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Cryopreservation of Atlantic croaker spermatozoa : optimization of procedures, evaluation of morphological changes, and assessment of motility
Abstract
The effects of various extenders, dilution ratios, cryoprotectants, equilibration times, freezing and thawing rates, and semen and egg quantities on fertilization capacity of post-thaw Atlantic croaker Micropogonias undulatus spermatozoa were examined to optimize cryopreservation procedures. Fertilization rates using NaCl, glucose, and sucrose solutions were comparable to those achieved with more complex extenders. No fertilization was obtained when methanol was the cryoprotectant. The optimum ratio of semen to DMSO to extender was 10%: 15%: 75%. No significant difference (P < 0.05) in fertilization rates was found among freezing rates ranging from -10°C/min to -150°C/min. The two-step freezing method gave a fertilization rate similar to that obtained with the conventional one-step freezing method. The spermatozoon of the Atlantic croaker is a primitive type in that it lacks an acrosome. The kidney-shaped head has a diameter of about 1.5 μm and is occupied by a granular and electron-dense nucleus. The short midpiece contains three spherical mitochondria and encircles the basal body of the flagellum but is separated from it. The flagellum consists of the typical 9 + 2 axoneme and surrounding plasma membrane but lacks a lateral ridge. Spermatozoa of Atlantic croaker diluted in either NaCl or sodium citrate solutions with or without DMSO were examined with the electron microscope before freezing in liquid nitrogen and after thawing. Damage following cryopreservation appeared to be greater to the mitochondria, plasma membrane, and 9 + 2 axoneme than to the nucleus. The incidence of post-thaw damage in spermatozoa diluted with NaCl solutions containing DMSO was remarkably lower than that with either pure NaCl solutions, pure sodium citrate solutions, or sodium citrate solutions containing DMSO. A computerized method (Hamilton-Thorn Motility Analyzer) was used to assess objectively the percentage of motile spermatozoa and various indexes of their motion. The percentage of motile spermatozoa with vigorous movement was significantly reduced (P < 0.05) in post-thaw spermatozoa. Examination of correlations between measurements of spermatozoan motility and fertility suggested the percentage of progressively motile spermatozoa can be the major consideration in developing multiple criteria for predicting the potential fertilizing ability of cryopreserved Atlantic croaker spermatozoa.
Description
Typescript (photocopy).Subject
Major wildlife and fisheries sciences1989 Dissertation G994
Atlantic croaker
Spermatozoa
Cryopreservation
Cryopreservation of organs, tissues, etc
Research
Collections
Citation
Gwo, Jin-Chywan (1989). Cryopreservation of Atlantic croaker spermatozoa : optimization of procedures, evaluation of morphological changes, and assessment of motility. Texas A&M University. Texas A&M University. Libraries. Available electronically from https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1117073.
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