ZIGLER, K.S.*; LESSIOS, H.A.: Evolution of bindin in the pantropical sea urchin genus Tripneustes

The sperm protein bindin mediates sperm-egg attachment and sperm-egg membrane fusion in sea urchins. Changes in this locus can thus cause gametic incompatibility and convert populations into different species. We examined bindin evolution in the genus Tripneustes. The genus Tripneustes is pantropical and contains three allopatrically distributed species: T. ventricosus on both sides of the Atlantic, T. depressus in the eastern Pacific, and T. gratilla in the central and western Pacific, as well as the Indian Ocean. Tripneustes mature bindin sequences were obtained from all species of the genus, and all regions of the tropics. Interspecific comparisons reveal no evidence for positive selection on bindin in Tripneustes, and minimal evolution in bindin on a global scale. These results indicate that rapid evolution under positive selection is not a general characteristic of bindin.