Cryopreservation of Sperm of the Endangered Razorback Sucker

• Published in: Transactions of the American Fisheries Society (1900) Vol. 127; no. 1; pp. 95 - 104
• Main Authors: Tiersch, Terrence R., Figiel, Chester R., Wayman, William R., Williamson, J. Holt, Carmichael, Gary J., Gorman, Owen T.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Taylor & Francis Group 01-01-1998; American Fisheries Society
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Conservation, protection and management of environment and wildlife; Fundamental and applied biological sciences. Psychology; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Xyrauchen texanus; United States; North America; America; Spermatozoa; Motility; Endangered species; Semen; Assisted procreation; Thawing; Colorado River basin; Method; Freezing; Freshwater environment; Vertebrata; Cryopreservation; Pisces; Stream; Cryoprotective agent; Population recovery
• ISSN: 0002-8487; 1548-8659
• DOI: 10.1577/1548-8659(1998)127<0095:COSOTE>2.0.CO;2

The endangered razorback sucker Xyrauchen texanus is endemic to the Colorado River system in western North America and is threatened with extinction because of limited recruitment. To assist in management and recovery efforts, we developed methods for the cryopreservation of sperm, evaluated the influence of various factors on motility of thawed sperm, and examined the effect on fertilization of cooling rate and the addition of caffeine. Sperm samples cryopreserved with 10% methanol (MeOH) had significantly higher postthaw motility than did samples preserved with 5% or 20% MeOH or with 5% or 10% dimethyl sulfoxide, N, N‐dimethylacetamide, glycerol, propylene glycol, or ethylene glycol. Sperm samples cryopreserved in 0.5‐mL and 2.5‐mL straws had significantly higher postthaw motility than did samples cryopreserved in 0.25‐mL straws. Exposure to 10% MeOH for up to 30 min did not significantly influence sperm motility before freezing or after thawing. Cooling rate (−21°C/min or −91°C/min) did not significantly influence sperm motility. Samples thawed in a water bath at 20°C, 30°C, or 40°C had significantly higher motility than did samples thawed on the laboratory bench (19°C). Refrigerated sperm had significantly higher motility after the addition of 0.005 M caffeine; however, caffeine did not increase the motility of thawed sperm. Fertilization percentage was 41 ± 31% for the egg quality control treatments (fresh sperm) in the freezing rate study. The freezing rate of −91°C/min yielded 66% fertilization relative to the control (actual value, 27 ± 26%), which was significantly higher than the 12% fertilization (actual, 5 ± 3%) yielded by the freezing rate of −21°C/min. Fertilization percentage was 25 ± 24% for the egg quality control treatments in the caffeine study. Caffeine‐treated sperm yielded 60% fertilization relative to the control (actual, 15 ± 13%), which was significantly higher than the 16% fertilization (actual, 4 ± 4%) yielded by sperm without caffeine treatment.