looks like she’s got her back towards us. She’s moving in there,” Durrant said as she pointed to a live picture of the fetus.
It was about the size of a double A battery back then.
“We watched it grow,” Durrant said. “We were doing measurements as the limb buds were forming. We saw the heart forming. Now it is so big that it is not up-close where we can see it. It has fallen down into her abdomen so it is way down in here now.”
Birth expected soon
The baby rhino inside Victoria is so big now that it is too hard to get a full picture on the ultrasound machine. But it is not like there is a baby bump.
“This is Victoria and you can’t tell from the outside that she’s pregnant unless you’re lucky enough to see her kick. You really can’t tell. She hasn’t gained that much girth,” Durrant said.
Durrant guessed the rhino is the size of a laundry basket now, although it is admittedly hard to tell.
The next critical point comes in a month or two. Durrant predicted Victoria will probably become restless and move away from the other rhinos when she delivers.
“It’s normally not terribly long. In humans, you often hear about women being in labor for hours, 10 hours, 20 hours, 30 hours. That does not happen with these animals. And you understand why in the wild that would not be a good thing. Prolonged labor in the wild, because the animal would be debilitated and subject to predations,” Durrant said.
A second rhino, Amani, has also been artificially inseminated.
Durrant hopes three more members of this small herd will be pregnant soon.
The next stage involves something that has never been done before, implanting an embryo that’s conceived in the lab.
But there’s an obstacle. That embryo has to be delivered through a long tight birth
“It’s large for one thing,” Durrant said. “It’s very deep in the abdominal cavity which makes it difficult to access as well. But it has a number of cartilaginous rings that interlock this way. So there’s no clear pathway through the cervix when you want to deposit semen or an embryo into the uterus.”
The cervix opens up a bit when the rhino is in heat, which allowed Durrant’s team to use a long straight metal catheter for artificial insemination. But that won’t work for embryo implantation.
“The embryo is going to be growing in vitro, in the lab, for about 10 to 12 days,” Durrant said. “So the cervix of this animal, these recipients, is going to be closed. So the only way we’re going to be able to get through that cervix is with something that’s not rigid and something that we can steer from outside the animal.”
Researchers need the right tool
That something is being developed about 30 miles away in a robotics lab on the UC San Diego Campus. In the lab of professor Michael Yip.
“The idea is that you have a long flexible device with tendons that run through the end all the way to the handle. And we can pull on those tendons like you would marionette a puppet. But in this case, we’re actually deflecting the end of this robotic tool,” Yip said.
Yip is modeling the new tool on endoscopes used to inspect a person’s colon or lungs without creating an incision.
The rhino version needs to be much smaller, however.
“This is basically like trying to hold on one end of a flexible spaghetti noodle and get the other end to move in a specific way it’s extremely difficult and nearly impossible. But with robotics we can actually solve that problem,” Yip said.
Once the device is inserted, the catheter can be maneuvered until it reaches a target location.
“Just like the branching out of your lungs. The same thing applies to animals that might have several different pathways for their reproductive systems. Much like the rhino which has two different uterine horns and you’re trying to make sure you’re entering the right channel versus the other,” Yip said.
UCSD undergraduate researcher Mrinal Verghese is helping Yip test potential controllers and there is hope the first prototype will be ready by the end of the year.
The finished product could end up having a controller like a computer gaming pad, an electronic pen, or a small knob on a handheld device. All benefit from a camera threaded through the catheter.
“(The camera) lets us bring more accuracy and precision to the control system with the ultimate goal of making it as intuitive as possible,” Verghese said.
Another feature of the catheter is that the tube is hollow.
“Once you get the device articulated into the right location, past the cervix, into the uterine horn, you can actually use that hollow channel to flush through the genetic material,” Yip said.
The catheter will be capable of delivering an embryo, through a twisting channel, into the correct uterine horn, for a groundbreaking procedure.
The first attempts at embryo implantation are not likely to happen for more than a year. And those early attempts will be with easier to create southern white rhinos embryos conceived in the lab.
“Once we’ve gotten the efficiency, worked out the kinks, so to speak, with the instrumentation and we feel confident in our technique, that’s when we’ll take one of those very precious northern white rhino embryos and put it into one of these southern white rhinos,” Durrant said.
The San Diego Zoo has cell lines from 12 different northern white rhinos stored in a repository known as the frozen zoo. Geneticists are working on the protocols that’ll turn the frozen tissue into reproductive cells. If both teams are successful the project could help bring the northern white rhino back from the edge of extinction.
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