A scanning electron microscopy study of the embryonic development of Pycnogonum litorale (Arthropoda, Pycnogonida)
A scanning electron microscopy study of the embryonic development of Pycnogonum litorale (Arthropoda, Pycnogonida)
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Pycnogonum litorale（节肢动物门，Pycnogonida）胚胎发育的扫描电子显微镜研究
DOI：
10.1002/jmor.10871
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发表时间：
2010
影响因子：
1.5
通讯作者：
G. Scholtz
中科院分区：
文献类型：
--
作者：
Jakob Machner;G. Scholtz
神秘的Pycnogonida（海蜘蛛）的系统发育位置仍然有争议。这在一定程度上是由于缺乏详细的数据，形态和个体发育，这在许多方面，异常组。特别是，对密子鱼胚胎发育的研究很少，而且部分相互矛盾。在这里，我们提出了第一个胚胎学研究的pycnogonid物种使用扫描电子显微镜（SEM）。本文描述了滨海密角藻从第一个可见的附属器原基到幼体的11个胚胎发育阶段。这三对附属物原基通过生长以及犁沟延伸到胚中而增加长度。口道的开口位于螯肢原基的前方，从一开始就有一个Y形的内腔。在进一步的胚胎发育过程中，嘴的位置向腹侧移动，直到它位于螯肢之间。喙原基生长为一个环口壁样结构，最初在腹侧更明显。由于P. litorale的长鼻原基没有显示出复合性质的迹象，因此对关于长鼻由最初分离的成分融合而进化的假设进行了批判性的讨论。特别是，我们的数据拒绝了后cheliforal元素在长鼻形成中的参与。此外，没有发现口前结构和吻形成的阶段，这可能是同源的唇其他节肢动物。因此，我们的研究支持的假设，一个完全缺乏唇的密子目。J. Morphol.，2010.© 2010 Wiley利斯公司
The phylogenetic position of the enigmatic Pycnogonida (sea spiders) is still controversial. This is in part due to a lack of detailed data about the morphology and ontogenesis of this, in many aspects, aberrant group. In particular, studies on the embryonic development of pycnogonids are rare and in part contradictory. Here, we present the first embryological study of a pycnogonid species using scanning electron microscopy (SEM). We describe the late embryogenesis of Pycnogonum litorale from the first visible appendage anlagen to the hatchling in 11 embryonic stages. The three pairs of appendage anlagen gain in length by growth, as well as by extension of furrows into the embryo. The opening of the stomodaeum is located far in front of the anlagen of the chelifores and has a Y‐shaped lumen from the onset. During further embryogenesis, the position of the mouth shifts ventrally, until it is located between the chelifores. The proboscis anlage grows out as a circumoral wall‐like structure, which is initially more pronounced ventrally. Hypotheses about the evolution of the proboscis by fusion of originally separated components are critically discussed, because the proboscis anlage of P. litorale shows no indications of a composite nature. In particular, a participation of post‐cheliforal elements in proboscis formation is rejected by our data. Further, no preoral structure and no stage in proboscis formation was found, which could plausibly be homologized with the labrum of othereuarthropods. Thus, our study supports the assumption of a complete lack of a labrum in Pycnogonida. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.