ABSTRACT
CHAPTER 9 EMBRYO CRYOPRESERVATION: WHAT WE KNOW UNTIL NOW
V. Robles, E. Cabrita, J.P. Acker and P. Herráez
1. APPLICATIONS OF EMBRYO CRYOPRESERVATION........................................... 265 1.1 Commercial aquaculture............................................................................. 266 1.2 Conservation of biodiversity.................................................................... 267 1.3 Other fields of application........................................................................ 268
2. CRYOPRESERVATION OF INVERTEBRATE EMBRYOS........................................ 268 3. PROBLEMS IN FISH EMBRYO CRYOPRESERVATION......................................... 271
3.1 Complex structure...................................................................................... 271 3.2 Chilling sensitivity..................................................................................... 272 3.3 Embryo size................................................................................................ 273 3.4 Cryoprotectant toxicity............................................................................. 274
4. FISH EMBRYOS CRYOPRESERVATION.................................................................. 274 4.1 Slow freezing vs. vitrification................................................................... 274 4.2 What has been done until now to overcome the major
problems in cryopreservation?................................................................ 276 4.2.1 Permeability............................................................................ 276 4.2.2 Chilling sensitivity................................................................. 279
5. BLASTOMERE, EMBRYONIC STEM CELLS AND PRIMORDIAL GERM CELL CRYOPRESERVATION: ARE THEY FEASIBLE ALTERNATIVES TO FISH EMBRYO CRYOPRESERVATION?............................................................ 280 6. FUTURE IN FISH EMBRYO CRYOPRESERVATION: WHAT SHOULD BE DONE NEXT?.............................................................................................................. 281
6.1 Use of new CPAs....................................................................................... 281 6.2 Exploration of new techniques to increase CPA
concentration into the embryos.............................................................. 283 6.3 Development of new methods to objectively assess
cryopreservation-induced damage in fish embryos............................. 285 6.4 Choice of the species................................................................................ 285
7. REFERENCES................................................................................................................ 286
1. APPLICATIONS OF EMBRYO CRYOPRESERVATION
The development of embryo freezing technologies revolutionized breeding of domestic animal as well as human reproductive technologies in the last decades. In the seventies successful cryopreservation was achieved with mouse embryos [1] and the first report on pregnancy using frozen bovine embryos was published [2]. Then, cryopreservation procedures were developed for cattle, sheep, horse, cat, rabbit,
mandrill, tití, mice, rat, monkey [3] and human embryos [4] and, more recently, in 2000, the first piglets from frozen embryos were born [5]. At present, survival rates at birth achieved with the transfer of thawed embryos are lower than that obtained with fresh ones, but the use of frozen/thawed embryos could be a routine breeding alternative in the near future for some species.
