Sperm cryopreservation of Japanese eel, Anguilla japonica

Improvement of techniques for sperm evaluation and cryobanking in European eel.

“…Although DMSO is the most used cryoprotectant for fish sperm (Gallego and Asturiano, 2018a;Martínez-Páramo et al, 2017), methanol has also been widely used in freshwater species such as sturgeons, salmonids, tench or Eurasian perch within others (reviewed by Asturiano et al, 2017). Furthermore, it has been recently used in cryopreservation protocols for Japanese eel sperm (Koh et al, 2017;Müller et al, 2017;. As cryoprotectant, methanol has been reported to penetrate more rapidly the cells and being less toxic than DMSO (Horváth et al, 2015).…”

“…Years later, Müller et al (2017) and Koh et al (2017) developed in parallel new sperm cryopreservation protocols for Japanese eel. Both protocols used methanol as cryoprotectant, which is osmotically inert and do not activate the sperm, and used similar extender solutions, ASP and ASP30 respectively.…”

“…Since these protocols consisted in small volumes of sperm, the most recent work of Nomura et al (2018) adapted the protocol of Koh et al (2017), to a larger-scale to be used for fertilization programs. In this work, they used 5 mL straws and adapted the cooling rate to that volume, and the cryoprotectants and extenders were as described in the latest protocol (Koh et al, 2017). Using this protocol, they obtained very good results in the fertilization trials, with no differences in egg hatching and survival rated when using fresh and cryopreserved sperm.…”

“…In parallel, Koh et al (2017) conducted a series of experiments focused on the use of K30 ASP (Ohta et al, 2001) as extender in an alternative cryopreservation protocol for Japanese eel sperm. The K30 ASP consisted of (in mM) 134.3 NaCl, 30 KCl, 20 NaHCO3, 1.6 MgCl2, 1.3 CaCl2, and buffered at pH 8.1 with 20 mM TAPS-NaOH.…”

“…Following the work of Koh et al (2017), Nomura et al (2018) established a large-scale cryopreservation protocol for Japanese eel sperm to be used for fertilization programs. They used 5 mL straws and adapted the cooling rate to that volume, and the cryoprotectants and extenders were as described in the latest protocol (Koh et al, 2017). Further, the fertilization trials did not show any difference in egg hatching or survival rates between cryopreserved sperm and fresh sperm.…”