Larouche-Bilodeau Charles, Guilbeault-Mayers Xavier, Cameron Christopher B
Sciences biologiques Université de Montréal Montreal QC Canada.
Ecol Evol. 2020 Nov 3;10(23):13544-13554. doi: 10.1002/ece3.6962. eCollection 2020 Dec.
We measured gill slit fluctuating asymmetry (FA), a measure of developmental noise, in adults of three invertebrate deuterostomes with different feeding modes: the cephalochordate (an obligate filter feeder), the enteropneusts (a facultative filter feeder/deposit feeder) and (a deposit feeder). FA was substantially and significantly low in and and high in . Our results suggest that the gills of species that have experienced a relaxation of the filter feeding trait exhibit elevated FA. We found that the timing of development of the secondary collagenous gill bars, compared to the primary gill bars, was highly variable in but not the other two species, demonstrating an independence of gill FA from gill bar heterochrony. We also discovered the occasional ectopic expression of a second set of paired gills posterior to the first set of gills in the enteropneusts and that these were more common in . Moreover, our finding that gill slits in enteropneusts exhibit bilateral symmetry suggests that the left-sidedness of larval cephalochordate gills, and the directional asymmetry of Cambrian stylophoran echinoderm fossil gills, evolved independently from a bilaterally symmetrical ancestor.
我们测量了三种具有不同摄食方式的无脊椎后口动物成体的鳃裂波动不对称性（FA），这是一种发育噪声的度量指标：头索动物（专性滤食动物）、肠鳃类动物（兼性滤食动物/沉积食性动物）和[此处原文缺失一种动物名称]（沉积食性动物）。在[此处原文缺失一种动物名称]和[此处原文缺失一种动物名称]中，FA显著较低，而在[此处原文缺失一种动物名称]中较高。我们的结果表明，经历了滤食性状松弛的物种的鳃表现出较高的FA。我们发现，与初级鳃条相比，次级胶原质鳃条的发育时间在[此处原文缺失一种动物名称]中高度可变，但在其他两个物种中并非如此，这表明鳃的FA与鳃条异时性无关。我们还发现，在肠鳃类动物中，第一组鳃后方偶尔会异位表达第二组成对的鳃，并且这些在[此处原文缺失一种动物名称]中更为常见。此外，我们发现肠鳃类动物的鳃裂表现出双侧对称性，这表明幼虫头索动物鳃的左侧性以及寒武纪柱星虫类棘皮动物化石鳃的定向不对称性是从双侧对称的祖先独立进化而来的。
