Cannibal-prey dynamics in young juveniles and postlarvae of the blue crab
Cannibal-prey dynamics in young juveniles and postlarvae of the blue crab
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DOI：
10.1016/s0022-0981(97)00052-x
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发表时间：
1997-08-01
影响因子：
2
通讯作者：
vanMontfrans, J
中科院分区：
文献类型：
--
作者：
Moksnes, PO;Lipcius, RN;vanMontfrans, J
尽管同类相食可以作为陆地系统中人口规模的密度依赖性调节剂，但对其对海洋环境的影响却知之甚少。在此，我们研究了同类相食对蓝蟹 Callinectes sapidus Rathbun 早期生活史阶段的影响，强调了同年纲的幼体和后期幼体（即大眼幼体）之间的同类相食行为。在实验室中生态系统中，我们研究了调节食人-猎物动态的各种因素，具体来说：（1）栖息地和同种动物的存在对幼体变态率的影响； (2) 变态率对群体内和群体间同类相食虾苗死亡率的影响； （3）栖息地和捕食者密度对幼年蓝蟹捕食者对不同密度的幼体猎物的功能反应的影响，以及（4）猎物大小和栖息地对捕食死亡率的影响。群体间同类相食导致每种螃蟹大小和栖息地类型组合的显着死亡率，并且对于所有小于五龄的猎物，在草地中的死亡率低于沙地。后期幼虫之间的同类相食与变态有关，并且在沙子中与密度相关，但在草中不存在。幼体的变态率在沙子中与密度呈负相关，但在草中则与密度无关且更高，这表明栖息地和群体内的激动可能会影响幼体的变态率。群体间同类相食与虾苗变态率呈负相关。在沙地和草地栖息地以及中等和高捕食者密度之间，幼年同类相食的蓝蟹的功能反应存在显着差异。幼蟹在沙子中表现出 II 型、反密度依赖的功能反应，导致幼体猎物密度低时死亡率非常高。在草丛中，螃蟹表现出较弱的 III 型密度依赖性反应，在低猎物密度下死亡率显着降低。因此，栖息地的复杂性改变了食人者与猎物相互作用中功能反应的形式，而草则提供了相对的栖息地避难所，以防止同类相食。将草丛中捕食者的数量加倍显着降低了每个捕食者的消耗率并消除了密度依赖性，表明种内密度可以定性地改变功能反应的形式。在螃蟹大小实验中，只有小于第五龄的猎物在草丛中获得了免受同类相食的栖息地避难所，而第五龄则在沙子中获得了相对大小的避难所。我们的结果表明，同龄类同类相食可能会导致定居大眼和第一幼龄的死亡，这取决于猎物密度。我们预计群体间的同类相食会导致定居在沙子中的群体的局部灭绝，特别是在低定居密度的情况下，以及在中等定居密度的草丛中导致高死亡率的情况。草丛中高密度定居点对掠食者的饱和表明，间歇性定居可以压倒当地的掠食者。此外，草床中大群体内密度依赖性的相互干扰可能会降低它们的捕食效率？表明草地生境中同种捕食者的聚集并不一定会导致捕食压力的增加。最后，第五龄蟹的群体间同类相食的相对尺寸避难所支持了围绕该螃蟹尺寸的个体发生栖息地变化，这可能受到群体内密度依赖的竞争行为的影响。我们认为，年内类同类相食是调节大眼幼蟹和幼年蓝蟹生存和扩散的主要过程。 (C) 1997 Elsevier Science B.V.
Although cannibalism can act as a density-dependent regulator of population size in terrestrial systems, little is known of its effects in the marine environment. Herein we investigate the influence of cannibalism upon the early life history stages of the blue crab, Callinectes sapidus Rathbun, emphasizing cannibalism between juveniles and postlarvae (i.e. megalopae) of the same year class. In laboratory mesocosms we examined various factors modulating cannibal-prey dynamics, specifically: (1) the effects of habitat and presence of conspecifics on postlarval metamorphosis rate; (2) the effect of metamorphosis rate on the mortality of postlarvae from both intra- and inter-cohort cannibalism; (3) the effects of habitat and predator density on the functional response of young juvenile blue crab predators to varying densities of postlarval prey, and (4) the effects of prey size and habitat on predation mortality.Inter-cohort cannibalism caused significant mortality in every crab size and habitat type combination, and was lower in grass than sand for all prey smaller than fifth instar. Cannibalism between postlarvae was associated with metamorphosis and was density-dependent in sand, but not present in grass. Metamorphosis rates of postlarvae were inversely density-dependent in sand, but density-independent and higher in grass, indicating that habitat and intra-cohort agonism likely affects postlarval metamorphosis rates. Inter-cohort cannibalism was negatively correlated with metamorphosis rates of postlarvae. The functional response of young juvenile cannibalistic blue crabs differed significantly between sand and grass habitats, and between medium and high predator densities. Juvenile crabs displayed a type II, inversely density-dependent functional response in sand, resulting in very high mortality at low densities of postlarval prey. In grass, the crabs displayed a weak type III, density dependent response, yielding significantly lower mortality at low prey densities. Thus, habitat complexity changes the form of the functional response in cannibal-prey interactions and grass provides a relative habitat refuge from cannibalism. Doubling the number of predators in grass decreased the consumption rates per predator significantly and eliminated the density-dependence, indicating that intraspecific density can qualitatively change the form of the functional response. In the crab size experiment, only prey smaller than fifth instars received a habitat refuge from cannibalism in grass, whereas fifth instars received a relative size refuge in sand.Our results demonstrate that intra-year class cannibalism can cause mortality upon settling megalopae and first juvenile instars that is dependent on prey density. We expect inter-cohort cannibalism to cause local extinction of cohorts settling in sand, especially at low settlement densities, and high mortality at moderate settlement densities in grass. Satiation of predators at high settlement densities in grass suggests that episodic settlement can overwhelm predators locally. Furthermore, density-dependent mutual interference within large cohorts in the grass beds likely reduces their predation efficiency? indicating that aggregation of conspecific predators in grass habitats does not necessary lead to an increase in predation pressure. Finally, a relative size-refuge from inter-cohort cannibalism for fifth instar crabs supports an ontogenetic habitat shift around this crab size, which may be influenced by density-dependent agonistic behavior within cohorts. We suggest that intra-year class cannibalism is a major process regulating both survival and dispersal in megalopae and juvenile blue crabs. (C) 1997 Elsevier Science B.V.