Babcock R C, Mundy C N, Whitehead D
Biol Bull. 1994 Feb;186(1):17-28. doi: 10.2307/1542033.
This study was undertaken to compare fertilization rates of the sea star Acanthaster planci that were predicted using sperm diffusion models with those that were determined under natural conditions in the field. During experimentally induced spawnings, measured fertilization rates for broadcast eggs were high. More than 70% of the eggs were fertilized at distances as great as 8 m downstream from a single spawning male starfish, and more than 20% were fertilized at separations of more than 60 m. Fertilization was still measurable, at 5.8%, 100 m downstream. Lateral diffusion of sperm away from the axis of flow produced fertilization rates of 13.8% at 8 m normal to the flow and 32 m downstream. The large volumes of sperm released by male A. planci are the primary cause of high rates of fertilization for eggs derived from widely spaced individuals. Models of sperm diffusion using high sperm release rates such as those found in this starfish accurately confirmed the fertilization rates measured in situ for two populations of A. planci with widely differing rates of sperm release. We observed some changes in starfish density and degree of aggregation in the study population for spawning periods during two spawning seasons, though these were not striking. High levels of aggregation may not be necessary for fertilization success in this starfish, due to the potential for long-distance fertilization and the probability that, for any spawning starfish, the total number of zygotes formed will be greater at some distance from the point of spawning. Although fertilization rates in areas distant from the sperm source were relatively low, the total area for potential gamete encounters is much greater and may make a large contribution to net fertilization. We predict that other behaviors, such as migration to shallow water, commonly associated with spawning in A. planci and other marine invertebrates will have measurable impacts on fertilization success. The potential for high levels of fertilization in A. planci was realized during natural spawnings. Fertilization rates as high as 99% were recorded when levels of spawning synchrony were high.
本研究旨在比较使用精子扩散模型预测的棘冠海星受精率与在野外自然条件下测定的受精率。在实验诱导产卵期间，散播卵的实测受精率很高。在距离单个产卵雄性海星下游8米处，超过70%的卵受精，在距离超过60米处，超过20%的卵受精。在下游100米处，受精率仍可测，为5.8%。精子从水流轴横向扩散，在垂直于水流8米且下游32米处产生的受精率为13.8%。雄性棘冠海星释放的大量精子是来自远距离个体的卵受精率高的主要原因。使用高精子释放率（如在这种海星中发现的）的精子扩散模型准确地证实了在原位测量的两个精子释放率差异很大的棘冠海星种群的受精率。在两个产卵季节的产卵期，我们观察到研究种群中海星密度和聚集程度有一些变化，不过这些变化并不显著。由于存在远距离受精的可能性，并且对于任何产卵海星来说，在距产卵点一定距离处形成的受精卵总数可能更多，因此高水平的聚集对于这种海星的受精成功可能并非必要。尽管远离精子源区域的受精率相对较低，但潜在配子相遇的总面积要大得多，可能对净受精有很大贡献。我们预测，其他行为，如迁移到浅水区，通常与棘冠海星和其他海洋无脊椎动物的产卵有关，将对受精成功产生可测量的影响。棘冠海星在自然产卵期间实现了高水平受精的潜力。当产卵同步性高时，记录到的受精率高达99%。
