MEPS 266:135-142 (2004)  -  doi:10.3354/meps266135

ABSTRACT: Recently, there has been much debate surrounding the importance of sperm limitation to the population dynamics and evolution of life-history traits of free-spawning marine invertebrates. The debate is hampered by a lack of measures of fertilisation success from natural spawning events. We observed the natural spawning of the intertidal anemone Oulactis mucosa during a low tide in SE Australia. The fertilisation success of individual females was assessed, as well as the degree of spawning synchrony among and within rockpools. We found that fertilisation success was extremely variable among females; females spawning in rockpools containing spawning males had much higher fertilisation success than females in pools without males. Spawned gametes remained in a viscous matrix throughout the low tide, and the movement of sperm among pools appeared to be minimal. Consequently, isolated females had very low rates of fertilisation success, and spawning synchrony in all-female pools strongly depended on the distance to the nearest neighbouring pool containing a spawning male. We suggest that spawning at low tide may minimise the problems associated with gamete dilution, but also results in poor communication among spawning individuals and thus limited genetic exchange at reproduction and low rates of synchrony.

KEY WORDS: Broadcast spawner · Reproductive success · Chemical communication