Hybridizing Old and New World camelids: Camelus dromedarius x Lama guanicoe

Thirty female dromedary camels were inseminated on a total of 50 occasions with 2-4 ml of fresh guanaco semen diluted with an equal volume of commerci ally available camel semen extender. Similarly nine female guanacos were in seminated on 34 occasions with 4-6 mi of fresh, diluted camel semen. Only t wo Of the dromedary females conceived. one aborted a female foetus on day 2 60 of gestation and the other gave birth to a stillborn female calf on day 365. Six conceptions occurred in the female guanacos. Two of these conceptu ses, diagnosed by ultrasound, were resorbed between days 25 and 40 of gesta tion, one female foctus was aborted on day 291, another female foetus was a borted on day 302, and one female calf was stillborn on day 365 of gestatio n. The sixth foctus, a male, was born prematurely but alive after a 328-day gestation. It had a phenotypic appearance intermediate between that of a c amel and a guanaco and its hybrid parentage was confirmed by the DNA finger printing of eight Ilama microsatellites. To our knowledge, this is the firs t viable hybrid cl-er to be produced between Old World and New World cameli ds, which have been reproductively isolated from one another for at least 1 1 million years. The preponderance of female hybrids is in accordance with Haldane's law Histological examination of their ovaries revealed a failure of meiosis, with only an occasional abnormal oocyte surrounded by follicle cells. Although the diploid chromosone number of camels and guanacos is the same (2n = 74), sufficient genetic change has taken place to make the pair ing of homologous chromosomes no longer possible.