Molecular Cytogenetic Approaches to the Conservation of Endangered Rhinoceros and
Tapir Species
The five species of rhinoceros and four species of tapir are all critically endangered or threatened. Despite intensive captive breeding programs, the reproductive rate of most species in these two families (Rhinocerotidae and Tapiridae) remains low. Recent technological improvements such as in vitro fertilization, ultrasound, artificial insemination, and hormonal treatments have proven difficult to use on rhinoceroses and are still under development. Chromosome variation may contribute to the low reproductive rate in captive populations, but little is known about the genetics of these two groups.
Numerous rhinoceros and tapir cell lines are preserved in the CRES Frozen Zoo®, acquired through decades of opportunistic sample collection. In fact, all extant species and subspecies of these two groups, with the exception of the very rare Javan rhinoceros, are accessioned in the repository. Concerted classical cytogenetic studies conducted previously at CRES have yielded much of the genetic data currently known about the Rhinocerotidae and Tapiridae, but many questions remain, including the identity of the rhinoceros Y chromosome.
The availability of the Frozen Zoo cell lines presents a unique opportunity for more comprehensive studies using current FISH (Fluorescent In Situ Hybridization) technology and capitalizing on recent advances in domestic horse genetics. Horses, rhinoceroses, and tapirs are close relatives comprising the order Perissodactyla. The genome of the domestic horse is under intense study, resulting in hundreds of genes being physically mapped to horse chromosomes. Horse genes can be mapped to rhinoceros and tapir chromosomes, which will enable us to positively identify chromosome pairs and characterize chromosome features that may contribute to poor reproduction in the endangered Perissodactyla species. These methods will also facilitate the development of standardized karyotypes, enhancing subspecies distinction and identification of genetically unsound individuals prior to their inclusion in breeding programs.
