Blin Maryline, Rabet Nicolas, Deutsch Jean S, Mouchel-Vielh Emmanuèle
Service de Biosystématique, Université Pierre et Marie Curie, Paris 6, France.
Dev Genes Evol. 2003 Mar;213(2):90-6. doi: 10.1007/s00427-003-0294-z. Epub 2003 Feb 1.
The crustaceans cirripedes (barnacles) are characterised by the lack of fully developed abdominal segments at any stage of their life cycle. However, in nauplius larvae of the cirripede Sacculina carcini, we detected five small engrailed stripes in a postero-dorsal region behind the sixth thoracic segment, that we interpreted as a vestigial abdomen. Here, we present additional morphological and genetic data on Sacculina to further characterise this structure. Scanning electron microscopy analysis confirms the existence of a segmented region in this part of the naupliar body. However, at the late naupliar stage, this structure stops its development and degenerates. This region expresses the Hox gene Abdominal-B, which may indicate that it actually corresponds to the posterior-most part of the Sacculina trunk. In addition, Abdominal-B expression differentiates two types of larvae that probably correspond to male and female larvae, respectively. In contrast, no abdominal-A expression can be detected in the vestigial abdomen. We discuss the possible implication of the loss or divergence of the Abdominal-A protein in the impaired development of abdominal segments in cirripedes.
甲壳纲蔓足亚纲动物（藤壶）的特征是在其生命周期的任何阶段都没有发育完全的腹部节段。然而，在藤壶蟹奴（Sacculina carcini）的无节幼体中，我们在第六胸节后方的后背部区域检测到五条小的 engrailed 条纹，我们将其解释为残余腹部。在此，我们展示关于蟹奴的更多形态学和遗传学数据，以进一步描述这一结构。扫描电子显微镜分析证实了无节幼体身体的这一部分存在一个分节区域。然而，在无节幼体后期，这个结构停止发育并退化。该区域表达 Hox 基因 Abdominal - B，这可能表明它实际上对应于蟹奴躯干的最后端部分。此外，Abdominal - B 的表达区分出两种可能分别对应雄性和雌性幼体的类型。相比之下，在残余腹部中未检测到 abdominal - A 的表达。我们讨论了 Abdominal - A 蛋白的缺失或差异在蔓足亚纲动物腹部节段发育受损中可能产生的影响。
