An Experiment with Medaka, Oryzias latipes, and a Critique of the Hypothesis that Teleost Egg Size Controls Vertebral Count

Abstract

In each of two sets of experiments, two female medaka, Oryzias latipes, that laid different-size eggs were crossed reciprocally with two males. Vertebral counts of the offspring differed significantly between batches, but there was no consistent correlation between egg size and vertebral count. Both the highest and lowest counts resulted from crosses with females laying large eggs. Other experiments are reviewed, and it is concluded that within the same race of fish there is no causal connection between vertebral number and egg size, although between different races or related species large adult size is often correlated with high vertebral count. The possible advantages of variation in vertebral number are discussed.