Reynolds S A, French K A, Baader A, Kristan W B
Department of Biology, University of California at San Diego, La Jolla 92093-0357, USA.
J Comp Neurol. 1998 Dec 14;402(2):168-80.
ABSTRACT The ontogeny of behavior in an organism must reflect developmental events in the nervous system, and it thus provides a noninvasive measure of neuronal development. This approach may be particularly fruitful in the medicinal leech because the neuronal basis of several behaviors has been characterized in adult leeches, providing a rich background against which behavioral development can be interpreted. We have investigated the order in which behaviors arise during the period of embryonic development and have determined the time at which each behavior is first expressed. Some behaviors, such as lateral ridge formation, germinal plate bending, spiral twisting, and sidewinding, were produced spontaneously by embryos. Others, such as shortening, circumferential indentation, local bending, and elongation, occurred only when they were elicited by weak mechanical stimulation. Such stimulation rarely evoked a behavioral response in young embryos (at 45% of the time required for complete embryonic development, 45% ED), but by 80% ED embryos responded to nearly 100% of the stimuli presented. In embryos older than 50% ED, the behavior most frequently evoked by stimulation of the anterior end, the posterior end, or the rear sucker was shortening. Stimulation of the midbody usually evoked behavior other than shortening, illustrating that the body was behaviorally compartmentalized, at least in part. Some behaviors observed during embryogenesis are never seen in adult leeches. For example, in response to stimulation of the midbody, young embryos produced a behavior that we have called "circumferential indentation," whereas older embryos produced local bending, a response previously described for adults. The switch from circumferential indentation to local bending may signal the formation of new synaptic connections.
摘要 生物体行为的个体发生必然反映神经系统中的发育事件，因此它提供了一种神经元发育的非侵入性测量方法。这种方法在药用水蛭中可能特别有成效，因为几种行为的神经元基础已在成年水蛭中得到表征，为解释行为发育提供了丰富的背景。我们研究了胚胎发育期间行为出现的顺序，并确定了每种行为首次表达的时间。一些行为，如侧嵴形成、生发板弯曲、螺旋扭转和侧行，是胚胎自发产生的。其他行为，如缩短、圆周压痕、局部弯曲和伸长，仅在受到弱机械刺激时才会出现。这种刺激在年轻胚胎（在胚胎完全发育所需时间的45%，即45%胚胎发育阶段）中很少引起行为反应，但到80%胚胎发育阶段时，胚胎对几乎100%的刺激都有反应。在超过50%胚胎发育阶段的胚胎中，刺激前端、后端或后吸盘最常引起的行为是缩短。刺激身体中部通常会引起除缩短之外的其他行为，这表明身体至少在一定程度上在行为上是分区的。在胚胎发生过程中观察到的一些行为在成年水蛭中从未见过。例如，对身体中部的刺激，年轻胚胎会产生一种我们称为“圆周压痕”的行为，而 older embryos produced local bending, a response previously described for adults. 从圆周压痕到局部弯曲的转变可能标志着新突触连接的形成。 （注：原文中“older embryos produced local bending, a response previously described for adults.”这部分英文似乎有误，按照正确语义翻译了整体内容）
