Initial Characterization of Male Southern Stingray (Hypanus americanus) Reproductive Parameters and Preliminary Investigation of Sperm Cryopreservation

• Published in: Animals (Basel) 2021-09, Vol.11 (9), p.2716
• Main Authors: Gillis, James D., Penfold, Linda M., Mylniczenko, Natalie D.
• Format: Article
• Language: English
• Subjects: Animals; Artificial insemination; Biology; Cooling; Cooling rate; Cryopreservation; Dasyatis americana; elasmobranch; Endangered & extinct species; Freezing; Glycerol; Hypanus americanus; Immunoassay; Investigations; Liver; Males; Motility; Plasma; Population genetics; Reproduction; Semen; Sperm; Spermatozoa; Spleen; Survival; Testosterone; Ultrasonic imaging
• ISSN: 2076-2615; 2076-2615
• DOI: 10.3390/ani11092716

This study investigated the reproductive biology and sperm cryopreservation of ex situ southern stingrays (Hypanus americanus) by semen collection and characterization and the development and validation of an enzyme-linked immunoassay for plasma total testosterone. Semen was collected in March and June using a manual massage technique, and the ejaculates were assessed for volume, pH, osmolarity, motility, status (0–5 scale: 0 = no forward progression, 5 = rapid linear progression) and total sperm count. Semen was extended in Hank’s elasmobranch ringer solution containing 10% DMSO, 10% glycerol or 5% glycerol with 5% N-methylformamide and cryopreserved using a conventional freezing method (~−50 °C/min) or a modified slow freezing method (~−3 °C/min). Body condition was scored from 1–5 and was noted to be low in March (1.93 ± 0.07) due to feeding practices and increased by June (2.93 ± 0.05) after dietary corrections were made. A concomitant increase (p < 0.05) in plasma total testosterone concentration and sperm motility was noted between March (8.0 ± 7.2 ng/mL, 5.71 ± 2.77%) and June (97.3 ± 11.3 ng/mL, 51.4 ± 14.3%). Samples cryopreserved using a modified slow freeze method (~−3 °C/min) had higher post-thaw motility and plasma membrane integrity than conventionally cryopreserved samples. Data indicate that southern stingray sperm morphometrics adheres to those of other elasmobranch species and that a slow cooling rate may be an avenue of research to improve southern stingray sperm survival during cryopreservation.