Spermatozoa motility, cryoresistance, and fertilizing ability in sterlet Acipenser ruthenus during sequential stripping

Abstract

We describe spermatozoa characteristics from sequential collections in sterlet, Acipenser ruthenus, following a single dose of carp pituitary extract (CPE). Sperm production and spermatozoa fertilizing ability, percent motility, and curvilinear velocity (VCL) were investigated in fresh and frozen/thawed sperm. Sperm was collected by two procedures: (A) stripping 3 times per 24 h at 3 h intervals on 3 consecutive days beginning 12 h after CPE treatment, and (B) stripping 3 times over 6 h beginning 36 h after CPE treatment. Spermatozoa motility and VCL were evaluated by video microscopy, and sperm production was measured as volume and concentration. Sperm samples were frozen by a conventional freezing procedure in a cryoprotective medium containing 10% methanol. Fertilization was conducted using a ratio of 105 spermatozoa/egg. Both sequential stripping procedures yielded larger volumes of viable spermatozoa than did a single collection. Sperm parameters such as density and volume varied widely depending on collection time. The highest numbers of spermatozoa per individual were collected 15-42 h post-CPE treatment in (A) and at 42 h post-CPE treatment in (B) (85+/-4% and 64+/-5% of total spermatozoa count, respectively). Median percent motility in spermatozoa before cryopreservation was 26-100% and 5-67% post-thaw. Fertilization rates obtained with frozen/thawed spermatozoa were 13-76% (median value). A significant increase in spermatozoa motility parameters and fertilizing ability at the second collection on each day was observed. Sequential stripping and spermatozoa cryopreservation in combination could improve the efficiency of sturgeon aquaculture. (C) 2012 Elsevier B. V. All rights reserved.