Fertilization success in Galeolaria caespitosa (Polychaeta: Serpillidae): gamete characteristics, role of sperm dilution, gamete age, and contact time ; Exito de la fertilización en Galeolari caespitosa (Polychaeta: Serpulidae): características de los gametos, papel de la concentración del esperma, edad de los gametos y tiempo de contacto

Variability in gamete traits and the factors affecting fertilization success were studied in a common gregarious broadcast-spawning serpulid polychaete Galeolaria caespitosa. Variability of egg size and sperm velocity were not related to the adult size. High sperm concentrations (107-108 sperm. ml-1) were required to achieve fertilization rates of 60-80%. The gamete contact time required to achieve high fertilization rates (70-80%) in G. caespitosa did not exceed 5 minutes of gamete exposure given sufficiently high sperm concentrations. This suggests that attachment of sperm to the egg takes place very rapidly, and a short-term exposure to highly concentrated sperm is a common feature of fertilization ecology of this gregarious species. A sharp decline in fertilization rates at high sperm concentrations usually attributable to polyspermy was not observed. Sperm were motile for up to 6 hours after activation; however, swimming velocity and fertilization success decreased after 2 hours. Eggs of G. caespitosa were fertilizable up to 10 hours after spawning, but the number of embryos resulting from fertilizations by fresh sperm decreased after 2 hours. The gamete traits of G. caespitosa appear to have evolved to enable this sessile organism to reproduce under conditions of high population density and increased risk of polyspermy. ; La variabilidad de los gametos y los factores que afectan el éxito en la fertilización han sido estudiados en una especie gregaria común, el serpúlido Galeolaria caespitosa. La variabilidad encontrada para el tamaño de los huevos y la velocidad del esperma no estuvo relacionada con el tamaño de los adultos. Elevadas concentraciones de esperma (107-108 esperma ml-1) se necesitaron para alcanzar ratios de fertilización del 60-80%. El tiempo de contacto de los gametos que se necesitó para alcanzar elevados ratios de fertilización (70-80%) en G. Caespitosa no excedió los 5 minutos si se daban suficientes concentraciones de esperma. Ello sugiere que la adhesión del esperma a los huevos se ...