Cryopreservation of Sperm of the Endangered Razorback Sucker

Abstract

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.

Marine Fish Sperm Cryopreservation and Quality Evaluation in Sperm Structure and Function

“…The research on fish sperm cryopreservation has achieved great advances since the first successful sperm cryopreservation in herring (Blaxter 1953). It provides many benefits such as ease of global germplasm shipping and supply (Tiersch et al 2004), selective breeding and hybridization with desirable characteristics (HendersonArzapalo et al 1994), and conservation of genetic diversity (Van der Walt et al 1993;Tiersch et al 2000;Ohta et al 2001). Furthermore, a frozen sperm bank could maintain the continuous and stable supply of gametes for hatchery seed production or laboratory experimentation.…”

Sperm Cryopreservation of Some Freshwater Fish Species in Malaysia

“…Cryopreservation technology provides long term ex situ conservation of indigenous and endangered species (Mongkonpunya et al, 2000;Tiersch et al, 2000). Cryopreserved semen could be stored indefinitely without deterioration provided proper maintenance and handling measures are well taken care of all time (Stoss & Donaldson, 1983;Armitage, 1987;Suquet et al, 2000).…”

Sperm quality assessments for endangered razorback suckers Xyrauchen texanus

“…Because the activation of sperm motility in razorback suckers occurs at osmolalities below 270 mOsm/kg, and the range of milt osmolalities at collection is typically wide due to contamination by urine (Tiersch et al 1998), this study was designed to address such variability. Samples were collected into a 1:1 dilution with calcium-free Hanks' balanced salt solution (HBSS) at either 302 (just above isoosmotic conditions) or 500 mOsm/kg (hyperosmotic to account for potential dilution) at pH 7.4.…”

“…Thus, far, advances in ART with razorback sucker milt are consequences of integrating field studies with annual samplings (Carmichael et al 1996) that have lead to sperm cryopreservation under hatchery conditions. In those studies, sperm motility estimates and fertilization trials comprised the evaluations of sperm cell quality (Tiersch et al 1998). However, combinations of assays are necessary for selecting germplasm for immediate use and for building functional genetic resource banks for endangered species (Bainbridge & Jabbour 1998).…”