. The Biological bulletin. Biology; Zoology; Marine biology. GORGONIAN FERTILIZATION RATES 49 100 80 - ^ 60 - 40 20 1900 Plexaura kuna O CONTROL ? DILUTED o o o n o D -D-O—DtOO 1930 July? 2000 D SP o D On O D o o 1930 2000 Julys Figure 1. Proportions oi Plexaura kuna eggs fertilized in individual samples collected on two nights at Korbiski Reef in 1993. Diluted and undiluted samples were collected from within m of each other at identical times. Half of the samples were diluted 20-fold after collection, but dilution had no effect on fertilization rates (see text). taining seawater but immed
. The Biological bulletin. Biology; Zoology; Marine biology. GORGONIAN FERTILIZATION RATES 49 100 80 - ^ 60 - 40 20 1900 Plexaura kuna O CONTROL ? DILUTED o o o n o D -D-O—DtOO 1930 July? 2000 D SP o D On O D o o 1930 2000 Julys Figure 1. Proportions oi Plexaura kuna eggs fertilized in individual samples collected on two nights at Korbiski Reef in 1993. Diluted and undiluted samples were collected from within m of each other at identical times. Half of the samples were diluted 20-fold after collection, but dilution had no effect on fertilization rates (see text). taining seawater but immediately washed had a fertiliza- tion rate of 15%, indicating that washing could prevent post-collection fertilizations. Eggs that were washed and then incubated with sperm-containing water had a fertil- ization of 60% and those that were exposed to sperm, washed and then again incubated with sperm had a fer- tilization rate of 71%. These latter controls indicate that mechanical effects of washing on both fertilized and un- fertilized eggs were negligible.) Fertilization rates in the water column as eggs drifted away from the reef had minimal effect on our field esti- mates of fertilization. Pseudoplexaura sp. eggs that were allowed to float in the water column for an additional 5- 7 m after release did not have greater fertilization rates than eggs collected 1 m downstream of the colony (38% at 1 m vs. 30% at 6-8 m; Mest P > , n = .013 paired samples). Water collected immediately downstream of the reef during Plexaura kuna spawning events was often ca- pable of fertilizing eggs, but fertilization rates in those experiments never exceeded 4%. Those values are prob- ably maximal estimates of downstream fertilizations, be- cause the water samples were taken only on days with low current flow (approx. cm/s), when mixing of the sperm would be lowest, and because incubations with those water samples (, exposure to sperm) lasted 12 h instead of the minutes of exposure
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