title: Effective freezing rate for semen cryopreservation in endangered Mediterranean brown trout (Salmo trutta macrostigma) inhabiting the Biferno river (South Italy).
abstract: This study was designed to determine: (i) the in vitro effects of different freezing rates on post-thaw semen quality of Mediterranean brown trout (Salmo trutta macrostigma) from the Biferno river; and (ii) the in vivo fertilization and hatching percentage of freezing rate giving rise to the best post-thaw semen quality. Pooled semen samples were diluted 1:3 (v:v) in a freezing extender composed of 300 mM glucose, 10% egg yolk and 10% dimethyl sulfoxide (DMSO). The extended semen was packaged in 0.25 ml plastic straws and frozen at different heights above the liquid nitrogen surface (1, 5 or 10 cm) for 10 min to give three different freezing rates. Semen samples were thawed at 30°C for 10 s. The variables assessed after thawing were sperm motility, duration of motility and viability. Our results clearly indicate a significant effect of freezing rate on post-thaw semen quality. Semen frozen 5 cm above the liquid nitrogen surface showed the best quality after freezing/thawing. Based on these in vitro data, 2 groups of 200 eggs were fertilized with fresh semen or semen frozen 5 cm above the liquid nitrogen surface. Fertilization and hatching rates recorded for eggs fertilized with frozen semen were significantly lower (25.4% and 22.5%, respectively) than the ones obtained using fresh semen (87.8% and 75.5%, respectively). An effective freezing protocol will allow for the creation of a sperm cryobank to recover the original population of Mediterranean brown trout in the Biferno river.
authors.affiliation: Department of Agricultural,Environmental and Food Sciences,University of Molise,via De Sanctis snc,86100 Campobasso,Italy.
authors.forename: Nicolaia
authors.initials: N
authors.lastname: Iaffaldano
authors.affiliation: Department of Agricultural,Environmental and Food Sciences,University of Molise,86100Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Di Iorio
authors.affiliation: Department of Agricultural,Environmental and Food Sciences,University of Molise,86100Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Manchisi
authors.affiliation: Mediterranean Trout Research Group-Centro di ricerche 'I Giardini dell'Acqua',42037 Collagna (RE),Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Esposito
authors.affiliation: Department of Agricultural,Environmental and Food Sciences,University of Molise,via De Sanctis snc,86100 Campobasso,Italy.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Gibertoni
mesh_terms: D000818:Animals; D015925:Cryopreservation / Q000379:methods*; D056727:Endangered Species; D005260:Female; D005307:Fertilization in Vitro; D005615:Freezing; D007558:Italy; D008297:Male; D045483:Rivers; D055101:Semen Analysis; D012662:Semen Preservation / Q000379:methods*; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology*; D014337:Trout
keywords: Freezing rate; Mediterranean brown trout (Salmo trutta macrostigma); Post-thaw semen quality; Reproductive performances; Sperm cryopreservation