TESTING LONG-TERM CRYOPRESERVATION OF BLUE SHRIMP Litopenaeus stylirostris SPERMATOPHORES
The blue shrimp was introduced in the 70s in Hawaï, New-Caledonia and French Polynesia leading currently to some breeding programs (Haffray et al., 2025). The long-term cryopreservation of the male genetic resource would be an interesting backup. Thus, this study aimed at testing the methodology used to cryopreserve the banana shrimp (F. merguiensis) spermatophores (Nimrat et al., 2022).
To do so, 118 mature males were sampled either in cryovials (the whole spermatophore ; n=140) or in straws (a suspension of the sperm mass). The fresh control consisted of the 20 males used for straw cryopreservation. The extender was the same calcium-free saline solution as in Nimrat et al. (2022), adding antibiotics (streptomycin-penicilin) and DMSO (dimethylsulfoxide) as cryoprotectant. There were 20 min of equilibration prior to freezing on a floating rack 3 cm above liquid nitrogen for 10 min before storing in the liquid nitgrogen tank. Viability controls (eosine staining under light microscopy) happened just after freezing, then one, two, three, five and seven months later. Thawing lasted 20 s for straws and 160 s for spermatophores at 30°C.
Results and Disucssion
The Viability in the fresh controls was 100%. The viability of the cryopreserved samples lowered over the eight-month storage in liquid nitrogen from 80% to 27%. The decrease was slower in straws than in cryovials (Figure 1). Howerver, the fertilization success is the ultimate test to ensure that cryopreservation can work as a backup for the genetic resources of the species. A pre-test was conducted with 6 mature females that were manually fertilized with 15 thawed spermatophores and several hundreds of larvae were obtained.
Figure 1: Assessment of sperm viability during cryopreservation either in cryovials (spermatophore) or in straws (sperm mass)
These preliminary results are the first mentioned in blue shrimp. It was a proof-of-concept but there is still room for methodology improvements so that the viability remains higher for a longer time. The most important being to ensure good storage conditions and regular supply in liquid nitrogen (a rise in temperature inside the tank is the strongest hypothesis to explain any decline in viability). The next step would be to apply a dedicated design for manual fertilization from thawed material to truly validate the whole process.
Acknowledgements
We feel very indebted towards the DRM who owns the shrimp line and VAIA hatchery in Tahiti financing 100% of the blue shrimp production through a public market with the CAPF: they let us use part of their broodstock in order to conduct the experiment. We warmly thank IsBlue for the mobility grant, the UPF for the training grant, OSO farming, Blue Genetics, Aquapesca and UPRA-NC Crevette for their financial support. We also thank also Ifremer (Vairao) for the place allocated to achieve the sampling of the animals.
References
Haffray P. et al., 2025. High residual additive genetic variability in a Pacific blue shrimp Litopenaeus stylirostris population after 36 generations of domestication from only 4 estimated founders. Aquculture. 609 : 742835
Nimrat S. et al., 2022. Chilled and cryopreserved spermatophores of banana shrimp (Fenneropenaeus merguiensis): Effects of antibiotics on sperm quality and bacterial abundance. Aquaculture. 560 : 738551.