Hypothermic storage of sturgeon sperm: methodology and ongoing history

Hypothermic storage of sperm in a liquid state without freezing, without the use of either liquid nitrogen or dry ice as well as special cryological equipment is an interesting and attractive research line in reproductive biology in terms of practical application. Historically, hypothermia is the very first approach to the preservation of genetic material, but, despite this, the methods of hypothermic storage of gametes and embryos have not received proper development and application in animal husbandry, giving way to cryopreservation. One of the main reasons for this is the high species-specific resistance to cold storage. The technologies for hypothermic storage of sperm existing today and recommended for use in fish farming and in sturgeon breeding in particular are still not effective enough and require further improvement. This short review outlines the history of the development of technologies for the hypothermic storage of sturgeon sperm, considers a number of methodological approaches, concepts and ideas behind these developments. The male reproductive system in sturgeons, the structure and physiology of spermatozoa have a number of features that distance them from teleost fishes, but partly relate to amphibians and higher vertebrates. This made it possible to apply to sturgeons some successful approaches and achievements in the development of methods for hypothermic storage of mammalian (mouse and human) sperm. Thus, the most effective and possibly promising approach is partial or complete replacement of seminal plasma with salt-free isotonic solutions based on sugars (oligosaccharides) and albumin. The purpose of this review is to draw the attention of fish farmers and researchers to developments and advances in hypothermic sperm storage.