Individual Variation in Semen Quality of Sumatran Rhinoceros (Dicerorhinus sumatrensis) Breeding Males: Implications for ART and Biobanking

Abstract

SARASVATHI CECILE. Individual Variation in Semen Quality of Sumatran Rhinoceros (Dicerorhinus sumatrensis) Breeding Males: Implications for ART and Biobanking. Supervised by MUHAMMAD AGIL, BAMBANG PURWANTARA, and THOMAS B. HILDEBRANDT.

The Sumatran rhinoceros (Dicerorhinus sumatrensis) is one of the world's most critically endangered mammals, with only three adult males currently maintained under ex situ conservation. Despite the importance of sperm cryopreservation for reproductive biobanking, comprehensive information regarding post-thaw sperm quality and DNA integrity in this species remains lacking. This study aimed to evaluate the post-thaw quality and functional competence of cryopreserved sperma obtained from the three remaining adult male Sumatran rhinoceroses. Cryopreserved ejaculates collected by electroejaculation were assessed for sperm motility and kinematics using computer-assisted sperm analysis (CASA), whereas morphology, viability, acrosome integrity, and DNA fragmentation were evaluated using Diff-Quik, eosin–nigrosin, Coomassie Brilliant Blue G-250, and Halomax® assays, respectively. Post-thaw sperm quality was generally compromised, characterized by low motility, reduced viability, and a high incidence of morphological abnormalities. Total morphological defects ranged from 49.22% to 64.99%, whereas sperm viability ranged from 23.03 ± 7.54% to 41.53 ± 6.80%. In contrast, acrosome integrity remained relatively high (>70%) in all individuals. Notably, sperm DNA fragmentation indices were consistently low, ranging from 0.91 ± 0.30% to 3.78 ± 1.12%, indicating substantial preservation of nuclear integrity despite compromised conventional sperm quality. These findings demonstrate that poor conventional sperm quality does not necessarily imply compromised nuclear integrity and highlight the substantial conservation value of cryopreserved semen from the three remaining adult male Sumatran rhinoceroses. The present study provides an important foundation for reproductive biobanking and future assisted reproductive applications aimed at preserving the genetic legacy of this critically endangered species.