Brood or broadcast? The adaptive significance of different reproductive strategies in the two intertidal sea stars Leptasterias hexactis and Pisaster ochraceus
Brood or broadcast? The adaptive significance of different reproductive strategies in the two intertidal sea stars Leptasterias hexactis and Pisaster ochraceus
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沉思还是广播？
DOI：
10.1007/bf00390651
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发表时间：
1975
期刊：
影响因子：
2.4
通讯作者：
B. Menge
中科院分区：
文献类型：
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作者：
B. Menge
本文考虑了两种不同繁殖方法在两种同时发生、竞争的海星中的适应性意义。较小的（平均湿重 3 至 8 克）Leptasterias hexactis 在冬季产卵相对较少，较大的幼鱼，而较大的（平均湿重 300 至 650 克）Pisaster ochraceus 每年春天产下相对较多的小卵。 L. hexactis 在大约 2 年内成熟为小尺寸（2 g 湿重），P. ochraceus 在大约 5 年内成熟为较大尺寸（70 至 90 g 湿重）（Menge，1974）。与许多广播小行星一样，P. ochraceus 的性腺和储存器官指数随时间呈负相关，最大储存器官指数与夏季摄食最大值相关（Mauzey，1966）。相反，L. hexactis 的器官指数和摄食量均增加，并呈正相关，直到初秋，此时摄食活动开始下降。此时男性性腺指数继续上升，而贮藏器官指数下降。相比之下，女性的两个器官指数均上升。产卵发生在十一月至一月。此后，雌性的储存器官指数下降，可能是因为雌性在育雏时消耗了能量储备；雄性的储存器官指数上升，可能是因为雄性不育雏，并且在有食物的情况下可以进食。造成P. ochraceus 和L. hexactis 年繁殖周期差异的主要原因是被释放的幼体的食物供应模式（播散的P. ochraceus 幼体为浮游食物，而L. hexactis 的育雏幼体为底栖猎物。对成熟前存活率和成熟后寿命的估计表明，幼体P. ochraceus 个体的生存概率远低于普通个体的存活概率。然而，一旦成熟，P. ochraceus 的预期寿命就会更长，假设这种环境中的浮游生物死亡率在广播物种中大致恒定，我认为小型广播物种在其预期寿命内无法产生足够的后代来取代自己。影响海洋无脊椎动物繁殖模式的因素包括（1）成虫和后代的食物供应，（2）浮游死亡率，（3）物种之间的相互作用和这些因素的纬度变化，以及（4）各种物理因素。生殖方法的进化，迄今为止这种可能性在很大程度上被忽视了，尽管有几个在生殖方法和大小方面不同的共生物种对的类似例子，但在这些例子中，成虫相互作用的作用尚不清楚。
This paper considers the adaptive significance of two different reproductive methods in two co-occurring, competing sea stars. The smaller (3 to 8 g mean wet weight) Leptasterias hexactis broods relatively few, large young in the winter, while the large (300 to 650 g mean wet weight) Pisaster ochraceus broadcasts relatively many, small eggs each spring. L. hexactis matures at a small size (2 g wet weight) in about 2 years, and P. ochraceus matures at a larger size (70 to 90 g wet weight) in about 5 years (Menge, 1974). As in many broadcasting asteroids, gonad and storage organ indices of P. ochraceus are inversely related over time, and maximum storage-organ index correlates with the summer feeding maximum (Mauzey, 1966). In contrast, both organ indices of L. hexactis and feeding increase and are positively correlated until early autumn, when feeding activity begins to decline. At this time the male gonad index continues to rise, and the storage-organ index drops. In contrast, both organ indices of females rise. Spawning occurs from November to January. Thereafter storage-organ indices decline in females, presumably because females draw upon energy reserves while brooding; storage-organ indices rise in males, presumably because males do not brood and can feed if food is available. The primary cause for the differences between annual reproductive cycles of P. ochraceus and L. hexactis is suggested to be patterns of food availability for the released young (planktonic food for the broadcasted young of P. ochraceus and benthic prey for the brooded young of L. hexactis. Estimates of pre-maturity survival and post-maturity longevity indicate that the probability of survival per individual of young P. ochraceus is vastly lower than that of L. hexactis. However, once mature, P. ochraceus has a much longer expected lifespan. Brooding is suggested to be a coadaptive consequence of competition-induced small size. Assuming planktonic mortality rates in this environment are roughly constant across broadcasting species, I suggest that a small broadcasting species could not produce enough offspring in its expected lifespan to replace itself. This hypothesis is partly supported by some simple simulations. Broadcasting is suggested to permit rapid location and utilization of spatially and temporally unpredictable, but highly desirable, resources by allowing rapid and widespread dispersal. Brooders presumably cannot disperse rapidly and must rely on more reliable, but perhaps less desirable, resources. Factors affecting reproductive patterns in marine invertebrates include (1) food availability for both adults and offspring, (2) planktonic mortality rates, (3) interactions between species and latitudinal changes in these factors, and (4) various physical factors. This paper suggests that competition and predation can have an important effect on the evolution of reproductive methods, a possibility heretofore largely ignored. Although several similar examples of co-occurring species' pairs which differ in reproductive method and size are available, the role of adult interactions is unknown in these examples.