Morphological alterations in cryopreserved spermatozoa of scallop Argopecten purpuratus

Abstract

The present work identifies and quantifies the morphological alterationsof scallop Argopecten purpuratus spermatozoa caused by long-termcryopreservation. Percentages of motility, fertilization and injuredspermatozoa were quantified by optic microscopy and scanned electronmicroscopy. These parameters were evaluated in sperm without treatment(CTR), spermatozoa incubated in cryoprotective solution but not freezed(ICS) and freezed-thawed spermatozoa (FTS). Spermatozoa of ICS treatmentremained motile longer than those of CTR, whereas those of FTS treatmentwere lowest. Morphology of the spermatozoa was affected in several waysby the freeze-thawing treatment; some had their head deformed orswollen, others had their cell membrane folded or broken; acrosomereaction; anomalous positions or absence of mitochondria as well asbroken, stiff or loss of lineal structure of tail. CTR and ICStreatments had higher percentages of undamaged sperm (87.7% and 79.0%respectively), while FTS samples had 14.2% of undamaged sperm. The tailwas the spermatic structure most commonly injured in FTS (77.0%), thepercentage of sperm with head injury was 55.1% and with acrosomereaction was 28.7%, whereas middle piece was affected in 23.9% ofsperm. Percentages of fertilization were 68.3%, 67.9% and 58.2% forCTR, ICS and FTS respectively, which were not significantly different.There was a higher correlation between injuries and motility thanbetween injuries and fertilization success. Correlation between motilityand fertilization was low (0.605 and 0.668 with motility at 5 and 30min, respectively).