Physiological Modifications to be Considered in Amphibian Sperm Cryopreservation.

KRAPF D.; O´BRIEN E.; ARRANZ, S.E.,

Cryopreservation in Aquatic Species

T. R. Tiersch and C. C. Green, editors. World Aquaculture Society

Lugar: Baton Rouge, Louisiana; Año: 2011; p. 100 - 106

Amphibians include over 4,500 species within three major lineages: caecilians,salamanders, and anurans. These lineages are linked by several unique physiological traits. Themost prominent being the lifestyle of many amphibians: the aquatic gill-breathing larval stageand the aquatic or terrestrial lung or skin-breathing adult stage.It is now generally accepted that there has been a major population decline of amphibiansin many parts of the world over the last 25 yr. The decline has been particularly evident inAustralia and parts of Latin America. Although the causes of this decline are still poorlyunderstood, it has been generally ascribed to pollution, increased UV-B radiation associated withthinning of the ozone layer and to a pathogenic chytrid fungus implicated in the decline of manyspecies (Frías-Alvarez et al. 2008).In the face of the inevitable further loss of species and populations, the use of amphibiansperm cryopreservation arises as potentially valuable approach, not as an economic resource, butfor the conservation of amphibian biological and genetic diversity. Moreover, this approachwould significantly reduce the number of males in captive breeding programs. Relatively fewstudies have investigated the effects of freezing and thawing of anuran sperm (Browne et al.1998, Browne et al. 2002d, Browne et al. 2002a, Browne et al. 2002b, Browne et al. 2002c,Constanzo et al. 1998, Sargent and Mohun 2005, Fitzsimmons et al. 2007, Mansour et al. 2009).Despite the low number of studies, the general feasibility of cryopreserving amphibian spermwith successful recovery of motility capacity and fertility is evident.Different strategies have been used to assess successful recovery after cryopreseration ofamphibian sperm. Among them, sperm integrity and recovery of motility were widely used.However, due to the current status of our knowledge, this could lead to misinterpretation ofactual sperm ability to fertilize an egg. In-vitro fertilizations with cryopreserved anuran spermhave been, in every case, far from similar to control samples using fresh sperm. In the light ofthese observations, this chapter will not revise amphibian sperm cryopreservation protocols, butwill try to point out physiological modifications that, if properly considered in cryopreservationtechniques, could result in a significant improvement of recovery rates.