Ippo was an accident.
But he was a beautiful accident. One that brings unexpected joys, marvels, adventures … and scientific discoveries.
Half donkey, half zebra, the charming little hybrid “zonkey” was born in an Italian animal rescue center near Florence. His mother, an Italian Amiata donkey, was bred unexpectedly by a Burchell’s plains zebra, a former circus animal, that jumped his fence at the center. Now age 5, Ippo is one of only four known zonkeys in the world (the others are in China, Mexico, and the Eurasian country of Georgia), and he’s the only male born from a donkey dam and zebra sire.
Such mixes don’t usually work—not even when people try to make them work, said Alessandra Iannuzzi, DVM, of the National Research Council of Italy’s Laboratory of Animal Cytogenetics and Genomics at the Institute of Animal Production Systems in Mediterranean Environments, in Naples.
But when they do—and especially when they happen in natural and unintended conditions such as this—it feels miraculous. For genomics researchers like Iannuzzi, the most miraculous part of all is the chromosome mix.
That’s because even though they’re both equids, zebras and donkeys have very different chromosomes. Donkey chromosomes are more numerous, at 62, compared to zebras, at 44. Their chromosomes also vary considerably in shape from one subspecies to another.
That creates a much bigger difference than the one between a donkey (62 chromosomes) and a horse (64 chromosomes), researchers said. Hybrid mules and hinnies result from more closely matched chromosomes than zonkeys do.
But as Iannuzzi and her fellow researchers recently discovered, Ippo’s chromosome matching worked out surprisingly well. He ended up with a number of chromosomes exactly in between that of his two parents—at the odd number of 53. That’s one-half the total number of chromosomes from both parents.
“Obtaining a stable embryo from maternal and paternal chromosomes that are so different in both number and shape represents a very rare genetic event,” Iannuzzi said. “It’s a sign of the high adaptive capacity of DNA.”
In fact, the long-eared striped equid is unwittingly giving international scientists a powerful look into the science of how equids (and other species) evolved.
“The data we’ve obtained from studying Ippo’s chromosomes gives very useful information on genetic recombination (literally, combining mixed chromosomes together), which is an important event in evolution,” Iannuzzi said.
In their study, Iannuzzi and colleagues studied Ippo’s chromosomes in great detail using a technique called “M-FISH,” which allowed them to “paint” certain parts of the chromosomes with a fluorescent dye to see how those parts matched with other similar sections.
They found, to their surprise, that the parts matched up well, even though Ippo received only 22 chromosomes from his sire compared to 31 from his dam.
“Chromosomes are made up of DNA and proteins and, therefore, their study involves an indirect study of a large portions of DNA,” Iannuzzi explained. “We studied them by the M-FISH technique, which involves the use of chromosomal painting probes (chromosome portions or whole chromosomes), combined with a fluorescent molecule, able to bind specifically to the complementary DNA and color the whole area of interest. In our case we used different probes at the same time, in order to cover all the chromosomes present in the hybrid. In this way, we colored all chromosomes at the same time and studied the DNA rearrangements in the hybrid in comparison to his parents.”
It was the first time scientists have used such a method to study chromosome matching, she said. Its success with Ippo could lead to many more applications of the technique in other scientific projects on DNA and chromosomes.
The “design” of Ippo’s chromosomes appears to have very efficiently used the chromosomes given from his different parents, Iannuzzi said.
“It turns out that the genetic material was entirely conserved and without spatial variations (missing or additional genetic material),” she said.
Future studies on Ippo will probably include his level of fertility and the effect of his unique hybrid status on his sperm, Iannuzzi said.