Hope for their survival now rests on the ability to develop innovative methods for repopulating the species, according to researchers from the University of California San Diego and San Diego Zoo Global in the US.
Scientists have created a flexible, snakelike robot that can perform artificial insemination and embryo transfer on rhinos, an advance that may potentially rescue the northern white rhinos from the brink of extinction. Decades of poaching and habitat loss have led to the dramatic decline of the northern white rhino — with just two northern white rhinos remaining in the world, both of whom are female.
Hope for their survival now rests on the ability to develop innovative methods for repopulating the species, according to researchers from the University of California San Diego and San Diego Zoo Global in the US. The device is a long, thin catheter that can be steered through a rhino’s cervix to deliver a specimen to the uterus, said Michael Yip, a professor at UC San Diego.
Navigating a female rhino’s reproductive anatomy is incredibly complicated. “The rhino cervix is very large and tortuous,” said Barbara Durrant, from the San Diego Zoo Global. It has a series of twists and turns like switchbacks on a steep mountain road. This goes on for eight to 12 inches. Add to that a fairly long vagina plus the uterine body leading up to the uterine horn, and that totals up to 27 inches worth of rhino anatomy to get through before depositing semen or an embryo.
To make their way through this labyrinth, the team currently uses a stainless steel catheter, five millimeters in diameter, with a 45-degree bend at the end. They have to guide this through the rhino’s cervix by hand. “It’s difficult and requires a bit of manipulation to negotiate and twist this through gently, so it doesn’t damage the cervical tissue,” Durrant said. This technique has worked so far for doing artificial insemination. It’s typically performed when a female rhino’s estrogen levels are high, which causes her cervical tissue to soften and open. However, it gets even trickier when researchers have to do an embryo transfer. This procedure is usually done later in the rhino’s cycle when her progesterone levels are high. That causes her cervix to stiffen and close.
“So, we can’t use anything that’s rigid,” Durrant said. Researchers used flexible robotic catheters — two to three-millimeter-diameter robots, measuring a couple metres in length, that can be shaped and manoeuvred through complex spaces deep in the body with high precision.
However, since neither of the remaining northern white rhino females are able to carry a pregnancy, Durrant’s team will use the robotic catheter on a related subspecies, the southern white rhino. The plan is to first create northern white rhino eggs and sperm using stem cells from previously collected frozen cell lines, then fertilise them to generate northern white rhino embryos.
Researchers would then use the robot to implant the resulting embryos in surrogates. “The ultimate goal is to produce a self-sustaining herd of northern white rhinos, first in captivity and then back into the wild,” Durrant said.