Cryopreservation of sperm from the endangered Formosan landlocked salmon (Oncorhynchus masou formosanus)

The Formosan landlocked salmon (Oncorhynchus masou formosanus) are at a hig h risk of extinction, and the sustained maintenance of the population will soon depend on aquaculture systems, which use cryopreservation of spermatoz oa to increase genetic diversity. We investigated the effectiveness of dime thyl sulfoxide (DMSO), dimethyl-acetamide (DMA), and methanol as cryoprotec tants in combination with 300 mM glucose as extender on the freezing of For mosan landlocked salmon spermatozoa. We also evaluated the morphological ch anges of Formosan landlocked salmon spermatozoa after their immediate dilut ion in the 300 mM glucose-DMSO extender and after freeze-thawing. The sperm atozoa frozen with DMSO as a cryoprotectant showed significantly higher pos t-thaw motility and fertility than spermatozoa frozen with DMA or methanol. The fertilization capacity of frozen-thawed Formosan landlocked salmon was comparable to that of fresh spermatozoa. Intersubspecies fertilization tri als between cryopreserved Formosan landlocked salmon spermatozoa and Amago salmon eggs showed high fertilization rates. Based on the findings, the pot ential value of using sperm bank to safeguard this endangered species is di scussed. (C) 1999 by Elsevier Science Inc.