Center for Species Survival, Smithsonian Conservation Biology Institute, Smithsonian Institution, Front Royal, VA, USA.
Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI, USA.
Sci Rep. 2021 Jan 8;11(1):61. doi: 10.1038/s41598-020-79732-x.
The declining reproductive viability of corals threatens their ability to adapt to changing ocean conditions. It is vital that we monitor this viability quantitatively and comparatively. Computer-assisted sperm analysis (CASA) systems offer in-depth analysis used regularly for domestic and wildlife species, but not yet for coral. This study proposes quality control procedures and CASA settings that are effective for coral sperm analysis. To resolve disparities between CASA measurements and evaluations by eye, two negative effects on motility had to be resolved, slide adhesion (procedural) and sperm dilution (biological). We showed that the addition of bovine serum albumin, or caffeine, or both to fresh sperm reduced adhesion in the CASA cassettes, improved motility and motile sperm concentration (P < 0.0001), yet these additions did not affect measurements of total sperm concentration. Diluting coral sperm reduced sperm motility (P = 0.039), especially from heat-stressed corals. We found CASA concentration counts comparable to haemocytometer and flow cytometer measures (P = 0.54). We also found that motile sperm per egg is a useful predictor of fertilisation success, using cryopreserved sperm. Standard measurements of coral reproductive characteristics inform our understanding of the impacts of climate change on reef populations; this study provides a benchmark to begin this comparative work.
珊瑚生殖能力的下降威胁到它们适应海洋环境变化的能力。定量和比较地监测这种生殖能力至关重要。计算机辅助精子分析（CASA）系统为家养和野生动物物种提供了深入的分析，这些分析被定期使用，但尚未用于珊瑚。本研究提出了适用于珊瑚精子分析的质量控制程序和 CASA 设置。为了解决 CASA 测量值与肉眼评估之间的差异，必须解决两个对运动能力有负面影响的问题，即载玻片粘连（程序）和精子稀释（生物学）。我们发现，向新鲜精子中添加牛血清白蛋白、咖啡因或两者都可以减少 CASA 盒中的粘连，提高运动能力和运动精子浓度（P<0.0001），但这些添加物不会影响总精子浓度的测量。稀释珊瑚精子会降低精子的运动能力（P=0.039），尤其是来自受热胁迫的珊瑚。我们发现 CASA 浓度计数与血球计数器和流式细胞仪的测量值相当（P=0.54）。我们还发现，每卵运动精子是预测受精成功的有用指标，可用于冷冻保存的精子。对珊瑚生殖特征的标准测量有助于我们了解气候变化对珊瑚礁种群的影响；本研究为开始这项比较工作提供了基准。
