Induction of acrosome reaction of spermatozoa in Eriocheir sinensis by low temperature

Abstract

The effects of temperatures, durations of treatment, and derivations from spermatophores or spermaries on in vitro acrosome reaction of the spermatozoa in the Chinese mitten crab Eriocheir sinensis were investigated. The results showed that the different temperatures resulted in extremely significant differences (p < 0.01) in the time of beginning acrosome reaction, the time of the maximum percentage of acrosome reaction, and the maximum percentage of acrosome reaction of the spermatozoa from spermatophores; and the low temperature (-20, -80 degrees C and liquid nitrogen) induced acrosome reaction of more than 90% spermatozoa while 15 and 4 degrees C didn't. Similar results occur in the spermatozoa, treated with -80 degrees C for 15 min, from spermaries but the time of beginning acrosome reaction and the time of the maximum percentage of acrosome reaction were obviously longer than those from spermatophores. In conclusion, low temperature can induce acrosome reaction, which is a novel and efficient operating method of inducing acrosome reaction; the spermatozoa might be affected physiologically to capacitate with chilling. The study may be beneficial to new understandings of mechanism of acrosome reaction and provide the foundational material for artificial fertilization and breeding of this crab and other commercial aquatic crustaceans.

Fig. 1

Effect of temperature on acrosome reaction (AR). a 15 and 4 °C cannot induce AR of the spermatozoa; b–e −20, −80 °C and liquid nitrogen can efficiently induce AR and the majority of spermatozoa undergo AR gradually from step 1 to step 4; b step 1 of AR (the initiation of the reaction and the protrusion of the apical cap); c step 2 of AR (the reversion of the acrosomal vesicle); d step 3 of AR (the extension of the acrosomal tubule); e step 4 of AR (shrinking and disappearance of the acrosomal vesicle and diminishing of nucleus); the arrows indicate the spermatozoa at the various given steps of AR in the corresponding pictures; the scale bar = 10 μm

Fig. 2

Effect of temperature and duration of treatment on the maximum percentage of acrosome reaction. Differences of majuscules on all bars indicate extreme significance of difference (p < 0.01) between each other; differences of lowercases on the same temperature bars indicate significance of difference (0.05 > p > 0.01) between each other; same lowercases on the same temperature bars indicate no significance of difference (p > 0.05) in this temperature group; LN liquid nitrogen; data in figure are means ± SEM (n = 3)

Fig. 3

Effect of temperature and duration of treatment on the time of beginning acrosome reaction. Differences of majuscules on all bars indicate extreme significance of difference (p < 0.01) between each other; identical lowercases on the same temperature bars indicate no significance of difference (p > 0.05) in this temperature group; LN liquid nitrogen; data in figure are means ± SEM (n = 3)

Fig. 4

Effect of temperature and duration of treatment on the time of the maximum percentage of acrosome reaction. Differences of majuscules on all bars indicate extreme significance (p < 0.01) of difference between each other; identical lowercases on the same temperature bars indicate no significance of difference (p > 0.05) in this temperature group; LN liquid nitrogen; data in figure are means ± SEM (n = 3)

Fig. 5

Comparison of the time of beginning acrosome reaction (TBA), the time of the maximum percentage of acrosome reaction (TMA), and the maximum percentage of acrosome reaction (MPA) of the spermatozoa from the spermaries with the spermatophores. Data in figure are means ± SEM (n = 3)