The effect of extended cold storage and the use of extenders on motility and swimming kinematics of shortnose sturgeon sperm

Abstract

Shortnose sturgeon are listed as a species of special concern in Canada and as endangered in the US. Increasing knowledge about this species, particularly in the area of reproductive biology, will better the management of wild populations and aid in the development of assisted reproduction protocols. However, access to wild sperm is limited, so short-term and long-term storage of sperm from sturgeon is crucial for reproductive studies. Here we report on testing and development of a short-term storage protocol for shortnose sturgeon. Milt samples were collected from wild shortnose sturgeon caught in the Wolastoq River. Subsets of semen were mixed with different extenders with or without oxygen; control treatments without extenders were also run. We used computer-assisted sperm analysis (CASA) to determine sperm motility and swimming kinematics for the different treatments. All groups were examined immediately after collection and treatment application, and then 1, 2, and 7 days after storage in a fridge (4°C) for experiment 1, and days 1, 3, 7, 10, 14, 17, 21, and 24 for experiment 2. The response variables motility, curvilinear velocity (VCL), linearity (LIN), and wobble (WOB) showed an overall decrease over time with differences between extender treatments. While untreated milt maintained some motility up to day 21, the addition of an extender reduced decline in motility and improved longevity up to day 24. Milt treated with the Park and Chapman extender had the slowest motility decline of extenders used, and milt treated with the modified Tsvetkova extender showed less potential for contamination.