Extraordinary host switching in siphonostomatoid copepods and the demise of the Monstrilloida: Integrating molecular data, ontogeny and antennulary morphology
Extraordinary host switching in siphonostomatoid copepods and the demise of the Monstrilloida: Integrating molecular data, ontogeny and antennulary morphology
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DOI：
10.1016/j.ympev.2007.02.004
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发表时间：
2007-05-01
影响因子：
4.1
通讯作者：
Johnston, David A.
中科院分区：
文献类型：
--
作者：
Huys, Rony;Llewellyn-Hughes, Julia;Johnston, David A.
桡足类动物表现出惊人的生活方式、寄主关系和形态的多样性，以至于它们与甲壳类动物的亲缘关系可能被掩盖了。十目桡足动物之间的形态关系尚不明确。在这里，我们使用SSU rDNA基因序列、比较形态学数据（触角感觉界面）和个体发生数据（尾支设置模式）来测试神秘的Monstrilloida的顺序状态。贝叶斯分析意外地揭示了Monstrilloida是在Siphonostomatoida的一个鱼寄生分支中筑巢的，并且与caligiform科（海虱）的茎类物种有共同的祖先。这种不可预见的关系与触角和尾支形态一致。异寄生的、与脊椎动物相关的祖先与怪物的分化涉及宿主利用、身体计划和生命周期策略的根本变化，这种结合在后生动物寄生虫中很少观察到，可能是独一无二的。成年怪物二级回归到自由生活，暴露于捕食者的生活模式，我们假设维持一个功能接近捕食者检测系统的压力已经延迟了5点触角感觉阵列的抑制（如在后桡足动物的caligform阶段）。本文讨论了虹口虫额丝的同塑进化。(C) 2007爱思唯尔公司版权所有。
Copepods exhibit an astounding variety of lifestyles, host associations and morphology, to the extent that their crustacean affinities may be obscured. Relationships among the ten copepod orders based on morphological characters remain equivocal. Here we test the ordinal status of the enigmatic Monstrilloida using SSU rDNA gene sequences, comparative morphological data (antennulary sensory interface) and ontogenetic data (caudal ramus setation patterns). Bayesian analysis unexpectedly revealed the Monstrilloida are nested within a fish-parasitic clade of the Siphonostomatoida and share a common ancestor with the stem species of the caligiform families (sea-lice). This unforeseen relationship is congruent with both antennulary and caudal ramus morphology. The divergence of the monstrilloids from an ectoparasitic, vertebrate-associated ancestor involved radical changes in host utilization, body plan and life cycle strategy, a combination rarely observed and probably unique in metazoan parasites. Adult monstrilloids secondarily returned to a free-living, predator-exposed mode of life and we postulate the pressure on maintaining a functional approaching-predator detection system has progenetically delayed the suppression (as in post-copepodid caligiform instars) of the 5-point antennulary sensory array. The homoplastic evolution of the frontal filament in Siphonostomatoida is discussed. (C) 2007 Elsevier Inc. All rights reserved.