Llopis-Belenguer Cristina, Balbuena Juan Antonio, Galván-Femenía Iván, Rodríguez-González Abril
Marine Zoology Unit, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Valencia, Spain.
Department of Computer Science, Applied Mathematics and Statistics, Universitat de Girona, Girona, Spain.
PLoS One. 2015 Nov 6;10(11):e0142365. doi: 10.1371/journal.pone.0142365. eCollection 2015.
Phenotypic variation results from the balance between sources of variation and counteracting regulatory mechanisms. Canalization and developmental stability are two such mechanisms, acting at two different levels of regulation. The issue of whether or not they act concurrently as a common developmental buffering capacity has been subject to debate. We used geometric morphometrics to quantify the mechanisms that guarantee phenotypic constancy in the haptoral anchors of Ligophorus cephali. Canalization and developmental stability were appraised by estimating inter- and intra-individual variation, respectively, in size and shape of dorsal and ventral anchors. The latter variation was estimated as fluctuating asymmetry (FA) between anchor pairs. The general-buffering-capacity hypothesis was tested by two different methods based on correlations and Principal Components Analyses of the different components of size and shape variation. Evidence for FA in the dorsal and ventral anchors in both shape and size was found. Our analyses supported the hypothesis of a general developmental buffering capacity. The evidence was more compelling for shape than for size and, particularly, for the ventral anchors than for the dorsal ones. These results are in line with previous studies of dactylogyrids suggesting that ventral anchors secure a firmer, more permanent attachment, whereas dorsal anchors are more mobile. Because fixation to the host is crucial for survival in ectoparasites, we suggest that homeostatic development of the ventral anchors has been promoted to ensure the morphological constancy required for efficient attachment. Geometric morphometrics can be readily applied to other host-monogenean models, affording not only to disentangle the effects of canalization and developmental stability, as shown herein, but to further partition the environmental and genetic components of the former.
表型变异源于变异来源与对抗调节机制之间的平衡。发育稳态和发育稳定性就是这样两种机制，它们在两个不同的调节水平上起作用。它们是否作为一种共同的发育缓冲能力同时发挥作用这一问题一直存在争议。我们使用几何形态测量学来量化保证头状 Ligophorus 吸盘锚定表型恒定的机制。通过分别估计背侧和腹侧锚定在大小和形状上的个体间和个体内变异来评估发育稳态和发育稳定性。后者的变异被估计为锚定对之间的波动不对称性（FA）。基于大小和形状变异的不同组成部分的相关性和主成分分析，通过两种不同方法检验了一般缓冲能力假说。在背侧和腹侧锚定的形状和大小上均发现了 FA 的证据。我们的分析支持了一般发育缓冲能力的假说。形状方面的证据比大小方面更有说服力，特别是腹侧锚定比背侧锚定更有说服力。这些结果与之前对指环虫的研究一致，表明腹侧锚定能确保更牢固、更持久的附着，而背侧锚定更具可移动性。由于对外寄生生物来说固定在宿主上对生存至关重要，我们认为腹侧锚定的稳态发育已得到促进，以确保有效附着所需的形态恒定性。几何形态测量学可以很容易地应用于其他宿主 - 单殖吸虫模型，不仅能够像本文所示那样区分发育稳态和发育稳定性的影响，还能进一步划分前者的环境和遗传成分。
