A Novel Cysteine Knot Protein for Enhancing Sperm Motility That Might Facilitate the Evolution of Internal Fertilization in Amphibians
(a) Sperm were suspended in modified Steinberg’s salt solution (ST) containing 1 mM P1, P2, or P3. The percentages of sperm showing circular motion were estimated over 5 min. Dose-dependent P3-initiated sperm motility was induced within the range of 1μM-1mM. (b and c) Sperm of R. arboreus (b) or B. japonicus (c) were suspended in ST or 1/10 ST (1 mM for R. arboreus or 10 mM for B. japonicus). (b) Percentages of motile sperm showing stable or unstable rotary motion over 5 min. (c) Percentages of motile sperm whose flagellum beat with a high amplitude or moderate amplitude over 1 min. Asterisks and double asterisks indicate significant differences at p<0.05 and p<0.01, respectively, against 1/10 ST by Student’s t-test.