Sperm nuclear decondensation in Barnea candida (mollusca, pelecypoda) oocytes does not require germinal vesicle breakdown.

Barnea candida oocytes, submitted to D-600 (100 microM) 15-20 seconds after insemination in order to inhibit Ca++ uptake but not acid release, fail to exhibit germinal vesicle breakdown (GVBD) whereas penetrated spermatozoa are able to decondense normally. Oocytes transferred in 100 mM Na-acetate seawater at pH 6.3, 1 minute after insemination, in order to inhibit acid release, fail to undergo GVBD and sperm nuclear decondensation. Upon return of these oocytes to normal seawater and treatment with an excess of KCl, they exhibit GVBD and decondensed sperm nuclei are seen within their cytoplasm. These results show that sperm nuclear decondensation does not require GVBD or Ca++ uptake but may be related to an intracellular pH increase.