Scientia Marina, Vol 70, No S3 (2006)

Fertilization success in Galeolaria caespitosa (Polychaeta: Serpillidae): gamete characteristics, role of sperm dilution, gamete age, and contact time


https://doi.org/10.3989/scimar.2006.70s3309

Elena K. Kupriyanova
School of Biological Sciences, Flinders University, Australia

Abstract


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.


Keywords


Galeolaria caespitosa; Serpulidae; Polychaeta; egg size; gamete longevity; sperm behaviour; fertilization success; gamete concentration and age

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