MORPHOLOGY, COMPOSITION AND FERTILIZATION OF CARP EGGS - A REVIEW

This paper is a review of the literature on eggs of carp (Cyprinus car pio L.) and some related species and includes data taken from the form er USSR and eastern European countries. Reported data relate to fecund ity, egg morphology and composition, and fertilization, Information is also available on the ovarian fluid composition with characterization of proteins and lipids. The fecundity of common carp is very high, ra nging from 100 000 to 300 000 eggs kg-l body weight per oogenetic cycl e, with one cycle/year in the case of females reared in an outside nat ural pond environment. The diameter and weight of the eggs are in the range of 1.24-1.42 mm and 0.86-1.41 mg, respectively. The ooplasm incl udes large amounts of yolk and various organelles (endoplasmic reticul um, Golgi apparatus, mitochondria), cortical granules and alveolae. Th e main characteristics of cyprinid ovarian fluid are an osmotic pressu re of about 300 mOsm, a Mg2+ concentration of 2.58 mM and a high ovari an fluid pH of 9. Energy in the form of ATP which is necessary for egg metabolism originates from glycolytic and oxidative reactions. The eg g has a relatively thick vitelline envelope (VE) or zona radiata which is reorganized into the fertilization envelope (FE) after fertilizati on, The micropyle located at the animal pole is a funnel-shaped struct ure leading spermatozoa to the ooplasmic surface on which a fertilizat ion cone develops after fertilization. A site of sperm attachment is i dentified on the plasma membrane at the level of the internal aperture of the micropylar canal. Major differences are observed between the t wo outermost VE and FE layers, as revealed by electron microscopy, enz yme or carbohydrate cytochemistry, and immunohistochemistry. FE extrac ts have strong bactericidal and fungicidal effects.