Kavanau J Lee
Med Hypotheses. 2006;66(1):3-9. doi: 10.1016/j.mehy.2005.08.036. Epub 2005 Oct 5.
Biotelemetry has revealed daily 15-h behavioral sleep periods in a cubomedusan jellyfish, Chironex fleckeri. Its sleep is expected to be phylogenetically most primitive, since jellyfish possess only two germ layers. They belong to the phylum Cnidaria, the 'simplest' multicellular organisms with an organized nervous system. Cubomedusae have a complex visual system with 24 eyes of four different types, each type specialized for a different task. Input to these eyes during visually guided fast-swimming predation requires enormous amounts of neural processing, possibly nearly saturating the capacity of their comparatively simple nervous system. These heavy neural demands may account for the need for fifteen hours of sleep. C. fleckeri is the only animal known for which sleep may be either present or absent, dependent on lifestyle. Limited knowledge of behavior of some other cubomedusae suggests that they also possess this faculty. The finding of sleep in C. fleckeri supports current proposals of sleep's origin and basic function. Evolutionary analyses link sleep to a conflict produced by excessive processing demands on multifunctional neural circuitry for detailed focal vision by complex lensed eyes. The conflict arises between the enormous demands of complex visual analysis and needs for split-second control of actions, on the one hand, and non-urgent processing of memories of ongoing and stored events, on the other. Conflict is resolved by deferring the non-urgent processing to periods of sleep. Without sleep, selection would favor the evolution of circuitry 'dedicated' to single or but few tasks, with corresponding lesser efficiency. Had complex lensed eyes of medusae originated as a consequence of selection for increased mating success of males pursuing females, it could have occurred before the evolution of fast-swimming bilateral (three-germ-layered) prey. But if it was a consequence of selection for increased prey-hunting success, the origin of such eyes probably awaited the coexistence of bilateral prey.
生物遥测技术揭示了箱形水母（Chironex fleckeri）每天有15小时的行为睡眠期。由于水母仅拥有两个胚层，预计其睡眠在系统发育上是最原始的。它们属于刺胞动物门，是具有有组织神经系统的“最简单”多细胞生物。箱形水母有一个复杂的视觉系统，由四种不同类型的24只眼睛组成，每种类型专门用于不同的任务。在视觉引导的快速游动捕食过程中，这些眼睛的输入需要大量的神经处理，可能几乎使其相对简单的神经系统的容量达到饱和。这些沉重的神经需求可能解释了需要15小时睡眠的原因。C. fleckeri是已知的唯一一种睡眠可能存在或不存在的动物，这取决于其生活方式。对其他一些箱形水母行为的有限了解表明它们也具有这种能力。在C. fleckeri中发现睡眠支持了当前关于睡眠起源和基本功能的提议。进化分析将睡眠与复杂透镜眼对详细焦点视觉的多功能神经回路处理需求过多所产生的冲突联系起来。一方面，复杂视觉分析的巨大需求与对动作瞬间控制的需求之间存在冲突，另一方面，与对正在进行和存储事件的记忆的非紧急处理之间也存在冲突。通过将非紧急处理推迟到睡眠期间来解决冲突。没有睡眠，选择将有利于“专门”用于单一或少数任务的神经回路的进化，相应地效率较低。如果水母的复杂透镜眼是由于选择增加追逐雌性的雄性的交配成功率而产生的，那么它可能在快速游动的双侧（三胚层）猎物进化之前就已经出现。但如果是由于选择增加捕食成功率而产生的，那么这种眼睛的起源可能等待着双侧猎物的共存。
