Maternal-fetal relations in antifreeze production in the eelpout Zoarces viviparus

The viviparous teleost Zoarces viviparus inhabits the coastal areas of the eastern North Atlantic and Baltic region. Antifreeze activity was measured in serum from pregnant females and embryos during their embryological development inside the ovary and found to be up to 0.95 degree C and 0.85 degree C respectively. Lower levels of antifreeze activity (up to 0.34 C) were discovered in the ovarian fluid. The result is higher hysteresis freezing points and thus less protection to freezing of the ovarian fluid compared to the serum in embryos and the maternal organism. The pertinence of this to the cold tolerance of Z. viviparus is presently unknown. SDS-PAGE of ovarian fluid shows only few protein bands and a difference in proportional density of proteins compared to maternal and embryo serum. This could indicate that another mechanism than rupture of blood vessels in the ovarian wall is of importance for the occurrence of small proteins in the ovarian fluid.