Levels of phosphoprotein in the eggs and ovaries of some fish species

1. Protein (alkali-labile) phosphorus levels are given as percentages of the dry weight of mature eggs of fishes (one elasmobranch and seven teleost species). Levels in the eggs of the five marine-spawning teleosts are much lower (10-300 times) than in the two freshwater-spawning teleosts examined. 2. The protein phosphorus content of the dry matter of developing plaice eggs decreases by a factor of 20 during the later stages of development (maturation) before ovulation. 3. It is proposed that protein-linked phosphate may be utilised, possibly as a source of energy, during the massive water uptake which accompanies egg maturation in many marine species, including plaice.